Inbreeding depression in sperm quality in a critically endangered amphibian
Kristin M. Hinkson, Sinlan Poo
Abstract
Small, isolated populations often experience increased inbreeding and decreased heterozygosity, which increases the potential risk of inbreeding depression. The relationship between inbreeding and sperm health is well-documented in a variety of taxa, but has yet to be explored in amphibians. The dusky gopher frog, Lithobates sevosus, is a critically endangered species with years of documented inbreeding and low genetic variability as a consequence of isolation and population size reduction. This study investigated the effects of inbreeding on sperm quality in captive L. sevosus using an outbred, sister species (Lithobates pipiens) as a standard for comparison. We found L. sevosus to have severely reduced sperm quality in terms of total motility, forward progressive motility, concentration, and viability. Additionally, we observed a significant, negative relationship between total sperm motility and mean kinship within captive-bred individuals. These data serve to enhance our understanding of the role inbreeding plays in amphibians, and to provide valuable insight into new risk factors declining amphibian populations may face.