UVM Theses and Dissertations
Format:
Print
Author:
Rella-Hapeman, Paul
Dept./Program:
Biology
Year:
2006
Degree:
PhD
Abstract:
Tissue samples (n=433) of fishers (Martes pennanti) were collected from seven states and one Canadian province to examine recent and evolutionary histories, population structure, and dispersal of fishers across northeastern North America. Differences in sequence diversity (mtDNA D-loop) were found among four reported refugial populations (Adirondacks, NY, White Mountains, NH, Moosehead Plateau, ME, and Cumberland Plateau, NB, Canada). An AMOVA indicates the majority of sequence variation is partitioned among populations and among regional groupings from New York, New England, and New Brunswick. Significant non-random associations among haplotypes were found using nested clade analysis indicating population fragmentation and range expansion events. Tests of the neutral Wright-Fisher model of evolution indicate population subdivision and/or decline in the Adirondacks and New Brunswick populations. Current population structure in fishers was examined using 11 polymorphic microsatellites. Bayesian clustering of genotypes resulted in K=4 current populations across the study area. High assignment scores were achieved for samples in pre-defined populations and Bayesian clustering and assignment methods gave similar results assigning samples from reintroduced populations to their known sources. Both admixture and the Wahlund effect may have contributed to significant deviations from Hardy-Weinberg and linkage equilibrium at select loci in most populations.
Significant differentiation was detected among all populations in pairwise comparisons of F[subscript ST], R[subcript ST], and allelic and genotypic differentiation. Results from an AMOVA revealed significant differentiation between geographic populations and between a regional comparison of New York, Vermont & New Hampshire, and Maine. Compared to expectations in populations at mutation-drift equilibrium, heterozygote excess was detected in Maine, Vermont, and New York indicating recent bottlenecks have occurred in each of these populations. Recent bottlenecks may be the result of overtrapping and habitat loss during the recent period between 1800 and the 1930s. Significant differences between male and female mean corrected assignment scores (mAIc) and estimates of F[subscript ST] support a female bias in dispersal in fishers. However, the lack of a significant difference in the variance in corrected assignment scores (vAIc) and mean relatedness values between males and females indicates that both sexes are dispersing and that some factor other than inbreeding avoidance or local mate and resource competition are creating the bias. High densities of fishers in sampled populations may play a role in both sexes dispersing by increasing local mate competition in males and resource competition in females. A combination of male-biased trapping and resulting skewed sex ratios toward females as suggested from previous research may ultimately explain the female bias in dispersal.
Significant differentiation was detected among all populations in pairwise comparisons of F[subscript ST], R[subcript ST], and allelic and genotypic differentiation. Results from an AMOVA revealed significant differentiation between geographic populations and between a regional comparison of New York, Vermont & New Hampshire, and Maine. Compared to expectations in populations at mutation-drift equilibrium, heterozygote excess was detected in Maine, Vermont, and New York indicating recent bottlenecks have occurred in each of these populations. Recent bottlenecks may be the result of overtrapping and habitat loss during the recent period between 1800 and the 1930s. Significant differences between male and female mean corrected assignment scores (mAIc) and estimates of F[subscript ST] support a female bias in dispersal in fishers. However, the lack of a significant difference in the variance in corrected assignment scores (vAIc) and mean relatedness values between males and females indicates that both sexes are dispersing and that some factor other than inbreeding avoidance or local mate and resource competition are creating the bias. High densities of fishers in sampled populations may play a role in both sexes dispersing by increasing local mate competition in males and resource competition in females. A combination of male-biased trapping and resulting skewed sex ratios toward females as suggested from previous research may ultimately explain the female bias in dispersal.