Genetic diversity and the implications of captive rearing for a small population of Black‐tailed Godwits

Headstarting is a captive rearing intervention where eggs are taken from the wild, artificially incubated and chicks are reared in captivity to fledging before being released into the wild. From an imperiled Black-tailed Godwit population in the UK, clutches have been collected for headstarting. While this conservation measure has reduced local extinction risk, it may have impacts on genetic diversity and population viability, especially when wild-sourced eggs must be collected from a small population. Here, we compare genetic diversity and relatedness of the UK population of 42 pairs with the much larger breeding population in the Netherlands (~30,000 pairs). We found that levels of heterozygosity and inbreeding are not currently compromised, but allelic richness in the UK population was 8.5% lower than in the Dutch population, and relatedness estimates suggest that 6.1% of the individuals in the UK population are closely related, at the level of half sibling and up, compared to 1.9% in the Dutch population.  Increasing levels of relatedness could in the future deplete genetic variation further in the absence of immigration or wild-sourced eggs from other populations.

Methods
Standard genotying at multiple microsatellite loci.