Sympatric ecological speciation in freshwater fish.

In this research project we will investigate a putative case of ecological specialization in freshwater fishes that likely resulted in sympatric speciation. Sympatric ecological speciation-with-gene-flow is a recent and important question in evolutionary biology, and the processes involved are still unclear and debated. The two sister species to be analyzed live in the Italian peninsula; the most abundant species lives in rivers with flowing waters, while its sister species is endemic to a large lake and show several ecological and morphological traits suggesting an adaptive evolution to the lacustrine mode of life. To unravel the evolutionary history of the emergence of the new lacustrine species, our proposal has three objectives: (i) to finely characterize the phenotypic and ecological differences between the sister species; (ii) to infer the evolutionary history and phylogeography of the sister species and related species; and (iii) to perform genomic analyses to identify the genomic regions that are involved in the adaptive divergence of the lacustrine species. The first task will be achieved by collecting field data to better characterize the habitats and the spawning places, and by describing the diet differences of the two species. The second task will be approached by collecting representatives of the riverine species in central Italy and by performing phylogeographic and phylogenetic analyses. To address the third task, we will perform a RAD-sequencing (Restriction site associated DNA) experiment. The genomes of several representatives of the lacustrine species will be compared to the genomes of several representatives of the riverine species. This comparison will permit to reveal the genomic regions that show signatures of diverging and positive selection, most likely containing the genes that are involved in the adaptation to the lacustrine mode of life.

We anticipate that the results of this research proposal will lead to the description and the understanding of the genetic basis of an unambiguous case of sympatric speciation event by ecological specialization. Our results will bring a significant contribution to the field of speciation, population genomics and genomics of adaptation. It will also certainly improve our understanding of the continuum between micro- and macro-evolutionary processes.