Date of Award
Doctor of Philosophy
Joseph D. Clark
Benjamin M. Fitzpatrick, Lisa I. Muller, Russel Zaretzki
In 1992, the U.S. Fish and Wildlife Service granted the Louisiana black bear threatened status under the U.S. Endangered Species Act, listing loss and fragmentation of habitat as the primary threats. The 1995 Recovery Plan outlines recovery goals designed to meet the objective of reducing threats to the Louisiana black bear metapopulation and supporting habitat. To meet that objective, the Recovery Plan requires 1) at least 2 viable subpopulations, 1 each in the Tensas and Atchafalaya River Basins, 2) movement corridors between the 2 viable subpopulations, and 3) long-term protection of the habitat supporting each viable subpopulation and interconnecting corridors for delisting to occur. To address criteria 1 and 2, my objectives were 1) to estimate demographic rates of Louisiana black bear subpopulations, 2) to evaluate genetic structure and interchange of Louisiana black bear subpopulations, 3) to develop data-driven projection models to assess long-term persistence of individual subpopulations and the metapopulation in Louisiana, and 4) to determine how different model assumptions and parameter values affect estimates of long-term persistence. I used telemetry, den check data, and DNA-based capture-mark-recapture to demographic rates. Bayesian hierarchical modeling methods were used to estimate temporal process variance and parameter uncertainty. I developed stochastic population projection models based on estimates of demographic rates, process variances, and parameter uncertainty to estimate probabilities of persistence. I used 2 genetic clustering analyses to evaluate genetic structure among subpopulations in Louisiana and used 2 genetic assignment tests to measure interchange among subpopulations. Based on most projection models, estimates of persistence probabilities indicate that a viable subpopulation exists within the Tensas River Basin and within the Upper Atchafalaya River Basin. However, simulations under the most pessimistic set of assumptions suggested that the probability of extinction was slightly less than 95% for the Upper Atchafalaya (93%). Genetic analyses revealed that Louisiana black bear subpopulations were genetically distinct from each other and that contemporary gene flow is occurring between the Tensas River Basin and Upper Atchafalaya River Basin via a recently reintroduced population located between the two at the Three Rivers Complex. Those results suggest movement pathways currently exist between viable subpopulations.
Laufenberg, Jared Scott, "Population dynamics and genetic structure of Louisiana black bears in the Lower Mississippi Alluvial Valley of Louisiana. " PhD diss., University of Tennessee, 2014.