Molecular Phylogeny And Divergence Time Estimations Of Some Groups Of Ostariophysan Fishes (Teleostei: Ostariophysi)

The Ostariophysi, a clade including Anotophysi (i.e., Gonorynchiformes) and Otophysi, is the second largest superorder within Teleostei. The latter contains four orders: Cypriniformes, Characiformes, Siluriformes, and Gymnotiformes. Resolving the higher-level relationships among ostariophysan and related fishes will aid in resolving basal teleostean divergence and provide basis to historical biogeographic analysis of major freshwater fish groups. However, there are still existing gaps and controversies in phylogenetics and historical biogeography within this superorder. We chose four groups, from different levels, to investigate the molecular phylogeny and divergence time estimates. Accordingly, this dissertation is divided into four major parts. The main conclusions and hypotheses of the present study are as follows.1. U17 snoRNA is a member of the H/ACA box class of small nucleolar RNAs involved in ribosomal RNA (rRNA) maturation. We used direct PCR to isolate the rps7â…¥intron region hosting the f copy of U17 snoRNA coding sequence from 49 fishes, which include 42 ostariophysan species plus 7 outgroup species. In additon to 4 sequences retrieved from GenBank, 59 sequences were used to perform comprehensive molecular phylogenetic analyses to study the origin and higher-level phylogenetic relationships of the Ostariophysi. The competing ostariophysan topologies were tested by using the approximately unbiased test (AU test), the Kishino-Hasegawa test (KH test), and the Shimodaira-Hasegawa test (SH test). Divergence times of major ostariophysan clades were estimated using Bayesian molecular clock method based on...