Studies On Molecular Phylogeny Of Lower Euteleostean Fishes (Telestei: Euteleostei) And Processes In Shaping Spatial Patterns Of Species Diversity Of Schizothorax (Teleostei) And Hynobius (Amphibia)

Teleostean fishes (Teleostei) consist of ca.96% of the 28,000 reported fish species across the world. Teleostei could be further divided into Osteoglossomorpha, Elopomorpha, Ostarioclupeomorpha (= Otocephala) and Euteleostei. Euteleostean fishes (Euteleostei) is the most species-rich fish group of Teleostei with ca.17,500 species. Euteleostei include two subdivisions, i.e., Protacanthopterygii and Neoteleostei. Protacanthopterygii, also named as lower euteleostean fishes, includes four orders (sensu Nelson,2006), i.e., Salmoniformes, Esociformes, Argentiniformes and Osmeriformes. Phylogeny of lower euteleostean fishes is one of the long-debated scientific problems in ichthyological systematics. In this thesis, phylogenetic relationships of lower euteleostean fishes were reconstructed, using mitochondrial genomes and nuclear multiloci, to resolve three problems:i) phylogenetic position of the enigmatic lower euteleostean taxa Lepidogalaxiidae; ii) phylogenetic relationships among all orders of lower euteleostean fishes; iii) phylogenetic relationships of osmeriform fishes.In addition, the processes in shaping spatial patterns of species diversity are also studied in this thesis. Two works were carried out to reveal the underlying causes for elevational patterns and disjunctive distributional patterns in species diversity:i) an endemic fish group in the Tibetan Plateau and its adjacent regions, Schizothorax, is selected as a model taxa to reveal ecological and evolutionary drivers for elevational patterns of fish diversity based on the relationships between species richness and climatic factors, area, diversification rate or time of colonization; ii) an amphibian group in the East Asian margins, Hynobius, is selected as a model taxa to reveal the role of Cenozoic tectonic evolution within East Asian margins in shaping the 'continent-islands'disjunctive distributional pattern of Hynobius.The major results are as follows:1. Phylogenetic position of Lepidogalaxiidae based on mitogenetic evidencePhylogeny of lower euteleostean fishes was reconstructed using mitochondrial genomes. The results show:i) Lepidogalaxiidae that was previously placed in Osmeriformes occupies the basal position of Euteleostei, as the sister group of all the other euteleostean fishes; ii) Galaxiidae that was previously placed in Osmeriformes forms a monophyletic group, and the erection of a new order Galaxiiformes is suggested; iii) Osmeriformes is refined to include only Retropinnidae, Osmeridae, Salangidae and Plecoglossidae.2. Phylogenetic relationships among all orders of lower euteleostean fishe based on nuclear gene evidencePhylogeny of lower euteleostean fishes was reconstructed based on ten nuclear gene fragments. The results show:i) Alepocephaloidei that was previously placed in Argentiniformes is the sister group of Ostarioclupeomorpha, thus the erection of an order Alepocephaliformes based on mitogenomic evidences is supported; ii) the opinion that Lepidogalaxiidae occupies the basal position of Euteleostei revealed from mitogenomic evidence is supported, thus the erection of a new order Lepidogalaxiiformes is suggested; iii) the monophyletic clade consisting of Argentiformes, Salmoniformes and Esociformes, and the sister taxon relationship between Osmeriformes and Stomiiformes revealed from mitogenomic evidences are supported; iv) Galaxiiformes is revealed to be the sister group of Neoteleostei (minus Stomiiformes).3. Molecular phylogeny of OsmeriformesPhylogeny of osmeriform fishes was reconstructed based on nine nuclear gene fragments. The results show:i) Retropinnidae occupies the basal position of Osmeriformes; ii) Salangidae and Plecoglossidae are a sister taxon relationship, and they together form the sister group of Osmeridae; iii) within Osmeridae, Mallotus occupies the basal position; Osmenis and Spirinchns + Allosmerus + Thaleichthys clade are a sister taxon relationship, and they together form the sister group of Hypomesus; iv) the interrelationships of Salangidae revealed by previous works of our laboratory is confirmed, that Protosalanx and Neosalangichthys form the subfamily Protosalanginae, while Salanx, Leucosoma and Salangichthys form the subfamily Salanginae; v) within Retropinnidae, Prototroctes occupies the basal position; Retropinna is found to be paraphyletic that Stokellia anisodon is revealed to be the sister species of Retropinna retropinna.4. The underlying causes for elevational patterns of Schizothorax fishes The genus Schizothorax is selected as a model taxa to reveal ecological and evolutionary drivers for elevational patterns of fish diversity. The results show:i) species richness of Schizothorax fishes peaks at mid-elevation of 1700-2200m; ii) rainfall, mid-domain effect, area and diversification rate are weak predictors of species richness; iii) temperature and time of colonization are the most important variables in explaining the elevational pattern of species richness.5. The underlying causes for disjunctive distributional patterns of East Asian Hynobius salamandersThe amphibian genus Hynobius is selected as a model taxa to reveal the role of Cenozoic tectonic evolution within East Asian margins in shaping the'continent-islands'disjunctive distributional pattern of Hynobius. The results show:i) the extant Hynobius species originated in southwestern Japan and Hokkaido Island in the Early Eocene; ii) a sister taxon relationship between Hynobius retardaius and all remaining species was the results of a vicariance event between Hokkaido Island and southwestern Japan in the Middle Eocene; iii) ancestral Hynobius in southwestern Japan dispersed into the Taiwan Island, central China,'Korean Peninsula and northeastern China'as well as northeastern Honshu during the Late Eocene-Late Miocene.In summary, novel opinions on the phylogeny of lower euteleostean fishes are presented in this thesis on the basis of molecular evidence using mitogenomes and nuclear genes:i) Lepidogalaxiidae occupies the basal position of Euteleostei, and the erection of a new order Lepidogalaxiiformes is suggested; ii) Argentiformes, Salmoniformes and Esociformes form a monophyletic clade; iii) the refined Osmeriformes including Retropinnidae, Osmeridae, Salangidae and Plecoglossidae is the sister group of Stomiiformes; iv) a newly-erected order Galaxiiformes is the sister group of Neoteleostei. Moreover, interrelationships of Osmeriformes are revealed as follows:(Retropinnidae, (Osmeridae, (Salangidae, Plecoglossidae))). The findings from this thesis greatly improve understandings on the phylogeny of euteleostean fishes, which could further aid researches on the historical biogeography of euteleostean fishes.Meanwhile, two major results have been achieved based on studies on the underlying causes for spatial patterns of species diversity:i) this thesis firstly reveals the important roles of the time-for-speciation effect and niche conservatism in shaping elevational patterns of fish diversity; ii) this thesis firstly reveal the important role of the tectonic evolution within East Asia margins during Eocene and Miocene in shaping the'continent-islands'disjunctive distributional pattern of Hynobius salamanders. A geological hypothesis that part of the present-day Taiwan Island is a relict area of the Diaoyudao Uplift in the Late Eocene is supported. A biogeographical hypothesis,'out of southwestern Japan', is proposed here as a new opinion on explaining the dispersal of biota among Japan, Korea Peninsula, mainland China and Taiwan Island.