the lichens of rarotonga, cook islands, south pacific ocean i: pyrenocarpous taxa

Lichenologist 32(1): 15-47 (2000)Article No. lich. 1999.0212Available online at http://www.idealibrary.com on IDEKL

THE LICHENS OF RAROTONGA, COOK ISLANDS,SOUTH PACIFIC OCEAN I: PYRENOCARPOUS

TAXA

p. M. MCCARTHY*

Abstract: Four new pyrenocarpous lichens are described from Rarotonga, CookIslands, South Pacific Ocean: Porina deminuta (Trichotheliaceae), Pyrenula ochraceo-flava var. pacifica (Pyrenulaceae), Strigula decipiens var. divisa (Strigulaceae) andVerrucaria fortuita (Verrucariaceae). The new combinations Porina eminentior (Nyl.)P. M. McCarthy and P. exocha (Nyl.) P. M. McCarthy are made for Thelenellaeminentior Nyl. {Clathroporina eminentior (Nyl.) Mull. Arg.) and Verrucaria exochaNyl. {Clathroporina exocha (Nyl.) Mull. Arg.), respectively. Brief descriptions andadditional notes are provided for 26 other taxa. The phytogeographical affinities andpossible origins of the pyrenocarpous lichens of Rarotonga and Lord Howe Islandare discussed. © 2000 The British Lichen Society

Introduction

In Europe and North America, interest in the taxonomy of lichens andappreciation of the importance of their biodiversity have never been greater.Elsewhere, however, with some exceptions (e.g. Argentina, parts of Brazil,India, Japan, Australia and New Zealand), the situation is very different. Thedisparity may be explained by remoteness, the lack of impetus that comesfrom resident lichenologists, or by the perceived irrelevance of lichenology,especially when set against more pressing priorities. This is certainly the casein much of South America, most of Africa and South-east Asia and in theislands dotting the 70 million square kilometres of the South Pacific Ocean.

Published accounts emphasizing the lichens of the Pacific islands firstappeared in the middle of the nineteenth century, beginning with some of thelarger and/or less remote islands and island groups such as New Caledonia,French Polynesia and the Hawaiian Islands. These were followed by floristicand taxonomic studies on Western Samoa, Easter Island, Islas Juan Fernandezand, more recently, the Bonin Islands (Ogasawara-shoto), the NorthernMariana Islands, Islas Galapagos, Isla del Coco, Norfolk Island, Lord HoweIsland and others. However, our understanding of many Pacific floras is stillat a preliminary stage, and future investigations will not only elucidatethe diversity of lichens in the region, they will almost certainly show that thesupposed level of endemism in some of the better-known floras (e.g. theHawaiian Islands and Islas Juan Fernandez) has been greatly exaggerated.Meanwhile, the remoteness of many islands and a shortage of resident

•Australian Biological Resources Study, GPO Box 787, Canberra, A.C.T. 2601, Australia.

0024-2829/00/010015 + 33 $35.00/0 © 2000 The British Lichen Society

16 THE LICHENOLOGIST Vol. 32

enthusiasts contribute to continued neglect; this is especially true of theSolomon Islands, Vanuatu, Fiji, Tonga, most of French Polynesia and, untilrecently, the Cook Islands.

Although a few lichens were reported from the Cook Islands in the literatureof the nineteenth century, the most significant contributions came fromSbarbaro (1939) and Rasanen (1944), both of whom studied Rarotonganspecimens collected by H. E. and S. T. Parks in 1929. Elix & McCarthy(1998) listed 30 taxa (with Pyrenula philippina var. padfica Sbarbaro the onlypyrenocarpous one), a figure that is clearly incomplete when compared withother better-known floras in the region, such as those of the Society Islands(221 taxa), Western Samoa (182) and Fiji (118).

Because of their inconspicuous appearance, pyrenocarpous lichens wereoften overlooked or only accidentally collected by the early expeditions.Nevertheless, a reasonably large number of taxa has accumulated over theyears. A recent literature survey of the lichens of the smaller Pacific islandslisted 81 species and infraspecific taxa of Pyrenulaceae, 49 Trichotheliaceae, 35Trypetheliaceae (mostly in New Caledonia), 23 Strigulaceae, 16 Verrucariaceaeand 15 Monoblastiaceae (Elix & McCarthy 1998).

During 5-11 June 1998 the author, with Prof. Jack Elix and Ms. SimoneLouwhoff, visited Rarotonga to study its lichens, especially pyrenocarpousgenera and Parmeliaceae. In addition to the target groups, we found anabundant and diverse flora comprising species of Collemataceae, Lobariaceae,Pannariaceae and Physdaceae as well as numerous Graphidaceae, Pertusar-iaceae, Thelotremataceae and crustose Lecanorales. In this paper four new taxaof Porina Ach. {Trichotheliaceae), Pyrenula Ach. {Pyrenulaceae), Strigula Fr.{Strigulaceae) and Verrucaria Schrad. {Verrucariaceae) are described, and 28additional taxa are documented. Remarkably, none of the specimens ofPyrenula collected matched the perfunctory description of P. philippina var.padfica provided by Sbarbaro (1939).

The Cook IslandsThe Cook Islands, a self-governing territory in free association with NewZealand, comprises 15 small islands and atolls in 2 million square kilometresof the South Pacific Ocean, flanked by Samoa and Tonga to the west and byFrench Polynesia to the east (Fig. 1). Rarotonga, the largest island, is situatedat latitude 21°12-15'S and longitude 159°44-50'W. Fringed by a coral reef,it is 11 km from east to west, 8 km from north to south, and has an area of67 square kilometres. Most of its 11 000 residents live near the coast, andcultivation is largely confined to a coastal strip 1-1-5 km wide.

Rarotonga appeared about 2 million years ago during a series ofvolcanic eruptions that continued until the island was almost 1500m high(McCormack & Kiinzle 1991). The volcano collapsed leaving a wide caldera,and subsequent eruptions, compaction and erosion have formed today'srugged and fertile interior with breccia pinnacles and cliffs, as well as outcropsand boulders of rather porous basalt. Seasonal and permanent water-coursesfollow steep-sided, forested valleys separated by razorback ridges that lead up

2000 Rarotonga pyrenocarpous lichens—McCarthy 17

FIG. 1. Above: the South Pacific Ocean between the Equator and latitude 40°S showing the CookIslands, Rarotonga (arrowed) and Lord Howe Island (O; see Discussion). Below: Rarotongashowing contours (100 m interval), major water-courses and main areas in which lichens were

collected. Scale: 2 km.

to sheer cliffs, compact summit plateaux and sharp peaks. Te Manga (653 m)is the highest point on the island; however, 13 other peaks are more than300 m in altitude (Fig. 1).

Like much of the South Pacific, Rarotonga is strongly influenced by thesouth-east trade winds. The period December to April is warm and humid,with a greater probability of storms and cyclones; the climate is milder andequable during May to November. The mean annual rainfall is 2040 mm, andthe mean annual temperature is 24°C.

The higher plant flora of the mountains comprises 370 species of floweringplants and ferns, 204 of which are native and 20 endemic (McCormack &Kiinzle 1995). Vegetation inland of the coastal plain exhibits a verticalcontinuum dominated by trees, shrubs, vines and/or ferns. Disturbed lowlandforest, at an altitude of 30-200 m, represents a partial recovery of areas


formerly given over to bananas, mangoes, coffee and other crops. It is nowdominated by trees such as Ardisia elliptica (Myrsinaceae), Cecropia peltata(Cecropiaceae), Hibiscus tiliaceus (Malvaceae), Homalium acuminatum [Flacour-tiaceae), Inocarpus fagifer (Fabaceae) and Paraserianth.es falcataria (Mimosaceae).The vegetation of steeper slopes above the disturbed forest and extending upto the cloud forest at c. 400 m is characterized by Bischofia javanica (Euphor-biaceae), Elaeocarpus tonganus {Elaeocarpaceae), Homalium acuminatum, Poute-ria gray ana (Sapotaceae) and the large ferns Angiopteris evecta and Marattiasalicina (Marattiaceae), while narrow ridges also have Casuarina equisetifolia(Casuarinaceae), Fagraea berteroana (Loganiaceae), Fitschia speciosa (Asteraceae)and Metrosideros collina (Myrtaceae). The last two trees also dominate thecloud forest, along with the more localized Ascarina diffusa (Chloranthaceae)and the fern Elaphoglossum savaiiense (Lomariopsidaceae) (McCormack &Kiinzle 1995).

Materials and MethodsMore than 150 saxicolous, corticolous and foliicolous specimens were collected and air-dried inRarotonga; they were later subjected to gamma irradiation to comply with Australian quarantinerequirements.

Hand sections and squash preparations were examined in water and in 10% KOH. Asci ofTrichotheliaceae were also examined in Congo Red, while those of Monoblastiaceae, Pyrenulaceae,Strigulaceae, Verrucariaceae and Celothelium were examined in Lugol's Iodine (IKI). Measurementsof algae, thalline hyphae, hamathecial filaments, ascus apices, ascospores less than 30 |im long andconidia were made at x 1000 magnification; those of entire asci and larger ascospores were madeat x 400 magnification. In the descriptions, perithecial and ascospore dimensions are presentedas mean values with extreme values in parentheses. Total numbers of perithecia, asci andascospores measured are in square brackets, for example [« = 50].

Fragments of yellow-orange Pyrenula spp. were separated from obvious organic substratummaterial and extracted by high-performance liquid chromatography (HPLC; Feige el al. 1993).

Holotypes and some duplicates are held in the Museum of New Zealand Te Papa Tongarewa,Wellington (WELT); the remaining specimens are in CANB.

Pyrenocarpous Lichens

1. Anisomeridium anisolobum (Mull. Arg.) AptrootThallus endophloeodal to thinly subepiphloeodal, smooth, continuous to

very sparingly rimose, whitish, UV —, delimited by a blackish prothallus.Perithecia black, semi-immersed, (0-24-)0-31(-0-38) mm diam. [ra = 35],± round in outline, with an apical or slightly eccentric ostiole. Asci broadlycylindrical, (6-)8-spored. Pseudoparaphyses weakly anastomosing. Ascospores ±biseriate, elongate-ellipsoid, usually bent, with a distinctly submedian septumand walls that are unevenly thickened on their inner surface, (14—)18(—22) x (6-)8(-10) nm [«=110]; proximal cell considerably smaller than thedistal and usually more pointed. Conidia not seen.

This is a common coastal species in many tropical and subtropical regions(Harris 1995). In the Pacific, it is already known from Is. Galapagos (Weber1993).


Specimens examined: Te Kou track, lower slopes, 21°13'S, 159°46'W, alt. c. 80 m, on bark, 1998,McCarthy 1208, 1244 (part) (CANB).

2. Anisomeridium carinthiacum (J. Steiner) R. C. HarrisThallus epilithic, effuse to ± determinate, continuous to sparingly rimose,

pale grey-green to medium green, smooth to minutely and irregularly uneven,20-50 urn thick, ecorticate, but often with an upper, 10-15 urn thick, alga-freezone; prothallus and basal layer absent. Perithecia very numerous, black,convex, hemispherical or subconical; involucrellum (0-18-)0-24(-0-31) mmdiam. [« = 40], brownish black in thin section, 25-40 um thick near the apex,40-70 urn thick at the base; surface smooth or minutely uneven, often radiallyrugulose; excipulum hyaline at the base and sides, darkening towards the apex;centrum 0-09-0-15 mm diam. Pseudoparaphyses weakly anastomosing. Ascicylindrical, 8-spored, 44-60 x 9-12 um. Ascospores 1-septate, ellipsoid and± isolocular to ovate and with distal cell larger, often constricted at theseptum, irregularly biseriate in the ascus, (10-) 14 (-19) x (4-) 5 (-6) um[n = 50]. Conidiomata very numerous, black, 60-100 um diam., hemisphericalto subglobose, producing simple, narrowly to broadly ellipsoid, 2-3 (-4) x 1-l-5(-2) um microconidia.

The thalli of the Rarotongan specimens are thinner than previously seen(usually 40-80 um thick). Harris (1975, 1995) noted a black hypothallus insome North American collections, but this does not occur in the type or in anyof the Australasian and Pacific specimens examined. Moreover, the micro-conidial dimensions cited by Harris for North American collections aresomewhat larger (4-5 x 1-5 um).

Three other saxicolous species of Anisomeridium are known from the Pacificregion, but all are quite distinct from A. carinthiacum. Anisomeridium laeviga-tum (P. M. McCarthy) R. C. Harris from New Zealand and A. pacificum(P. M. McCarthy) R. C. Harris from the Hawaiian Is. have thicker thalliand/or larger perithecia and ascospores (McCarthy 1993a). Anisomeridiumaustraliense (P. M. McCarthy) R. C. Harris, from eastern Australia and LordHowe I. has, among other distinguishing features, 3-septate ascospores of21-36 x 5-13 um (McCarthy 1992).

This inconspicuous and probably overlooked species is known from centralEurope, the northern and north-eastern United States, tropical and cool-temperate Australia, New Zealand and Lord Howe Is. In Rarotonga, Aniso-meridium carinthiacum grows on shaded aquatic and semiaquatic basalt andshaded basalt and breccia boulders in more open situations.

Selected specimens examined: Avana Stream, c. 300 m E of water tanks, 21°14'S, 159°45'W, alt.c. 60 m, 1998, McCarthy 1215 (part) (WELT); Te Kou track, Takuvaine Stream, 21'14'S,159°46'W, alt. c. 100 m, 1998, McCarthy 1200 (WELT); Te Kou track, upper slopes, 2r i3 'S,159°46'W, alt. c. 300 m, 1998, McCarthy 1205 (part) (CANB).

3. Anisomeridium consobrinum (Nyl.) AptrootThallus endophloeodal to subepiphloeodal, continuous, white, UV + yellow,

forming large colonies delimited by a blackish prothallus. Peritheciablack, almost completely immersed, (0-22-)0-34(-0-48) mm diam. [« = 40],


round to ellipsoid in outline, with an apical or eccentric ostiole. Ascielongate-cylindrical, 8-spored. Pseudoparaphyses weakly anastomosing.Ascospores ± uniseriate, ellipsoid, with a median or submedian septum and arather thick wall, (20-)25(-30) x (8-)ll-5(-14) um [« = 70]; proximal cellusually more rounded. Macroconidia broadly ovate to broadly ellipsoid,thick-walled, (16-)18(-20) x (7-5-)9-5(-ll) urn [« = 38].

The lichen was first described from New Caledonia, and it is also knownfrom northern Australia and Papua New Guinea (Aptroot et al. 1995; Harris1995). Anisomeridium ambiguum (Zahlbr.) R. C. Harris, from the Caribbeanregion and the Seychelles (specimen seen in CANB), has more fusiformascospores (Harris 1995) and appears doubtfully distinct.

Specimen examined: Taputarangi track, 21°12'S, 159°48'W, alt. c. 120 m, on bark, 1998,McCarthy 1256 (CANB, WELT).

4. Celothelium cinchonarum (Mull. Arg.) Vain.Thallus white, endophloeodal. Ascomata dark brown to black, 0-12-

0-25 mm diam., usually fused in rounded or irregularly stellate groups of10-40, up to 3 (-4) mm wide; ostioles apical to eccentric, remaining discrete.Hamathecium of anastomosing paraphysoids. Asci elongate-cylindrical,arranged vertically, 8-spored, with a rounded apex and a minute ocularchamber. Ascospores colourless, filiform, 10-25-septate, (50-)69(-88) x (1-5-)2(-3)nm [M = 30] .

This lichen is known from the Neotropics, the Hawaiian Is., Indonesia andPapua New Guinea (Aguirre-Hudson 1991; Aptroot et al. 1997). The singleRarotongan specimen was collected from a small tree on a very exposed andwindswept ridge in the middle of the island.

Specimen examined: base of Te Rua Manga, 21°14'S, 159°46'W, alt. c. 350 m, 1998, McCarthy1257 (CANB, WELT).

5. Porina aff. cestrensis (Tuck, ex Mich.) Mull. Arg.Thallus epiphloeodal, pale greyish green to medium green, continuous

to sparingly rimose, rugulose to verruculose, 20-40 urn thick, ecorticate.Perithecia sparse, superficial, hemispherical to subglobose, dull black, (0-19-)0-24(-0-3) mm diam. [n=14], not overgrown by the thallus; involucrellumviolet-black in thin section, 40-60 um thick; excipulum uniformly violet-black, c. 20 urn thick. Mature asci not seen. Ascospores elongate-fusiform,5(-6)-septate, (22-)27(-35) x (5-)6(-7-5) um [ra=10], with a c. 2 um thickgelatinous sheath.

The thalli, collected fortuitously on a branch dominated by Pyrenulaspecies, are small and scattered, and are in the process of being overgrown byadjacent lichens. One small thallus, ± identical to the others, supports threeperithecia that are unremarkable in their dimensions and pigmentation.However, the ascospores have (8-) 9 (-10) septa, taper noticeably towards theproximal apex and measure (49-)57(-65) x (7-)8-5(-10) (xm [n=19].


This lichen is very similar to P. cestrensis, a common corticolous speciesmainly found in eastern North America, and recently reported from theNorthern Mariana Is. (Harada & McCarthy 1997). Harris (1995), referringto the 'Trichothelium cestrense complex', distinguished a continuum of popu-lations with ascospores of varying and overlapping shape dimensions and withnumbers of septa from 7 to 12 (but not 5). Moreover, Harris (1975, 1995)examined large numbers of North American collections, so it is unlikely thatthe mere acquisition of further Pacific specimens will resolve the taxonomy ofthis difficult complex.

Specimen examined: Te Kou track, lower slopes, 21°13'S, 159°46'W, alt. c. 80 m, on bark, 1998,McCarthy 1244 (part) (CANB).

6. Porina deminuta P. M. McCarthy sp. nov.Thallus epilithicus, medioviridis, (15-)25^0(-60) \im crassus, continuus vel areolatus, ecortica-tus, madefactus gelatinosus. Perithecia semiimmersa vel superficialia, hemisphaerica vel sub-globosa. Involucrellum nudum, atrofuscum vel purpureonigrum, (0-14-)0-18(-O25) mmdiametro, 20-40 fim crassum, ad basim excipuli descendens. Centrum 0-1-0-15 mm diametro.Asci 75-90 x 10-16 um. Ascosporae 7-septatae, plerumque fusiformes, (2O-)26(-30) x (4-5-)6(-8) irn.

Typus: Cook Islands, Rarotonga, Te Kou track, Takuvaine Stream, 21°14'S, 159°46'W, alt. c.80 m, on deeply shaded, semi-aquatic basalt, 7 June 1998, P. M. McCarthy 1262 (WELT—holotypus).

(Fig. 2)

Thallus epilithic, effuse to determinate, medium green, smooth to verrucu-lose, usually dull, (15-)25-40(-60) urn thick, continuous to rimose or are-olate, somewhat gelatinous when wetted, ecorticate, heavily impregnated withminute rock fragments and crystals, K - . Areolae plane, angular, 0-2-0-4 mmwide. Algae Trentepohlia; cells 6-12 x 6-10 um. Hyphae c. 2 urn wide.Prothallus not apparent. Basal layer absent.

Perithecia semi-immersed to superficial, moderately numerous, convex,hemispherical, subconical or subglobose. Perithecial apex rounded. Ostioleinconspicuous. Involucrellum (0-14-)0-18(-0-25) mm diam. [«=57], glossyblack in surface view, dark olive-brown or purple-black in thin section,20-40 um thick, K —, contiguous with the excipulum and extending toexcipulum-base level, not or scarcely overgrown by the thallus. Centrumglobose to depressed-ovate, 0-1-0-15 mm diam. Excipulum uniformly hyalineor slightly darker towards the ostiole, 10-15 um thick. Subhymenium c. 10 umthick. Paraphyses unbranched, c. 1 um wide. Periphyses absent. Asci elongate-cylindrical or obclavate, with a rounded or subtruncate apex and a distinct,apical chitinoid ring turning orange-red in Congo Red, 75-90 x 10-16 um[w=5]. Ascospores colourless, 7-septate, mostly elongate-fusiform, occasionallyelongate-cylindrical, straight, slightly curved or faintly sigmoid, with roundedto subacute ends, irregularly biseriate in the asci, (20-)26(-30) x (4-5-)6(-8) jim [«=100]; gelatinous sheath 0-5-1 (-2) um thick; contents clear.

Conidiomata: not seen.


FIG. 2. Porina deminuta (holotype). A, habit of thallus and perithecia; B, sectioned perithecium(semi-schematic); C, ascospores. Scales: A = 0-5 mm; B = 0-2 mm; C = 10 \im.

Notes. Porina deminuta has a very thin greenish thallus, minute blackperithecia and rather small, fusiform, 7-septate ascospores. It is one of anumber of broadly similar, mainly tropical species, and while there is somepossibility of confusion, careful examination should immediately distinguish itfrom its relatives.

Porina adflata Mull. Arg., from Brazil, has a similar but darker thallus thatovergrows the very small perithecia; however the ascospores are almostdiscontinuously shorter, and most have rounded ends and five septa(McCarthy 1993c). A second species, P. malmei P. M. McCarthy, firstdescribed from Brazil, but recently collected in eastern Australia, has a quitedistinctive, smooth, grey thallus, larger perithecia with a broader centrum, ablackish excipulum and ascospores with mostly rounded apices (McCarthy1993c). Both P. howensis P. M. McCarthy from Lord Howe I. and P. flumineaP. M. McCarthy & P. N. Johnson from New Zealand have larger perithecia(up to c. 0-35 mm diam.); moreover, the former has an involucrellum that isorange-brown to brown in section and contains algal cells almost to the ostiole(McCarthy 1997a), whereas P. fluminea has persistently 5-septate ascospores(McCarthy & Johnson 1995).


Distribution and Habitat. Porina deminuta was collected from deeply shaded,semi-aquatic basalt in rainforest at two localities in Rarotonga.

Additional specimens examined: Te Kou track, Takuvaine Stream, near type locality, 1998,McCarthy 1239 (CANB); Avana Stream, c. 300 m E of water tanks, 21°14'S, 159°45'W, alt. c.60 m, 1998, McCarthy 1258, 1259 (CANB).

7. Porina exocha (Nyl.) P. M. McCarthy comb. nov.Basionym: Verrucaria exocha Nyl., Flora 52: 125 (1869). — Clathroporina exocha (Nyl.) Mull. Arg.,Bull. Herb. Boissier2, App. 1: 93 (1894). Typus: New Zealand, on bark, 1867, C. Knight (H-NYL1591! — holotypus).

McCarthy (19956) suggested that Porina Mull. Arg. (1883) and Clathro-porina Mull. Arg. (1882) should form a single genus. To permit the transfer ofthe few Clathroporina names to the far more diverse and cosmopolitan Porina,a proposal was made to conserve Porina Ach. (1809) against Porina Mull. Arg.(McCarthy 1996), and this was accepted by the Committee for Fungi (Gams1998).

Porina exocha is a very common, mainly corticolous species, in northernNew Zealand and in Norfolk I., 3200 km WSW of Rarotonga (McCarthy19956). However, it is unknown in Australia, and a recent report from PapuaNew Guinea (Aptroot et al. 1997) was based on a misidentified specimen ofP. farinosa C. Knight (duplicate in CANB). This lichen is locally abundant inforest on the northern slopes of Rarotonga.

Specimens examined: Taputarangi track, 21°12'S, 159°48'W, alt. c. 80 m, 1998, McCarthy 1211,1219 (CANB, WELT); N track to Te Rua Manga, 21°13'S, 159°46'W, alt. c. 200 m, 1998, Elix42959 (CANB).

8. Porina farinosa C. KnightThis lichen is rather similar to P. exocha, but has smaller perithecial verrucae

enclosing very much smaller centra, and smaller ascospores (McCarthy19956). In addition, the thalli of freshly collected Rarotongan specimens aremore closely appressed to the bark and tend to have a more distinctly yellowishrather than pinkish brown tone.

Porina farinosa occurs in many tropical regions, and in the Pacific it has beenreported from New Caledonia and Tonga (McCarthy 19956). In Rarotonga,it is locally abundant on the bark on forest trees mainly at lower elevations.

Selected specimens examined: Te Kou track, 21°13'S, 159°46'W, alt. c. 80 m, 1998, McCarthy1247 (CANB, WELT); N track to Te Rua Manga, near crossing of Avatiu Stream, 21°13'S,159°46'W, alt. c. 120 m, 1998, McCarthy 1265 (CANB); Avana Stream, c. 300 m E of watertanks, 21°14'S, 159°45'W, alt. c. 60 m, 1998, McCarthy 1300 (WELT).

9. Porina guentheri (Flot.) Zahlbr.Thallus epilithic, thin, rimose, occasionally areolate, smooth to minutely

uneven, pale greyish green or pale to medium green. Perithecia numerous,superficial, usually hemispherical to subglobose, occasionally convex, dullblack, (0-3-)0-42(-0-6) mm diam. [« = 241], not overgrown by the thallus;


involucrellum 60-100 urn thick near the apex, usually violet-black in thinsection; centrum 0-24-0-4 mm diam.; excipulum hyaline to dark olive-brown.Ascospores elongate-fusiform, 7(-9)-septate, (21-)26(-40) x (4-5-)6-5(-9) ^m[w=110], usually with a 1-2 urn thick gelatinous sheath.

The occurrence of Porina guentheri in Rarotonga was not expected, but itsabundance and wide distribution indicate a well-established lichen of semi-aquatic and comparatively dry habitats. This is also a reasonably commonsilicolous species in cool-temperate and arctic-alpine regions of both hemi-spheres (McCarthy 1993c), but prior to this, it had been reported on only oneoccasion between latitudes 35°N and 30°S (Aptroot et al. 1997).

There are some differences between the Rarotongan specimens and thosefrom more temperate latitudes. The perithecia of temperate specimens tend tobe smaller, (0-23-)0-36(-0-48) mm diam. [w=250], and the ascospores areslightly narrower, (22-5-)25-5(-49) x (3-5-)5(-6-5) um [n=209] (McCarthy1993c). However, the broader ascospores of the Rarotongan specimens arepartly due to the presence of a sharply denned, 1-2 um thick gelatinous sheathwhich, when treated with 10% KOH, usually disintegrates. With regard to thelarger perithecia of the Rarotongan specimens, it may be significant that theonly previous report of P. guentheri from the tropics (Papua New Guinea;Aptroot et al. 1997) appears to have been based on the description providedby Purvis & James (1992). The latter authors cited perithecia of 0-4-0-7 mmdiam. for this species, but this exaggeration was almost certainly due tomisidentification of specimens of P. grandis (Korb.) Zahlbr. in BM.

At present, the differences between temperate and tropical P. guentheri arenot sufficiently pronounced that they fall outside limits of phenotypic, buttaxonomically non-significant, variation. However, if large-fruited P. guentheriis collected elsewhere in the tropics, and the differences are maintained oraccentuated, it may be appropriate to establish an infraspecinc taxon toaccommodate such populations.

Selected specimens examined: Taputarangi track, 21°12'S, 159°48'W, alt. c. 60 m 1998, McCarthy1236 (CANB); Taputarangi track, ridge below summit of Tereora Hill, 21°12'S, 159°48'W, alt.c. 220 m, 1998, McCarthy 1274 (CANB); Avana Stream, c. 300 m E of water tanks, 21°14'S,159°45'W, alt. c. 60 m, 1998, McCarthy 1228 (CANB); Te Kou track, upper slopes, 21°13'S,159°46'W, alt. c. 300 m, 1998, McCarthy 1205 (part) (CANB); Raemaru track, steep slope tosummit, 21°13'S, 159°48'W, alt. c. 200 m, 1998, McCarthy 1252 (CANB).

10. Porina mastoidea (Ach.) Mull. Arg.One of the better-known tropical pyrenolichens, P. mastoidea, usually has a

comparatively robust, pale thallus and medium-sized to large (0-35-0-9 mmdiam.), hemispherical perithecial verrucae with a concolorous to more com-monly brown-black periostiolar cap (McCarthy 1993c). The ascospores of theRarotongan specimens are 7(-8)-septate and (39-)53(-63) x (8-)10(-13) um[rc=100]. Measurements of (39-)49(-65-5) x (6-)9(-12-5) [« = 302] fromthroughout the range of the species were cited by McCarthy (1993c).

Although there has been a difference of opinion over the range of ascosporesize in P. mastoidea and the status of some smaller-spored Neotropical


synonyms (McCarthy 1993c; Harris 1995), the broadening of its circumscrip-tion to include 11-15-septate ascospores up to 120 |jm long and 20 |im wide(Aptroot & Sipman 1993; David & Hawksworth 1995) is inappropriate. Thisnot only greatly exaggerates the limits of an entity that has remainedremarkably constant for almost 200 years, it also subsumes other well-definedand quite distinct taxa such as P. americana Fee and P. intemigrans (Nyl.)Mull. Arg.

Porina mastoidea is common on bark and rock in the Neotropics and theeastern Palaeotropics, although it is not yet known from Africa or India(McCarthy 1993c; Makhija et al. 1994). In the Pacific it occurs in Guam, I. delCoco, Lord Howe I., Marquesas Is., New Caledonia and the NorthernMariana Is. (Elix & McCarthy 1998).

Selected specimens examined: Taputarangi track, 21°12'S, 159°48'W, alt. c. 60 m, 1998,McCarthy 1214 (CANB, WELT); Avana Stream, c. 300 m E of water tanks, 21°14'S, 159°45'W,alt. c. 60 m, on bark, 1998, McCarthy 1213 (CANB).

11. Porina nucula Ach.Porina nucula has a well-developed, sandy brown thallus, subglobose

perithecial verrucae measuring (0-36-)0-59(-0-76) mm diam., with a vestigialinvolucrellum and mostly 7-septate ascospores of 35-65(-83) x 11-18 um(McCarthy 19946). Its distribution may best be denned as sporadicallytropical, and in the Pacific islands it is known only from New Caledonia (Elix& McCarthy 1998). Like many tropical Porina species, the thallus andperithecial verrucae contain deposits of calcium oxalate. However, such is theconcentration in one corticolous Rarotongan specimen, after the decay ofthe living parts of the lichen, a petrified 'thallus' remains complete with thehollow, white shells of perithecial verrucae.

In addition to the corticolous specimen, a single saxicolous colony was seenin Rarotonga. This is the first reported occurrence of this species on rock,although it is conspecific with the fragmentary type specimen of P. pallidaMull. Arg. which was collected from siliceous rocks on Thursday I. in theTorres Strait between Australia and Papua New Guinea (Miiller 1895;McCarthy 1993c).

Specimens examined: Te Kou track, upper slopes, 21°13'S, 159°46'W, alt. c. 350 m, on Fitschiaspeciosa, 1998, McCarthy 1206 (CANB, WELT); N track to Te Rua Manga, on breccia boulderon forest floor, 21°13'S, 159°46'W, alt. c. 100 m, 1998, McCarthy 1234B (CANB).

12. Porina perminuta Vain.Thallus epicuticular, pale greyish green to medium green, very thin, smooth,

rounded, up to c. 0-3 mm diam., coalescing. Perithecia very numerous,superficial, usually hemispherical, occasionally attenuated at the base, glossyblack or with a whitish tomentum, (0-07-)0-l(-0-13) mm diam. [w = 50];involucrellum purplish black. Asci elongate-ovate to obclavate, 52-60 x 13-18 urn [n-12]. Ascospores 3-septate, cylindrical or fusiform, (15-)19(-24) x(3-)4(-5)um [w=100].

Porina perminuta was first described from Tahiti in the Society Is., and it waslater collected in the Philippines (Santesson 1952); it has recently been


reported from the Northern Mariana Is. (Harada 1994a) and Papua NewGuinea (Aptroot et al. 1995). In Rarotonga it is abundant on pinnules of thefern Angiopteris evecta near a stream in a deeply shaded valley.

Specimen examined: Te Kou track, near Takuvaine Stream, 21°14'S, 159°46'W, alt. c. 100 m,1998, McCarthy 1278 (CANB, WELT).

13. Porina subinterstes (Nyl.) Mull. Arg.Nuovo Giorn. Bot. Ital. 21: 364 (1889). — Verrucaria subinterstes Nyl., Bull. Soc. linn. Normandie,ser. 2, 7: 178 (1873). Typus: Andaman Islands, on siliceous rock, 5. Kurz 97 [M! — neotypus,fide McCarthy (1993c)].

Porina curtula Malme, Ark. Bot. 23A(1): 20 (1929). Typus: Brazil, Sao Paulo, Santos, on bark,6 October 1894, G. O. A. Malme [S! — lectotypus, fide McCarthy (1993c)].

McCarthy (1993c) separated P. subinterstes (then known only from theAndaman Is. in the Bay of Bengal) from the southern South AmericanP. curtula, principally by the diameter of the dark periostiolar cap (i.e. theexternal view of the involucrellum). The former taxon had a blackish,0-15-0-35 mm diam. cap [not 0-15-0-35 mm thick as stated at the time(McCarthy 1993c)], whereas this feature was 0-05-0-1 (-0-14) mm diam. inP. curtula. The large suite of Rarotongan specimens includes perithecia withbroad, narrow or vestigial periostiolar caps. In all specimens, however, theperithecial verrucae are characteristically small, and these coupled with thesmall, narrow, 7-septate ascospores distinguish P. subinterstes, as it is nowcircumscribed, from larger taxa such as the pantropical P. tetracerae and thewestern Pacific P. papuensis P. M. McCarthy.

When Makhija et al. (1994) nominated the duplicate of Kurz 97 in H aslectotype, they appear to have been unaware that a neotype had already beenselected (McCarthy 1993c). Makhija et al. (1994) stated that the specimen inH lacked ascospores; in fact, it lacked perithecia, hence the need forneotypification.

The thalli of the Rarotongan specimens are epilithic, determinate, up toc. 5 cm diam., pale to medium grey-green, yellowish brown or grey-brown,50-100(-150) urn thick, sparingly to richly rimose or areolate, matt to ratherglossy, smooth to rugulose or verruculose, impregnated with rock fragmentsand crystals and K—. There is a 6-12 ^m thick uppermost layer that isamorphous or ± prosoplectenchymatous with 2-3 |iim thick hyphae. Theprothallus is dark silvery grey to blackish, and the thallus is usually subtendedby a brownish black, 30-60 um thick basal layer. Perithecia are moderatelyto very numerous and immersed in thallus-dominated, shallowly convex tohemispherical, (0-29-)0-38(-0-5) mm diam. [« = 93] thalline verrucae. Theperithecial apex is plane to convex, with a pale pinkish grey, mediumgrey-brown or dark brown, periostiolar area that is (0-05-)0-1-0-25(-0-3) mmdiam. The sectioned involucrellum ranges from apical, orange-brown and± vestigial to dimidiate, reddish brown and 30-60 um thick or with an outer,c. 20 jxm thick, dark brown layer, enclosing orange-brown involucrellar andthalline hyphae, algae and minute rock crystals. The excipulum is hyaline topale yellowish brown, and the centrum is 0-14-0-22 mm diam. Asci areelongate-cylindrical and 80-105 x 9-12 \m\ [« = 20]. The ascospores are


7-septate, cylindrical to ± elongate-fusiform, usually straight and withrounded or pointed ends, often with a c. 2 um thick gelatinous sheath and(17-)24(-31) x (3-5-)5(-6) um [n = 285]. Conidiomata are immersed inthe thallus, 50-80 um diam., medium to dark grey-brown at the apex,hyaline below and contain elongate-fusiform to rather broadly fusiform,2-4 x 0-7-1-5 um conidia.

Porina subinterstes is already known from siliceous rock in the Andaman Is.,from bark in south-eastern Brazil and from rock in Paraguay. In Rarotonga, itis common on moderately to deeply shaded basalt and breccia in lowlandforest and on the rocks in and beside streams. Unlike the similarly abundantP. guentheri, it rarely occurs above 100 m, and was not seen on exposed ridgesand cliffs.

Selected specimens examined: Taputarangi track, 21°12'S, 159°48'W, alt. c. 100 m, 1998,McCarthy 1238 (CANB); Avana Stream, c. 300 m E of water tanks, 21°14'S, 159°45'W, alt. c.60 m, on deeply shaded semi-aquatic rocks, 1998, McCarthy 1227 (part), 1259 (CANB); Te Koutrack, Takuvaine Stream, 21°14'S, 159°46'W, alt. c. 80 m, on deeply shaded, semi-aquatic basalt,1998, McCarthy 1204, 1242 (CANB, WELT); N track to Te Rua Manga, on shaded basaltboulder on forest floor, 21°13'S, 159°46'W, alt. c. 80 m, 1998, McCarthy 1209, 1252 (CANB,WELT).

14. Porina tetracerae (Ach.) Mull. Arg.This lichen is far less common locally than P. subinterstes, and whereas both

species tend to occupy similar habitats, P. tetracerae can be distinguished by itslarger perithecial verrucae and more elongate, fusiform ascospores (McCarthy1993c). A pantropical species on bark and rocks, in the Pacific it is alreadyknown from the Hawaiian Is., I. del Coco, Is. Galapagos, New Caledonia,Northern Mariana Is. and Western Samoa (Elix & McCarthy 1998).

Selected specimens examined: Avana Stream, c. 300 m E of water tanks, 21°14'S, 159°45'W, alt.c. 60 m, on deeply shaded bark, 1998, McCarthy 1216 (WELT); Te Kou track, TakuvaineStream, 21°14'S, 159°46'W, alt. c. 100 m, on deeply shaded, semi-aquatic basalt, 1998, McCarthy1204 (part), 1264 (CANB); Papua Stream, below Papua Falls, 21°14'S, 159°47'W, alt. c. 40 m,on moderately shaded, semi-aquatic basalt, 1998, McCarthy 1260 (CANB).

15. Pyrenula astroidea (Fee) R. C. HarrisThallus epiphloeodal, corticate, smooth, continuous, pale grey or pale to

medium yellowish brown, usually sparsely pseudocyphellate, UV - . Peritheciaimmersed and largely overgrown by the thallus or semi-immersed,black, obpyriform, (0-48-)0-69(-0-9) mm diam. [w = 20], tilted or lyingon their sides and fused at the ostioles in groups of 2-5. Hamatheciuminterspersed with granules only near the ostiole. Ascospores pale tomedium brown, muriform, 8 per ascus, with 8 ranks of mostly 4-6 locules,(32-)42(-50) x (14-)19(-24) um [n=100]; post-mature ascospores darkenand collapse.

This lichen is probably pantropical (Harris 1989); in the Pacific it is knownfrom the Hawaiian Is., Is. Galapagos, New Caledonia, Society Is. and WesternSamoa (Elix & McCarthy 1998).


Selected specimens examined: Te Kou track, among taro plots, 21°13'S, 159°46'W, alt. c. 100 m,1998, McCarthy 1243 (WELT); Muri Lagoon, c. 60 m S of mouth of Avana Stream, 21°14'S,159°43'W, alt. c. 1 m, on Hibiscus, 1998, McCarthy 1249 (pan) (CANB).

16. Pyrenula aff. citriformis R. C. HarrisThallus endophloeodal and ecorticate to subepiphloeodal and thinly corti-

cate, continuous, smooth, whitish, greenish white, or pale greyish brown,lacking pseudocyphellae, usually UV — (rarely UV+yellow). Prothallus a thinblackish line or not apparent. Perithecia semi-immersed to almost superficial,rounded to ellipsoid in outline, convex, hemispherical, subconical or subglo-bose and variously attenuated at the base, (0-48-)0-65(-0-92) mm diam.[« = 81]; apex plane to rounded; ostiole inconspicuous or noticeably paler thanthe involucrellum. Involucrellum black, superficially smooth to rugulose,dimidiate to ± entire, moderately thick. Centrum IKI - . Hamatheciumheavily interspersed with minute granules, even when very immature. As-cospores obliquely uniseriate in elongate-cylindrical asci, pale to mediumbrown, elongate-ellipsoid, broadly ellipsoid or citriform, (13-) 17 (-21) x (6-)9-5(-12) urn [«=163], with a thick endospore; locules at first angular,becoming more rounded; apical locules contiguous with the exospore orseeming to protrude; post-mature ascospores darken and collapse.

Pyrenula citriformis was first described from southern and eastern U.S.A.(Harris 1989). Harris characterized it by its UV - thallus, similar to that of themainly UV+yellow and more northern P. pseudobufonia (Rehm) R. C. Harris,and by its smaller, 0-3-0-6 mm diam. perithecia containing citriform asco-spores (Harris 1989, 1995). It was later reported from India (Upreti 1991)and Papua New Guinea (Aptroot et al. 1997). Most of the Rarotonganspecimens were collected from smooth-barked trees, and most, but not all,produced perithecia that were appreciably larger than those cited in theprotologue, the centrum also lacking the IKI+blue-green reaction of NorthAmerican specimens.

Referring to P. citriformis and its allies, Harris (1989) made the point that'every region of the world has some variant; as a result the taxonomy is verydifficult'. Indeed, as many as 20 species of Pyrenula with citriform ascosporesor those with 'protruding' apical locules have been described or reportedfrom the eastern Paleotropics, including Malesia, northern Australia andMelanesia. Consequently, the qualifier affine is applied to the Rarotongancollections pending a revision of all similar taxa known from outside NorthAmerica.

Selected specimens examined: Taputarangi track, ridge below summit of Tereora Hill, 21°12'S,159° 48'W, alt. c. 220 m, 1998, McCarthy 1217, 1298 (CANB); Raemaru track, below summitcliff, 21°13'S, 159°48'W, alt. c. 250 m, 1998, McCarthy 1231, 1232 (part), 1245 (CANB).

17. Pyrenula concatervans (Nyl.) R. C. HarrisThallus epiphloeodal, thickly corticate, smooth, pale to medium yellowish

brown, dotted with white pseudocyphellae, UV - . Perithecia almost com-pletely immersed, (0-22-)0-29(-0-35) mm diam. [n-20], with a compara-tively thin involucrellum that encloses the excipulum. Hamathecium not


interspersed with granules. Ascospores uniseriate in the ascus, rather palebrown, with 5 transverse septa, (25-)29-5(-37) x (10-)13(-16) \im [w=100],with a thick endospore; locules at first angular, becoming more rounded andfinally disappearing as the ascospore fills with a reddish oily substance; medianlocules of broadest ascospores occasionally dividing once vertically.

A pantropical, lowland species (Harris 1989, 1995), its range includes theHawaiian Is. and Is. Galapagos (Elix & McCarthy 1998).

Selected specimens examined: Taputarangi track, ridge below summit of Tereora Hill, 21°12'S,159°48'W, alt. c. 200 m, 1998, Louwhoff 518 (CANB); Raemaru track, steep slope to summit,21°13'S, 159°48'W, alt. c. 200 m, 1998, McCarthy 1245 (CANB); Muri Lagoon, c. 60 m S ofmouth of Avana Stream, 21°14'S, 159°43'W, alt. c. 1 m, on Hibiscus, 1998, McCarthy 1249 (part)(CANB).

18. Pyrenula confinis (Nyl.) R. C. HarrisThallus endophloeodal, whitish, usually UV+yellow (although a single

UV —, but otherwise identical specimen was collected from Koromiri I.).Perithecia mostly semi-immersed, black, (0-25-)0-36(-0-5) mm diam. [« = 29],hemispherical above; involucrellum rather thin, spreading slightly at the base.Hamathecium not interspersed with granules. Ascospores uniseriate orbiseriate, pale brown, submuriform, usually with 4 rows of (2-)4 locules,(ll-)14-5(-18) x (8-)10-5(-13)um [«=120].

This pantropical, coastal species (Harris 1989, 1995) is already known fromNew Caledonia (Elix & McCarthy 1998).

Selected specimens examined: Muri Lagoon, opposite Taakoka I., 21°15'S, 159°44'W, alt. c. 1 m,on seashore Hibiscus, 1998, McCarthy 1224 (CANB); Muri Lagoon, Koromiri I., 21°15'S,159°43'W, alt. c. 1 m, 1998, McCarthy 1231 (CANB); Raemaru track, steep slope to summit,21°13'S, 159°48'W, alt. c. 250 m, 1998, McCarthy 1233 (CANB).

19. Pyrenula leucostoma Ach.Thallus epiphloeodal, corticate, smooth, pale to medium greyish brown,

lacking pseudocyphellae, UV - . Perithecia partly immersed, but largely over-grown by the thallus, subglobose, (0-38-)0-56(-0-7) mm diam. [w=20], witha thin involucrellum that encloses the excipulum. Hamathecium not inter-spersed with granules. Ascospores medium brown, muriform, with 8 ranksof mostly 4-6 locules each, (38-)49(-60) x (15-)21(-27) ^m [w = 50];post-mature ascospores darken and collapse.

This highly variable species is rather common in the Neotropics (Harris1989, 1995), and it is also known from Papua New Guinea and north-easternAustralia (as Anthracothecium libricolum (Fee) Mull. Arg.; Filson 1996).Among the Pacific islands, P. leucostoma has been reported from the HawaiianIs., Is. Galapagos, New Caledonia, the Society Is. and Western Samoa (Elix &McCarthy 1998).

Specimen examined: Taputarangi track, 21°12'S, 159°48'W, alt. c. 100 m, 1998, McCarthy 1220(WELT).


20. Pyrenula macularis (Zahlbr.) R. C. HarrisThe thallus and perithecia are very similar to those of P. concatervans

(above). However, the ascospores are muriform, with 5-7 transverse divisionsseparating ranks of 2-4 locules and are (26-)32(-46) x (12-) 15(-20) um[w = 87]; postmature ascospores fill with a reddish oily substance beforecollapse.

Although the ascospores of the Rarotongan specimens are similar in sizeto those of Australian collections examined (e.g. McCarthy 19936; 34-46-5 x 14-5-18 um), they are marginally smaller than those cited by Harris(1989,1995) for North American collections (40-53 x 17-22 um) and byAptroot et al. (1997) for Papuan ones (40-55 x 15-23 um).

This corticolous lichen is common in the coastal and lowland habitats ofmost tropical regions (Harris 1989); however, it has not previously beenreported from the Pacific islands.

Selected specimens examined: Muri Lagoon, opposite Taakoka I., 21°15'S, 159°44'W, alt. c. 1 m,on bark, 1998, McCarthy 1224 (CANB); Muri Lagoon, c. 60 m S of mouth of Avana Stream,21°14'S, 159°43'W, alt. c. 1 m, on Hibiscus bark, 1998, McCarthy 1293 (CANB).

21. Pyrenula nitidula (Bres.) R. C. HarrisThallus endophloeodal and ecorticate to subepiphloeodal and thinly corti-

cate, smooth, pale greenish grey, greyish brown or pale yellow-brown, lackingpseudocyphellae, UV — . Perithecia semi-immersed to almost superficial, atfirst weakly convex and often with a whitish 'veil' of bark cells, becoming morestrongly convex, hemispherical or subconical, (0-35-)0-53(-0-75) mm diam.[w = 80], with a thick, black, dimidiate involucrellum that is, sometimes,impregnated with large colourless crystals. Hamathecium not interspersed withgranules, IKI - . Ascospores obliquely uniseriate in the asci, very pale tomedium brown, elongate-ellipsoid, broadly ellipsoid or citriform, (13-)17(-21) x (7-)lO(-12) um [w=157], with a thick endospore; locules at firstangular, becoming more rounded; apical locules contiguous with the exosporeor seeming to protrude.

This lichen is known from the Caribbean (Harris 1995), and was reportedfrom Papua New Guinea by Aptroot et al. (1997), it differs from P. aff.citriformis (above) and related taxa by its smaller perithecia that are free ofhymenial granules. Although previously unknown from the Pacific islands, itis moderately common in Rarotonga, mainly on smooth-barked trees.

Selected specimens examined: Muri Lagoon, opposite Taakoka I., 21°15'S, 159°44'W, alt. c. 1 m,on seashore Hibiscus, 1998, McCarthy 1291 (WELT); Raemaru track, below summit cliff,21°13'S, 159°48'W, alt. c. 250 m, on Hibiscus, 1998, McCarthy 1232 (part) (CANB); Raemarutrack, ridge below summit cliff, 21°13'S, 159°48'W, alt. c. 200 m, 1998, McCarthy 1290 (CANB).

22. Pyrenula ochraceoflava (Nyl.) R. C. Harris var. ochraceoflavaThallus subepiphloeodal, mostly whitish, but patchily yellow-orange (then

K+purple), UV — . Perithecia semi-immersed to almost completely immersed,


FIG. 3. Pyrenula ochraceoflava var. pacifica (holotype). A, habit of thallus and perithecia on roughCocos bark; B, sectioned perithecium and adjacent thallus (semi-schematic); C, ascospores (var.pacifica (above), var. ochraceoflava (below), (Elix 42728)). Scales: A=O5 mm; B = 0-2mm;

C&D=10um.

dark brown to almost black, (0-28-)36(-0-49) mm diam. [n—25], with a thininvolucrellum. Hamathecium not interspersed with granules. Asci elongate-cylindrical to elongate-clavate. Ascospores very pale brown, narrowly ellipsoid,submuriform, with 4 tiers of (l-)4 locules, (14-)16(-19) x (7-5-)9-5(-ll) \im[w=50; Fig. 3].

Variation in thallus colour is clarified when the chemistry is elucidatedby HPLC [7-chloroemodin (major), 7-chloroparietinic acid (trace), 'anthra-quinone X' (trace; ±) , 7-chloroemodinol (trace; ± ) , 7-chloroemodicacid (trace), 7-chloroemodin (trace; ± ) , 7-chlorocitreorsein (trace; ± ) ,7-chloro-l, 6, 8-trihydroxy-3-methylanthrone (trace; ± ) , 5, 7-dichloro-1, 6,8-trihydroxy-3-methylanthrone (trace; ± )]. Identical chemistry was observed


in a specimen from Queensland (H. Streimann 45486, CANB), while one fromIs. Galapagos {W. A. Weber. Lichenes exsiccati 145, CANB) also containedtrace amounts of fragilin, atranorin and norstictic acid.

This is a common lowland (and especially coastal) lichen throughout muchof the tropics (Harris 1989; Awasthi 1991; Aptroot et al. 1997); in the Pacificit is known from the Caroline Is., Is. Galapagos, New Caledonia, Tuamotuand Western Samoa (Elix & McCarthy 1998). The ascospores dimensions ofthe Rarotongan specimens are somewhat smaller than those cited elsewhere(13-25 x 9-14 urn; Harris 1989, 1995; Aptroot et al. 1997).

Specimen examined: Muri Lagoon, 21°15'S, 159°44'W, alt. c. 1 m, on Cocos nucifera, 1998, Elix42728 (part) (CANB).

23. Pyrenula ochraceoflava (Nyl.) R. C. Harris var. pacificaP. M. McCarthy var. nov.Thallus subepiphloeodalis, flavoaurantiacus, K+purpureus. Ascomata perithecioidea, plerumque2/3-1/3-immersa, externe aurantiacofusca vel rubrofusca, (0-22-)0-32(-0-44) mm diametro. Asci8-spori, 58-80 x 13-20 um. Ascosporae plerumque subglobosae et pallidofuscae, submuriformes,transverse 1-septatae, (10-)12-5(-15) x (8-)10-5(-12) um.

Typus: Cook Islands, Rarotonga, Muri Lagoon, c. 100 mS of mouth of Avana Stream, 21°14'S,159°43'W, alt. c. 1 m, on trunk of Cocos nucifera, 9 June 1998, P. M. McCarthy 1277(WELT—holotypus; CANB—isotypus).

(Fig. 3)

Thallus crustose, subepiphloeodal, yellow-orange (or patchily whitish,especially in deep shade), forming extensive colonies, uneven and continuousto quasiareolate (due to uneven and cracked surface of the bark), with ahyaline to yellow-orange, 20-40 um thick epiphloeodal layer, UV —, ecorti-cate. Algae Trentepohlia, in a 25-50 |nm deep layer among bark cells; cells6-10 x 5-10 um; interstitial hyphae c.2 um thick. Prothallus not apparent.

Ascomata perithecioid, very numerous, usually solitary, outwardly orange-brown to dark reddish brown, usually covered by a thin layer of yellow-orangethallus, at first completely immersed, becoming convex and 2/3-immersed to1/3-immersed and hemispherical, rarely subglobose and attenuated at thebase, (0-22-)0-32(-0-44) mmdiam. \n- 100]. Ascomatalapex usually concave,with a 70-170 um wide depression, occasionally plane or slightly convex.Ostiole central, dark brown, plane to papillate, 40-80 am wide. Ascomatal wallusually with an external, 20-60 um thick, orange-brown layer, consisting ofgelatinized, elongate-periclinal hyphae, K+violet or dark purple (thin sec-tion); internally dark brown, c. 20-60 um thick at the apex, 20-30 um thick atthe sides and base; surface dull, smooth to minutely uneven. Excipulumuniformly brownish black, or with hyaline patches at the base, 20-30 umthick. Centrum subglobose, 0-18-0-3 mm diam. Subhymenium 15-30 umthick. Paraphyses simple, c. 1 um thick, not interspersed with granules or oilglobules. Periphyses absent. Hymenial gel IKI - . Asci fissitunicate, 8-spored,elongate-cylindrical to elongate clavate, 58-80 x 13-20 um [n=10]; apexsubacute; ocular chamber inconspicuous. Ascospores very pale to medium


brown, broadly ellipsoid to subglobose, submuriform, with or without a fainteuseptum separating 2 ranks of (2-)4 angular to rounded locules, obliquelyuniseriate or irregularly biseriate in the ascus, (10—) 12• 5(— 15) x (8-)10-5(-12) (im [n-234]; apices rounded; exospore c. 1 urn thick; gelatinous sheathabsent; post-mature ascospores darker brown, eventually collapsing.

Conidiomata not seen.

Chemistry. K+purple, UV — . HPLC: 7-chloroemodin (major), 'anthra-quinone X' (minor), parietin (minor or trace), 7-chloroemodinol (trace),7-chloroemodic acid (trace), 7-chloroparietinic acid (trace).

Notes. While the pigmented thallus and perithecia of P. ochraceoflava var.pacifica are its most conspicuous feature, its principal diagnostic characters arethe size and shape of its ascospores and, above all, the presence of a singletransverse septum separating 2 tiers of up to 4 locules. However, because oftheir small size and subglobose shape, care must be taken with observingseptation, especially in rather thick microscopic preparations. Sometimesascospores are then viewed obliquely or from above, and give the impressionof either having three overlapping rows of locules, or a central locule ringed byfour or five others.

A similarly pigmented thallus and perithecial morphology are seen in P.ochraceoflava var. ochraceoflava (see above), and both were collected even fromthe same seashore tree in Rarotonga. In terms of thallus chemistry, they arequite similar, both varieties being dominated by 7-chloroemodin, and eachwith a variously overlapping suite of minor and trace substances. However, thetype variety differs in its generally narrower and more elongate ascosporesalways with 4 tiers of (l-)4 locules (Fig. 3); the 3 transverse septa are apparenteven when very immature. By contrast, the ascospores of var. pacifica areconstant in their shape and in the presence of 2 clusters of locules separatedby a single, but usually evanescent, euseptum. Although possibly an instanceof incipient speciation, the differences observed between these sympatricpopulations indicate that the new taxon warrants recognition at a level nohigher than variety.

A third taxon is known with a yellow-orange thallus, small perithecia andsubmuriform ascospores. Pyrenula ochraceoflavens (Nyl.) R. C. Harris fromFlorida and the West Indies, has ascospores of 23-35 x 11-17 p.m with up to7 rows of 6 locules (Harris 1989). Interestingly, thallus chemistry is ratherdifferent to that of P. ochraceoflava, and variable in the two specimensexamined. A specimen from Florida (Dade County, Everglades Natl Park, 9miles from Homestead entrance, 29 January 1965, G. T. Johnson s.n., CANB)contains parietin (major) and traces of emodin and 7-chloroemodin, whereasone from the U.S. Virgin Is. (W. R. Buck 3412A, CANB) contains eumitrinderivative (major), fragilin (major), unknown (major), 7 chloroparietinic acid(minor) and 7-chloroemodin (minor).

In a possible indication of greater diversity of yellow-orange Pyrenula speciesin the Pacific, Taylor (1950) reported P. ochraceoflava (as Anthracotheciumochraceoflavum (Nyl.) Mull. Arg.) from Bikini Atoll, in the northernMarshall Is. However, although the brief description of the thallus and


perithecia conforms to the accepted circumscription of this species, the16-28 x 9-12 ).im ascospores were stated to have 6-8 rows of 2-4 locules.

Distribution and Habitat. Pyrenula ochraceoflava var. pacifica is known fromtwo localities c. 1-5 km apart at Muri Lagoon on the south-east coast ofRarotonga. The type specimens were part of an extremely abundant popu-lation on a single coconut palm trunk (especially on the seaward face);associated lichens included Buellia species, Calicium species, Chrysothrixcandelaris, Lecanora species, and Phaeophyscia aff. orbicularis.

Additional specimens examined: type locality, 1998, Elix 42780 (CANB); Muri Lagoon, 21°15'S,159°44'W, alt. c. 1 m, on bark of Cocos nucifera, 1998, Elix 42728 (part) (CANB).

24. Strigula decipiens (Malme) P. M. McCarthy var. decipiensThallus epilithic, thin, pale greyish green, rather depauperate, peeling

in places and partly overgrown by cyanobacteria. Perithecia black, semi-immersed, (0-2-)0-27(-0-31) mm diam. [«=10], with a thin, dimidiateinvolucrellum and a hyaline excipulum. Ascospores with 7 transverse septa,showing no trace of longitudinal or diagonal divisions, (17-)21-5(-27) x (5-5-)6-5(-8) fim [« = 60]. Conidiomata semi-immersed, black above, hyalinebelow, c. 0-1 mm diam., containing elongate-cylindrical, (5-)7-septatemacroconidia, (16-) 19(-22) x (3-)4(-5) (im [n-32]; many with a narrow,4-6 \im long gelatinous appendage at the proximal end.

Strigula decipiens var. decipiens has been reported from southern Brazil andLord Howe Is. (McCarthy 1997ft). Macroconidia were not observed inprevious collections.

Specimen examined: N track to Te Rua Manga, on shaded basalt boulder on forest floor,21°13'S, 159°46'W, alt. c. 80 m, 1998, McCarthy 1241 (CANB).

25. Strigula decipiens var. divisa P. M. McCarthy var. nov.Thallus subepilithicus, continuus vel rimosus, laevigatus vel minute inaequalis, obscure pallidoviridigriseus, (30-)50(-70) um crassus. Perithecia 1/3-2/3-immersa. Involucrellum nigrum,(0-18-)0-27(-0-35) mm diametro, 30-60 urn crassum. Asci cylindrici, 50-70 x 10-14 um.Ascosporae submuriformes, (18-)22(-26) x (5-5)7-5(-9) um. Conidiomata non visi.

Typus: Cooklslands, Rarotonga, Avana Stream, c. 300 m E of water tanks, 21°14'S, 159°45'W,alt. c. 60 m, on deeply shaded semi-aquatic basalt, 6 June 1998, P. M. McCarthy 1215(WELT—holotypus).

(Fig. 4)

Thallus crustose, subepilithic, determinate, continuous to sparingly rimose(mainly around perithecia), pale greenish grey, distinctly green when wetted,heavily impregnated with rock fragments and crystals, smooth to minutely andirregularly uneven, matt, (30-)50(-70) |xm thick, thinly corticate. Cortexhyaline, amorphous, c. 10 |im thick. Algae Trentepohlia; cells broadly ellipsoidto globose, 6-15 x 4-10 |im; interstitial cells 2-3 um thick. Prothallussomewhat paler than older parts of the thallus.

Perithecia moderately numerous, solitary or paired, 1/3-2/3 immersed, oftenpartly overgrown by the thallus. Apex mostly convex, occasionally ± hemi-spherical. Ostiole apical, inconspicuous or in a shallow, 20-30 |um diam.


FIG. 4. Strigula decipiens var. divisa (holotype). A, habit of thallus and perithecia; B, sectionedperithecium (semi-schematic); C, ascospores. Scales: A=0-2mm; B = 01 mm; C=10|im.

depression. Involucrellum extending to excipulum-base level, arching awayfrom the excipulum, uneven, with embedded rock fragments and crystals, dullblack, dark greenish black in thin section, (0-18-)0-27(-0-35) mm diam.[« = 33], 30-60 um thick near the apex and at the base. Excipulum hyaline atthe base and sides, darkening towards the apex, 10-15 um thick. Centrumdepressed-ovate, 0-14-0-2 mm diam. Subhymenium 10-20 urn deep. Paraphy-ses persistent, sparingly or richly branched, 0-7-1 (im thick. Periphyses absent.Asci fissitunicate, 8-spored, narrowly to broadly cylindrical, 60-70 x 10-14 um [n=10]; contents IKI + red-brown; walls IKI - ; lateral walls c. 1 urnthick at maturity; apical dome 3-6 um thick; ocular chamber hemispherical totubercular or conical, 1-2 um broad and tall. Ascospores colourless, fusiform toelongate-cylindrical, straight or slightly curved, with 7 (-9) transverse septaand (0-)2(-4) longitudinal or diagonal septa, often tapering towards theproximal end and slightly constricted at the septa, uniformly thin-walled,irregularly biseriate in the ascus, (18-)22(-26) x (5.5-)7.5(-9) u m [n-\\5];contents clear to finely granular.

Conidiomata not seen.

Notes. Submuriform ascospores of this type are also seen in S. rupestris P. M.McCarthy from Lord Howe I., but that lichen has a thicker thallus, (0-29-)0-43(-0-62) mm diam. perithecia with a 50-120 mm thick involucrellum anda 0-2-0-35 mm diam. centrum (McCarthy 19976). Conversely, the thallusand perithecia are almost identical to those of S. decipiens (Malme) P. M.


McCarthy (see above); however in the latter, the ascospores remain (5-)7-septate, although they are similar in size (McCarthy 19976). In view ofthis well-defined distinction, but one of comparatively limited taxonomicsignificance, the recognition of a new variety of 5. decipiens is appropriate.

Habitat and Distribution. Strigula decipiens var. divisa is known only fromsmooth semi-aquatic rocks at the type locality, a 5-m wide rocky streamheavily shaded by a steep cliff and overhanging rainforest vegetation. Associ-ated pyrenocarpous species include Anisomeridium carinthiacum, Porinademinuta, P. subinterstes, P. guentheri and Verrucaria mundula.

26. Strigula smaragdula Fr.: Fr.Minute, greenish, orbicular thalli of this foliicolous lichen were observed,

mostly near small holes in leaves grazed by insects. Most contained onlyconidiomata with 1-septate, 8-10 x 2-3 im macroconidia, although a few0-25-0-4 mm diam. perithecia were seen, with 1-septate, 13-20 x 3-5-5 urnascospores.

This is one of the most common and well-known foliicolous lichens (untilrecently called S. elegans (Fee) Mull. Arg.; Santesson 1952). In the Pacific ithas been reported from the Hawaiian Is., I. del Coco, Lord Howe I., NewCaledonia and Tonga (Elix & McCarthy 1998).

Specimen examined: N track to Te Rua Manga, near crossing of Avatiu Stream, 21°13'S,159°46'W, alt. c. 100 m, on leaves of Inocarpus fagifer, 1998, McCarthy 1301 (CANB).

27. Strigula sp. AThallus epilithic, richly rimose, pale greyish green, c. 50 um thick, forming

a rather large colony. Perithecia very few, black, semi-immersed, (0-25-)0-3(-0-37) mm diam. [n=20, including decayed perithecia with only the blackishring of the involucrellum base remaining]; involucrellum c. 40 um thick;excipulum hyaline. Ascospores muriform, with (7-)9-l 1 transverse septa,each transverse cell with (l-)3 longitudinal divisions, (32-)37(-43) x

(11—)14(—17) | m [n=2l]. Conidia not seen.

The small perithecia coupled with the dimensions of the fully muriformascospores almost certainly point to an undescribed species (see McCarthy19976). However, the specimen contains only a handful of mature perithecia,and would make an inadequate type. Confirmation of its identity requiresadditional material.

Specimen examined: N track to Te Rua Manga, on exposed breccia boulder among taro plots,21°13'S, 159°46'W, alt. c. 70 m, 1998, McCarthy 1234 (CANB)

28. Trichothelium marianense H. HaradaThallus epicuticular, pale greyish green to pale green, very thin, smooth,rounded, up to c. 0-5 mm diam., coalescing. Perithecia scarce to moderately


numerous, superficial, subglobose and attenuated at the base, dull black,(0-l-)0-13(-0-17) mm diam. [ra = 53]; involucrellum greenish black. Setae(3-)4-5(-8), 70-150(-200) um long; colour variable, ranging from mainlyhyaline or off-white, but with a blackish base, to blackish in the proximal halfand pale in the distal to predominantly blackish but with a hyaline tip. Ascielongate-cylindrical to obclavate. Ascospores persistently 3-septate, cylindricalto fusiform, (17-)20-5(-26) x (3-)4(-5) um [w = 53].

This lichen was recently described from the Northern Mariana Is., Micro-nesia (Harada 1994b). In Rarotonga it is moderately abundant at twolocalities in deeply shaded and comparatively humid forested valleys where itis associated with Dimerella species, Porina perminuta, Sporopodium phyllocharis,Strigula smaragdula and minute species of the liverwort family Lejeuneaceae.

Specimens examined: Te Kou track, near Takuvaine Stream, 21°14'S, 159°46'W, alt. c. 100 m,on pinnules of Angiopteris evecta, 1998, McCarthy 1279 (CANB); N track to Te Rua Manga, nearcrossing of Avatiu Stream, 21°13'S, 159°46'W, alt. c. 100 m, on leaves of Inocarpus fagifer, 1998,McCarthy 1280 (CANB, WELT).

29. Verrucaria fortuita P. M. McCarthy sp. now.Thallus epilithicus, continuus vel rimosus, laevigatus, 15-30 (im crassus, albidus vel pallidogri-seus. Perithecia fusconigrum vel nigrum, fere omnino immersa. Involucrellum (0-11—)0-15(-0-2) mm diametro, 25-40 (im crassum, ad basim excipuli descendens. Periphyses 10-18 x1-1-5 (im. Asci 28-35 x 9-12 um. Ascosporae ellipsoideae vel subglobosae, (5-)7(-8) x(3-5-)4-5(-5-5) um.

Typus: Cook Islands, Rarotonga, Taputarangi track, 21°12'S, 159°48'W, alt. c. 80 m, onshaded boulder on forest floor, 6 June 1998, P. M. McCarthy 1310 (WELT—holotypus).

(Fig. 5)

Thallus epilithic, determinate, whitish to pale grey, becoming greenish whenwetted, sparingly rimose, smooth, dull to slightly glossy, 15-30 um thick.Algae chlorococcoid, globose, 4-8 um diam., scattered throughout the thallus,apart from an uppermost, 5-10 um layer of rounded, 2-3 um diam. hyphae;interstitial cells thin-walled, angular, 2-4 um diam. Prothallus not apparent.Basal layer absent.

Perithecia sparse, almost entirely immersed in the thallus, solitary,(0-11-)0-15(-0-2) mm diam. [n— 10]. Perithecial apex plane to slightly convex.Ostiole inconspicuous. Involucrellum dark brown to blackish, contiguous withthe excipulum, and extending down to excipulum-base level, 25-40 um thicknear the apex. Excipulum hyaline at the base, medium to dark brown near theostiole, 10-15 urn thick. Centrum globose to obpyriform, c. 0-09-0-14 mmdiam. Periphyses simple to sparingly branched, 10-18 x 1-1-5 um. Paraphysesabsent. Asci fissitunicate, clavate, 8-spored, 28-35 x 9-12 um [w = 6]. Hyme-nial gel I+brownish red. Ascospores simple, colourless, narrowly to broadlyellipsoid or subglobose, (5-)7(-8) x (3-5-)4-5(-5-5) um [«=53]; contentsclear and monoguttulate.

Notes. Several species of Verrucaria with diminutive perithecia and/orascospores inhabit intertidal or freshwater habitats; a number of others occur


FIG. 5. Verrucaria fonuita (holotype). A, habit of thallus and perithecia; B, sectioned perithecium(semi-schematic); C, ascospores. Scales: A=O2mm; B = 0-l mm; C=10nm.

on terrestrial rocks, mostly at temperate or cooler latitudes in the NorthernHemisphere (McCarthy 1988). However, none possesses the combination ofcharacters exhibited by V. fonuita, and while the centimetre-wide typespecimen is much smaller than would normally be desirable or acceptable, itsdistinctiveness is so pronounced that the description of this new species isreasonable.

Habitat and Distribution. This lichen is known only from its type locality nearthe north coast of Rarotonga, where it grows with Porina guentheri on theshaded surface of a small breccia boulder on the forest floor. The epithetfonuita alludes to die accidental collection of the type specimen, and, becauseof its diminutive and inconspicuous appearance, probably indicates the mostlikely way in which this will be repeated.

30. Verrucaria aff. fuscella (Turner) WinchThallus epilithic, determinate, pale grey to medium greenish grey, richly

and deeply areolate, smooth, dull, 30-60 nm diick; basal layer black, 100-250 (im thick, also covering the walls of the areolae. Perithecia numerous,l-2(-3) per fertile areole, almost entirely immersed in the thallus, (0-15-)0-2(-0-25) mm diam. [«=10]; apex dark grey-brown to black, plane toconcave, (0-ll-)0-16(-0-2) mm diam. [« = 32]; involucrellum 60-80 ^mthick, contiguous with the excipulum and merging with the basal layer;


excipulum hyaline at the base, medium to dark brown near the ostiole;centrum 0-1-0-13 mm diam. Periphyses simple to sparingly branched, 20-30x1-5-2 ^m. Ascospores narrowly to broadly ellipsoid, (10-)14(-16) x(5-)7(-9)um [M = 60] .

Verrucaria fuscella is one of a group of common, but often poorly delimited,species with comparatively thick, deeply areolate dialli, small immersedperithecia with a thin involucrellum and small to moderately large ascospores.Most occur in western Eurasia, but there have also been reports fromNorth Africa, North America and southern Australia. Verrucaria fuscella, V.glaucina auct. and their allies are mainly calcicolous, but some occur at leastoccasionally on siliceous rocks (Clauzade & Roux 1985; Nimis 1993).

This is not the first time such an anomalous disjunction has been observedin this group of Verrucaria species. McCarthy (1994a) reported V. lecideoidesvar. minuta Hepp from siliceous rocks in cool-temperate and semi-aridlocalities in southern Australia, and whereas that lichen usually grows onlimestone in central and southern Europe, no significant morphological oranatomical differences could be detected. Unfortunately, die identity of theRarotongan specimen is uncertain due to the unresolved delimitation ofV. fuscella and its allies.

This lichen is abundant on basalt outcrops on an exposed cliff-top in thenorth-west of Rarotonga.

Specimen examined: Taputarangi track, 21°12'S, 159°48'W, alt. c. 120 m, 1998, McCarthy 1274(CANB, WELT).

31. Verrucaria howensis P. M. McCarthyThallus medium grey-green to dark green, sparingly rimose to areolate,

30-60 um thick. Perithecia moderately to very numerous, semi-immersed,convex, hemispherical or subconical, black, (0-13-)0-19(-0-24) mm diam.[M=57]; apex rounded to excavate; excipulum pale to dark brown. Ascosporeselongate-ellipsoid to subglobose, (6-)8(-10) x (3-5-)4-5(-6) urn [w=100].

Previously known only from Lord Howe I. (McCarthy 1990), where itis one of the most common pyrenocarpous lichens; in Rarotonga it wasoccasionally seen on basalt and breccia in both sheltered and exposed habitats.

Selected specimens examined: Taputarangi track, 21°12'S, 159°48'W, alt. c. 100 m, 1998,McCarthy 1223 (CANB); Avana Stream, c. 300 m E of water tanks, 21°14'S, 159°45'W, alt. c.60 m, 1998, McCarthy 1227 (part) (CANB).

32. Verrucaria mundula P. M. McCarthy var. mundulaThallus medium green, filmy, gelatinous when wetted, continuous, c. 20 (xm

thick. Perithecia moderately numerous, convex to hemispherical, glossyblack, (0-12-)0-15(-0-18) mm diam. [n=25]; apex rounded; excipulum paleto dark brown. Ascospores mostly elongate-ellipsoid, (8-) 11 (-14) x (4-5-)5-5(-6-5)um [n = 50].


TABLE 1. Biogeographical elements among pyrenocarpous lichens in Rarotonga

Distribution Taxa

± Pantropical Anisomeridium anisolobum, Celothelium cinchonarum, Porina farinosa,P. mastoidea, P. nucula, P. subinterstes, P. tetracerae, Pyrenulaastroidea, P. concatervans, P. confinis, P. leucostoma, P. macularis,P. ochraceoflava var. ochraceoflava, Strigula smaragdula

W Pacific Anisomeridium consobrinum, Porina exocha, P. perminuta,Trichothelium marianense, Verrucaria howensis, V. mundula var.mundula

Endemic Porina deminuta, Pyrenula ochraceoflava var. pacifica, Striguladecipiens var. divisa, Verrucaria fortuita

Anomalous/incomplete Anisomeridium carinthiacum, Porina aff. cestrensis, P. guentheri,Pyrenula aff. citriformis, P. nitidula, Strigula decipiens var. decipiens,Verrucaria aff. fuscella

This aquatic lichen was first described from cool-temperate to wet-tropical areas of eastern Australia (McCarthy 1995a), and was subsequentlycollected on Lord Howe I. In Rarotonga it grows on deeply shaded, aquaticbasalt.

Specimens examined: Avana Stream, c. 300 m E of water tanks, 21°14'S, 159°45'W, alt. c. 60 m,1998, McCarthy 1226 (CANB); N track to Te Rua Manga, Avatiu Stream, 21°13'S, 159°46'W,alt. c. 100 m, 1998, McCarthy 1303 (WELT).

DiscussionThe physical isolation of Rarotonga from highly diverse lichen floras comesinto focus when the distance from continental and other large land-masses isconsidered: 2800 km from New Zealand, 4600 km from Australia, 5400 kmfrom New Guinea and 8000 km from South America. However, in spite of itsremote location, the rugged topography, elevation and the resulting diversityof habitat have ensured the development of quite a rich pyrenocarpous lichenflora dominated by Pyrenula and Porina, with lesser numbers of Verrucariaceae,Strigulaceae and Monoblastiaceae. In terms of their broader distributions, mosttaxa are pantropical (44%), western Pacific (19%) or (provisionally) endemic(13%); inevitably, large gaps in known distributions mean that a significantminority (22%) cannot readily be categorized (Table 1). Apart from thetaxa listed here, two species each of Verrucaria and Pyrenula and one ofArthopyrenia were also collected, but remain unidentified.

The presence of a large number of confirmed or discontinuous pantropicalspecies was to be expected, as was the strong western Pacific element.Obviously, part or all of the endemic element may yet be shown to occur onother South Pacific islands and beyond. Alternatively, this may have evolvedlocally from extinct or extant progeners since the emergence and veryturbulent early geological history of the island. The co-occurrence of thepantropical Pyrenula ochraceoflava var. ochraceoflava and the possibly endemicvar. pacifica on seashore palms may signify active, local diversification.


TABLE 2. Biogeographical elements among pyrenocarpous lichens in Lord Howe Island

Distribution Taxa

± Pantropical Porina eminentior, P. mastoidea, P. rufula, Strigula maculata,S. nitidula, S. smaragdula

W Pacific Porina tahitiensis, Trichothelium javanicum, Verrucaria howensis,V. mundula var. mundula

E Australasian Anisomeridium australiense, Porina alunilicola, Strigula fossulicola,S. oceanica, Verrucaria meridionalis

± Antitropical Agonimia tristicula, Porina chlorotica, P. leptalea, Verrucariapraetermissa

Endemic Lithothelium austropacificum, Pocsia mucronata, Porina howeana,P. mariae, P. ocellatoides, Strigula fractans, S. rupestris

Anomalous/incomplete Anisomeridium carinthiacum, Strigula decipiens var. decipiens, Topeliarosea

However, the gaps in our understanding of South Pacific lichens areconsiderable, and var. pacifica may also occur elsewhere.

A noteworthy feature of the flora of Rarotonga and throughout much of thetropical and subtropical South Pacific is the poor representation of Trypethe-liaceae. This family is diverse in southern Asia, Malesia, New Caledonia,north-eastern Australia and the Neotropics. However, species of TrypetheliumSpreng., Laurera Rchb. and Polymeridium (Mull. Arg.) R. C. Harris areextremely uncommon in southern Pacific latitudes (Fig. 6). This distributionis in marked contrast to that of the Pyrenulaceae and Trichotheliaceae, which arenot only numerous in continental tropical regions and offshore islands, butalso extend to many of the most remote Pacific islands.

Comparison with Lord Howe IslandThere are obvious difficulties in comparing the lichen floras of Pacific islands.In most cases, floristic studies are too incomplete, whereas others are in needof reappraisal to assess the apparently over-estimated endemism. However,there may be some value in comparing the pyrenocarpous lichens ofRarotonga with those of Lord Howe I., an Australian territory in thesouth-western Pacific, which I visited in 1995 and studied with a similar levelof intensity.

Lord Howe I., although only a quarter of the area of Rarotonga, has asimilar geology, topography and habitat diversity. However, it is 10 degreesfarther south, and temperatures are cooler at all times of year. Lord Howe I.is also much older (the main periods of volcanic activity took place 6-7 millionyears ago), less isolated (580 km from the nearest point on the Australiancoast; Fig. 1), and is influenced by easterly winds as well as northerly andwesterly storm tracks. Finally, in terms of floristic influences, it is close enoughto the Australian mainland, northern New Zealand and New Caledonia forthose land-masses and their diverse lichen floras to have had a far moresignificant long-term impact.


TABLE 3. Diversity of species and infraspecific taxa of selected pyrenocarpousgenera in Lord Howe Island and Rarotonga, and numbers common to both

Genus

AgonimiaAnisomeridiumCelotheliumLithotheliumPocsiaPorina s. lat.StrigulaTopeliaTrichotheliumVerrucariaTotal

Lord Howe Island

12

-11

108116*

31

Rarotonga

_

31--

10*4*-16*

25

Common/Total

0/11/40/10/10/11/192/100/10/22/106/52

* indicates that not all species have been named.

Although Pyrenula species were not collected by me in 1995, the biogeo-graphical elements among the pyrenocarpous lichens of Lord Howe I. aremore diverse than in Rarotonga. This can be explained by its more southerlylocation, a cooler climate and by its proximity to eastern Australia and NewZealand (Table 2). The pantropical element, dominated by foliicolous lichens,shares only two taxa with Rarotonga. More significant, however, are the strongeastern Australasian and antitropical elements, neither of which has more thana token presence in Rarotonga. The former includes foliicolous and shade-loving and semi-aquatic lichens, as well as Verrucaria meridionalis P. M.McCarthy, the only intertidal species known from the Pacific islands. Theantitropical element is essentially intrusive in Lord Howe I., and while it isdiverse, the species are not abundant.

The 'endemic' element in Lord Howe I. is contracting. Verrucaria howensis,first described from there, has now been collected in Rarotonga, and thefoliicolous Strigula fossulicola P. M. McCarthy, Streimann & Elix andi>. oceanica P. M. McCarthy, Streimann & Elix were observed among olderNew Zealand collections (Serusiaux 1998) shortly after their formal descrip-tion. As with the Rarotongan endemics, future investigations in the westernPacific will see this component diminish further.

Porina is similarly diverse and abundant in Rarotonga and Lord Howe I.,but only one of the 19 species is common to the two islands (Table 3). Withregard to the most robust and large-spored species, P. eminentior* is abundantin Lord Howe I. (and in eastern Australia and New Caledonia), whereasP. exocha is prominent in Rarotonga (as well as northern New Zealand andNorfolk I.), together with the pantropical P. farinosa. A surprising absentee*Porina eminentior (Nyl.) P. M. McCarthy, comb. nov. Basionym: Thelenella eminentior Nyl.,Ann. Sci. nat. Bot., ser. 4, 15: 54 (1861).—Verrucaria eminentior (Nyl.) Nyl., Bull. Soc linn.Normandie, ser. 2, 2: 125 (1868).—Anthracothecium eminentius (Nyl.) Mull. Arg., Linnaea 63:44 (1880).—Clathroporina eminentior (Nyl.) Mull. Arg., Flora 65: 517 (1882). Typus: NewCaledonia, 'ad corticem {Baloghiae drupaceae?)'', J. A. I. Pancher (H-NYL 1580!—holotypus).

The nomenclatural proposal and decision outlined under P. exocha (above) also apply here.

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from Rarotonga is P. tahitiensis, which is found to the east in French Polynesiaand to the west (and in great abundance) on Lord Howe I. Saxicolous Strigulaspp. are equally diverse but far less abundant in Rarotonga, and foliicolousspecies have a very tenuous presence (as minute colonies of 5. smaragdula). Inspite of the greater availability of suitable aquatic and more xeric habitats inRarotonga, Verrucaria species are comparatively rare.

Origin and DispersalAlthough dispersal of propagules via ancient land bridges and its furtheranceby tectonic movement may help to explain some disjunct lichen distributions,these are not pertinent to Rarotonga, given its isolation from continental florasand its recent volcanic origin. While birds have been convincingly postulatedto be among the principal vectors of flowering plant seeds to some of the moreremote Pacific islands, seawater notation may also be a significant mechanismof dispersal (Carlquist 1996). However, the most influential agent of long-distance dispersal of more minute lichen propagules in the Pacific is almostcertainly wind (Jorgensen 1983; Stenroos & Smith 1993; Smith 1995; Wedin1995). In Rarotonga, this may have been supplemented by ascospores andthallus fragments carried by seabirds migrating from the north and west, and,since the discovery of the island more than 2300 years ago, by humanexploration, colonization and trade (perhaps on the hulls, masts, sparsand booms of the large, ocean-going canoes of Polynesian fishermen andexplorers).

Ascospores are the most significant type of incoming lichen propagule. Ofthe species listed here only Porina mastoidea and P. tetracerae regularly produceisidium-like outgrowths, although, apart from Verrucaria spp., the thalli ofmost others sometimes or usually contain conidiomata. Smith (1995) sug-gested that pigmented or larger ascospores or those with thicker walls might bebetter able to withstand the rigours of dispersal to the Hawaiian Is. This offersan attractive, if conjecturable, explanation for the colonization of Rarotongaand many of the most remote Pacific islands by Pyrenulaceae, which alwayssatisfy at least two of the criteria for successful long-distance dispersal.

While most or all of the pyrenocarpous lichens of Lord Howe I. arriveddirectly from continental sources (e.g. Australia) or from smaller but floristi-cally very rich land-masses (e.g. New Caledonia or New Zealand), many of theRarotongan taxa must have come by long-distance, wind-borne migrationfrom the west or step-wise via other South Pacific islands. Some of the islandsin the region are much larger than Rarotonga, and have far greater environ-mental diversity in which 1000-2000 m high peaks and plateaux and theirassociated vegetation types and microhabitats are not uncommon. Thus it isprobable that the less remote, but more diverse floras of Fiji (a fragment ofGondwana), Samoa, Tonga and the Society Is. have been and continue to besignificant sources of propagules, particularly given the prevalence of cyclonicwinds during the wet season.

A similar pattern of dispersal has been suggested for polypodiaceousferns (Balgooy et al. 1996), some of which, for example species of Belvisia,Platycerium and Pyrrosia, are among the most distinctive and luxuriant


epiphytes in Rarotongan forests. Polypodiaceae are most diverse in Malesia,and probably have been dispersed by minute spores borne eastwards on windsthrough the Bismarck Archipelago, Solomon Is., Vanuatu, Fiji, Samoa,Society Is. and the Marquesas Is., as well as south to New Caledonia andnorth to Micronesia. Balgooy et al. (1996) observed that those species thatpenetrate farthest into the Pacific are the most likely ones to also extend northand/or south, a pattern of distribution possibly similar to that of somepyrenolichens in Rarotonga, such as the foliicolous Porina penninuta andTrichothelium marianense.

Foliicolous lichensThe impoverished state of the foliicolous lichen flora of Rarotonga is a littlesurprising. Initially at least, there appeared to be sufficient hosts in favourablymoist and sheltered microhabitats. However, comparatively low rainfall andthe mountainous, but not especially high terrain mean that conditions arerarely humid enough to support foliicolous lichens. The two localities at whichlichens were seen were deep within steep-sided valleys, in a forest glade besidea stream, and largely protected from desiccating winds.

Comparison with Lord Howe I. may again be informative. There, even witha true cloud-forest at altitudes of 750-850 m, only 12 foliicolous species(including 7 pyrenocarpous taxa) were observed, and all but three wereconfined to stunted shrubs in this habitat. Indeed, the 'cloud forests' ofRarotonga (at 400-650 m) are certainly drier and have a more sparsevegetation with fewer suitable hosts.

Contrast widi these rather depauperate floras the rich foliicolous commu-nities in coastal mountainous areas of the wet tropics of north-easternAustralia, where more than 100 species occur (Filson 1996). I. del Coco, inthe eastern Pacific Ocean, is even more remarkable. This island is less thanhalf the size of Rarotonga, only 600 km from the coast of Central America,and supports almost 100 species of foliicolous lichens (Lucking & Lucking1995). Diversity is apparently ensured by the 6000-7000 mm annual rainfall.

In general, the foliicolous lichens of the Pacific islands are still quite poorlyknown. Apart from I. del Coco, which benefits from proximity to theAmericas, suitable hosts and a very high rainfall, other more remote islandshave far less diverse floras, for example, Is. Galapagos (15 species; Weber1986) and Hawaiian Is. (25 obligate species; Smith et al. 1997). Because oftheir low elevation, inadequate rainfall and a shortage of hosts trees, most ofthe isolated islands and island groups will have few, if any foliicolous taxa.However, other larger and more mountainous South Pacific islands can beexpected to have far more diverse foliicolous floras. Already, more-or-lesscasual collections from New Caledonia, Society Is. and Western Samoa haveyielded 19-25 taxa on each (Elix & McCarthy 1998); more intensivefield-work is certain to add many more.

I am grateful to Jack Elix and Simone Louwhoff for their company and assistance in the field,Gerald McCormack (Cook Islands Natural Heritage Project) for providing useful backgroundinformation, and the Australian Research Council for financial support. Jack Elix also carried outHPLC of Pyrenula specimens.


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Accepted for publication 27 March 1999

the lichens of rarotonga, cook islands, south pacific ocean i: pyrenocarpous taxa

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