BirdIslandGenomic: A genomic perspective on the evolution in small populations of island endemic birds – BirdIslandGenomic

Oceanic islands provide great opportunities for studying biological evolution. In this project, we propose to investigate island evolution from the genomic point-of-view. Understanding the influence of population size variation on molecular evolution is currently a major topic in the field. Since island species have evolved in isolated and small populations, they provide an unique opportunity to study the impact of non-adaptive forces on biological evolution.

Here we propose to gather a population genomic dataset composed of two island/mainland pairs of species, using endemic birds of Réunion Island and their mainland south-Africa relative as model organisms. Indeed, we are convinced that mainland/island comparison provide one of the best empirical set-up to study the impact of non-adaptive forces on genome evolution in natural population. Four completely sequenced genomes, eight transcriptomes and a genome-wide polymorphism obtained composed of fourty individuals will be used to unravel the influence of population size on the accumulation of deleterious mutations in the genome. The effect of population size variation will be evaluated in various classes of sites including protein-coding genes with synonymous sites and non-synonymous sites, flanking regions but also non-coding sites apparently under evolutionary constraint such as the so-called ultra-conserved elements and regulatories regions. Our goal will be to establish if different regions of the genome are differentially affected by the reduction of population size. To do that, other fundamental forces that affect molecular evolution will be taken into account. These are recombination rate that will be estimated thanks to other closely relate species and genes expression level, that will be estimated using transcriptome dara.

Next, the evolution of genome architecture (e.g., on genome size) will be compared between the mainland and the island species. According to recent theory, the evolution of genome architecture could also be influence by non-adaptive force such as genetic drift. So far, however, most of the empirical evidences come from comparison between distantly related species where difference in species biology could represents confounding factors. We argue that the mainland/island comparison provide an unique opportunity to study the micro-evolution of genome architecture and to test the importance of genetic drift in the emergence of genomic complexity. Finally, the very large and comprehensive datasets generate during this project will also be used to tackle two fundamental topics of evolutionary biology: i) the evolution of sex chromosomes and ii) the genomic of speciation.