Black-fronted terns (Chlidonias albostriatus) are nationally and internationally classified as Endangered and only breed in the braided rivers of the South Island, New Zealand. They are in strong decline due to a multitude of threats, predominantly predation as well as ongoing habitat degradation and loss. There is an urgent need to manage black-fronted tern populations and reverse the current population trends. Critical information about the species’ biology, particularly the connection of breeding colonies within and between catchments, is however currently lacking. The aim of this research is to fill this gap by assessing the current connectivity between black-fronted tern breeding colonies and characterise the level of genetic diversity within and between them.
We collected DNA of 422 black-fronted terns covering 31 breeding colonies spanning their entire breeding range. Genetically distinct populations were inferred using spatially and non-spatially explicit Bayesian clustering algorithms as well as applying a Discriminant Analysis of Principal Components using 17 microsatellite markers. To complement this, we undertook a phylogeographic analysis using mitochondrial sequence data.
We did not find any evidence for an isolation-by-distance pattern on a national scale and clustering and multivariate analyses indicate that genetic diversity within and connectivity between breeding populations is high, despite the strong population declines.
We recommend that black-fronted terns are managed as a single evolutionary significant unit (ESU) aiming at retaining the high genetic diversity and connectivity between breeding populations throughout the country.