Population differentiation in the white-fronted chat (Epthianura albifrons) at a continental scale: implications for dispersal, biogeography and conservation

The capacity for dispersal is an important determinant of a species’ resilience to decline from the serial extinction of local populations. Dispersal of animals can be difficult to measure directly but population genetics provides a powerful tool for identifying dispersal limits. This study used microsatellite markers to investigate population structuring of the white-fronted chat (Epthianura albifrons) across its geographic range. Because the species is threatened in the north-eastern part of its range, the primary aim was to identify barriers limiting dispersal. Isolation by distance was not apparent across the 3000 km mainland range but populations on three oceanic islands, and two mainland sites surrounded by urbanisation, were genetically distinct from each other and the other mainland sites. The small populations that were surrounded by urbanised land had significantly lower genetic diversity (allelic diversity and heterozygosity) than the other mainland populations, with the oceanic island populations showing intermediate levels of diversity. These results suggest that although being a partially nomadic species, which facilitates its dispersal over continuous habitat, the species does not have the flight capacity of some other small passerines and is sensitive to habitat discontinuity. Populations inhabiting small areas of coastal saltmarsh in areas with large human populations are likely to face increasing threat levels.