Data from: Genetic analyses reveal hybridization but no hybrid swarm in one of the world's rarest birds

Abstract: Hybridization facilitated by human activities has dramatically
altered the evolutionary trajectories of threatened taxa around the globe.
Whereas introduced mammalian predators and widespread habitat loss and
degradation clearly imperil the recovery and survival of the New Zealand
endemic black stilt or kakī (Himantopus novaezelandiae), the risk
associated with hybridization between this critically endangered endemic
and its self-introduced congener, the pied stilt or poaka (H. himantopus
leucocephalus) is less clear. Here we combine Bayesian admixture analyses
of microsatellite data with mitochondrial DNA sequence data to assess the
levels of hybridization and introgression between kakī and poaka. We show
that birds classified as hybrids on the basis of adult plumage are indeed
of hybrid origin and that hybridisation between kakī and poaka is both
extensive and bidirectional. Despite this, we found almost no evidence for
introgression from poaka to kakī, thus negating a popular belief that kakī
represent a hybrid swarm. To our knowledge, ours represents the first
comprehensive study to document a lack of widespread introgression for a
species at risk despite a recent history of extensive bidirectional
human-induced hybridization. We attribute this rather surprising result,
in part, to reduced reproductive success in female hybrids combined with a
transient male-biased kakī sex ratio. To maximize the evolutionary
potential of kakī, we use these data to recommend conservation management
activities aimed to maintain the genetic integrity and to maximize the
genetic diversity of this iconic rare bird.