title: Habitat relationships and gene flow of Martes americana in northern Idaho
Creators: name: Wasserman, Tzeidle Nichole
Publisher: name: Western Washington University
Year: 2008

description: <p>Forest fragmentation can have a dramatic effect on landscape connectivity and dispersal of animals, potentially reducing gene flow within and among populations. American marten populations (Martes americana) are sensitive to forest fragmentation and the spatial configuration of patches of remnant mature forest has an important impact on habitat quality. This study represents an extensive multiple scale habitat relationships analysis conducted for American marten. In conjunction with Idaho Department of Fish and Game (IDFG) and the U.S. Forest Service, genetic data on marten populations across the Idaho Panhandle National Forest was used to build habitat relationships models. Over 3 years of winter fieldwork during 2004, 2005, and 2006, I detected martens at 569 individual hair snare stations distributed across a 3,000 square kilometer study area covering the Selkirk, Purcell, and Cabinet Mountain ranges. I investigated habitat relationships of this population of Martes americana in the Idaho Panhandle National Forest (IPNF) at three spatial scales: Plot, Home Range, and Multiple-Scale. I used bivariate scaling to measure each environmental variable across a broad range of radii ranging from 90m-1080m around each sample station. I used an information-theoretic approach to rank 45 a priori candidate models that described hypothesized habitat relationships at each spatial scale. At the plot scale, marten presence was positively predicted by the Percentage of Landscape (PLand) comprised of large sawtimber, and negatively predicted by PLand of seedling/sapling timber type. At the home range scale, the probability of detecting a marten decreased with increasing amounts of fragmentation and highly contrasted edges between patches of large sawtimber and patches of seedling/sapling and non-stocked patches. In the multiple-scale analysis, I used a variable screening step to find variables that were universal and consistent throughout all models in order to build candidate models. PLand comprised of large homogeneous patches of large sawtimber was a positive predictor of marten presence, while highly contrasted edges and fragmentation were strong negative predictors of marten presence. The scale at which martens selected habitats varied greatly across variables. Martens actively selected for high quality habitat at the fine scale (plot level) and strongly avoided areas comprised of seedling/sapling and non-stocked timber areas. Martens negatively responded to high contrast edges and strongly avoided them. Juxtaposition and configuration of patches of large sawtimber was important to marten habitat selection. This study demonstrates the importance of investigating marten habitat at multiple spatial scales and provides insights to linkages among scales and how martens respond to forest fragmentation. Genetic information was used to model genetic relationships of this marten population with respect to environmental and spatial variables within my study landscape. Over three field seasons 70 individual marten were detected across the study area. The genetic similarities were based on the pair-wise percentage dissimilarity among all individuals based on 7 microsatellite loci. I compared their genetic similarities with several landscape resistance hypotheses. The landscape resistance hypotheses describe a range of potential relationships between movement cost and landcover, elevation, roads, Euclidean distance and valleys between mountain ranges as barriers. The degree of support for each model was tested with causal modeling on resemblance matrices using partial Mantel tests. Hypotheses of Isolation by Distance and Isolation by Barrier were not supported, and Isolation by Landscape Resistance proved to be the best model describing genetic patterns of Martes americana in the IPNF. Elevation 1600m with a standard deviation of 600m was the most highly supported landscape resistance model correlated to genetic structure of marten in this landscape. Correlating genetic similarity of individuals across large landscapes with hypothetical movement cost models can give reliable inferences about population connectivity. By linking cost modeling to the actual patterns of genetic similarity among individuals it is possible to obtain rigorous, empirical models describing the relationship between landscape structure and gene flow, and to produce species specific maps of landscape connectivity, and can provide managers with critical information to better administer our forests for meso-carnivores and other species of concern.</p>