The ability to scan genomes for barriers to gene flow in a quantitative framework is a major advance in evolutionary/population genomics. gIMble, the computational tool developed by the ModelGenomLand team has already been used to infer species barriers by several labs in a wide range of systems including flowering plant, ants and Drosophila. These analyses have made it possible to intersect inferences of barriers with other sources of information on species barriers (e.g. data on expression differences and incompatibilities). For example, the ModelGenomeLand team has shown that long-term barriers (acting over millions of generations) overlap with regions of reduced introgression in a hybrid zone (100s of generations, PLosGenetics). Previous attempts to demonstrate the congruence of barriers across timescales have so far largely yielded negative results.
While theoretical models have shown that inter-chromosomal rearrangements can act as triggers of speciation processes, our speciation genomic studies in Brenthis butterflies (published in MBE, G3 and MolEcol) are the first evidence that support a direct role for chromosomal fusions in speciation. Alex Macintosh, the PhD student leading this work has been awarded the International Birnstiel Prize for Doctoral Research in Molecular Life Sciences.
Another surprising result is the discovery of a new sex chromosome system in Melanargia Marbled White butterflies. Analyses led by RA Decroly have demonstrated that the decay of butterfly W chromosomes can be reversed through rare recombination in females and leads to plateaus of sex chromosome divergence (published in MBE).
Analyses of the speciation genomic data generated by the project are ongoing. A key next step is to understand how ‘leaky’ species barriers are, and to characterise the beneficial variation that continues to be shared between emerging species.
