effect of the east siberian barrier on the echinoderm dispersal in the arctic ocean

ISSN 0001�4370, Oceanology, 2010, Vol. 50, No. 3, pp. 342–355. © Pleiades Publishing, Inc., 2010.Original Russian Text © A.N. Mironov, A.B. Dilman, 2010, published in Okeanologiya, 2010, Vol. 50, No. 3, pp. 371–386.

342

INTRODUCTION

The Arctic Ocean became a scene for interactionsof three faunas in the Neogene including the high�lat�itude Arctic, boreal Northern Pacific, and borealNorthern Atlantic ones. The trans�Arctic speciesexchange between the Atlantic and Pacific is the moststudied process. As a result of this exchange disjunctspecies ranges occurred which were named by“amphiboreal” [3] or “discontinuous circumboreal”ranges [59]. Discontinuous circumboreal rangesappeared when the species penetrated from theNorthern Pacific towards the Northern Atlantic butnot vice versa, as was showed in the beginning of theXXth century for many species [1, 14, 20, 52, 74, etc.].This colonization route was further proved by palae�ontology data, mostly by the mollusk fauna analysis[6, 7, 9, 10, 25, 26, 34, 45, 58, 61, 65, 75, etc.] andgenetic analysis [47, 57, 69, 70, 76].

If the opinions on prevailing trend of trans�Arcticexchange coincide, then there is still serious disagree�ment about the ratio of the species of Pacific andAtlantic origin in the shallow�water Arctic fauna. Thisproblem is widely discussed on the example of echin�oderms. The detailed biographical analysis by Dya�konov [20] revealed that, in the Arctic, 24% of theechinoderm species were of Atlantic origin, 29% wereArctic autochthonous species, and 47% came from thePacific (122 species in total). In the meantime, the

fauna of the continental plateau (excluding 16 deep�water species) were mostly represented by species ofPacific origin (54%) [20]. Anisimova [48] suggestedthat “…the Arctic faunas most closely related to theAtlantic species and probably originated from theAtlantic Ocean” (p. 192). Smirnov [72] supported thisopinion as “…the modern fauna of the Arctic echino�derms have close relationships to the Northern Atlan�tic fauna” (p. 135); however, he supposed the Pacificorigin for the species widely present in both the Atlan�tic and Pacific oceans and for some boreal Atlantic–Arctic species.

A significant part and even the bulk of the bottomfauna of the Arctic Ocean are represented by widelyrepresented species that are characterized by circum�Arctic or nearly circum�Arctic ranges. The most out�standing examples are the East Siberian Sea and theeastern Laptev Sea, where the species ranges are usu�ally disjunct or are characterized by the presence of theeastern or western range limit. It was suggested that thebarrier for dispersion might be the trans�arctic ridge,which lays from the New Siberian Islands to ElsmereLand and was pronounced in the Pleistocene [15]. Aswas proposed by Gorbunov [12], the New SiberianIslands, which bound the East Siberian Sea from thewest, were “…connected with the mainland, and a gla�cier penetrated into the sea and thus disconnected theinteractions between the high�Arctic fauna of the open

Effect of the East Siberian Barrier on the Echinoderm Dispersal in the Arctic Ocean

A. N. Mironov and A. B. DilmanShirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia

E�mail: [email protected] October 22, 2008

Abstract—The distributional patterns were analyzed for 43 species and 33 genera of echinoderms in theLaptev and East Siberian seas and for 59 species and 35 genera of the asteroid species in the Arctic Ocean.The probable colonization route through the Arctic was suggested for each species based on (1) the distribu�tional patterns of the Arctic species, (2) the distributional patterns of the closely related species, and (3) thelocation of the center of the diversity of the species belonging to a certain genus. The species of the Pacificorigin prevailed in the asteroid fauna of the Arctic seas. The asteroid species diversity and the ratio of the spe�cies of Pacific origin decreased from the Barents towards the Laptev Sea and increased, respectively, in theEast Siberian and the Chukchee seas. The species range limits were found for 19 species in the East SiberianSea compared to only 3 species in the Laptev Sea. The East Siberian Sea was a limiting area for the dispersalof four species groups: (1) invaders from the North Pacific dispersing along the Asian coast of the Arctic (shal�low�water stenobathic species), (2) invaders from the North Pacific dispersing along the American coast ofthe Arctic and further on back into the Arctic along the Eurasian coast (secondarily Atlantic species); (3)originally invaders from the Northern Atlantic; (4) representatives of the Arctic autochthonous fauna. A greatwidth of the biotic boundaries (i.e., the zones of the species range boundaries crowding) was typical for theArctic Basin, which was a sign of their young geological age.

DOI: 10.1134/S0001437010030057

MARINE BIOLOGY

OCEANOLOGY Vol. 50 No. 3 2010

EFFECT OF THE EAST SIBERIAN BARRIER ON THE ECHINODERM DISPERSAL 343

sea eastwards and westwards, which resulted in thecontinental draught between the glacier’s edge and theCentral Arctic continental slope” (p. 59). The presenceof the “underwater island relicts” around the New Sibe�rian Islands supports Gorbunov’s theory. These relictislands were formed by the ancient ice and weredestroyed completely during the last 270–50 years [19].

It is interesting to notice that the same hypothesisexplained the fate of the legendary Sannikov’s Land[8, 35, 44]. According to this theory, the New SiberianIslands were the part of Eastern Siberia in the EarlyQuaternary period and were sunk later, and Sannikov’sLand was part of the pre�New�Siberian Islands andwas a volcanic remains. By the other hypothesis, San�nikov’s Land just melted as many other islands fromthe New Siberian Islands group.

The East Siberian species range disjunctions arealso explained by the hydrological peculiarities of thisregion, including the limit of the Atlantic and (or)Pacific water penetration, the anticyclonic circulationof the Arctic water masses, the prevalence of the Arcticestuarine water mass, and the significant freshwaterincome to the Arctic Basin [5, 11, 25, 38, 46, etc.].

All the hypotheses listed above are presented in areview by Nesis [35]. He arrived at the conclusion thatnone of the factors listed above might have created aneffective barrier for the species penetration and thusdid not result in the west�Arctic and east�Arctic distri�bution pattern. In the meantime, east�Arctic speciesare stenobathic and shallow�water, inhabit at depthsnot deeper than 100–200 m, while the west�Arcticspecies are eurybathic and live in the lower sublittoraland upper bathyal. On this basis Nesis hypothesizedthat the species range disjunctions and the modernvertical distribution of the west�Arctic and east�Arcticspecies are related to the environmental differencesbetween the Eastern and Western Arctic during theQuaternary glacial period [35, 37]. In other words, theWestern Arctic shelf was covered by glaciers during thecold periods; these glaciers penetrated far and deepinto the Arctic Ocean and thus prevented the shallowwater fauna from settling down. Those species thatadapted successfully became eurybathic but lost theopportunity to inhabit the inner shelf with a widerange of hydrological conditions. In contrast, theEastern Arctic shelf was not affected by the glaciers;thus, the stenobathic species that inhabited the shal�low waters had the opportunity to conserve their eury�biont character and stayed on the inner shelf.

The species range limits and disjunctions may bealso explained by the insufficient dataset on the EastSiberian Sea fauna. Later, already after publishing ofhis theory, Nesis shown that discontinuous ranges ofsome Arctic cephalopods are intrinsically circumpo�lar. After that he used his theory not for explanation ofthe range disjunctions but only to explain the differ�ences in vertical distribution of the west�Arctic andeast�Arctic population of the same species [37].

Most of the biogeographical schemes are not char�acterized by the presence of a border that divides theAsian Arctic shelf in the eastern and western parts.Those schemes that include such a border differ in itslocation: (1) the western East Siberian Sea, around145°E [62]; (2) the central East Siberian Sea, around160°–170°E [4]; and (3) the eastern East SiberianSea, around ~175°E [16, 38]. The patchiest schemewas proposed by Naumov and Fedyakov [60], where thisborder was located far to the west at 110°E (the westernLaptev Sea). According to Nesis the East Siberian andChukchee–Canadian provinces widely overlay in theLaptev Sea and western East Siberian Sea [36].

The Laptev Sea and the East Siberian Sea are theleast studied among the other Arctic seas. That is whythe monograph of Zenkevich does not contain thechapter on the fauna of the East Siberian Sea [24]. Thesituation changed in the last two decades, when severalbooks were issued by the Zoological Institute of theRussian Academy of Sciences. The knowledge of thedynamics of the invertebrate fauna is quite prominent:311 species were described in 1932, 522 species in1963, 1084 species in 1994, 1337 species in 1998, 1472species in 2001, and about 1500 species in 2004 [40].Therefore, the significant amount of data on the inver�tebrate fauna allows starting a new analysis of the bio�geographical history.

The present study combines the modern data onthe echinoderm distribution in the Laptev and theEast Siberian seas and includes the analysis of the seastar fauna for the whole shelf of the Arctic region. Themodern echinoderm fauna is divided into three bio�geographical groups of Northern Pacific, NorthernAtlantic, and primarily Arctic (autochthonous) origin.An attempt to evaluate the impact of the East Siberianbarrier is presented based on the comparative analysisof these three groups’ distribution and the changes inthe biogeographical structure of the fauna along theArctic coasts.

MATERIALS AND METHODS

The analysis was mostly based on the previouslypublished data on 59 sea star species’ (35 genera) dis�tribution on the Arctic shelf (0–300 m depth) (Table 1)and on 43 echinoderm species (33 genera) distributionin the Laptev and East Siberian seas (Table 2). Thedataset was combined from numerous publications,namely, the most important ones [2, 12, 20–22, 28,41–43, 48, 49, 50, 53–55, 56, 63, 73]. The echino�derm fauna of the Laptev Sea was cited from [41–43,73]. The biogeographical database on the Arctic bot�tom fauna was also included into the analysis(http://www.zin.ru/projects/arccoml). This databasewas mostly created by colleagues from the ZoologicalInstitute of the Russian Academy of Sciences and theShirshov Institute of Oceanology of the Russian Acad�emy of Sciences, including the authors of the presentmanuscript. The species whose taxonomical status was

344


MIRONOV, DILMAN

Table 1. Sea star species distribution in three biogeographical areas (the Arctic, Northern Pacific, and Northern Atlantic)

Genera

Number of species

Species originTotally for the genus Arctic Northern

AtlanticNorthern

Pacific

Asterias 7 1A* + 1P* 2 5 Pacific

Astropecten 105 1A 14 10 Atlantic

Bathybiaster 2 1A 1 – Atlantic

Brisinga 20 1A 3 – Atlantic

Ceramaster 15 1AP 2 8 ?

Crossaster 10 1AP + 1E* 3 5 Pacific

Ctenodiscus 5 1AP 1 1 Pacific

Diplopteraster 6 1AP 1 1 Pacific

Evasterias 4 1P – 4 Pacific

Henricia 79 5A + 3P + 1E (+2E?) 11 37 Pacific and Atlantic

Hippasteria 15 1A 2 11 ?

Hymenaster 51 1AP 10 7 ?

Hymenodiscus 16 1A 2 5 ?Atlantic

Icasterias 1 1E – – ? (autochthonous)

Korethraster 1 1A 1 – ?Atlantic

Leptasterias (Endogenasterias) 2 1AP 1 1 Pacific

L. (Hexasterias) 9 1AP 1 9 Pacific

L. (Leptasterias) 22 1A + 1P + 1E 9 10 Pacific

Leptychaster 11 1AP 1 6 Pacific

Lethasterias 4 1P – 3 Pacific

Lophaster 11 1A 1 2 Pacific

Luidia 48 1A 4 9 Atlantic

Marthasterias 1 1A 1 – Atlantic

Pedicellaster 8 1A 1 4 Pacific

Peltaster 4 1A 2 – Atlantic

Pontaster 1 1A 1 – ?Atlantic

Porania 4 2A 3 – Atlantic

Poraniomorpha 5 4A 5 – Atlantic

Pseudarchaster 21 1AP 2 5 Pacific

Psilaster 12 1A 2 1 ?

Pteraster 43 3AP + 1P 8 17 Pacific

Solaster 20 1AP + 1A + 1P + 1E 6 10 Pacific

Stephanasterias 1 1AP 1 1 Pacific

Stichastrella 2 1A 2 – Atlantic

Tremaster 2 1A 1 – Atlantic

Tylaster 1 1E – – ? (autochthonous)

Urasterias 1 1A 1 – ?Atlantic

Note: *A—the Arctic species also represented in the Atlantic; P—the Arctic species also represented in the Pacific; E—Arctic endemicspecies. Only genera presented in the Arctic are considerate. The southern limits of the Northern Atlantic and Northern Pacificare conventionally located at 30°N.



Table 2. Echinoderm species found in the Laptev and the East�Siberia seas, their origin, and their relationship to with the faunaof the Northern Pacific and the Northern Atlantic

Species in�dex number Species Depth, m Species common

with the Atlantic/Pacific Species origin

Crinoidea1 Heliometa glacialis 14–1900 +/+ Pacific2 Poliometra prolixa 18–1960 +/– ?Atlantic

Holothurioidea3 Ekmania barthii 0–600 +/+ Pacific4 Eupyrgus scaber 7–480 +/– Pacific5 Molpadia arctica 51–1016 –/– Atlantic6 Myriotrochus eurycyclus 8–446 –/– Pacific7 Myriotrochus rinkii 5–720 +/+ Pacific8 Ocnus glacialis 11–200 –/+ Pacific9 Pentamera calcigera 5–500 +/+ Pacific

10 Psolus peronii 18–61 –/+ Pacific11 Psolus phantapus 0–500 +/+ Pacific12 Trochoderma elegans 8–700 –/– ? (autochthonous)

Echinoidea13 Strongylocentrotus pallidus 5–1960 +/+ Pacific

Asteroidea14 Crossaster papposus 0–1200 +/+ Pacific15 Ctenodiscus crispatus 10–2200 +/+ Pacific16 Henricia beringiana 10–75 (?202) –/+ Pacific17 Henricia perforata 2–2000 +/– ?Atlantic18 Hymenaster pellucidus 15–3240 +/+ ?19 Icasterias panopla 1–1073 –/– ? (autochthonous)20 Koreaster hispidus 85–1230 +/– ?Atlantic21 Leptasterias groenlandica 0–276 +/+ Pacific22 Leptasterias polaris 0–200 +/+ Pacific23 Lophaster furcufer 6–2555 +/– Pacific24 Pontaster tenuispinus 18–3440 +/– ?Atlantic25 Poraniomorpha bidens 53–2780 –/– Atlantic26 Poraniomorpha tumida 9–2198 +/– Atlantic27 Pteraster militaris 6–2152 +/+ Pacific28 Pteraster obscurus 10–930 +/– Pacific29 Pteraster pulvillus 15–3700 +/+ Pacific30 Solaster syrtensis 27–360 +/– ?Pacific31 Urasterias linckii 1–762 +/– ?Atlantic

Ophiuroidea32 Amphiodia crateroidermata 7–1000 –/+ Pacific33 Amphiura sundevalli 3–1800 +/+ Pacific34 Gorgonocephalus arcticus 5–1992 +/– Pacific35 Ophiacantha bidentata 7–4730 +/+ Pacific36 Ophiocten sericeus 5–4500 +/– ? (Atlantic)37 Ophiopleura borealis 10–2500 +/– Atlantic38 Ophiopus arcticus 199–1950 –/– ? (autochthonous)39 Ophioscolex glacialis 36–2500 +/– Atlantic40 Ophiura maculata 2–290 –/+ Pacific (?)41 Ophiura robusta 3–1000 +/– Pacific (?)42 Ophiura sarsii 3–3000 +/+ Pacific43 Stegophiura nodosa 0–565 +/+ Pacific

346


MIRONOV, DILMAN

unclear were excluded from the analysis according tothe synonymy presented in the “List of Sea Star Spe�cies” [53–56].

The Arctic Ocean area is defined in accordancewith its geomorphologic borders with the Atlantic edgelocated along the Faroe Islands–Iceland transect and thePacific edge crossing the Bering Strait [29]. These geo�morphologic borders do not correspond to the edges ofthe biogeographical provinces [51, Figs. 9–10]. Thenumber of sea star species was calculated separately foreight regions, including the Norwegian, Barents,Kara, Laptev, East Siberian, and Chukchee seas andtwo American Arctic areas, Hudson Bay and theCanadian Arctic sector (140°–105°W).

The extensive collection of sea stars originally ana�lyzed by one of the authors (AD) included samplesfrom the Norwegian Sea, around Iceland, in theFarer–Shetland region, and in the Kara Sea. Theresults of this analysis were in accordance with thepresent pattern of the sea star distribution in the Arctic[28]. Additionally, the sea star collection obtained byMoskalev [33] in the Chukchee Sea (Arctic Drift Sta�tion 22) was available for the analysis. As a result, theeastern range limit of two species, Hymeaster pellicidusand Icasterias panopla, was moved eastwards to theChukchee Sea.

The species range disjunctions on the Laptev andEast Siberian seas shelves were defined with 5° of lon�

110°E 120° 130° 140° 150° 160° 170° 180°

Spe

cies

inde

x n

umbe

r

123456789

10111213141516171819202122232425262728293031323334353637383940414243

Laptev Sea East Siberian Sea

Fig. 1. Echinoderm species distribution on the Laptev and the East Siberian Sea shelves. The horizontal line indicates the speciespresence for a certain longitudinal gradient. The line breaks indicate the species range disjunctions (shown only for a 5° distanceand more). The species range limits are indicated by a four�arm asterisk. The species index number corresponds to Table 2.



gitudinal accuracy. Range was defined as discontinu�ous if the disjunction if the break reached 10° or moreand if the same species was not also found for theregion at depths of 1000 m and less (i.e., the northernlimits were also taken into account). The speciesfound for the East Siberian Sea and not found for theChukchee Sea are treated as having their eastern rangelimit in the East Siberian Sea. A biotic boundary(boundary of the biotic complexes or biogeographicalregions) is defined as a zone where the limits of severalspecies ranges come close together. A species range isregarded here as a continuous area contoured by a sin�gle line connecting the most outlying points of a spe�cies occurrence (a concept of species range continu�ity). A biotic complex is a group of organisms inhabit�ing an area outlined by zones of crowding ofboundaries of species ranges [30].

Each species was tested for its colonization route(Northern Pacific or Northern Atlantic origin) to theArctic. Assumptions were made on the basis of threecriteria: (1) the distributional patterns of the species inthe Atlantic/Pacific, (2) the distributional patterns ofthe closely related species, and (3) the location of thecenter of the diversity of the species belonging to a cer�tain genus. The relationship between species of thesame genus was assessed by the comparative morpho�logical analysis and, in some cases, by previously pub�lished genetic data [47, 70, 76]. The colonizationroute of certain species was based on the biogeograph�ical history of the genus; i.e., if a certain genus pene�trated from the Northern Pacific to the NorthernAtlantic and then some species of this genus settled inthe Arctic, the whole genus complex was treated as

being of Pacific origin. The criteria listed above areonly indirect evidence for the colonization routes intothe Arctic and allow only some suggesting as to whatway might be the most possible one. Therefore, theprobability of a mistake in the colonization routeassessment is high. However, a significant databaseincluding dozens of species and genera allows trackingthe tendencies in the biogeographical history of theArctic. We define the Northern Pacific/Atlantic originof the studied species as the area from which certainspecies appeared in the Arctic but not the area of thespecies appearance itself.

RESULTS

The sea star species number decreases from theNorwegian Sea (44 species) towards the Laptev Sea(16 species); then, it increases a bit in the East Siberianand Chukchee seas (17 and 18 species, respectively).The number of all the echinoderm species in the EastSiberian Sea (39) is also more than in the Laptev Sea(37 species). Most species of the Laptev Sea (34 spe�cies, or 92%) have no range limits in this area, and onlythree species have east limits of its distribution in thissea (Fig. 1). Another pattern is observed for the EastSiberian Sea, where the species range limits are foundfor about half of the species list (19, or 48.7%). In themeantime, these range limits are the eastern borders ofdistribution for 14 species. Comparing with the smallnumber of the range limits in the Laptev andChukchee seas, the increased number of limitsappeared in the East Siberian Sea looks like a zone ofthe crowding, and thus the biotic boundary in this sea

Sp

ecie

s ra

tio

, %

100

90

80

70

60

50

40

30

20

10

0

NorwegianSea

Barents Sea

Kara Sea

East Siberian

Chukchee Western Canada

Hudson

1 2

BaySeaSea Laptev

Sea

91

29

87

37

82.6

39.1

81

37

76

53

44

72

79

57

78

64

Fig. 2. The ratio of the sea star species (%) common to the Northern Pacific and the Northern Atlantic (0–300 m depth range)in different Arctic areas: 1—common to the Northern Atlantic; 2—common to the Northern Pacific.

348


MIRONOV, DILMAN

may be suggested. However, this boundary is slightlyexpressed, because the crowding zone is considerablywide including nearly all the East Siberian Sea fromNew Siberian Shoals to Chaunskaya Bay.

Only six species (16%) have a discontinuous rangesin the Laptev Sea compared to 23 species (59%) in theEast Siberian Sea. However, we don’t consider therange disjunctions in the west Laptev Sea near off Sev�ernaya Zemlya. Most range disjunctions (17) arefound for the central East Siberian Sea (160°– 170°E).The most outstanding exception is the Arctic endemicspecies Molpadia arctica (Fig. 1, species no. 5), whichinhabits the central part of the sea and is totally absentin the western and eastern parts.

The echinoderm fauna of the East Siberian andLaptev seas, as the fauna of the whole Arctic Ocean,includes mostly eurybathic species; only 12% (5 spe�cies among 43) are stenobathic (i.e., are not founddeeper than 300 m) and 53% (23 species among 43)inhabit the areas deeper than 1000 m (Table 2). Themajority in the group of echinoderms with the westrange limits in the studied area (4 out of 5 in total) isconstituted by stenobathic species, while all specieswith east range limits are eurybathic (occurring deeper300 m).

Among 59 sea star species distributed in the shelf ofthe Arctic Ocean 30 species (51%) are common onlywith the Atlantic fauna (Atlantic–Arctic species);nine (15%) species—only with the Pacific (Pacific–Arctic species); fourteen species (24%) are recorded inboth the Atlantic and Pacific regions (Atlantic–Pacific–Arctic species); and six species (10%) formthe group of the Arctic endemics. The share of speciescommon with the Atlantic region is higher than thatobserved for the Pacific–Arctic ones (Fig. 2) with theChukchee Sea as the only exception, where 13 speciesare common to the Pacific and only 8 to the Atlantic.The relative amount of the sea star species of Pacificorigin increases significantly eastwards from the Nor�wegian Sea to the Barents Sea, stays the same in theKara and Laptev seas, increases greatly in the EastSiberian Sea, reaches its maximum in the ChukcheeSea, and stays high in the Canadian Arctic (Fig. 2).Taking into account all the echinoderms, the samepattern is observed for the Laptev and East Siberianseas; the relative amount of the species of the Pacificorigin increases from 43% to 54% with the same num�ber of endemics (six species in each sea; 16% and 15%,respectively).

The data on certain genera allow concluding defi�nitely on the colonization routes in the Arctic, while

NorwegianSea

Barents Sea

KaraSea

Chukchee Western Canada

Hudson BaySeaSea

Laptev East Siberian

Sea

Spe

cies

num

ber

30

25

20

15

10

5

0

18

21

5

9

24

7

14

9

2

4

11

15

1

9

3

10

5 5

2 2 2 222

1 2 3

Fig. 3. The ratio of the sea star species (%) of Pacific and Atlantic origin (0–300 m depth range) in different Arctic areas: 1—Atlantic origin; 2—Northern Pacific origin; 3—unknown origin.

Fig. 4. The colonization routes of the modern species that are limited by the East Siberian Sea in the Arctic: 1—from the North�ern Pacific along the Asian coast of the Arctic; 2—from the Northern Pacific along the American coast of the Arctic up to theNorthern Atlantic and further on back into the Arctic along the Eurasian coast (secondarily Atlantic species); 3—from theNorthern Atlantic (originally Atlantic species); 4—the Arctic autochthonous species. The stroked areas indicate the zones of thespecies ranges’ boundaries crowding.



1

2

3

4

180°

–90°

0°

80°

70°

60°

50°

2

1

3

90°

350


MIRONOV, DILMAN

180°

90°

80°

70°

50°

60°

0°

1

180°

90°

80°

70°

50°

60°

0°

2

180°

90°

80°

70°

50°

60°

0°

3

180°

90°

80°

70°

50°

60°

0°

4



the data on others are ambiguous. The genera Amphio�dia, Evasterias, Lethasterias, Ophiopholis, Stegophiura,and Strongylocentrotus are characterized by theabsence of Northern Atlantic and Atlantic–Arcticspecies and by the presence of closely related speciesin the Pacific. Thus, the Northern Pacific origin ofthese genera is obvious. The genera Bathybiaster, Bris�inga, Ophiopleura, Peltaster, Porania, Poraniamorpha,Stichastrella, and Tremaster are characterized by theabsence of Northern Pacific and Pacific–Arctic spe�cies and by the presence of closely related species inthe Atlantic. Thus, the Northern Atlantic origin ofthese genera may be proposed. The genera includingthe Pacific–Arctic or Atlantic–Pacific–Arctic speciesare defined as the taxa of Pacific origin. They are usu�ally represented by larger number of species in theNorthern Pacific compared to the Northern Atlantic,for example Crossaster, Leptyaster, Lophaster,Ophioscolex, Pedicellaster, Pseudarchaster, Pteraster,and Solaster (Table 1).

The suggestion of the Pacific or Atlantic origin forsome genera is discussible. For example, the NorthernPacific dispersion route is proposed for the Gorgono�cephalus based only on the fact that the Atlantic–Arc�tic species G. arcticus is replaced by G. caryi(=G. stimpsoni) and G. japonicus in the NorthernPacific. The last two species may probably be one spe�cies, G. arcticus. The same pattern is found in theOphiacantha, including more than 150 species. Thegenus’s distributional pattern and, especially, that ofthe Atlantic–Pacific–Arctic species O. bidentata,which penetrates down to Japan and the Azores, doesnot allow concluding Pacific or Atlantic origin withcertainty. The Pacific origin of O. bidentata wasdefined only by the presence of the closely related spe�cies O. omoplata and O. adiophora in the NorthernPacific [22].

The genus Ceramaster is an example of an ambigu�ous colonization route. The Atlantic origin for thisgenus may be proposed according to the distributionalpattern of C. granularis, which is found for the Arctic,Northern Atlantic, and along the South Africa coast(C. granularis trispinosuis) and is totally absent in theNorthern Pacific [21]. However, the Northern Pacificis characterized by a higher Ceramaster species num�ber compared to the Northern Atlantic, and C. granu�laris is also found in this region [54]. Thus, we con�clude this genus is of unclear origin.

The group of unclear origin includes the fourendemic monotypic genera: Icasterias, Ophiopus, Tro�choderma, and Tylaster, since no colonization routemay be proposed for them. Four other genera—Kore�thaster, Poliometra, Pontaster, and Urasterias—are

found only in the Arctic and Far Northern Atlantic.Two of the three proposed criteria cannot be appliedfor these genera, and thus the suggestion of the Atlan�tic origin of these taxa seems quite unsupported.

Among the 35 sea star genera inhabiting the Arctic(including the boreal waters of the Norwegian Sea),fourteen of them (40%) are of Northern Pacific origin,the same amount (40%) came to the Arctic from theNorthern Atlantic, and the origin of six species (17%)remains unclear (Table 1). The Henricia (3%) mighthave penetrated to the Arctic from both the Pacific andAtlantic in the early colonization period. The speciesgroups of “pertusa” and “perforata” have different ori�gins (Pacific and Atlantic, respectively) and differ sig�nificantly by their morphological and biochemicalcharacteristics [71].

Therefore, in total, the number of echinodermgenera of the Pacific and Atlantic origin is nearly thesame. In the meantime, the species diversity is higherfor the Northern Pacific origin (33 species, or 60%)compared to the Northern Atlantic origin (21 species,or 36%). The fauna of the Laptev and the East Siberianseas are also formed mostly by the Pacific species(28 species, or 65%) compared to the Atlantic ones(11 species, or 26%) (Table 2).

The sea star species of the Pacific origin dominatein all the Arctic seas (Fig. 3). The longitudinal dynam�ics of the Atlantic/Pacific species ratio is similar to thedynamics of the common species; the most consider�able changes take place in the Laptev and the EastSiberian seas. Two areas may be defined for the Eur�asian Arctic shelf: the western (the Barents, Kara, andLaptev seas) and the eastern (the East Siberian andChukchee seas) ones. The first area is characterized bya decrease of the Pacific species number eastwards,while the second one is characterized by the oppositeprocess in the same longitudinal direction. Taking intoaccount all the echinoderm species, the ratio of thePacific species increases from 59% (the Laptev Sea) to67% (the East Siberian Sea).

Among species for which the East Siberian Sea isthe limit of distribution four groups can be defined(Fig. 4). Species of the first group have their west rangelimits in the East Siberian Sea (they are designated asnos. 10, 16, 22, 32, and 40 in the Table 2 and Fig. 2).These species are shallow�water, stenobathic (onlyone species is recorded deeper 300 m) and of Pacificorigin. The other three groups mainly comprise ofeurybathic species which have their east limits in theEast Siberian Sea. The second group includes speciesof the Pacific origin presented in the Atlantic (nos. 11,27, 29, 30, 35, and 41), so named secondarily Atlanticspecies. The third group is the largest, includes 8 spe�

Fig. 5. Hypothetical scheme of the gradual colonization of the Pacific species in the Arctic and Atlantic resulting in the second�arily Atlantic species appearance: 1—Pacific Upper Miocene period (closed Bering Strait phase); 2—Eastern Arctic LowerPliocene period (warming, transgression, and open Bering Strait phase); 3—Amphiboreal Pleistocene period (phase of maximalglacial distribution); 4—West�Arctic postglacial period when the secondarily Atlantic species appeared.

352


MIRONOV, DILMAN

cies from 19 (42%) and comprises species of the Atlan�tic origin and (nos. 2, 5, 17, 20, 25, 26, 37, and 39).Forth group unites species of the monotypic genera,endemic for the Arctic Ocean and probably autochth�onous (nos. 12 and 38).

DISCUSSION

The range disjunctions and limits in the East Sibe�rian Sea cannot be explained by the lack of data on itsfauna. Despite the fact that new data were obtained inthe last decades on the species composition and distri�bution in this region, the the range disjunctions andlimits remain. The species that are characterized bythe eastern limits in the East Siberian Sea are mostlyrepresented by eurybathic ones; therefore, some ofthem may have a circum�Arctic distribution in thebathyal and may be found later in the Chukchee Sea atdepths of more than 300 m.

The shelf of the East Siberian Sea is a zone of thecrowding of species range boundaries, which dividesthe Arctic basin into the Eastern and Western biogeo�graphical regions. These two regions surround theArctic Basin and come to contact with its oppositemargins probably in the Canadian Arctic, as was pro�posed in numerous publications devoted to the distri�butional patterns of many bottom species [12, 13, 16–18, 35, 51, 63, 64, 66, 67] and described in [35]: “…thecrowding zone in the Canadian Arctic is a wide areaand includes the Canadian Arctic Archipelago and theadjacent areas from the McKenzie River Delta or theAmundsen Gulf to the Fox Basin or Ellesmere Land;the border lies on the transect Boothia Peninsula–Somerset Island–Bathurst Island…” (p. 4).

The biogeographical boundaries are slightlyexpressed in the Arctic Basin. The bottom fauna distri�bution is well�documented for the Barents Sea, wherethe boreal species are replaced by the Arctic ones.However, several opinions exist on the location of theborder between the Northern Atlantic and the Arcticprovinces, which may change its position from theLofoten Islands to Novaya Zemlya [39, Fig. 22]. Actu�ally the species range limits are distributed all over thewhole Barents Sea, as also occurs in the East SiberianSea. A wide transition zone may be defined instead ofthe narrow border between the Northern Atlantic andthe Arctic provinces [36, 38, 39, 48, 62]. The schemeproposed by Scarlato and Golikov [62] included thewide transition zone from the southwestern BarentsSea and Spitsbergen (Svalbard) to the Novaya Zemlyacoast. This scheme includes two more transition zones(“ecotones”) between the boreal and Arctic provinces:from southeastern Greenland to the NewfoundlandIslands in the Atlantic Ocean and from the BarrowCape (the border between the Chukchee and Beaufortseas) southwards to 62°N in the Bering Sea. The sig�nificant width of the crowding zones in the Arctic maybe a sign of the young geological age of the biotic bor�

ders, which started to form only in the last postglacialperiod.

The presence of the crowding zone and of numer�ous range limits and disjunctions reflect?the fact thatthe East Siberian Sea acts as a biogeographical barrierfor dispersion of many species. The barrier effect of thecrowding zone in this region as the barrier effect of anyother biotic boundary [32], is a result of impacts ofseveral biotic and abiotic factors. The most obviousabiotic factors are the geomorphologic compartmen�talization and the harsh environment in the past andpresent, the different glacial environment, the signifi�cant fresh water income, and the peculiarities of theglobal circulation in the Arctic basin (which werethoroughly described in the Introduction section).Nesis [35] criticized existing theories and argued thatthe dramatically changed physical and chemical char�acteristics of environment must provide a completebarrier for the species dispersion. However, the tra�versable barriermay also have had the effect of a bio�geographical barrier, especially when the crowdingzone is formed here. Most of the biotic borders in theOcean, including the well�expressed ones, wereformed in the locations of abiotic barriers, whichmight be easily penetrable for many species.

We suppose that the biotic component of the bar�rier effect appears during the evolution processes ofbiotic boundary and adjacent biotic complexes [31,32]. Initial barrier for the species dispersion has an abi�otic origin and relates to the changes of the abiotic fac�tors only. Then, the species gradually adapt to the dif�ferent environmental conditions existing on both sidesof the barrier. This results in the appearance of two dif�ferent communities and succession systems, whichprovide more comfortable environments for the localspecies compared to the alien ones (i.e., coming fromthe other side of the border). The development of dif�ferent succession systems leads to the gradual conver�gence of the species range limits in the regions whereglobal changes of the abiotic environmental charac�teristics take place. This convergence of the range lim�its resulting from the species adaptations and the for�mation of a new group of communities with similarsuccession was suggested to designate as the groupingadaptation effect [31, 32]. The weak expression of thecrowding zone in the East Siberian Sea is an indicationthat the process of the convergence of the speciesrange limits has only recently started and the bioticcomponent of the East Siberian barrier is not signifi�cant.

The effect of the East Siberian barrier may be alsotracked in the dynamics of both the biodiversity andbiogeographical structure of the fauna. In the direc�tion from the Norwegian Sea to the Laptev Sea boththe species number and the share of species dispersedfrom the Pacific decrease (Fig. 3). These parametersincrease for the East Siberian and for the Chukcheeseas. The ratio of the species in common with thePacific Ocean is nearly the same in the western seas



(the Barents, Kara, and Laptev), but this ratio signifi�cantly increases in the East Siberian Sea and arrives atits maximum in the Chukchee Sea. The echinodermfàuna of the last two seas differs significantly from thefauna of Barents, Kara and Laptev Seas by smallershare of the boreal�Atlantic (relatively warm water)species with wide distribution [48; Fig. 11�2]. The bio�geographical structure principally changes in the EastSiberian Sea also according to the depth gradient. Theboreal�Arctic species prevail in the Arctic speciesdown to the depths of 650–800 m in the Kara andnorthern Barents seas, while the same group domi�nates only for the 0–120 m depths in the East SiberianSea [48; Fig. 11�7].

Present analysis supports Dyakonov’s theory [20]about the dominating of the species of Pacific origin inthe Arctic fauna. At first glance, such a statementlooks like a paradox, especially taking into account theprevalence of the species common with the AtlanticOcean. However, most of these species are the second�arily Atlantic ones (i.e., primarily Pacific�origin spe�cies). We suggest a hypothetical scheme of the second�arily Atlantic species appearance in the Arctic (Fig. 5).The first period occurred in the Late Miocene, whenthe ancestors of these species inhabited the NorthernPacific. This period is reflected by the modern distri�bution pattern of the subgenus Lepasterias (Hexaste�rias), except for one species (H. polaris) among ten.The second period (the Early Pliocene) was character�ized by the opening of the Bering Strait and globalwarming; thus, Pacific species had an opportunity toinvade the Arctic and to distribute along the Canadiancoast far to the northwestern Atlantic Ocean. Thisperiod is supported by the modern distribution ofL. (Hexasterias) polaris. The Bering Strait closed andopened several times. The active trans�Arcticexchange of the faunas of the Northern Pacific and theNorthern Atlantic started between 3.1 million yearsago and 4.1 million years ago (Early Pliocene) whenthe Bering Strait was open [57, 68]. Most of thePacific�origin species invaded the Arctic during thatperiod. The third period lasted until the Late Pleis�tocene, when the phases of global warming and cool�ing down alternated. During the cold periods, the spe�cies of the Pacific origin were superseded from theArctic to the Northern Atlantic. The third period cor�responds to the modern distribution of the numerousamphiboreal species [34], for example, the sea urchinEchinarachnius parma. The fourth period is associatedwith the last postglacial period, which started about12–10 thousand years ago. In that time, the primarilyPacific species that invaded the Northern Atlantic, ortheir descendants, repeatedly colonized the Arctic andattained an Atlantic–Arctic distribution pattern(Table 2; species nos. 11, 27, 29, 30, 35, and 41).Therefore, the secondarily Atlantic species are theresult of the significant southward shift of the Pacificspecies limits to the Northern Atlantic during the peri�ods of cooling�down and regression and their retroac�

tive migrations northwards during the climate warm�ing and transgression.

Among the four species groups that differ in theircolonization routes, only one invaded into the Arcticwestwards along the Siberian Arctic coast (Fig. 4); allthe others moved along the Eurasian coast eastwards.The secondarily Atlantic species (Table 2; speciesnos. 11, 27, 29, 30, 35, and 41) primarily dispersedfrom the Northern Pacific along the American Arcticcoast and only then came from the western side to theEast Siberian barrier. The group of monotypic genera(Table 2; species nos. 12 and 38) was probably formedin the Arctic and never moved from this region. Thespecies that are characterized by their western andeastern limits in the East Siberian Sea also differ intheir vertical distributional patterns: the first group isformed by stenobathic species and the last by eury�bathic species. This characteristic of the echinodermfauna in the modern Arctic supports the hypothesis ofintensive natural selection by the depth niches occupa�tion [35, 37]. The eurybathic species were more flexiblein the southward shifts of their species’ range limits,which took place in the Western Arctic and NorthernAtlantic during the glacial periods.

All the echinoderm species of the Pacific origin,which are also characterized by the eastern range lim�its in the East Siberian Sea, are also secondarily Atlan�tic ones. The other groups of bottom invertebrates arealso characterized by the presence of the Pacific spe�cies with eastern limits in the East Siberian Sea but arenot found in the Northern Atlantic. We suggest thatthese species in their dispersion from the east to thewest nearly rounded the Arctic Basin and did notappear in the Northern Atlantic; a rare example of twosponge species exists—Asbestopluma bihamatifera andMycale thaumatochela [27].

ACKNOWLEDGMENTS

This study was supported by the subproject “ArcticMarine Fauna: Data Accumulated in Russia” (theCoML “Arctic Ocean Diversity” program) and by theRussian Foundation for Basic Research (project 08�05�00470).

REFERENCES

1. A. P. Andriyashev, Essays on Zoogeography and Origin ofIchthyofauna of the Bering Sea and Adjacent Waters(Leningr. Gos. Univ., Leningrad, 1939) [in Russian].

2. N. A. Anisimova, “Type Echinodermata,” in Life andConditions of Its Existence in the Benthic Zone of the Bar�ents Sea (Izd. KNTs RAN, Apatity, 1986), pp. 147–153[in Russian].

3. L. S. Berg, “On the Causes of Similarity of Faunas ofthe Northern Parts of the Atlantic and Pacific Oceans,”Izv. Akad. Nauk, Ser. 6. 12, 1835–1842 (1918).

4. I. P. Bogdanov, “Gastropods Oenopotinae of the EastSiberian Sea,” Issled. Fauny Morei 49 (57), 123–130(1994).

354


MIRONOV, DILMAN

5. S. V. Vasilenko, “Consistent Patterns of Distributionand Biogeographic Structure of the Fauna of Cumacea(Crustacea, Peracarida) of the Laptev Sea, Northwest�ern Part of the East Siberian Sea, and Adjacent Deep�Water Part of the Arctic Ocean in Relation to Charac�teristics of Hydrological Regime,” Issled. Fauny Morei54 (62) 15–57 (2004).

6. Yu. I. Galkin, “Gastropods Trochidae of Far�East andNorthern Seas of the USSR, in Identification Guide tothe Fauna of the USSR, (1955), Vol. 57, pp. 1–132.

7. Yu. B. Gladenkov, Marine Upper Cainozoic of NorthernRegions (Nauka, Moscow, 1978) [in Russian].

8. V. V. Glushkov, “The Last Refuge of Onkilons,” Priroda(Moscow, Russ. Fed.), No. 4, 92–96 (2008).

9. A. N. Golikov, “Mollusks Buccinidae of the WorldOcean,” Fauna SSSR. Nov. Ser., No. 121, 1–508(1980).

10. A. N. Golikov, “Stages and Boundaries of Cainozoic.Analysis of the Course of Geological Time and Devel�opment of the Fauna of Marine Gastropods,” Tr. Zool.Inst. AN SSSR 130, 31–52 (1985).

11. A. N. Golikov, “Shell�Bearing Gastropods of the EastSiberian Sea,” Issled. Fauny Morei 49 (57), 67–122(1994d).

12. G. P. Gorbunov, “Benthic Population of the Novosi�birsk Shoals and the Central Part of the Arctic Ocean,”in Transactions of the Drifting Expedition of Glavsevmor�put on the Icebreaking Ship G. Sedov, 1937–1940,(1946), Vol. 3, pp. 30–138.

13. G. P. Gorbunov, “Bivalve Mollusks (Bivalvia) of theChukchi Sea and the Bering Strait,” in Extreme North�east of the USSR, issue 2, (Akad. Nauk SSSR, Moscow,1952), pp. 216–278 [in Russian].

14. E. F. Gur’yanova, “On the Problem of Origin and His�tory of Development of the Polar Basin Fauna,” Izv.Akad. Nauk SSSR 5, 679–704 (1939).

15. E. F. Gur’yanova, “The Polar Basin Fauna and thePathways of Its Exchange with the Faunas of Neighbor�ing Regions of the World Ocean,” in Proc. 2nd All�Union Geograph. Congr., (Geografgiz, Moscow, 1949),Vol. 3, pp. 202–203 [in Russian].

16. A. F. Gur’yanova, “Gammarids of the Seas of theUSSR and Adjacent Water Areas,” in IdentificationGuides to the Fauna of the USSR, (1951), Vol. 41, pp. 1–1033.

17. E. F. Gur’yanova, “Zoogeography of the Arctic Basin,”in Observations Made Onboard of Research Drifting Sta�tions “Severnyi polyus�3” and “Severnyi polyus�4”,1954–1955, (Mors. Transp., Leningrad, 1957), Vol. 1,pp. 343⎯362 [in Russian].

18. E. F. Gur’yanova, “Characteristics of the Fauna of theArctic Ocean and Their Role for Understanding theHistory of Its Formation,” in The Arctic Ocean and ItsCoast in Cainozoic (Gidrometeoizdat, Leningrad,1970), pp. 126⎯161 [in Russian].

19. O. V. Dudarev, A. N. Charkin, I. P. Semiletov, et al.,“On Contemporary State of Underwater Island Relicson the East Siberian Shelf,” Dokl. Akad. Nauk 419 (2),255–261 (2008).

20. A. M. D’yakonov, “Interactions of Arctic and PacificMarine Faunas as Exemplified by Zoogeographic Anal�ysis of Echinoderms,” Zh. Obshch. Biol. 4 (2), 125–153 (1945).

21. A. M. D’yakonov, “Starfishes of Seas of the USSR,” inIdentification Guides to the Fauna of the USSR, (1950),Vol. 34, pp. 1–212.

22. A. M. D’yakonov, “Ophiurans in Seas of the USSR,” inIdentification Guides to the Fauna of the USSR, (1954),Vol. 55, pp. 1–136.

23. I. A. Zhirkov, Polychaetes of the Arctic Ocean (Yanus�K,Moscow, 2001) [in Russian].

24. L. A. Zenkevich, Biology of Seas of the USSR (Izd.Akad. Nauk SSSR, Moscow, 1963) [in Russian].

25. A. I. Kafanov, “The Status of the Arctic Sea Biogeo�graphic Zone (As Assessed by Paleontological Data),”in Paleoecology of Communities of Marine Invertebrates(DVNTS Akad. Nauk SSSR, Vladivostok, 1979),pp. 100–129 [in Russian].

26. A. I. Kafanov, “Subfamily Mytilinae Rafinesque, 1815(Bivalvia, Mytilidae) in Cainozoic of the NorthernPacific Region,” in Fauna and Distribution of Mollusks:The Northern Pacific Region and the Polar Basin(DVNTS Akad. Nauk SSSR, Vladivostok, 1987),pp. 65–103 [in Russian].

27. V. M. Koltun, “Cornacuspongida of Northern and Far�East Seas of the USSR,” in Identification Guides to theFauna of the USSR, (1959), Vol. 67, pp. 1–236.

28. A. B. Krayushkina (A. B. Dil’man), “Geography ofStarfishes and Holothurians of the Norwegian Sea,” inBenthos of Seas of Russia and Northern Atlantic Regions,Ed. by A. P. Kuznetsov and O. N. Zezina (Izd. VNIRO,Moscow, 2000), pp. 41–61 [in Russian].

29. O. K. Leont’ev, “Morphometry,” in The Arctic andSouthern Oceans (Nauka, Leningr. Otd., Leningrad,1985), pp. 17–18 [in Russian].

30. A. N. Mironov, “Faunistic Approach to Studying Con�temporary Ecosystems,” Okeanologiya 30 (6),pp. 1006–1012 (1990).

31. A. N. Mironov, “Adaptations and Limits of Species Dis�persion,” in Adaptation Aspects of Marine Fauna For�mation, Ed. by A. P. Kuznetsov and O. N. Zezina (Izd.VNIRO, Moscow, 2002), pp. 95–111 [in Russian].

32. A. N. Mironov, “The Nature of Biotic Limits,” in Gen�eral Problems of Marine Biogeography: In Memory ofAcademician O.G. Kusakin, Ed. by A. I. Kafanov(Dal’nauka, Vladivostok, 2004), pp. 67–97 [in Rus�sian].

33. L. I. Moskalev, “Benthic Fauna of the Upper Part of theChukchi Sea Shelf,” in Environmental Studies of theShelf, Ed. by A. P. Kuznetsov (Inst. Okeanol. ANSSSR, Moscow, 1980), pp. 73–98 [in Russian].

34. K. N. Nesis, “Pathways and Time of Formation of Dis�junctive Range of Amphiboreal Species of MarineBenthic Animals,” Okeanologiya 1 (5), 893–903(1961).

35. K. N. Nesis, “Hypothesis on the Cause of Origin ofWestern and Eastern Arctic Ranges of Marine BenthicAnimals,” Biol. Morya 5, 3–13 (1983).

36. K. N. Nesis, “Cephalopods of the Arctic Ocean and ItsSeas,” in Fauna and Distribution of Mollusks: TheNorthern Pacific Region and the Polar Basin (DVNTSAkad. Nauk SSSR, Vladivostok, 1987), pp. 115–136[in Russian].

37. K. N. Nesis, “What Can Tell the Geographic Distribu�tion of Modern Cephalopods abount Their Plio–Pleis�tocene Migrations?,” in General Problems of MarineBiogeography: In Memory of Academician O.G. Kusakin(Dal’nauka, Vladivostok, 2004), pp. 112–131 [in Rus�sian].

38. V. V. Petryashev, “Mysids (Crustacea, Mysidacea) ofthe Eurasian Sub�basin of the Arctic Basin and Adja�



cent Seas (Barents, Kara, and Laptev),” Issled. FaunyMorei 54 (62), 124–145 (2004).

39. V. N. Semenov, “Zoobenthos: General Information,”in Life and Conditions of Its Existence in the Benthic Zoneof the Laptev Sea (Murmansk. Morsk. Biol. Inst., Apa�tity, 1986), pp. 67–79 [in Russian].

40. B. I. Sirenko, “On the Study of the Fauna of the LaptevSea and Adjacent Water Areas,” Issled. Fauny Morei 54(62), 5–8 (2004).

41. A. V. Smirnov and I. S. Smirnov, “Echinoderms of theLaptev Sea,” Issled. Fauny Morei 37, 411–462 (1990).

42. A. V. Smirnov and I. S. Smirnov, “Echinoderms of theEast Siberian Sea,” Issled. Fauny Morei 49 (57), 131–182 (1994).

43. A. V. Smirnov and I. S. Smirnov, “New Findings ofEchinoderms in the Laptev Sea (on the Basis of Mate�rials of Expeditions of 1993–1998),” Issled. FaunyMorei 56 (64), 93–147 (2006).

44. V. N. Stepanov, “On the Fate of Sannikov Land, BungeLand, and Novosibirsk Archipelago,” Problemy Ark�tiki, No. 1, 19–34 (1948).

45. O. V. Suzdal’skii, Paleogeography of Arctic Seas of theSSSR in Neogene and Pleistocene (Nauka, Leningrad,1976) [in Russian].

46. P. V. Ushakov, “Chukchi Sea and Its Benthic Fauna,” inExtreme North�East of the USSR (Akad. Nauk SSSR,Moscow, 1952), Vol. 2, pp. 3–78 [in Russian].

47. J. A. Addison and M. W. Hart, Colonization, Dispersal,and Hybridization Influence Phylogeography of NorthAtlantic Sea Urchins (Strongylocentrotus droebahien�sis), Evolution 59 (3), 532–543 (2005).

48. N. A. Anisimova, “Distribution Patterns of Echino�derms in the Eurasian Sector of the Arctic Ocean,” inThe Arctic Seas (Van Nostrand Reinhold Co., NewYork, 1989), pp. 281–301.

49. E. G. Atkinson and J. W. Wacasey, “Benthic Inverte�brates Collected from Hudson Bay, Canada, 1953 to1965,” Canadian Data Report of Fisheries and AquaticSciences 745, 1–132 (1989a).

50. E. G. Atkinson and J. W. Wacasey, “Benthic Inverte�brates Collected from the Western Canadian Arctic,1951 to 1985,” Canadian Data Report of Fisheries andAquatic Sciences 744, 1–121 (1989b).

51. J. C. Briggs, Marine Zoogeography (McGraw Hill Co.,New York, 1974).

52. H. Broch, “Oktocorallen des Nördlichhsten Pazifis�chen Ozeans und Ihre Beziehungen zur AtlantischenFauna,” Avhandl. Norske Videnskap Akademi(Matematisk�Naturvidenscabelig Klasse, Oslo, 1935),Vol. 1, pp. 1–53.

53. A. M. Clark, “An Index of Names of Recent Asteroidea.Part 1: Paxillosida and Notomyotida,” EchinodermStudies 3, 225–347 (1989).

54. A. M. Clark, “An Index of Names of Recent Asteroidea.Part 2: Valvatida,” Echinoderm Studies 4, 187–366(1993).

55. A. M. Clark, “An Index of Names of Recent Asteroidea.Part 3: Velatida and Spinulosida,” Echinoderm Studies5, 183–250 (1996).

56. A. M. Clark and C. Mah, “An Index of Names ofRecent Asteroidea. Part 4: Forcipulatida and Bris�ingida,” Echinoderm Studies 6, 229–347 (2001).

57. J. J. Dodson, S. Tremblay, F. Colombani, et al., “Trans�Arctic Dispersal and the Evolution of a CircumpolarMarine Fish Species Complex, the Capelin (Mallotusvillosus),” Mol. Ecol. 16 (23), 5030–5043 (2007).

58. J. W. Durham and F. S. MacNeil, “Cenozoic Migra�tions of Marine Invertebrates through the Bering StraitRegion,” in The Bering Land Bridge (Stanford Univ.Press, Stanford, California, 1967), pp. 326–349.

59. S. Ekman, Zoogeography of the Sea (Sidgwick and Jack�son, London, 1953).

60. V. V. Fedyakov and A. D. Naumov, “Marine Bivalvia ofthe Arctic Ocean,” in The Arctic Seas (Van NostrandReinhold Co., New York, 1989), pp. 303–324.

61. Yu. B. Gladenkov, “Cenozoic Molluscan Assemblagesin Northern Regions of the Atlantic and PacificOceans,” Int. Geol. Rev. 21, 880–890 (1979).

62. A. N. Golikov and O. A. Skarlato, “Evolution of ArcticEcosystem during the Neogene Period,” in The ArcticSeas (Nostrand Reinhold Co., New York, 1989),pp. 257–279.

63. E. H. Grainger, “Sea Stars (Echinodermata: Asteroi�dea) of the Arctic North America,” Bull. Fish. Res.Board Canada 152, 1–70 (1966).

64. J. W. Hedgpeth, “Pycnogonida of North AmericanArctic,” J. Fish. Res. Board Canada 20 (5), 1315–1348(1963).

65. A. I. Kafanov, “Systematics of the Subfamily Clinocar�diinae Kafanov, 1975 (Bivalvia, Cardiidae),” Malaco�logia 19 (2), 297–328 (1980).

66. I. Lubinsky, “Marine Bivalve Mollusks of the CanadianCentral and Eastern Arctic: Faunal Composition andZoogeography,” Can. Bull. Fish. Aq. Sci. 2107, 1–111(1980).

67. E. MacPherson, “The Marine Mollusks of Arctic Can�ada: Prosobranch Gastropods, Chitons and Scapho�pods,” Nat. Mus. Can. Pub. Biol. Oceanogr. 3, 1–149(1971).

68. L. Marincovich and A. Y. Gladenkov, “New Evidencefor the Age of Bering Strait,” Quatern. Sci. Rev. 20,329–335 (2001).

69. R. Nikula, P. Strelkov, and R. Välnölä, “Diversity andTrans�Arctic Invasion History of MtDNA Lineages inthe North Atlantic Macoma Balthica Complex(Bivalvia: Tellinidae),” Evolution 61, 928–941 (2007).

70. S. R. Palumbi and B. D. Kessing, “Population Biologyof the Trans�Arctic Exchange: Mitochondrial DNASequence Similarity between Pacific and Atlantic SeaUrchins,” Evolution 45, 1790–1805 (1991).

71. H. Ringvold and J. Dtien, “Biochemical Differentia�tion of Two Groups within the Species�Complex Hen�ricia Gray, 1840 (Echinodermata, Asteroidea) usingStarch–Gel Electrophoresis,” Hydrobiologia, 459,57–59(2001).

72. A. V. Smirnov, “Arctic Echinoderms: Composition,Distribution and History of the Fauna,” in Echinodermsthrough Time (A.A. Balkema, Rotterdam, 1994),pp. 135–142.

73. A. V. Smirnov and I. S. Smirnov, “Echinodermata,”Explor. Fauna Seas 51 (59), 122–125 (2001).

74. T. Soot�Ryen, “Pelecypoda with a Discussion of Possi�ble Migrations of Arctic Pelecypods in Tertiary Times,”in Norwegian North Polar Expedition with the “Maud”,1918–1925, Sci. Res. 5 (15), 1–35 (1932).

75. G. J. Vermeij, “Anatomy of an Invasion: The Trans�Arctic Interchange,” Paleobiology 17, 281–307 (1991).

76. J. P. Wares, “Biogeography of Asterias: North AtlanticClimate Change and Speciation,” Biol. Bull. 201, 95–103 (2001).

effect of the east siberian barrier on the echinoderm dispersal in the arctic ocean

Documents