Genetic Structure, Diversity, and Connectivity of Alabama Black Bear (Ursus americanus) Populations

Abstract

Black bear (Ursus americanus) abundance and distribution has declined drastically across the southeastern United States, where a range reduction of 80% has occurred. In this study, the structure, diversity, and connectivity of two Alabama bear populations was examined from a genetic perspective. Microsatellite markers were employed to assess heterozygosity, allelic trends across populations, descriptive F-statistics, and connectivity with neighboring populations. It was confirmed that two separate subspecies occur within Alabama borders: U. a. floridanus in the Mobile River Basin (MRB) region and U. a. americanus subspecies in Northeastern Alabama (NAL) region. The MRB exemplifies major genetic concerns associated with fragmentation and isolation. Measures of genetic diversity demonstrated extreme low variability (polymorphism at 60% of loci; A = 1.58; Na = 2.000 ± 0.447 alleles; He = 0.246 ± 0.128; Ho = 0.256 ± 0.133). NAL population was confirmed as a re-colonizing front dispersing from the Smokey Mtn National Park in Tennessee. Prior to this study, bears had been absent from NAL for >100 years. The source population for NAL showed substantial genetic variability (Ho = 0.698 ± 0.061; He = 0.735 ± 0.017; Na = 6.400 ± 0.400; A = 3.12). However, due to random sampling, NAL bears are at risk for genetic loss through founders’ effect. We observed a disparate average number of alleles per loci between NAL and its source (Na = 4.000 ± 0.000 and Na = 6.400 ± 0.400 respectively). Continued genetic monitoring, research focused on habitat use, dispersal, and conservation management are imperative to ensure the long term viability of Alabama black bears.