SINE挿入を指標とした系統解析によって明らかとなったヒゲクジラ類の系統関係と過去の急速な放散(<特集>生物イベントとしての哺乳類の海生適応)

概要

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Baleen whales (suborder Mysticeti) comprise eleven extant species that are classified into four families. Although several phylogenetic hypotheses about these taxa have been proposed, their phylogenetic relationships still remain confusing. SINE (short interspersed repetitive element) insertion data are now regarded as almost ideal shared derived characters at the molecular level, and we have applied this method to this problem. Here, we successfully reconstruct the phylogenetic relationships of these whales by characterizing 40 informative SINE loci. One of the intriguing conclusions is that balaenopterids and eschrichtiids radiated very rapidly during a very short evolutionary period. During this period, when newly inserted SINE loci retained ancestral polymorphisms, speciation occurred and these SINEs were sorted incompletely into each lineage, thus resulting in inconsistencies regarding the presence or absence of the SINE. This is in sharp contrast to the phylogeny of toothed whales, for which no SINE inconsistencies have been found. Furthermore, we found monophyletic groupings between humpback and fin whales, and also between (sei + Bryde's) and blue whales, both of which have not previously been recognized. The comprehensive SINE insertion data, together with the mitochondrial DNA phylogeny that was recently completed, provide a nearly complete picture of the evolutionary history of baleen whales.
2005-03-25