Microsatellite variation and rare alleles in a bottlenecked Hawaiian Islands endemic: Implications for reintroductions

Abstract

Conservation of genetic biodiversity in endangered wildlife populations is an important challenge to address since the loss of alleles and genetic drift may influence future adaptability. Reintroduction aims to re-establish species to restored or protected ecosystems; however, moving a subset of individuals may result in loss of gene variants during the managementinduced bottleneck (i.e. translocation). The endangered Laysan teal Anas laysanensis was once widespread across the Hawaiian archipelago, but became isolated on Laysan Island (415ha) from the mid-1800s until 2004 when a translocation to Midway Atoll (596ha) was undertaken to reduce extinction risks. We compared genetic diversity and quantified variation at microsatellite loci sampled from 230 individuals from the wild populations at Laysan (1999 to 2009) and Midway (2007 to 2010; n=133 Laysan, n=96 Midway birds). We identified polymorphic markers by screening nuclear microsatellites (N=83). Low nuclear variation was detected, consistent with the species' insular isolation and historical bottleneck. Six of 83 microsatellites were polymorphic. We found limited but similar estimates of allelic richness (2.58 alleles per locus) and heterozygosity within populations. However, 2 rare alleles found in the Laysan source population were not present in Midway's reintroduced population, and a unique allele was discovered in an individual on Midway. Differentiation between island populations was low (F ST =0.6%), but statistically significant. Our results indicate that genetic drift had little effect on offspring generations 3 to 6yr postrelease and demonstrate the utility of using known founder events to help quantify genetic capture during translocations and to inform management decisions.