The molecular evolution of the spiral-horned antelope (Mammalia: Tragelaphini)

[摘要] ENGLISH ABSTRACT:The evolutionary history of the African tribe Tragelaphini (spiral-horn antelope)is controversial. Past phylogenetic relationships among species were basedon morphology or limited fossil evidence and are in conflict with mitochondrialDNA sequencing studies that have been conducted more recently. Althoughthe group is distinguished from other African ungulates by the presence ofspirally-twisted horns, the nine recognized extant species differ considerablyin morphology, feeding habits and their habitat preference. The present studyaims to resolve the phylogenetic uncertainties of the Tragelaphini usingnuclear DNA sequence data derived from four independent DNA loci (MGF,PRKCl, SPTBN and THY). These data were combined with all previouslypublished DNA sequences to produce a molecular supermatrix comprisingapproximately 6000 characters. Both parsimony and model basedphylogenetic analyses of the nuclear DNA support the associations resultingfrom the analysis of mitochondrial genes. These findings suggest that themorphological characters previously used to delimit species within the groupare subject to convergent evolution. The molecular phylogeny presentedherein suggests that early members of Tragelaphini diverged from the otherbovids during the mid-Miocene approximately 15.7 million years beforepresent (MYBP). The common nyala (Tragelaphus enqest; and lesser kudu(Tragelaphus imberbis) representing the most basal species, separated fromthe other tragelaphids approximately 7.1 MYBP. This was subsequentlyfollowed by the radiation of those species adapted to a more tropicalenvironment and they include the mountain nyala (Tragelaphus buxtom),bongo (Tragelaphus euryceros), sitatunga (Tragelaphus spekel) andbushbuck (Tragelaphus scriptus), and the arid adapted clade comprising thegiant eland (Taurotragus derbianus), common eland (Taurotragus oryx) andgreater kudu (Tragelaphus strepsiceros). It is thought that this split occurredat the Miocene-Pliocene boundary approximately 5.4 MYBP. The timing ofevolutionary events within the tribe suggests climatic oscillations andsubsequent biotic shifts as the major driving forces underpinning speciation inthe tribe Tragalaphini.

[发布机构] Stellenbosch University