Abstracts (first author)
The genomic landscape of speciation in the repeated adaptive radiations of Nicaraguan crater lake cichlid fishes
Understanding the factors that drive and constrain populations to build up reproductive barriers and diverge is a key objective in evolutionary biology. Based on the framework of ecological speciation, next-generation-sequencing tools allow researchers today to investigate the dynamics of divergent selection and gene flow at a genomic level. Although this endeavor has been very fruitful for our understanding of speciation, no generalities have emerged so far and more empirical data from different taxonomic groups and ecological settings are needed. One of the main questions, for example, concerns the importance of the temporal succession of restricted genomic islands of divergence (divergence hitchhiking) versus a genome-wide progression of divergence (genome hitchhiking). Having colonized several isolated crater lakes from the same source population, Midas cichlid fishes (Amphilophus cf. citrinellus) in Nicaragua have diverged into convergent ecotypes recently, repeatedly, and in sympatry; features that make this an interesting setting for studying the genomics of ecological speciation. Furthermore, the partly repeated and probably still ongoing radiations are at different stages of divergence, which makes this system one of the rare cases to investigate the temporal succession of this process. Here we investigate genomic divergence in the entire Midas cichlid species complex using double-digest restriction-site-associated-DNA sequencing (ddRAD-seq). With 700 individuals our data set covers the whole currently known diversity of the species complex and allows for a multitude of meaningful population genomic comparisons. By mapping the thousands of generated RAD loci on a preliminary Midas cichlid genome assembly, we are able to address questions concerning the genomic landscape of repeated but differently progressed speciation events and provide candidate regions that might harbor the genetic basis of adaptation and speciation in the Midas species cichlid complex.