Molecular Phylogeny And Biogeography Of Stegana (Diperta: Drosophilidae) From East China

Stegana Meigen,1830 is one of the most species-rich genera in the subfamily Steganinae,currently comprised a total of 247 described species.Most of which are distributed in East Asia.The evolutionary history of Stegana has attracted considerable attention of evolutionary biologists.However,phylogenetic relationships within Stegana were not well resolved in the previous studies because of insufficient sampling.A broad-scale molecular phylogenetic analysis of the Stegana from East Asia(167 species,including 56 undescribed species)was performed via the mitochondrial and nuclear data.Based on the phylogenetic frame,the origin,diversification and dispersal of the Stegana from East Asia were discussed by the biogeographic analyses.In addition,species is the basic concept for understanding biodiversity.Biodiversity of the subgenus Oxyphortica was explored by the mitochondrial and nuclear data and molecular species delimitation result for species within the subgenus Oxyphortica by different approaches were assessed.The main findings are summarized as follows:(1)We obtained 150 samples of the subgenus Oxyphortica for molecular species delimitation using the mitochondrial markers(COI and ND2)and the nuclear markers(28S and CAD).MOTUs,molecular operational taxonomic units,identified by ABGD,b GMYC,b PTP approaches by COI or ND2 were mostly congruent with each other.However,some close relationship species could not be identified by these single locus approaches.By contrast,the multiple loci species delimitation approach,BP&P,received more reliable MOTUs.(2)A robust of Phylogeny of the Stegana was obtained and 5 major monophyletic clades with strong supports were recovered within the genus.The subgenura Oxyphortica and Orthostegana were both recovered as monophyletic group with strong support.A unique evolutionary lineage within the genus was recovered with two undescribed species,S.sp.21 and S.sp.22,from Southwest China.The subgenus Steganina was recovered as paraphyletic group.It was divided into two subclades,one clade comprising the ornatipes and nigrolimbtata groups and one species S.jianqinae,and the other comprising the rest of the Steganina.The former subclade of the subgenus Steganina gather with the subgenus Stegana in clade E.At species group level,our phylogeny indicated that the subgenus Oxyphortica was composed of six major monophyletic clades,including 4 unique evolutionary clades and 2 clades corresponding to the established species groups,the convergence and nigripennis groups.Within the subgenus Steganina,monophyly of the nigrolimbata,undulata,shirozui groups were all received great supports.However,monophyly of the biprotrusa,castanea,coleoptrata groups were not supported by our phylogeny.(3)Performance of the 9 genetic markers was evaluated by the phylogenetic informativness profiles.The ND2 displayed highest PI profiles from the species level to the subgeneric level.The other two mitochondrial fragments,COI and COII,showed the highest level of informativeness at the species level.In the PI profiles,CAD,atp A,HSPA4,TUBA1 and EF2 had low but relatively gentle slopes,suggesting these nuclear markers can provide informativeness for the phylogeny of Stegana from the species level to the subgenus level.(4)The biogeography analyses indicated that the ancestors of Stegana were distributed in Southwest China and began to diver at the late Oligocene.The subgenera arose from the late Oligocene to the early Miocene and most speciation events within Stegana were occurred from 10 Ma to 3 Ma(late Miocene to early Pliocene).The biodiversity pattern of Stegana in East Asia was the result of interaction between the tectonic movement between the India and Eurasian plates,and the climate change since the Oligocene.