A single pleiotropic locus influences the rate of hybridisation between two sibling species of Lygaeus bugs

The evolution of reproductive isolation lies at the heart of understanding the process of speciation. Of particular interest is the relationship between pre- and post-zygotic reproductive isolation, and the genetic architecture of traits that contribute to one or both forms of reproductive isolation. The sibling species of seed bug Lygaeus equestris and L. simulans show a classic pattern of asymmetric pre-zygotic reproductive isolation, with female L. equestris hybridising with male L. simulans, but with no hybridisation in the reciprocal direction. We have recently described a mutant pale colour form of L. simulans, that inherits as a single Mendelian locus and is pleiotropic for a number of other life history and behavioural traits. Here we tested whether this locus also influences pre- and post-zygotic reproductive isolation. Two sets of experimental crosses revealed that behavioural isolation varied with mutant versus wild-type phenotype for male L. simulans, with the pale form less...