Cultural traditions and the evolution of reproductive isolation: ecological speciation in killer whales?

Human evolution has clearly been shaped by gene–culture interactions, and there is growing evidence that similar processes act on populations of non-human animals as well. Recent theoretical studies have shown that culture can be an important evolutionary mechanism due to the ability of cultural traits to spread rapidly both vertically and horizontally, resulting in decreased within-group variance and increased between-group variance. Here, we collate the extensive literature on population divergence in killer whales (Orcinus orca) and argue that they are undergoing ecological speciation as a result of dietary specializations. While we cannot exclude the possibility that cultural divergence predates ecological divergence, we propose that cultural differences in the form of learned behaviors between ecologically-divergent killer whale populations have resulted in sufficient reproductive isolation in sympatry to lead to incipient speciation.