a systematic re-examination of four laminaria …molecular phylogenetic approach in recent years,...

—165—

About thirty species of Laminaria (includ-ing Saccharina) are known worldwide, oc-curring in temperate to frigid zones (Druehl2000). In Japan, 13 species of this genus arecurrently distributed mainly along the coast-lines of Hokkaido and of Pacific in northernTohoku (Kawashima 1989, Yoshida 1998,Yoshida et al. 2005). These Japaneselaminarians can be classified roughly intofour groups based on morphological charac-teristics and their distribution (Kawashima2004, Yotsukura et al. 2006). Among theJapanese Laminaria, four species belongingto the L. japonica group (L. japonica J. E.Areschoug, L. religiosa Miyabe, L.ochotensis Miyabe and L. diabolica Miyabe)are morphologically similar and lack striking

delineating features. Okamura (1896), Ueda(1933), and Yabu (1964) have debated thevalidity of these species.

In this report, the systematics of these fourspecies was re-examined based on our resultsand published findings of morphological ob-servations, crossbreeding experiments andmolecular phylogenetic analyses.

Morphological approachLaminaria japonica was first described by

Areschoug (1851). Subsequently, detailedmorphological characteristics of sporophyteof this species were investigated and alsoL. religiosa, L. ochotensis and L. diabolicawere described as new species by Miyabe(1902). The four species of the L. japonica

植物研究雑誌J. Jpn. Bot.83: 165–176 (2008)

A Systematic Re-Examination of Four Laminaria Species:L. japonica, L. religiosa, L. ochotensis and L. diabolica

Norishige YOTSUKURAa, Shoji KAWASHIMA

b, Tadashi KAWAIc,＊, Tsuyoshi ABE

d

and Louis D. DRUEHLe

aMuroran Marine Station, Field Science Center for Northern Biosphere, Hokkaido University,Muroran, Hokkaido, 051-0003 JAPAN;

b , Hakodate, Hokkkaido, 041- JAPAN;c,＊Hokkaido Wakkanai Fisheries Experimental Station, Wakkanai, Hokkaido, 097-0001 JAPAN;

E-mail: [email protected] Hokkaido University Museum, Hokkaido University, Sapporo, Hokkaido, 060-0810 JAPAN;

eBamfield Marine Science Centre, Bamfield, BC, V0R 1B0, CANADA＊Corresponding author

(Received on September 18, 2007)

The systematics of Laminaria japonica J. E. Areschoug, L. religiosa Miyabe,L. ochotensis Miyabe and L. diabolica Miyabe, which are similar morphologically andrestricted to the coastline of northern Japan, was re-examined. From the morphologicalobservations, it was concluded that the discrimination of the four species based on theirmorphological features was problematic. The results of crossbreeding experiments andmolecular phylogenetic analyses suggest that these species are not genetically isolated.Consequently, we concluded that these four species should be revised as four varieties ofone species: L. japonica J. E. Areschoug var. japonica, var. religiosa, var. ochotensis andvar. diabolica.

Key words: Japanese kelp, Laminaria, Saccharina, systematic re-examination.

group share the following characteristics:“Thick fibrous haptera, arranged in a colum-nar or pseudo-columnar manner, resulting ina large and strong holdfast. The stipe is thickand lamina are either linear-lanceolate orbamboo-leaf surfaced. The median fascia isdistinct and occupies 1/3 to 1/2 the width oflamina. The mucilage ducts are well devel-oped in the stipe and lamina (occasionally intwo layers)” (Miyabe 1902). Yoshida (1998)distinguished these species by holdfast shape(arrangement of haptera), lamina shape

(basilar shape), degree of the curl around themargin, width and thickness of the lamina.However, these morphological characteris-tics are inconsistent, and the morphologicalvariability within a species can be dramaticdepending on plant age and environmentalcharacteristics.

Regarding the holdfast of L. japonica,L. ochotensis, and L. diabolica, new hapteraarise in tiers, each new tier covering the pre-ceding tier, forming a conical, bell-shaped,or hemispheric shape (Figs. 1B, F, H). The

植物研究雑誌第83巻第3号平成20年6月166

Fig. 1. Morphological variations of holdfast of four extant laminarian species growing in Hokkaido. A‒B.Laminaria japonica. A. One-year-old sporophyte on 30 July 1986 at Yunokawa, Hakodate. B. Two-year-oldsporophyte on 6 August 1984 at Yunokawa, Hakodate. C‒D. L. religiosa. C. One-year-old sporophyte on 24September at Nagahama, Okushiri. D. Two-year-old sporophyte on 6 June 1996 at Genna, Otobe. E‒F. L.ochotensis. E. One-year-old sporophyte on 25 July 1985 at Horomoi, Shari, F: Two-year-old sporophyte on 17September 1999 at Akaiwa, Rebun. G‒H. L. diabolica. G. Two-year-old sporophyte on 11 August 1963 atKyouei, Rausu. H. Two-year-old sporophyte on 2 August 1987 at Aikiappu, Akkeshi. Scale bar = 5 cm.

Journal of Japanese Botany Vol. 83 No. 3June 2008 167

Fig.

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haptera of L. religiosa, when observed fromdirectly above, give the appearance ofspokes of a wheel (Fig. 1C). However, manyof the former species (L. japonica, L.ochotensis, and L. diabolica) exhibit irregu-lar sequences, like L. religiosa, at stagesbefore sufficient growth has occurred, par-ticularly in the first-year of growth (Figs.1A, E, G) and even the latter species(L. religiosa) exhibits no significant differ-ence from the other three species in the sec-ond-year of growth (Fig. 1D).

Usually, L. religiosa is considered to be anannual species. However, it is known thateven within its area of distribution, biennialsporophytes can be found. It seems this spe-cies has the genetic potential to be a biennial,a trait shared by the other species.

The outline of the lamina, the shape of thelamina base, and the width of the medianfascia, for these four species vary greatly ac-cording to the locality, age, and whether thekelp is wild or cultured (Fig. 2). Especiallyin the vicinity of species overlaping, a num-ber of individuals for both species will showspecific characteristics of the other species(Kawashima 1989).

In general, during the first-year of growth,the lamina bases exhibit cuneate or acuteshapes, while in the second-year of growth,the bases become species specific. However,even in the older sporophyte, the morpho-logical characteristics for each species arenot consistent (Fig. 2).

The shapes of the holdfasts and laminaeare variable and are not reliable to distin-guish the four species. Moreover, the widthand thickness of the lamina cannot be usedas an absolute measure for identification pur-poses. For example, Yoshida (1998) showedthat the lamina width of L. japonica was20–30 cm, while that of L. ochotensis wasless than 20 cm. Commercially, L. japonicais distinguished by its economic propertieswhich reflect regional differences (laminalength, width, and length/width ratio).However, in every region, there were secondyear sporophytes with lamina widths of lessthan 20 cm (Sanbonsuga and Torii 1974). OnL. ochotensis, similar regional differencesare observed between individuals that growin the Sea of Japan and the Sea of Okhotsk.Those individuals that grow in the Sea ofOkhotsk tend to show large lamina widths,


Fig. 3. Morphological variation of ten two-year-old sporophytes in Laminaria ochoitensis from Horomoi, Shari.

and individuals with lamina width of morethan 20 cm are observed frequently (Fig. 3).

Morphological characteristics used to dis-tinguish taxa have been reported to changegeographically in succession (Ueda 1933)and vary markedly depending on growingenvironments (Hasegawa 1967, Sanbonsuga1978, Sanbonsuga and Torii 1973, 1974,Notoya and Kirihara 1989, Funano 1991,Nabata et al. 1993). Therefore, it is thusoften difficult to classify these laminarianalgae based on lamina using classificationsystem by Miyabe (1902). Similarly, dis-crimination of the four species based on theirmorphological characteristics can also beproblematic.

An integrated morphological study of 13Japanese Laminaria species, including thefour discussed here, revealed considerableoverlap of the 10 morphological parametersmeasured (Druehl et al. 1988). By applyingmultivariate analyses, they resolved fivemorphological groups. Lamina width andstipe length most strongly discriminatedthese groups. One group contained collec-tions of L. religiosa, L. diabolica and L.japonica and another group contained collec-tions of L. ochotensis and L. diabolica. Withthe exceptions of L. longipedalis Okamuraand L. yendoana Miyabe their analyses couldnot resolve individual Japanese species.

Hybridization approachReciprocally crossed L. japonica, L.

religiosa, L. ochotensis and L. diabolicadeveloped normal sporophytes in all combi-nations. Furthermore when the hybridizedsporophytes were tank-cultured in deep-seawater at Iwanai, Hokkaido, which isdifferent from the seawater of the fourspecies’ natural habitat, the growth and mor-phology of all the plants were the same untilsporogenesis (Table 1).

Hybridization experiments on the fourspecies have been conducted (L. japonica, L.religiosa and L. ochotensis in six combina-

tions and L. japonica and L. diabolica in twocombinations). All hybrids showed normalgrowth (Yabu 1964) and F2 sporophytesformed by the self-propagation of F1 sporo-phytes reciprocally of crossed L. japonica, L.religiosa, L. ochotensis and L. diabolicaoccurred in high frequencies (Funano 1978,1980).

The four species are more or less distrib-uted continuously around Hokkaido:Laminaria religiosa along the westernshores, L. ochotensis on northern shores, L.diabolica on eastern shores, and L. japonicaon southeast shores from the Tsugaru Straitsto the Muroran region (Hasegawa 1959,Kawashima 1989) (Fig. 4).

The female gametophytes of the four spe-cies share the same sexual pheromones:lamoxirene (Müller et al. 1985) and there areno marked differences in the period ofsporogenesis and the time of appearance ofthe new generation. It is therefore difficult toassume that there is sufficient reproductiveisolation to warrant the differentiation of thefour species.

Molecular phylogenetic approachIn recent years, molecular phylogenetic

analyses have been conducted on laminarianalgae to clarify the nucleotide sequence ofseveral genes. For Laminaria in Japan, thenucleotide sequence of ribosomal DNA in-ternal transcribed spacer regions 1 and 2(ITS-1 and ITS-2), which are encoded in thenucleus, and the intergenetic region betweenRuBisCo L and RuBisCo S (RuBisCospacer) encoded in the chloroplasts, havebeen determined (Yotsukura et al. 1999,Yotsukura 2005). They found no nucleotidesequence differences among L. japonica,L. religiosa, L. ochotensis and L. diabolica.

When the nucleotide sequences of the ITSand RuBisCo spacer of individuals collectedwidely from the habitat of the four specieswere investigated, the nucleotide arrange-ments agreed completely between all



Tab

le1.

Mea

sure

men

tof

seve

ral

mor

phol

ogic

alch

arac

ters

ofhy

brid

ized

spor

ophy

tes

amon

gfo

urex

tant

lam

inar

ian

spec

ies

cultu

red

inde

ep-s

eaw

ater

Fem

ale

Mal

e

Len

gth/

Wid

thra

tioof

LA

Wid

thra

tioof

LA

/MF

Len

gth

ratio

ofL

A/L

MT

hick

ness

ratio

ofM

F/L

MA

ngle

ofla

min

aba

se

Min

Mea

nM

axSD

Min

Mea

nM

axSD

Min

Mea

nM

axSD

Min

Mea

nM

axSD

Min

Mea

nM

axSD

L.

japo

nica

×

L.

japo

nica

.

L.

reli

gios

a.

L.

ocho

tens

is.

L.

diab

olic

a.

5.7

4.2

7.8

9.2

5.9

6.3

12.3

12.3

6.3

10.1

18.0

18.0

0.2

2.3

4.0

3.7

2.8

3.4

2.8

0.8

3.3

4.6

4.0

2.5

4.7

5.3

5.0

4.5

0.8

0.7

1.0

1.3

0.1

0.1

0.0

0.3

1.2

1.2

1.1

1.3

1.4

1.4

1.1

1.7

1.0

1.0

1.1

1.1

5.7

1.1

3.0

4.0

8.5

2.2

4.6

4.7

15.0 4.0

7.0

5.0

3.9

1.1

1.5

0.5

70 50 50 70

72.0

50.0

50.0

73.3

80 50 50 80

4.5

0.0

0.0

5.2

L.

reli

gios

a×

L.

japo

nica

.

L.

reli

gios

a.

L.

ocho

tens

is.

L.

diab

olic

a.

2.8

4.6

3.6

4.1

5.3

6.5

5.8

6.3

7.5

10.2 8.9

12.3

1.6

2.6

2.3

2.4

2.3

2.6

2.6

2.8

3.7

3.3

3.0

3.2

4.8

4.0

3.3

3.7

1.0

0.7

0.3

0.4

0.3

0.2

0.1

0.2

1.4

1.3

1.3

1.3

1.7

1.6

1.4

1.7

1.0

1.1

1.2

1.1

3.3

1.6

3.0

2.7

4.7

2.8

4.1

4.2

6.0

3.7

5.5

8.0

1.2

0.8

0.9

1.5

40 50 50 50

51.7

50.0

50.0

53.6

60 50 50 60

4.1

0.0

0.0

5.0

L.

ocho

tens

is×

L.

japo

nica

.

L.

reli

gios

a.

L.

ocho

tens

is.

L.

diab

olic

a.

3.1

6.2

10.0 6.0

6.1

7.2

12.4 7.0

7.8

9.1

13.6 7.8

2.0

1.1

1.4

0.7

2.7

3.7

1.3

2.2

3.1

4.2

1.4

2.9

4.6

5.0

1.5

3.3

0.7

0.6

0.1

0.4

0.2

0.2

0.1

0.1

1.3

1.3

1.2

1.4

1.6

1.6

1.3

1.5

1.2

1.0

1.1

1.3

2.0

2.1

3.5

2.0

3.9

2.7

6.9

3.4

6.0

3.5

10.0 5.5

1.9

0.5

3.0

1.3

60 50 60 50

64.3

50.0

62.0

52.0

70 50 70 60

5.3

0.0

4.5

4.5

L.

diab

olic

a×

L.

japo

nica

.

L.

reli

gios

a.

L.

ocho

tens

is.

L.

diab

olic

a.

4.6

4.0

5.0

2.6

11.8 4.9

7.6

11.7

21.1 6.6

11.0

16.3

4.6

1.1

2.0

4.9

2.5

4.2

2.6

2.1

4.9

4.6

3.0

3.2

12.8 5.2

3.4

4.3

3.3

0.4

0.4

0.9

0.2

0.1

0.2

0.3

1.2

1.2

1.2

1.3

1.6

1.3

1.6

1.7

1.0

1.1

1.0

1.0

2.5

3.0

2.6

2.0

4.3

4.3

3.8

5.0

6.5

6.0

5.0

15.0

1.3

1.2

1.0

5.0

50 50 50 50

50.0

51.4

55.0

55.0

50 60 60 60

0.0

3.8

5.3

5.5

Eac

hch

arac

ter

(Ang

le:

°)w

asm

easu

red

asde

scri

bed

inK

awam

ata

(200

1).

LA

:la

min

a;M

F:m

edia

nfa

scia

;L

M:

late

ral

mar

gin

ofla

min

a;M

ean:

valu

eof

mea

n;SD

:st

anda

rdde

viat

ion;

Min

:va

lue

ofm

inim

um;

Max

:va

lue

ofm

axim

um.

samples for each DNA region (Table 2).Comparison of the ITS and RuBisCo spacersis considered useful for identifying geneticvariation among various species or genus ofbrown algae (Stache-Crain et al. 1997, Yoonet al. 2001). Among laminarialean generasuch as Alaria, Halosiphon, Macrocystis,Phyllariopsis, Saccorhiza, the nucleotidesequence of ITS and/or RuBisCo spacer hasbeen used to detect regional variationsamong the same species (Kraan and Guiry2000, Coyer et al. 2001, Kraan et al. 2001,Sasaki et al. 2001). Laminaria are thought tohave evolved relatively recently (Stam et al.1988) with divergences observed in the nu-cleotide sequence of the ITS and/or RuBisCospacer within species belonging to suchvarious laminarialean taxonomic groups(Rousseau et al. 2001). Consequently, it isthought that the levels of intraspecies varia-tion seen within Laminaria are relativelyhigh. However, because no mutations were

detected between individuals of L. japonica,L. religiosa, L. ochotensis and L. diabolicain the ITS and RuBisCo spacer (Yotsukuraet al. 1999, Yotsukura 2005), it is presumedthat the genetic differences are not suffi-ciently large to justify more than one species.

Genetic variation of Japanese laminarianalgae was investigated by comparing the nu-cleotide sequence of 5S rDNA spacer region(Yotsukura 2005, Yotsukura et al. 2006),which has a faster rate of nucleotide substitu-tion than ITS in land plants (Soltis and Soltis1999). They reported that L. japonica,L. religiosa, L. ochotensis and L. diabolicagrouped together irrespective of species as-signment or location and that the genetic dis-tance among these four species was less thanbetween them and other laminarian species.Some individuals could not be sequenceddirectly and often exhibited two-pattern se-quences after cloning (Fig. 5). It is presumedthat these are thalli that had arisen from natu-


Fig. 4. Distribution of four extant laminarian species in this study.

ral hybridizations between individuals withdifferent DNA sequences. With the aim ofverifying this presumption, hybridizationswere conducted using gametophytes withdifferent 5S rDNA spacer sequences. Theresulting sporophytes contained bothsequence pattens. Furthermore, the gameto-phytes derived from zoospores released fromthese sporophytes showed the same se-quences as the original gametophytes (Fig.5). This suggests strongly that the individu-als with two 5S rDNA spacer sequence pat-terns are sporophytes that have arisen fromnatural hybridizations between genetically

different individuals. Various sequences ana-lyzed in the L. japonica group appear to sup-port the notion that active genetic exchangestake place in this group.

ConclusionThough most morphological characteris-

tics of L. japonica, L. religiosa, L. ochotensisand L. diabolica are unstable, several areshared by these species: Mucilage canalspresent in both stipe and lamina; hapteremainly in vertical rows (verticillate while thefrond is young); stipe: short (3–12 cm);lamina entire; median fascia thick and broad


Table 2. GenBank accession number of the sequence of ribosomal DNA internal transcribed spacer regions 1 and2 (ITS-1 and ITS-2) and the intergenetic region between RuBisCo L and RuBisCo S (RuBisCo spacer) for fourextant laminarian species from northern Japan

SpeciesSample IDGenBank Accession No. of 5SrDNA spacer in Yotsukuraet al. (2006) (Collection date, Collection site)

ITS-1･ITS-2･RuBisCo spacerGenBank Accession Number

Laminariajaponica

L. religiosa

L. ochotensis

L. diabolica

AB255823 (29. i. 2000, Charatsunai, Muroran)AB255814 (15. x. 2000, Kakkumi, Minamikayabe)AB255827 (3. iv. 2000, Kobui, Esan)AB255815 (29. ii. 2000, Furukawa-cho, Hakodate)AB255816 (6. iii. 2000, Shiogama, Fukushima)AB255817 (25. vi. 2002, Ooma, Aomori pref.)AB255825 (26. vi. 2002, Sai, Aomori pref.)AB255818 (8. v. 2002, Odanosawa, Aomori pref.)AB255819 (10. x. 2002, Ishimochi, Aomori pref.)AB255821 (20. iv. 2002, Minmaya, Aomori pref.)AB255820 (21. v. 2001, Omoe. Iwate pref.)

AB255804 (19. v. 2000, Genna, Otobe)AB255798 (4. vii. 2000, Isoya, Suttsu)AB255799 (16. xii. 2002, Tomori-gyokou, Tomari)AB255802 (9. xii. 2002, Notsuka, Iwanai)AB255800 (14. ii. 2000, Osyoro, Otaru)AB255809 (18. i. 2000, Minedomari, Atsuta)AB255801 (21. v. 2001, Omoe, Iwate pref.)

AB255790 (8. ii. 2000, Tomamae-gyokou, Tomamae)AB255793 (26. i. 2002, Hourai, Wakkanai)AB255791 (19. iv. 2002, Hakunai, Soya)AB255792 (19. iv. 2002, Boushiiwa, Abashiri)

AB255783 (17. xi. 1998, Hunami-cho, Rausu)AB255785 (25. v. 2001, Heinai-cho, Nemuro)AB255784 (27. ii. 2002, Aikappu, Akkeshi)

AB428798・AB428799・AB428800,AB428801・AB428802・AB428803,AB428804・AB428805・AB428806,AB428807・AB428808・AB428809,AB428810・AB428811・AB428812,AB428813・AB428814・AB428815,AB428816・AB428817・AB428818,AB428819・AB428820・AB428821,AB428822・AB428823・AB428824,AB428825・AB428826・AB428827,AB428828・AB428829・AB428830

AB428831・AB428832・AB428833,AB428834・AB428835・AB428836,AB428837・AB428838・AB428839,AB428840・AB428841・AB428842,AB428843・AB428844・AB428845,AB428846・AB428847・AB428848,AB428849・AB428850・AB428851

AB428852・AB428853・AB428854,AB428855・AB428856・AB428857,AB428858・AB428859・AB428860,AB428861・AB428862・AB428863

AB428864・AB428865・AB428866,AB428867・AB428868・AB428869,AB428870・AB428871・AB428872

(1/3–1/2 as wide as the total breadth of thelamina); and bullations present only onyoung laminae.

These morphological characteristics arecommon to the four species. Above all, thebullations that occur on the leaf surfaces areseen only during the first year of sporophytegrowth. This formation of bullations allowsclear distinction of L. angustata Kjellmangroup species, which never form bullations,from L. cichirioides Miyabe group species,which always form bullations.

According to the biological species con-cept, a species can be defined as “a group ofactually or potentially interbreeding naturalpopulations which are reproductively iso-lated from other such groups” (Mayr 2000).Based on the aforementioned previous find-ings, it appears that there is still evidence ofgenetic exchange among the four Laminariaand that genetic divergence is limited.Furthermore, the constraint of reproductiveisolation does not appear to apply to the spe-cies concerned. Consequently, as has beenproposed previously by Okamura (1896) and

Yabu (1964), these four species should begrouped as a single biological species:Laminaria japonica. While Okamura (1896)divided the four species into two varieties,later Yabu (1964) divided them into four.However, the proposal did not cite abasionym and thus did not follow theInternational Code of Botanical Nomen-clature.

Morphological and genetic differences donot support the retention of the four species.The four Laminaria species studied gene-rally grow in different areas and each hassubtle, differentiating morphological charac-teristics on the morphology of the laminabase and the lamina margin (Kawashima2004).

Recently, phylogenetic relationshipsamong laminarialean algae were examined indetail (Lane et al. 2006). This study brokethe genus Laminaria into two clades:Laminaria and Saccharina. Yotsukura(2005), employing molecular phylogeneticanalyses of Japanese laminarians, distin-guished two lineages (non-digitate type and


Fig. 5. DNA banding pattern of polymerase chain reaction amplifying 5S rDNA spacer with primer pairs 5S-F1and 5S-R1 in Laminaria species (cf. Yotsukura et al. 2006). Lane 1. The sporophyte originated from a femalegametophyte (nucleotide length of 5S rDNA spacer: 232bp) and a male gametophyte (232bp) of L. religiosafrom Notsuka, Iwanai (lr-n). Lane 2. The sporophyte originated from a female gametophyte of lr-n and a malegametophyte (247bp) of L. japonica from Charatsunai, Muroran (lj-c). Lane 3. The sporophyte originated froma female gametophyte of lj-c (247bp) and a male gametophyte of lr-n. Lanes 4‒13. Subcloning of 5S rDNAspacer in Lane 2. Lane 14. Stable 100bp DNA ladder. Lane 15. The female gametophyte originated from a zoo-spore isolated from the sporophyte treated in Lane 2. Lane 16. The male gametophyte originated from a zoo-spore isolated from the sporophyte in Lane 2. Lane 17. Stable 1kbp DNA ladder. Arrows indicate bandsoriginated from lj-c and arrowheads indicate bands originated from lr-n.

digitate type). The non-digitate forms, in-cluding the four species we are reporting on,belong to the Saccharina clade.

We propose to treat L. japonica, L.religiosa, L. ochotensis and L. diabolica asfollows.

Saccharina japonica (J. E. Areschoug)C. E. Lane, C. Mayes, L. D. Druehl & G. W.Saunders in J. Phycol. 42: 509 (2006).

Laminaria japonica J. E. Areschoug,Phyc. Cat.: 29 (1851).

var. religiosa (Miyabe) Yotsukura,Kawashima, T. Kawai, T. Abe & L. D.Druehl, stat. nov.

Laminaria religiosa Miyabe in HokkaidoSuisan Chosahokoku 3: 21 (1902); inOkamura, Nippon Sorui Meii: 131 (1902).Type: Japan: Hokkaido, Fukuyama, K.Miyabe, Aug.1894 (SAPA).

Saccharina religiosa (Miyabe) C. E. Lane,C. Mayes, L. D. Druehl, & G. W. Saundersin J. Phycol. 42: 509. 2006.

var. ochotensis (Miyabe) Yotsukura,Kawashima, T. Kawai, T. Abe & L. D.Druehl, stat. nov.

Laminaria ochotensis Miyabe inOkamura, Nippon Sorui Meii: 130 (1902).Type: Japan: Hokkaido; Tentokari, Y.Kawaguchi, 28 August1894 (SAPA).

Laminaria japonica J. E. Areschoug var.ochotensis (Miyabe) Okamura, NipponKaiso Shi: 249 (1936).

Saccharina ochotensis (Miyabe) C. E.Lane, C. Mayes, L. D. Druehl, & G. W.Saunders in J. Phycol. 42: 509 (2006).

var. diabolica (Miyabe) Yotsukura,Kawashima, T. Kawai, T. Abe & L. D.Druehl, stat. nov.

Laminaria diabolica Miyabe in HokkaidoSuisan Chosahokoku 3: 47 (1902); inOkamura, Nippon Sorui Meii: 131 (1902).Type: Japan: Hokkaido; Rausu, Matsuoka,23 September1894 (SAPA).

Laminaria japonica J. E. Areschoug f.diabolica (Miyabe) Yu. E. Petrov in Nov.

Sist. Rast. [Bot. Inst. Akad. Nauk SSSR] 9:51 (1972).

Saccharina diabolica (Miyabe) C. E.Lane, C. Mayes, L. D. Druehl, & G. W.Saunders 2006 in J. Phycol. 42: 509 (2006).

The authors thank Mr. T. Muto and Mr. H.Akino (Hokkaido Nuclear Energy Environ-mental Research Center), Mr. S. Sakamotoand Mr. M. Nakaya (Iwanai Local IndustrySupport Center) and Mr. S. Tomiyasu(Hokkaido Government Abashiri Subpre-fectural Office) for their technical assistant.

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四ツ倉典滋a, 川嶋昭二b, 川井唯史c, 阿部剛史d,L. D. ドゥリュール e：日本産コンブ属植物 4 種(マコンブ, ホソメコンブ, リシリコンブ, オニコンブ) の分類学的再検討北日本沿岸に分布の中心を持ち, 形態的類似性の高いコンブ属植物 4種 (マコンブ, ホソメコンブ, リシリコンブ, オニコンブ) の分類学的再検討を行なった. 4種はこれまで形態的特徴によって分けられてきたが, 形態形質の多くは不安定であり, それぞれを形態的に識別することは難しい.これらコンブ属 4種はそれぞれ “局所的に” かつ“他の何れかの種の分布域と接して” 分布しており, 交雑実験および分子系統解析の結果から現在

遺伝子交流が起こっていると推察される. 従って,これまで独立種として扱われてきたこれら 4種はマコンブ (Laminaria japonica J. E. Areschoug) として統一し, そのなかに分布域の異なる 4 変種(var. japonica, var. religiosa, var. ochotensis, var.diabolica) を設けるのが適当と考えられる.(a北海道大学北方生物圏フィールド科学センター,

b函館市 ,c北海道立稚内水産試験場,

d北海道大学総合博物館,eカナダ・バムフィールド海洋科学センター)

a systematic re-examination of four laminaria …molecular phylogenetic approach in recent years,...

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