S5.4 Jan. 5 Do Genome Duplications Play a Role in Key Transitions? WAGNER, G. P. *; CROW, K. ; LYNCH, V. ; Yale University; Yale University; Yale University email@example.com
A survey of gene duplications in early metazoan, vertebrate and plant phylogenies suggests an association between major transitions and gene duplication events. The evidence for a causal connection between genome duplication and major innovations and/or radiations, however, is weak on several grounds. First, evidence for an association between a genomic event and innovations or cladogenetic events is not strong, with a few exceptions including the origin of teleosts and the higher flowering plants. Second, major transitions can happen without genome duplications, like the origins of birds, and mammals. Third, genome duplications occur quite frequently in plants, fishes, and amphibians. Hence the apparent association between genome and gene duplications and major transitions could either be a perceptual artifact or caused by another mechanism than genome duplications causing innovations. We note that genome duplications, which coincide with an adaptive radiation may have a higher probability of leading to the permanent integration of paralog genes, than genome duplications, which are not associated with adaptive radiations. We propose that adaptive radiations may increase the chance for the retention of duplicated genes by adaptive processes which take advantage of the genetic material offered by the duplication event. Hence the chance that two paralogs can be traced back to a major radiation event is higher than by chance. We provide molecular evidence from Hox gene evolution that ancient paralogs tend to be differentiated by divergent selection immediately following the duplication event, while those paralogs which originated independent of a radiation tend to evolve under strong purifying selection, with little evidence of adaptive changes occurring after speciation events. Hence it may be that adaptive radiations drive the evolution of genome structure and not vice versa.