Genetic Variation in Captive Populations of Barrens Topminnow

Abstract

The Barrens topminnow (Fundulus julisia), a freshwater killifish native to the Barrens Plateau in Tennessee, has suffered continual population declines since the 1980’s. These declines can be attributed to multiple factors including droughts, habitat loss, and harassment by the invasive Western Mosquitofish (Gambusia affinis) which have been widely introduced across the Southeastern United States. As of 2019, this species was federally listed under the Endangered Species Act. In an effort to mitigate further population declines, a number of captive refuge populations were established in the early 2000s as a source for future introductions. These captive populations were initiated from brood stocks from three natural populations (Pond Spring in the Elk River drainage, and Hickory and McMahan Creek in the Caney Fork Drainage) and have been used as a source for establishing new population in the wild. There is concern about the adaptive potential and genetic health of these newly established populations as loss of genetic diversity and inbreeding can accumulate rapidly in captivity. Here we used genotype data from 14 microsatellite loci to investigate genetic variation in captive stock populations of the Barrens Topminnow and compare measures of genetic variation to estimates from native source populations. Results from these genetic surveys will be used to inform captive breeding strategies that will best preserve the long-term persistence and adaptive potential of this species.