Evidence for adaptive introgression in plants

Natural interspecific hybridization has been observed in a diverse array of taxa [1-3], and the production of such hybrids can have a wide range of evolutionary consequences. For instance, natural hybridization can act as a ‘destructive’ force, resulting in the fusion of taxa that do not reveal strong reproductive isolation [1]. Alternatively, it can result in evolutionary novelty via the production of new reproductively isolated hybrid species [1-3], or by the transfer of potentially adaptive traits through a process known as introgressive hybridization. In a recent article in BMC Evolutionary Biology, Fitzpatrick et al. [4] tested for introgressive hybridization by performing a genome-wide scan of native salamander (Ambystoma californiense) populations, and identified genomic regions that have rapidly fixed alternative alleles derived from a recently intro duced, invasive species (Ambystoma mavortium). This rapid assimilation of non-native alleles suggests that selective processes were involved in their fixation.