Temporal Genetic Diversity and Effective Population Size of the Reintroduced Aplomado Falcon (Falco femoralis) Population in Coastal South Texas

Abstract

Reintroductions are an important tool in conservation for preserving and enhancing biodiversity and preventing extinction, and post-release monitoring is essential to evaluate and inform conservation management and maximize recovery success. By quantifying genetic diversity levels and effective population size (Ne) over time, managers can gauge to what degree additional efforts are needed to increase the likelihood of population persistence. The endangered Northern Aplomado Falcon (Falco femoralis septentrionalis) population in South Texas was reestablished and supplemented with captive-bred individuals originating from 27 founders collected in eastern Mexico (San Luis Potosí, Veracruz, Tabasco, and Chiapas). A total of 927 Aplomado Falcons were released at 23 locations along the southern coast of Texas between 1985 and 2004, and in 2012 and 2013. To assess the species' reintroduction and recovery, we applied a genetic monitoring approach using sampled nestlings (n = 267) from a total of 108 nests in 2004–2005 and 2012–2016. Based on ten microsatellite loci, levels of genetic diversity (i.e., allelic richness and heterozygosity) remained stable over the sampled time period, with no indication of inbreeding. Diversity levels were comparable to a subset of samples collected from the captive population founders (n = 11). Similarly, individuals from the South Texas population showed strong admixture with the founding population, and levels of both Ne and of effective breeding (Nb) showed no signs of decline over the sampled time period. To what degree overlapping generations and the release of additional Aplomado Falcons during the sampled time period limited our assessment of the South Texas population is not fully known. Continued monitoring across multiple generations is advisable to assess the population's ability to persist.