Population genomics of the pink pigeon (Nesoenas mayeri). RAD-seq Nesoenas mayeri

In this study we demonstrate using the pink pigeon (Nesoenas mayeri), that ignoring genetic data during the Red List assessment can lead to an underestimation of the extinction risk. In 1990, the pink pigeon free-living population consisted of approximately ten individuals. Prior to this bottleneck, 12 individuals had been collected to establish a captive breeding population in a wildlife sanctuary in Mauritius. From the late 1980s onwards, captive-bred individuals from this sanctuary have been released into the free-living population in a demographic rescue programme, resulting in a near-stable population of around 400 individuals between 2000 and 2020. Consequently, the species has been down-listed twice, from ‘Critically Endangered’ to ‘Endangered’ in 2000, and from ‘Endangered’ to ‘Vulnerable’ in 2018. However, analysis of RAD-sequencing and microsatellite data demonstrates genetic variation continues to decline rapidly. Quantitative genetic analysis of fitness and pedigree studbook data from zoo populations in Europe and America reveals the species carries a high genetic load of circa 15 lethal equivalents for this trait in captivity. This results in significant inbreeding depression, that with continued inbreeding, is likely to result in extinction in the wild within the next 100 years. Computer simulations show demographic rescue has been instrumental in the recovery of the free-living population, and that genetic rescue with captive-bred birds from zoos can recover some lost variation, reduce the genetic load, and prevent extinction. The pink pigeon requires continued conservation management, and its still-precarious conservation status is not appropriately captured by the current Red List assessment. Where relevant data is available, we propose introducing an addendum to the Red List assessment to reflect the status of a species’ gene pool and the severity of genomic erosion.