Population genetic connectivity of an endemic New Zealand passerine after large-scale local extirpations: a model of re-colonization potential

Little is known about how a 70% loss of native forests has affected the genetic connectivity of remnant bird populations in New Zealand. We use the common and widely distributed New Zealand Bellbird Anthornis melanura as an indicator species of population connectivity for well-flighted birds. Using eight microsatellite loci, we identified five main genetic populations in the North Island, South Island, sub-Antarctic Auckland Islands and two small remnant island populations adjacent to a large region of avian extirpations in northern North Island. Only one remnant island population, on a 30-year-old conservation reserve at Tiritiri Matangi, displayed a clear signature of recent genetic bottleneck. The 7% migration rate at Tiritiri Matangi indicates that bottlenecks can be maintained despite habitat rehabilitation, possibly through behavioural barriers to gene flow. Adjacent to the same extirpation zone, Bellbirds on the Poor Knights Islands were found to have low genetic diversity and low re-colonization potential. Two gaps concordant with deforestation patterns separated the Kapiti Coast of southern North Island from populations to both the north and the south. In summary, we identified linked avian habitats, as well as isolated and inbred populations and suggest that Bellbirds are good re-colonizers. We emphasize the importance of genetic studies that assess animal dispersal among newly rehabilitated habitat patches.