Обзорные статьи Introduction This article was provoked by the article by I.Yu. Parnikoza, D.N. Maidanuk, and I.A. Koze retska [1] recently published in «Cytology and Ge УДК 74.9 : 574.91 (292.3) netics» (Kiev). We cannot completely agree with S.L. MOSYAKIN 1,L.G. BEZUSKO 1, A.S. MOSYAKIN 1,2 one of the main conclusions of the authors, who 1 M.G. Kholodny Institute of Botany, National Academy of Sciences postulated the Tertiary (Oligocene Pliocene) relict of Ukraine, 2 Tereshchenkivska Street, Kyiv, 01601 Ukraine status for both angiosperm taxa in Antarctica, and [email protected] because of that we provide here some additional 2 National University «KyivMohyla Academy», 2 H. Skovorody Street, information and comments on the topics consid Kyiv, 04070 Ukraine ered in the article by Parnikoza et al. ORIGINS OF NATIVE VASCULAR Due to the tremendous progress in and growing availability of molecular methods, the science of PLANTS OF ANTARCTICA: COMMENTS historical biogeography is now undergoing rapid FROM A HISTORICAL and dramatic transformation which can be regarded as a true «molecular revolution» [2–9]. In fact, PHYTOGEOGRAPHY VIEWPOINT instead of vague and non testable hypotheses and assumptions, we have now in many cases a solid evidence indicating possible centers of origin, migra tion pathways and timing of evolutionary radiations for many previously enigmatic biogeographical cases concerning many taxa of plants, animals, fungi, and even protists. It means that we see the transformation of a previously empirical field of science into a combination of real experimental and historical science, conclusions of which are falsifiable in the true scientific, Popperian sense. Molecular phylogeographic, phylogenetic, and populational genetic approaches proved to be the The article provides an overview of the problem of origin most productive ones in reconstructing the history of the only native vascular plants of Antarctica, Deschampsia and development of geographical patterns in plants. antartica (Poaceae) and Colobanthus quitensis (Caryophy The most interesting examples bearing concep llaceae), from the viewpoint of modern historical phytogeog tual implications to our topic are, in our opinion, raphy and related fields of science. Some authors suggested recent results obtained in biogeography in the the Tertiary relict status of these plants in Antarctica, while fields of studying of classical vicariance and/or dis others favour their recent Holocene immigration. Direct data persal models, island biogeography (especially cases (fossil or molecular genetic ones) for solving this controversy is of dispersal to and evolution on oceanic islands), still lacking. However, there is no convincing evidence sup porting the Tertiary relict status of these plants in Antarctica. nothal biogeographical links (especially various ex Most probably D. antarctica and C. quitensis migrated to planations of nothal disjunctions), Late Pleistoce Antarctica in the Holocene or Late Pleistocene (last inter ne and Holocene history of the Arctic and boreal glacial?) through bird aided long distance dispersal. It biota (especially studies using combined methods should be critically tested by (1) appropriate methods of of phylogeography and paleobiology), and some molecular phylogeography, (2) molecular clock methods, if others, which we cannot discuss here in detail be feasible, (3) direct paleobotanical studies, (4) paleoclimatic cause of space and time limitations. reconstructions, and (5) comparison with cases of taxa with Of course, it is impossible to cover sufficiently similar distribution/dispersal patterns. The problem of the ori in the present article the vast scientific areas men gin of Antarctic vascular plants is a perfect model for integra tion of modern methods of molecular phylogeography and tioned above. However, we will provide here some phylogenetics, population biology, paleobiology and paleo general ideas, striking examples, references to sev geography for solving a long standing enigma of historical eral most important and useful review articles, plant geography and evolution. and, finally, our comments regarding the current concepts of the origins of Antarctic vascular plants, © S.L. MOSYAKIN,L.G. BEZUSKO, A.S. MOSYAKIN, 2007 including the interesting concept proposed by
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Parnikoza et al. [1]. Our brief review is by necessity However, recently the vicariance models, espe a broad stroke picture in which we cannot go into cially those appealing and referring to Gondwanan too much detail of the discussed extensive issues. biotic interactions, fell out of fashion for several However, we believe that interested readers will reasons, which will be briefly discussed below using consult the references we cite here and get a wider several case topics. and deeper vision of the important biogeographical Insular endemics and longdistance dispersal. A and evolutionary problems, which are being suc flow of recent molecular phylogenetic and phylo cessfully solved with the aid of methods of molecu geographic studies of insular floras and faunas indi lar ecology, phylogeography, population genetics, cated in many cases long distance migration path and other modern approaches. ways and showed that suggestions of the relict sta tus and ancient age of many oceanic endemics are Results and discussion often far from being justified [2, 15–20]. It is espe Dispersal and vicariance models in phytogeogra cially true for remote oceanic islands and archipel phy. First of all, it should be emphasized that mod agos that have never been part of any continent ern historical biogeography is, by definition, a his and, consequently, are not suitable for vicariance torical and evolutionary science [3, 5]. It means that biogeographical models. reconstruction of historical traits in dispersal and The Hawaii is probably the best studied archi distribution of organisms is impossible without ta pelago in that respect [21–25]. Some evolutionary king into consideration the evolutionary processes links of endemic Hawaiian plants explained by occurring in space and time. Non evolutionary his long distance dispersal are truly amazing. For exa torical biogeography is thus a conceptual nonsense. mple, the endemic Hawaiian woody species of vio Vicariance models imply gradual migrations lets (Viola sect. Nosphinium, family Violaceae) from the centers of origin and further changes of which were considered evolutionary «primitive» in ancestral ranges, with their subsequent splitting in fact evolved quite recently (probably in the Middle most cases of disjunction. Classical examples of Pliocene) from the subarctic amphi Beringian vicariance models are explanations of present day ancestors probably related to the modern herba distribution patterns by past continental movements ceous species of the polyploid V. langsdorffii Ledeb. (mobilism, or modern plate tectonics), orogenesis, aggregate through a long distance dispersal by birds transgressions and regressions of seas, shifts of physi from Alaska or East Siberia and subsequent explo ographic, climatic and biotic zones, etc. sive radiation [21]. We can mention also the African On the other hand, dispersal models imply gra links of Hawaiian Hesperomannia A. Gray (Astera dual or geologically momentary dispersal events, ceae) [23] and the origin of a morphologically during which organisms or their dispersal units diverse group of several Hawaiian endemic genera migrate over some physical barriers and become of Lamiaceae (Haplostachys Hillebr., Phyllostegia successfully established in a new territory, and such Benth. and Stenogyne Benth.) from North Ameri migrations are naturally accompanied and followed can taxa of Stachys L. sensu lato [24]. Other striking by evolutionary transformations. examples indicating North American, South Paci Vicariance based models were especially fashio fic, African and Asian sources of recent colonization nable after the triumph of the Wegenerian mobilis of the Hawaii are extensively discussed in recent tic theory and further development of the modern literature [17, 22, 25]. theory of global plate tectonics. However, vicarian It is especially important to stress that the ce was also a respected concept even long before Hawaiian Islands are in fact a volcanic «conveyor that. If we consider enigmatic distribution patterns belt» in the Pacific, with a chain of volcanic islands of many plants in the Southern Hemisphere, this emerging as the crust plates move over the mag concept can be traced back to works of J.D. Hoo matic «hot spots» in the mantle [22]. It means that ker. In more detail these models and explanations the islands themselves are comparatively young, are discussed in several review articles [4, 5, and they are arranged linearly according to their 10–14] and references therein, which are recom age, from the oldest northwestern islands (e.g., mended to the reader for further acquaintance with Kauai) having ca. 5.1 million years of history to the problem. the youngest southeastern islands (like the island
ISSN 0564–3783. Цитология и генетика. 2007. № 5 55 S.L. Mosyakin, L.G. Bezusko, A.S. Mosyakin of Hawaii itself) just ca. 430 thousand years old long distant dispersal phenomena [11, 14, 15, 29]. [22, 25]. Yet this geologically young archipelago For further discussion see also reviews by Eskov in houses a tremendous biotic diversity, with many Russian [12, 13] and Mosyakin in Ukrainian [5] unique endemic taxa of high taxonomic ranks that and references therein. evolved during just a few millions of years. It is The changing views on the history (or histories) commonly agreed that the Hawaiian biota is in fact of the Nothal floras were reflected also in the recent a long distance dispersal biota [16, 25]. proposal to modify the system of Takhtajan’s floral In respect to the problem of the initial arrival of kingdoms [30]. In particular, Cox [31] proposed to D. antarctica and C. quitensis to Antarctica, the abandon the Antarctic Floral Kingdom and allo examples of oceanic island biotas and colonization cate its constituent parts to the neighboring king of such islands from migration sources located doms. Cox justly indicated that «The Antarctic flo thousands of kilometers away show us that the ral Kingdom contains some (but not all) of the Drake Passage (ca. 900 km) cannot be regarded as remains of a once continuous southern Gondwa an ultimate barrier for eventual long distance na cool temperate flora, now scattered into a relict migrations from southern South America to distribution by the processes of plate tectonics, and Maritime Antarctica, even considering such addi present only where the persistence of cool, moist tional obstacles as the Antarctic Polar Front and climates has allowed it to survive» [31]. We can add the Antarctic Circumpolar Current. Of course, the to that that some phytogeographic similarities of physical obstacles to migration of plants across the various parts of the Antarctic Kingdom are caused Drake Passage probably limited considerably the not only by plate tectonics events, but also, consid number of species that actually performed such erably, by long distance dispersal events. Conse random migrations. Another problem for migrants quently, the Chile Patagonian Region should be is to take a foothold in the new area and success allocated to the Neotropical Kingdom. The Fernan fully colonize the inhospitable Antarctic shores, dezian Region and the Region of the South Sub which was possible only to hardy plants preadapt antarctic islands should be also placed there ed to harsh environmental conditions. Thus, prob because of their long distance dispersal links to the ably much more species in fact migrated from time Neotropis. New Zealand and its surrounding is to time across the Drake Passage, but only two lands should be transferred to the Australian species happened to be preadapted to the new con Kingdom. ditions, which partly explains the scarcity of the Thus, appeals of Parnikoza et al. [1] to publica Antarctic angiosperm flora. tions emphasizing the high past biodiversity of Nothal floristic links: a legacy of Gondwana, Gondwana and its fragments in the Cretaceous migrations from the north, or longdistant dispersal and the Cenozoic has little or no implication to the phenomena? Recent studies convincingly demon question when and how modern Deschampsia and strated that many presumably Gondwanan groups Colobanthus migrated to Antarctica. We know that in fact attained their present distribution through Antarctica in the distant past was a much hospitable Laurasian migrations or/and long distance disper place than it is now; probably the great southern sal [11–14]. Even Nothofagus, the long cherished continent was the scene of evolution and migration icon of adepts of nothal vicariance models [26, of many important taxa now constituting the Not 27], probably experienced long distance dispersal hal biota [29, 32–34], but interpretations of these events in the course of its evolution [28]. However, data from the viewpoint of the modern biotic situa it does not mean that all Gondwana based histor tion should be done carefully. It should be also evi ical biogeographical explanations should be rejec dent that a find of a presumably caryophyllaceous ted. In fact, the Nothal biota of the Southern flower Caryophylloflora paleogenica G. J. Jord. & Hemisphere shows a complicated mix of different Macphail in the Middle to Upper Eocene of Tas biogeographical models and patterns: there we can mania [35], mentioned by Parnikoza et al. [1], has find examples of the real legacy of Gondwana (but nothing to do with the present day distribution of only in some ancient enough groups!), southward Colobanthus (Caryophyllaceae) in Antarctica. Mo migrations from the north (so called boreotropical reover, the taxonomic placement of that Eocene migrations), and numerous cases of transoceanic fossil in the family Caryophyllaceae sensu stricto is
56 ISSN 0564–3783. Цитология и генетика. 2007. № 5 Origins of native vascular plants of Antarctica: comments from a historical ... tentative; probably this ancient plant belonged to the southern continent was less isolated and its cli some group of caryophyllids in a wider sense. mate was more favorable for naturalization of these Late Pleistocene and Holocene history of the Arc taxa. Probably it was indeed less isolated and more tic and boreal biota. Arctic, subarctic and Alpine favorable, but how is it related to the actual time of plants are favorite models used in numerous mole immigration of the two species in question? In the cular phylogeography studies, especially in Euro Cretaceous Antarctica was even less isolated from pe. Reviews of these studies from the viewpoint of other Gondwana fragments and climatically more the problem of Pleistocene relicts and refugia and favorable than it was in the Oligocene Pliocene Holocene floral migration routes have been recen and, judging from molecular clock based and fos tly published in Ukrainian [6, 7]; many other sil calibrated age estimates, orders Caryophyllales recent review publications are useful for a better vi and Poales, and probably even phylogenetically sion of the Late Pleistocene and Holocene history basal representatives of the families Caryophy of the Arctic and boreal biota [4, 8, 9, 36–40]. llaceae and Poaceae, have differentiated already in Moreover, it has been shown that, contrary to the Late Cretaceous [10, 43, 44]. Should we becau simplistic views of exclusively gradual «step by se of that assume that Colobanthus and Descha step» dispersal of most plants [41], the real Late mpsia migrated to Antarctica already in the Late Pleistocene – Early Holocene recolonization of Cretaceous? Or probably in the Paleocene? Is glacial and periglacial areas of Eurasia and North there anybody voting for the Eocene? In the America by plants developed mostly according to Oligocene palms were growing in Ukraine, but it the long distance dispersal scenario [15]. At the does not necessarily mean that palms currently same time, hundreds of molecular phylogeography grown in Crimea are relicts and direct descendants studies and state of the art paleobotanical investi of those Ukrainian Oligocene palms. gations showed that the concept of the «glacial Sometimes researchers (usually except geolo steamroller» (or, better to say in this case, an «ice gists and paleontologists) have problems with feel roller»?) that exterminated nearly all life in glaciated ing the vastness of the geological timescale. It is and adjacent areas is also probably an exaggera simply nonsensical, from geological and paleobio tion. Thus, «tabula rasa» and «survival in situ» mo logical viewpoints, to guess as a migration age the dels are not mutually excluding; both these expla age limit covering about 32 million years, or nations work for some taxa and specific areas, de roughly a half of the whole Cenozoic [1]. The Early pending on many factors [4, 6, 7, 9, 37, 38, 40, 42]. Oligocene started ca. 34 million years ago (Mya), No surprise–life is much more diverse than our while the Pliocene Pleistocene boundary is cur mental models of it. rently placed at ca. 1.8 Mya [45]. By analogy, comparing the available biogeogra Moreover, it is hard (in fact, impossible) to phic cases of Arctic and Antarctic vascular plants, believe that Antarctic populations of both species, we can assume that (1) survival of Deschampsia and D. antarctica and C. quitensis, remained unchanged Colobanthus in Antarctica in situ since pre Pleis since the Oligocene, Miocene, or even Pliocene, tocene times has a very low probability, (2) their and developed no visible morphological or considera Holocene migration (or probably even several ble genetic distinctions from their relatives on the migration events) to Antarctica is the most feasible South American continent. That notion simply explanation, and (3) their survival in situ during denies evolution, adaptive or neutral. the Last Glacial Maximum (LGM) since one of Parnikoza et al. [1] properly cited the results of interglacials is less probable, but not excluded. Holderegger et al. [46], who found that Antarctic Origins of native vascular plants of Antarctica: populations of D. antarctica show low genetic still in the mist. Here we will try to show some faults diversity. That fact may have several explanations, in discussion of Parnikoza et al. [1] when they including the following most obvious ones: (1) attempt to prove the relict status of D. antarctica Antarctic D. antarctica and C. quitensis are recent and C. quitensis in Antarctica and to pinpoint the migrants that originated from limited founder age of their migrations. According to Parnikoza et stocks; the descendants of the founding popula al. [1], D. antarctica and C. quitensis migrated to tions simply had no time for genetic differentiation Antarctica «during the Oligocene Pliocene», when in Antarctica (the most parsimonious explanation,
ISSN 0564–3783. Цитология и генетика. 2007. № 5 57 S.L. Mosyakin, L.G. Bezusko, A.S. Mosyakin by the way); and (2) there is a constant gene flow ed due to high selective pressure of environmental and/or migrations between the isolated Antarctic conditions and/or random non selective cata island populations of D. antarctica and C. quitensis, strophic events, such as advance of glaciers, sea mixing their gene pools to the level of «low genet level oscillations, and extreme climatic episodes. A ic diversity» [46]. If these species are capable of reliable answer favoring any of these options can be self pollination and/or asexual reproduction (and obtained only through phylogenetic and phylogeo they are!), then the assumption of their long term graphic studies involving wide scale sampling of isolation in combination with a genetic «melting the species from all (or most of) known range frag pot» simply loses ground. ments in Antarctica and many representative sam Let us consider just two examples: Chenopodium ples from South America. tomentosum Thouars (Chenopodiaceae) [47] and Recent ITS analysis of C. quitensis demonstrated Rumex frutescens Thouars (Polygonaceae) [48, 49], a relatively high genetic similarity among the studied both endemic to remote South Atlantic islands of Andean and Antarctic populations (sequence diver the Tristan da Cunha (Tristan d’Acugna) group gence = 1.17 %) despite the considerable geogra (ca. 2800 km from Africa and ca. 3200 km from phical distance (> 3300 km) [51]. It should be also the South American mainland), both evidently noted that C. quitensis is a selfing species, which is resulted from recent and single long distance dis also capable of asexual reproduction. Of course, persal events, both having very close relatives in there was considerable ecotypic differentiation re South America (taxa of the Chenopodium ambro vealed, which should be expected in plants inhabit sioides L. aggregate in the first case, and Rumex ing so extreme and geographically isolated habitats cuneifolius Campderá and other representatives of differing considerably in local ecological conditions. the predominantly South American subsection Gianoli et al. [51] quite logically assume Andean Cuneifolii Rechinger f. in the second), but still dif origin of Antarctic populations of Colobanthus and fering from them to the species or at least sub its recent dispersal by migratory birds. Of course, species level. Why Antarctic plants do not differ, we agree with Parnikoza et al. [1] that the ITS specifically or at least subspecifically or varietally, region sequences are probably not good markers of from their South American conspecific relatives, if recent microevolutionary changes in Colobanthus, they parted several million years ago? and other methods should be applied instead of or Chwedorzewska [50], baseding on AFLP ana in addition to ITS phylogeny. However, before lysis, reported that genetic diversity within the obtaining new data it would be safer to stick to the Antarctic populations of D. antarctica was greater most parsimonious explanations. than respective genetic diversity values within the If, as we have seen above, less than 5 million analyzed Arctic populations of D. brevifolia R. Br. years was enough time in the Hawaii for evolution and D. alpina (L.) Roem. & Schult. sampled in of endemic genera and spectacular evolutionary Svalbard (Spitsbergen). Moreover, southern popu radiation of diverse species groups having in many lations of D. antarctica revealed less diversity than cases just one recent ancestor per group that ar northern populations living in less harsh condi rived by long distance dispersal, if very recent tions. These preliminary data can be interpreted in migrants from South America to the islands of several ways. As we have seen from other examples Tristan da Cunha were able to form distinct species (see above), low genetic diversity values within a differing from their South American relatives, then species in a particular area may indicate a recent why, if we assume the «Oligocene Pliocene» mig arrival of the species to that area and the founder ration of Deschampsia and Colobanthus to Antarc effect. On the other hand, in the case of D. antarc tica, these Antarctic plants developed no distinc tica even a high genetic diversity can be interpret tions from their South American ancestors? Of ed as either (1) in situ genetic differentiation in iso course, one may say that tropical islands are prob lated fragmented habitats and gradual but limited ably more stimulating for evolutionary changes dispersal «by step stones» or (2) a result of several than the harsh Antarctic environment is. However, independent long distance migration events. There numerous examples demonstrate that in fact an is also another option involving a bottleneck effect, escape from biotic competition enables dramatic when large portions of a population were eliminat island radiations, while abiotic environmental
58 ISSN 0564–3783. Цитология и генетика. 2007. № 5 Origins of native vascular plants of Antarctica: comments from a historical ... stress is the leading factor promoting such radia gestions on refugia of Antarctic vascular plants. tions. Consequently, the amazing evolutionary Large scale deglaciation in Antarctic coastal areas conservatism indirectly implied by the assumption started with a general warming trend after 8.4 ka of the «Oligocene Pliocene» origin of the two (thousand years ago). Before that many now ice Antarctic species is simply inexplicable. free Antarctic areas were glaciated [53–57]. It is A recent molecular study of phylogenetic rela evident from a multitude of sources that the global tionships of Deschampsia antarctica using ITS shed climatic history of the Late Pleistocene and Early little light to the problem. In the trees obtained by Holocene was rather complex. The warming trend Fernández Souto et al. [52] D. antarctica was of the last deglaciation was interrupted by the grouped with five other Deschampsia species, but Younger Dryas event that lasted for almost showed out in three different positions: (1) as a 1200 years (12.7–11.5 ka) and resulted in a reverse clade sister to all other Deschampsia species (ex to almost glacial conditions. A short cold event cluding D. flexuosa (L.) Trin.), (2) as a sister group occurred also around 8 ka. of D. cespitosa (L.) P. Beauv. – D. alpina (L.) Roem. For example, the deglaciation on South Georgia & Schult. – D. sukatschewii (Popl.) Roshev., and commenced prior to 18.6 ka; colder conditions (3) as sister to D. mejlandii C.E. Hubb. – D. christo returned after 14 ka and lasted during the Younger phersenii C.E. Hubb. In plain English it just means Dryas (12.7–11.5 ka) without significant changes, that the authors failed to pinpoint the phylogenet while the transition to postglacial conditions ic position of D. antarctica, probably because of occurred between 8.4 and 6.5 ka and was inter limitations of the methods or sequences used, or be rupted by a cold event that began ca. 7.8 ka and cause of inadequate taxon sampling. Fernández lasted for ca. 400 years [58]. It is highly improba Souto et al. [52] seem to be surprised by the ble that Deschampsia and Colobanthus survived revealed fact that «Deschampsia does not appear such dramatic events in situ without any response, monophyletic as D. flexuosa is not included in this e.g. reductions of their ranges. clade». It probably escaped their attention that D. We should also not forget about eustatic sea level flexuosa has been since long ago considered genef changes that reshaped and remodelled the coastal ically distinct from Deschampsia s. str. and trans Antarctic areas and their biotas [59] and, conse ferred into segregate genera, either Lerchenfeldia quently, influenced the potential and actual habi Schur (as L. flexuosa (L.) Schur) or Avenella Parl. tats of Deschampsia and Colobanthus; that makes (as A. flexuosa (L.) Drejer), and is currently treat their preservation in situ during diverse and dra ed taxonomically as a member of Avenella. This matic Pleistocene events even more improbable. little example shows that some experience in tradi However, a suggestion of survival of D. antarc tional taxonomy is not unneeded even for molecu tica and/or C. quitensis during the LGM is no lar taxonomic studies. heresy. It might well be the case that these two Fascinating finds of a rich (of course, rich by angiosperms indeed survived the LGM in Antarctic Antarctic standards) fossil Neogene flora of the islands, but it should be proved. In fact, the present Meyer Desert Formation (the biostratigraphic age climatic situation in Antarctica is rather unusual as less than 3.8 Ma, which means an Early Pliocene compared to most periods of the Pleistocene, cor or more recent age) in the Transantarctic Moun responding roughly to interglacial conditions [53, tains prove that continental Antarctic in the Late 57], especially if compared to the Last Glacial Neogene was more suitable for terrestrial life than Maximum, both in the Northern [60] and Southern most people expected [32]. However, this fact has [55, 59] hemispheres. Some range expansions of no bearing to proving the relict status of Colobanthus several Antarctic species southward were observed and Deschampsia in their present Antarctic ranges, recently; it is usually viewed as a response to glob as well as presence of broadleaf trees in boreal al warming, although other causes, like normal cli areas of Europe during interglacials does not nec matic oscillations, should be also considered. essarily mean that these trees survived in situ dur Anyway, the present day climatic conditions in ing glacial phases until the present day. Antarctica are much more favorable to plants than Glacial and climatic history of Antarctica should conditions there during the Last Glacial Maximum be also considered in detail before making any sug or other glacial maxima of the Pleistocene. Please
ISSN 0564–3783. Цитология и генетика. 2007. № 5 59 S.L. Mosyakin, L.G. Bezusko, A.S. Mosyakin note that D. antarctica and C. quitensis (the first Tertiary age and relict status of these plants in species being more widespread than the second) Antarctica. It might have been better to critically occupy now only a comparatively narrow northern assess an ample set of available evidence from clas strip of Maritime Antarctica, and these plants are sical historical biogeography, phylogeography, already living virtually on the brink of survival. paleobotany, paleoclimatology and some other These considerations make the ideas of in situ sur fields, not necessarily data regarding the two taxa vival of D. antarctica and C. quitensis in Antarctica and the territory considered, but also (and mainly) since the Paleogene or even since the Early Pleis comparative data regarding other taxa and other tocene rather problematic. areas with similar phytogeographical traits. Endemism and distribution patterns of various Judging from both direct and indirect evidence groups of plants and fungi (including lichens) occur and comparison with biogeographical analogues, ring in Antarctica indicate that the Pleistocene the most reasonable and consistent with facts sug survival was possible for some lichens, less proba gestion would be that of the Holocene or Late ble for mosses [61], and rather improbable for the Pleistocene (last interglacial?) age of migration of two considered species of vascular plants [see dis the ancestral stock of D. antarctica and C. quitensis cussion in 62]. That was already evident to biogeo to Antarctica through bird aided long distance dis graphers of the first half of the 20th century. For persal events. Thus, these species (or one of them) example, consider discussions in the classical are either Holocene migrants or, at best, relicts of books by Wulff [63, 64], who often favored vicari a recent intergalical. In the last case they probably ance based mobilistic historical explanations of survived the Last Glacial Maximum (LGM) in plant distribution patterns, but did not extend such coastal refugia in Maritime Antarctica or adjacent explanations to the two extant native species of islands. However, these age estimations should be Antarctic angiosperms. The reasons of the scarcity critically tested by (1) appropriate methods of of the vascular flora of Antarctica should be also molecular phylogeography involving extensively reconsidered from the viewpoint of both ecological sampled plants from Antarctica and South Ame and migrational factors. As Aleksandrova [65] cor rica, (2) molecular clock methods, if feasible, (3) rectly noted, the presence of just two species of direct paleobotanical (including paleopalynologi flowering plants in Antarctica cannot be explained cal) studies, (4) paleoclimatic reconstructions, and by extreme ecological factors only, because the (5) comparison with similar cases documented for ecological conditions for plants there are not worse taxa with similar distribution/dispersal patterns. On than, for example, on the Franz Josef Land in the ly in these directions lies the positive and reliable Russian Arctic. Consequently, we should consider answer to the long intriguing question of the ori such additional explanations as migrational obsta gins of D. antarctica and C. quitensis in Antarctica. cles and isolation of the region. The problem of the origin of Antarctic vascular Indeed, solid evidence would be definitely need plants is a perfect model for integration of modern ed for supporting the idea of the pre Pleistocene methods of molecular phylogeography and phylo age of Colobanthus and Deschampsia in Antarctica, genetics, population biology, paleobiology and but, as we see, no such evidence is available yet, paleogeography for solving the long standing enig while the bulk of both direct and indirect available ma of historical phytogeography. data discussed in the present article speak in favor of the Holocene or, at best, Late Pleistocene age of РЕЗЮМЕ. Дан обзор проблемы происхождения the present day Antarctic flowering plants. аборигенных сосудистых растений Антарктики Des champsia antartica (Poaceae) и Colobanthus quitensis Conclusions (Caryophyllaceae) с точки зрения исторической фито The suggestion of Parnikoza et al. [1] of an географии и родственных направлений науки. Неко торые авторы считают, что эти растения в Антарктике Oligocene Pliocene origin of Deschampsia antarc являются реликтами третичных времен, а другие ис tica Desv. and Colobanthus quitensis (Kunth) Bartl. следователи склоняются к концепции их недавней го is most probably a gross overestimation. No data in лоценовой миграции. Прямых данных (как ископае their article, either literature or original, give con мых, так и молекулярно генетических) для решения vincing evidence supporting their concept of the этой проблемы пока что не хватает. Тем не менее, нет
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убедительного подтверждения третичного реликтового tion of oceanic island plants // Molecular Systematics статуса этих растений в Антарктике. Вероятнее всего, of Plants, II: DNA Sequencing / Eds D.E. Soltis, P. D. antarctica и C. quitensis мигрировали в Антарктику в Soltis, J.J. Doyle. – New York : Kluwer Acad. Publ., голоцене или позднем плейстоцене путем расселения 1998. – P. 410–441. на дальние расстояния с помощью птиц. Эта концеп 3. Crisci J.V. The voice of historical biogeography // J. ция должна быть критически проверена с помощью Biogeogr. – 2001. – 28. – P. 157–168. соответствующих методов молекулярной филогеогра 4. Hewitt G.M. 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