Genetic effective size and fragmentation of the threatened Leopard Darter, Percina pantherina

Authors: Michael R. Schwemm, Anthony A. Echelle, Ronald A. Van Den Bussche

Year: 2010 (xlii)

Abstract

A history of low abundance and limited distribution has characterized Percina pantherina, a percid endemic to the Little River system, SE Oklahoma and SW Arkansas. Concerns of habitat fragmentation by reservoir construction and agricultural/silvicultural perturbations have been apparent since its federal listing in 1978. Here, we compare levels of heterozygosity and population subdivision and estimate genetic effective sizes to evaluate the potential loss of genetic variation. Genetic variation at eight microsatellite loci revealed relatively low levels of allele richness (A_R= 3.74 to 6.60) and heterozygosity (H_e = 0.461-0.636) within populations. Tributary streams (now separated by at least one reservoir) differed significantly in allele frequencies, with 10.2% of the genetic diversity attributable to differences among tributaries. Maximum Likelihood (MIGRATE) and Bayesian (MSVAR) coalescence approaches indicate that current effective populations sizes are similar with those from summary statistics (ONeSAMP and LDNe) and about three orders of magnitude smaller than the ancestral population sizes and one order smaller than the long-term effective sizes. The point estimates of time since the start of the decline (69 to 398 yrs) and the associated 95% support limits are consistent with the hypothesis that low diversity is a result of fragmentation in the last century.