Study Of Mechanism Of Diversification Pattern Of Ostariophysi

The Ostariophysi which include 1287 genera,about 10022 species,and belongs to Clupeocephala.The Ostariophysi occupy about 68% of the freshwater species.They are distributed in all continents and major land masses except Antarctica.Ostariophysi,be thought an excellent biogeographic model with a large population and widely distributed,are predominantly freshwater – inhabiting species.They have been interest for biogeographers for many years.There have been many studies on this group in recent years.Yet,many controversy exist as to the historical biogeography and origin of the Ostariophysi.How do Ostariophysi have been migrated across oceans forming the current distribution? So,we readdress the question of the biogeography of the Ostariophysi,providing a comprehensive phylogenetic relationships based on taxon-rich dataset(13 protein-coding gene from mitochondrial genes,761 taxa).we then estimate the divergence time of Ostariophysi and reconstruction the historical biogeography.Finally,we providing a more comprehensive understanding of diversification patten of Ostariophysi.1.The Phylogenetic relationships of OstariophysiWe downloaded 761 fish mitochondrial gene sequences from the web GeneBank.All sequences were used to perform comprehensive molecular Phylogenetic analyses to study the higher-level Phylogenetic relationships of Ostariophysi.We used Bayesian inference and maximu likelihood methodsto constructingthe Phylogenetic trees of Ostariophysi.Our results show that(1)the Otophysans were recovered as monophyletic.The internal Phylogenetic relationships of Otophysans is(((Characiformes,Gymnotiformes),Siluriformes),Cypriniformes).(2)The Gymnotiformes,Siluriformes and Cypriniformes were monophyletic independent.However Characiformes is a non-monophyletic group,it has two clades-Citharinoidei and Characoidei.The group Citharinoidei was placed as the sister group of Gymnotiformes,and the clade(Citharinoidei + Gymnotiformes)as the sister group of the Characoidei group.(3)The Gonorynchiformes was placed as a sister group of Clupeiformes.The Gonorynchiformes also was recovered as a sister group of Otophysans.2.Divergence time estimates and historical biogeography of OstariophysiTo calibrate our chronogram we selected thirteen fossils from the ray-finned fish fossil record.Divergence time and their 95% credibility intervals were simultaneously inferred using Bayesian method implementing by BEAST.Our results show that the divergence time of Citharinoidei and Gymnotiformes was 95.34 Ma.The origin of Gymnotiformes is placed at 76.99 Ma.The divergence time of Characoidei group was 97.58 Ma.Our estimates for timing of Gonorynchiformes,Clupeiformes,Siluriformes,Cypriniformesdivergences,103 Ma,110.67 Ma,103.41 Ma and 112.26 Ma;The biogeographic analyses were implemented by using BioGeo BEARS in R.We compared the Bayarelike and Bayarelike+J models to determine the influence of founder event dispersal on biogeographic patterns.The AIC criterion selected the Bayarelike+J model as the best-fitting model.Our results suggest that the Ostariophysi origined in the Pangaea period.The ancestor of Characiformes originated in South America.Some species of Citharinoideigroup migrated to Asia.The Siluriformes originated in South America about Cretaceous period(103.41 Ma).An ancestral species of Siluriformes may have had to spread through Africa in order to reach Asia.Cypriniformes originated in Asia at the early Cretaceous period(112.26 Ma).And then minnows spread from Asia to Africa.The Ostariophysi's migrations may have take place in the Cretaceous,when the Pangaea continents begin to separate but with some contact on each continents.Their existing distribution pattern have some connected with the continents drifting.3.Diversification tempo of OstariophysiWe used the packages TreeSim and GeiGer to assess the diversification pattern of Ostariophysi.To examine the diversification rate change over time,semilogarithmic LTT plots were constructed in Treesim.The confidence intervals of the LTT plots were generated on 1000 trees sampled from the converged BEAST trees.Our result show that the diversification pattern rising with time.We used MEDUSA(Modeling Evolutionary Diversification Using Stepwise AIC)to investigate the tempo of diversification of the Ostariophysi.The MEDUSA analysis was conducted in R using the packages GeiGer with the default setting,including the AIC criterion and mixed model.We estimated the whole group diversification rate to be 0.026 lineages per million years(0.026 lineages/Ma).The diversification rate of Some Cypriniformes group is 0.029 lineages/Ma.The highest diversification rate is cyprinus(0.399 lineages/Ma).The diversification rate of bagridae is 0.062 lineages/Ma.