A systematic review of interspecific breeding in woodpeckers

Hybridization is a common phenomenon in birds. Woodpeckers (Picidae) are no exception, as approximately 20% of species are known to hybridize and, for many others, interspecific mating is suspected. However, the mechanisms and consequences (phenotypic and genetic) of hybridization are understood for only a fraction of woodpecker species. Here, we conduct a systematic review on the literature that deals with hybridization in woodpeckers and examine the available geographical and genetic data. According to the published data, most woodpeckers that hybridize inhabit the Neotropics, followed by the Nearctic and the Palaearctic. Hybridization appears to be less common in the Afrotropic and Indotropic regions. Indeed, it seems that the irregular distribution of woodpecker hybridization is determined by geo‐climatic constraints and is most likely biased by evolutionary history. As expected, hybrids are usually found among closely related congeneric pairs of species, although members of 60% of hybridizing woodpecker pairs do not seem to be closest relatives of each other. Closely related woodpeckers show similarities in their respective reproductive biology, ecology and ethology, and so had less time for genetic incompatibilities to build up. Hybridization plays a substantial role in woodpecker evolution and ecology; therefore, this phenomenon deserves further study using genomics and citizen science.