title: Different processes lead to similar patterns: a test of codivergence and the role of sea level and climate changes in shaping a southern temperate freshwater assemblage.
abstract: BACKGROUND
  Understanding how freshwater assemblages have been formed and maintained is a fundamental goal in evolutionary and ecological disciplines. Here we use a historical approach to test the hypothesis of codivergence in three clades of the Chilean freshwater species assemblage. Molecular studies of freshwater crabs (Aegla: Aeglidae: Anomura) and catfish (Trichomycterus arealatus: Trichomycteridae: Teleostei) exhibited similar levels of genetic divergences of mitochondrial lineages between species of crabs and phylogroups of the catfish, suggesting a shared evolutionary history among the three clades in this species assemblage.
  
  
  RESULTS
  A phylogeny was constructed for Trichomycterus areolatus under the following best-fit molecular models of evolution GTR + I + R, HKY + I, and HKY for cytochrome b, growth hormone, and rag 1 respectively. A GTR + I + R model provided the best fit for both 28S and mitochondrial loci and was used to construct both Aegla phylogenies. Three different diversification models were observed and the three groups arose during different time periods, from 2.25 to 5.05 million years ago (Ma). Cladogenesis within Trichomycterus areolatus was initiated roughly 2.25 Ma (Late Pliocene-Early Pleistocene) some 1.7-2.8 million years after the basal divergences observed in both Aegla clades. These results reject the hypothesis of codivergence.
  
  
  CONCLUSIONS
  The similar genetic distances between terminal sister-lineages observed in these select taxa from the freshwater Chilean species assemblage were formed by different processes occurring over the last ~5.0 Ma. Dramatic changes in historic sea levels documented in the region appear to have independently shaped the evolutionary history of each group. Our study illustrates the important role that history plays in shaping a species assemblage and argues against assuming similar patterns equal a shared evolutionary history.
authors: Evolutionary Ecology Laboratories, Department of Biology, Brigham Young University, Provo, UT 84602, USA. brbarber76@gmail.com
authors: Brian R
authors: BR
authors: Barber
authors: Peter J
authors: PJ
authors: Unmack
authors: Marcos
authors: M
authors: Pérez-Losada
authors: Jerald B
authors: JB
authors: Johnson
authors: Keith A
authors: KA
authors: Crandall
mesh_terms: D000818:Animals; D002397:Catfishes / Q000235:genetics*; D002677:Chile; D057231:Climate Change; D003445:Crustacea / Q000235:genetics*; D005618:Fresh Water; D049810:Genetic Speciation; D008957:Models, Genetic; D009792:Oceans and Seas; D010802:Phylogeny