Study On Phylogenetics And Biogeography Of Cave Fishes In Southern And Southwestern Of Guizhou

Guizhou is an inland province of Southwest China with typical karst landform,with its southern and southwestern parts being the ideal habitats and the center for many cavefish species to be born in and spread from.An abundant variety of species have been recorded:four genera,Sinocyclocheilus,Triplophysa,Oreonectes and Paracobitis,under two families,Cyprinidae and Nemacheilidae,of the order Cypriniformes.Comprehensive and accurate analyses about classification status and systematical relationship are used on Sinocyclocheilus,Triplophysa,Oreonectes.This study focused on the Sinocyclocheilus,Triplophysa and the endemic Oreonectes species of the Pearl River Basin in southern and southwestern Guizhou.Phylogenetic tree was constructed for these species from combined sequence data of Cytb,ND4 and ND5 genes.Divergence was estimated based on relaxed molecular clock hypothesis.Phylogenetic relationship,population evolution model,ancestral area reconstruction and historical distributed pattern were analyzed based on systematic geology,tectonic events and climate changes.In addition,Study on convergent evolution in cavefishes could solve some human congenital diseases in the future.Results are presented as follows:1.23 Cave-fish specimens were collected in southern and southwestern parts of Guizhou,with 9 from Sinocyclocheilus,9 from Triplophysa and 5 from Oreonectes identified on the basis of morphological and molecular systematic studies.Among these specimens,7 Sinocyclocheilus,4 Triplophysa and 2 Oreonectes individuals were not identified to known species.It is suggested that these species be described as new species and named after collecting locations except one specimen from genus Triplophysa.Species diversity of southern and southwestern Guizhou was clarified.The validation and independence for Guizhou concealed cavefish species were discovered and proved.2.The genus Sinocyclocheilus is polyphyletic,its ancestor diverged 6.39 Mya ago with both separation and diffusion.The genus Triplophysa is monophyletic,diverged from ancestors 24.86 Mya ago.The border between the ancient Yangtze river basin(ancient Jinsha drainage systems)and the ancient Pearl river basin(Beipanjiang drainage sys-tems)at the northwestern Wumeng Montain is the origin of cavefish and non-cave fish of Triplophysa mainly with diffusion evolution model.The genus Oreonectes is monophyletic,diverged from ancestors 31.67 Mya ago mainly with separation evolution model.3.Factors which led to the current distribution pattern of those cavefish were analyzed by molecular genetics approaches jointly with geographical knowledge,tectonic events and climatic changes.These factors include geological events as the rise of Qinghai-Tibet Plateau and Yunnan Plateau,the formations of Wumeng montain and Miao montain,Youjian tectonic construction and Guangxi Arch.Their effects on the formations of surface water and underground water systems were also explored.4.The analyses above indirectly reflect the development degree of karst landforms in the southern and the southwestern Guizhou,further verifying that these areas are appropriate habitats for cave organisms.A paradigm of fast speciation in extreme cave environment for small populations was discovered and elaborated.