Flycatchers’ genomes bring new insights into the genomic basis of evolution
How exactly do lineages diverge to the point that they can be considered separate species, and especially reach reproductive isolation, is still an ongoing question in evolutionary biology. Classical views of speciation hypothesize the existence of speciation genes, defined as loci contributing to reproductive isolation (Nosil and Schluter 2011). Although such loci have been clearly described in a few cases (Presgraves 2010), the mechanisms remain impossible to generalize. Two central issues remain unresolved: Whether genetic incompatibilities arise mostly through adaptive or neutral mutations; Whether these isolating mutations occur at specific loci in the genome. In a recent paper, Hans Ellegren and his colleagues at Uppsala University describe the new insights brought by the comparison of whole genome data from two sister species of Old World flycatchers. The collared flycatcher Ficedula albicollis and the pied flycatcher F. hypoleuca (fig. 1) have been separate species for about 2 millions years, and their reproductive isolation is still incomplete as they can produce fertile male hybrids (but infertile females). Consistently, gene flow is strongly reduced but not null between the two species. The researchers first established a map of the flycatcher genome by assembling short reads from a collared flycatcher and using the known …
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