The subspecies concept influences multiple aspects of biology and management. The 'molecular revo... more The subspecies concept influences multiple aspects of biology and management. The 'molecular revolution' altered traditional methods (morphological traits) of subspecies classification by applying genetic analyses resulting in alternative or contradictory classifications. We evaluated recent reptile literature for bias in the recommendations regarding subspecies status when genetic data were included. Reviewing characteristics of the study, genetic variables, genetic distance values and noting the species concepts, we found that subspecies were more likely elevated to species when using genetic analysis. However, there was no predictive relationship between variables used and taxonomic recommendation. There was a significant difference between the median genetic distance values when researchers elevated or collapsed a subspecies. Our review found nine different concepts of species used when recommending taxonomic change, and studies incorporating multiple species concepts were more likely to recommend a taxonomic change. Since using genetic techniques significantly alter reptile taxonomy there is a need to establish a standard method to determine the species-subspecies boundary in order to effectively use the subspecies classification for research and conservation purposes.
Sporadic reports of cougars (Puma concolor) have occurred in Michigan since its official classifi... more Sporadic reports of cougars (Puma concolor) have occurred in Michigan since its official classification as extirpated in the 1930s. We collected 297 scats from 12 areas in Michigan with heavy sighting reports of cougars. Ten scats produced DNA profiles consistent with cougars. One scat was identified as having a North American origin; the other nine scats produced no useable sequences. One pre-Columbian sample, from a Native American burial site; also matched the current North American genotype. Based on the distance between cougar scats, we conclude that there were at least eight cougars in Michigan during the 3 y of this study. The mtDNA sequences also suggest that at least some of the matrilines currently and historically found in Michigan are the same as those found in current and historical western populations.
de esperarse. Mis resultados sugieren que aunque algunas poblaciones muestran autocorrelación tem... more de esperarse. Mis resultados sugieren que aunque algunas poblaciones muestran autocorrelación temporal, esta no es evidente y la autocorrelación ambiental podría no ser un buen predictor de autocorrelación de tasas de incremento. Los modeladores de poblaciones deberán determinar si la autocorrelación existe en poblaciones de interés antes de modelar su viabilidad o la probabilidad de persistencia puesto que no todas las poblaciones son afectadas por la autocorrelación de la misma manera.
Reintroduced populations are generally smaller and more isolated than native populations; thus ev... more Reintroduced populations are generally smaller and more isolated than native populations; thus even when reintroduced populations are demographically stable, a lack of genetic variation may present a threat to long-term persistence. We examined the demographic structure and genetic variation of the marten reintroduction into the Upper Peninsula of Michigan. Male : female and juvenile : adult female ratios indicate that the Michigan population is demographically stable. Michigan martens had higher allelic diversity (A ¼ 7.4) compared to the average diversity found among Canadian populations (A ¼ 5.8) and similar levels of observed heterozygosity (H Canadian ¼ 0.64, H Michigan ¼ 0.63), excluding Newfoundland martens. We found no significant differences in the allelic diversity or heterozygosity between the reintroduced Michigan population and the source population for the reintroduction, that of Chapleau, Ontario. Surprisingly, we found no evidence of a genetic bottleneck in the Michigan population. We suggest that the genetic success of this reintroduction is a result of the multiple reintroductions and subsequent intrastate translocations that mimicked gene flow. The success was further aided by the presence of small remnant populations that remained in Michigan, as evidenced by the presence of private alleles in Michigan.
Obtaining a sufficient number of DNA samples from ice-breeding marine phocids, in a noninvasive m... more Obtaining a sufficient number of DNA samples from ice-breeding marine phocids, in a noninvasive manner, has proven difficult and has limited the ability to use molecular genetics on these species. We evaluate the ability to genotype ringed seals using a novel source of DNA, skin cells shed by the seal as it moults on sea ice. We found that shed skin samples yielded a lower quantity and purity of DNA compared to tissue samples. Nevertheless, the shed skin cells were a viable source of DNA for microsatellite analysis; we found no significant difference in allelic diversity or heterozygosities between tissue samples and shed skin cells. This source of DNA should allow the rapid collection of a large number of noninvasively collected DNA samples in ice-breeding phocids.
A spatial gradient in the interactions between American minks (Neovison vison) and muskrats (Onda... more A spatial gradient in the interactions between American minks (Neovison vison) and muskrats (Ondatra zibethicus) occurs in the Hudson's Bay Company fur harvest returns of Canada. Evidence for strong dependence of minks on muskrats exists in northwestern Canada, whereas evidence for weaker interactions exists in central and eastern Canada. We tested the hypothesis that minks consume fewer muskrats and more alternative prey in some areas, using fur records from 56 Hudson's Bay posts. Both muskrats and small microtines were found to explain mink dynamics, with small microtines and other alternative prey gaining importance in the eastern portion of our study area. Mink fur returns exhibited a range of cycle lengths from 2.6 to 13 years encompassing typical small microtine periodicities of 3-5 years and typical muskrat periodicities of 8-13 years. A time lag of 0 years occurred between mink and muskrat harvest data frequently in the eastern portion of our study area, hypothesized to be a result of minks consuming alternative prey. To biologically verify small microtines as a potential prey source, we modeled mink and muskrat population dynamics assuming small microtines were an alternative prey by modifying the Turchin and Hanski (1997) model. Simulated mink and muskrat time series replicated observed periodicity and time-lag range, suggesting that minks can be generalist predators and consume alternative prey. Finally, we examined species richness and land cover as potential drivers of mink prey-switching, but were unable to find support for either hypothesis, suggesting that additional environmentalor competition-related interactions influence mink population dynamics.
We analyzed the hypothesized relationships of temporal, spatial, and harvest trends with frequenc... more We analyzed the hypothesized relationships of temporal, spatial, and harvest trends with frequency of red fox (Vulpes vulpes) color morphs in 57 Hudson's Bay Company posts over a 20-to 26-year period, but found none of the strong relationships postulated to exist. A meta-analysis of each data set suggested a weak inverse relationship between latitude and frequency of the red morph. Meta-analysis further indicated a weak positive relationship with time and the frequency of the red phase, although this trend was not due to climate change. No relationship was found between harvest size and color phase, or between a 1-year lagged harvest size and color phase, which evaluated the effects of dispersal. The data sets did not allow conclusive determination of the mechanisms behind the trends, but it is postulated that a slight selective advantage is found for the dark morphs at high latitudes, while the temporal increase in frequency of the red phenotype is probably the result of northward dispersal from southern populations.
Like some species of pika (Ochotona) and tree squirrel (Tamiasciurus), the banner-tailed kangaroo... more Like some species of pika (Ochotona) and tree squirrel (Tamiasciurus), the banner-tailed kangaroo rat (Dipodomys spectabilis) is a solitary, philopatric larder-hoarder that practices unisexual territoriality. Seeking to understand how this unusual combination of traits might influence the mating system, we used systematic trapping at mounds (burrows) and spool-and-line tracking to examine male and female visits to each other. Where genetic data exist, unisexual larder-hoarders such as D. spectabilis have been found to be polygynandrous. We asked whether the fact that females sometimes mate with more than 1 male is a passive side effect of imperfect mate defense by males, or whether females actively engage in behaviors that encourage multiple mating. During the nonbreeding season, adults of both sexes were rarely captured at mounds other than their own. In contrast, during the breeding season females as well as males were significantly more likely to be captured away from their home mounds, most often at mounds belonging to adults of the opposite sex. Spooland-line tracking during the breeding season confirmed these results. Consistent with the expectation that they engage in competitive mate searching, adult males visited adult females' mounds significantly more than expected by chance and without regard to age, size, or relatedness. More surprisingly, adult females exhibited similar behavior, expanding their home ranges and disproportionately visiting the mounds of large adult males during the nights preceding estrus. Increased (and apparently directed) female mobility during the days preceding estrus may serve as a means of shaping the pool of competing mates and is worthy of more attention in this and other, ecologically similar species.
The illegal harvest of natural resources (i.e., poaching) has the potential to threaten the persi... more The illegal harvest of natural resources (i.e., poaching) has the potential to threaten the persistence of many plant and animal species. In Michigan bobcats (Lynx rufus) are distributed throughout the Upper Peninsula (UP) and the northern half of the Lower Peninsula (LP) and are a biologically and economically important species. The popularity of bobcat hunting and trapping in Michigan, along with different harvest regulations between the 2 peninsulas, has created the need for a reliable method of identifying incidences of poaching. Because the bag limit is higher in the UP, we hypothesized that some bobcats harvested in the LP are being registered as originating from the UP. We used 8 polymorphic microsatellite markers and the statistical package STRUCTURE to assign individuals to the population in which they had the highest likelihood of occurrence based on their genotype. We evaluated the influence of using posterior probability threshold values from T . 0.9-0.999 on the number of animals classified as poached. Based on this range, STRUCTURE produced correct assignment rates of 53-82%. All instances of genetic re-assignment involved bobcats claimed as harvested in the UP but genetically assigned to the LP following the suspected method of bobcat poaching in Michigan. This approach provides a reliable method of determining the source population for bobcats harvested in the state and should provide enforcement agencies with a useful way of identifying potential poaching cases. (WILDLIFE SOCIETY BULLETIN 34(1):150-155; 2006)
Population genetics has fueled a substantial growth in studies of dispersal, a life-history trait... more Population genetics has fueled a substantial growth in studies of dispersal, a life-history trait that has important applications in ecology and evolution. Mammals typically exhibit male-biased gene flow, so this pattern often serves as a null hypothesis in empirical studies. Estimation of dispersal using population genetics is not without biases, so we utilized a combination of population genetic methods and simulations to evaluate gene flow within the American badger (Taxidea taxus (Schreber, 1777)), a highly elusive and poorly understood mustelid. A total of 132 badgers captured between 2001 and 2002 were genotyped at nine microsatellite loci to investigate fine-scale genetic structure consistent with philopatry in females and dispersal in males. Resultant genetic patterns were largely consistent with a panmictic population with little evidence for sex-biased dispersal, and simulations confirmed that our sampling scheme did not substantially impact our statistics. An overall deficiency of heterozygotes was observed across the Lower Peninsula, which indicates either a Wahlund effect, mixing of separate populations, or inbreeding. Our study emphasizes the importance in deciphering between actual behavioral mechanisms and sampling effects when interpreting genetic data to understand other factors that influence dispersal like population density and territoriality.
Historically, the Eastern Box Turtle (Terrapene c. carolina) was found in 31 counties in Michigan... more Historically, the Eastern Box Turtle (Terrapene c. carolina) was found in 31 counties in Michigan's Lower Peninsula, although it has been extirpated from 13 of those counties in the last ten years. One possible cause of the decline is roadbased habitat fragmentation with resulting demographic and genetic consequences. Accurately identifying population structure is necessary to determine conservation units and aid in the recovery of Terrapene c. carolina. We genotyped 163 turtles at eight microsatellite loci from three locations in southwestern Michigan covering 360 km 2 . We found high levels of genetic variation (H = 0.83; A = 16) and low levels of genetic differentiation (F ST = 0.006) in the system. The three areas exist as a single population and there was a low rate (11%) of misassignment across the sites. There was initial evidence of a genetic bottleneck in two of the three populations and the system as a whole. However, additional analysis failed to find a mode-shift in allele frequencies and did not detect any further evidence of a bottleneck in any of the populations. We conclude that the conflicting genetic indication of a bottleneck, despite the geographic evidence, is due to the long generation time of Terrapene c. carolina. Further, our study suggests that the retention of genetic variation despite population declines allows managers flexibility in dealing with the conservation of long-lived species.
We investigated population structure and genetic diversity for bobcats (Lynx rufus) in Michigan, ... more We investigated population structure and genetic diversity for bobcats (Lynx rufus) in Michigan, USA, which are distributed throughout the upper peninsula (UP) and the northern half of the lower peninsula (LP) of Michigan. Specifically, we assessed the influence of natural and artificial barriers to dispersal on the genetic population structure of the bobcat across Michigan, as well as in each peninsula. We used 5 microsatellite markers and the statistical package STRUCTURE to identify populations and assign individuals to their population of origin. STRUCTURE identified one population in each peninsula, indicating that the UP and LP are genetically isolated by the Straits of Mackinac which divide the UP and LP. Despite a greater density of roads in the LP, we found no evidence that they have led to intrapeninsular population structure. Our results suggest that, from a genetic standpoint, management agencies do not need to be concerned about the fragmenting effects of roads when producing management plans for bobcats. (JOURNAL OF WILDLIFE MANAGEMENT 71(1): 96-102; 2007)
The forage-selection hypothesis (FSH) explains sexual segregation in ungulates as a function of d... more The forage-selection hypothesis (FSH) explains sexual segregation in ungulates as a function of different dietary requirements producing different levels of habitat optimality, whereas the reproductive-strategy hypothesis (RSH) explains sexual segregation as a function of different survival strategies between the sexes. Based on observations of habitat use by elk (Cervus elaphus) in Yellowstone National Park, Wyoming with regard to varying levels of wolf encounter risk, we found that our determination of whether the RSH or FSH best applied to sexual segregation varied by the scale at which we were measuring habitat use. At broad spatial scales we found no significant avoidance of wolves by elk. At the habitat scale we found that habitat use by elk was consistent with predictions of the reproductive strategy in that female elk used habitats that offered a balance of forage and escape terrain for themselves and calves, and that the degree to which escape terrain was present was dependent upon the risk of wolf encounter. At the scale of the habitat patch we found that differences in forage availability likely drove the differences in habitat use. Our results highlight the importance of scale when investigating habitat use, nonlethal predation effects, and sexual segregation in ungulates.
The subspecies concept influences multiple aspects of biology and management. The 'molecular revo... more The subspecies concept influences multiple aspects of biology and management. The 'molecular revolution' altered traditional methods (morphological traits) of subspecies classification by applying genetic analyses resulting in alternative or contradictory classifications. We evaluated recent reptile literature for bias in the recommendations regarding subspecies status when genetic data were included. Reviewing characteristics of the study, genetic variables, genetic distance values and noting the species concepts, we found that subspecies were more likely elevated to species when using genetic analysis. However, there was no predictive relationship between variables used and taxonomic recommendation. There was a significant difference between the median genetic distance values when researchers elevated or collapsed a subspecies. Our review found nine different concepts of species used when recommending taxonomic change, and studies incorporating multiple species concepts were more likely to recommend a taxonomic change. Since using genetic techniques significantly alter reptile taxonomy there is a need to establish a standard method to determine the species-subspecies boundary in order to effectively use the subspecies classification for research and conservation purposes.
Sporadic reports of cougars (Puma concolor) have occurred in Michigan since its official classifi... more Sporadic reports of cougars (Puma concolor) have occurred in Michigan since its official classification as extirpated in the 1930s. We collected 297 scats from 12 areas in Michigan with heavy sighting reports of cougars. Ten scats produced DNA profiles consistent with cougars. One scat was identified as having a North American origin; the other nine scats produced no useable sequences. One pre-Columbian sample, from a Native American burial site; also matched the current North American genotype. Based on the distance between cougar scats, we conclude that there were at least eight cougars in Michigan during the 3 y of this study. The mtDNA sequences also suggest that at least some of the matrilines currently and historically found in Michigan are the same as those found in current and historical western populations.
de esperarse. Mis resultados sugieren que aunque algunas poblaciones muestran autocorrelación tem... more de esperarse. Mis resultados sugieren que aunque algunas poblaciones muestran autocorrelación temporal, esta no es evidente y la autocorrelación ambiental podría no ser un buen predictor de autocorrelación de tasas de incremento. Los modeladores de poblaciones deberán determinar si la autocorrelación existe en poblaciones de interés antes de modelar su viabilidad o la probabilidad de persistencia puesto que no todas las poblaciones son afectadas por la autocorrelación de la misma manera.
Reintroduced populations are generally smaller and more isolated than native populations; thus ev... more Reintroduced populations are generally smaller and more isolated than native populations; thus even when reintroduced populations are demographically stable, a lack of genetic variation may present a threat to long-term persistence. We examined the demographic structure and genetic variation of the marten reintroduction into the Upper Peninsula of Michigan. Male : female and juvenile : adult female ratios indicate that the Michigan population is demographically stable. Michigan martens had higher allelic diversity (A ¼ 7.4) compared to the average diversity found among Canadian populations (A ¼ 5.8) and similar levels of observed heterozygosity (H Canadian ¼ 0.64, H Michigan ¼ 0.63), excluding Newfoundland martens. We found no significant differences in the allelic diversity or heterozygosity between the reintroduced Michigan population and the source population for the reintroduction, that of Chapleau, Ontario. Surprisingly, we found no evidence of a genetic bottleneck in the Michigan population. We suggest that the genetic success of this reintroduction is a result of the multiple reintroductions and subsequent intrastate translocations that mimicked gene flow. The success was further aided by the presence of small remnant populations that remained in Michigan, as evidenced by the presence of private alleles in Michigan.
Obtaining a sufficient number of DNA samples from ice-breeding marine phocids, in a noninvasive m... more Obtaining a sufficient number of DNA samples from ice-breeding marine phocids, in a noninvasive manner, has proven difficult and has limited the ability to use molecular genetics on these species. We evaluate the ability to genotype ringed seals using a novel source of DNA, skin cells shed by the seal as it moults on sea ice. We found that shed skin samples yielded a lower quantity and purity of DNA compared to tissue samples. Nevertheless, the shed skin cells were a viable source of DNA for microsatellite analysis; we found no significant difference in allelic diversity or heterozygosities between tissue samples and shed skin cells. This source of DNA should allow the rapid collection of a large number of noninvasively collected DNA samples in ice-breeding phocids.
A spatial gradient in the interactions between American minks (Neovison vison) and muskrats (Onda... more A spatial gradient in the interactions between American minks (Neovison vison) and muskrats (Ondatra zibethicus) occurs in the Hudson's Bay Company fur harvest returns of Canada. Evidence for strong dependence of minks on muskrats exists in northwestern Canada, whereas evidence for weaker interactions exists in central and eastern Canada. We tested the hypothesis that minks consume fewer muskrats and more alternative prey in some areas, using fur records from 56 Hudson's Bay posts. Both muskrats and small microtines were found to explain mink dynamics, with small microtines and other alternative prey gaining importance in the eastern portion of our study area. Mink fur returns exhibited a range of cycle lengths from 2.6 to 13 years encompassing typical small microtine periodicities of 3-5 years and typical muskrat periodicities of 8-13 years. A time lag of 0 years occurred between mink and muskrat harvest data frequently in the eastern portion of our study area, hypothesized to be a result of minks consuming alternative prey. To biologically verify small microtines as a potential prey source, we modeled mink and muskrat population dynamics assuming small microtines were an alternative prey by modifying the Turchin and Hanski (1997) model. Simulated mink and muskrat time series replicated observed periodicity and time-lag range, suggesting that minks can be generalist predators and consume alternative prey. Finally, we examined species richness and land cover as potential drivers of mink prey-switching, but were unable to find support for either hypothesis, suggesting that additional environmentalor competition-related interactions influence mink population dynamics.
We analyzed the hypothesized relationships of temporal, spatial, and harvest trends with frequenc... more We analyzed the hypothesized relationships of temporal, spatial, and harvest trends with frequency of red fox (Vulpes vulpes) color morphs in 57 Hudson's Bay Company posts over a 20-to 26-year period, but found none of the strong relationships postulated to exist. A meta-analysis of each data set suggested a weak inverse relationship between latitude and frequency of the red morph. Meta-analysis further indicated a weak positive relationship with time and the frequency of the red phase, although this trend was not due to climate change. No relationship was found between harvest size and color phase, or between a 1-year lagged harvest size and color phase, which evaluated the effects of dispersal. The data sets did not allow conclusive determination of the mechanisms behind the trends, but it is postulated that a slight selective advantage is found for the dark morphs at high latitudes, while the temporal increase in frequency of the red phenotype is probably the result of northward dispersal from southern populations.
Like some species of pika (Ochotona) and tree squirrel (Tamiasciurus), the banner-tailed kangaroo... more Like some species of pika (Ochotona) and tree squirrel (Tamiasciurus), the banner-tailed kangaroo rat (Dipodomys spectabilis) is a solitary, philopatric larder-hoarder that practices unisexual territoriality. Seeking to understand how this unusual combination of traits might influence the mating system, we used systematic trapping at mounds (burrows) and spool-and-line tracking to examine male and female visits to each other. Where genetic data exist, unisexual larder-hoarders such as D. spectabilis have been found to be polygynandrous. We asked whether the fact that females sometimes mate with more than 1 male is a passive side effect of imperfect mate defense by males, or whether females actively engage in behaviors that encourage multiple mating. During the nonbreeding season, adults of both sexes were rarely captured at mounds other than their own. In contrast, during the breeding season females as well as males were significantly more likely to be captured away from their home mounds, most often at mounds belonging to adults of the opposite sex. Spooland-line tracking during the breeding season confirmed these results. Consistent with the expectation that they engage in competitive mate searching, adult males visited adult females' mounds significantly more than expected by chance and without regard to age, size, or relatedness. More surprisingly, adult females exhibited similar behavior, expanding their home ranges and disproportionately visiting the mounds of large adult males during the nights preceding estrus. Increased (and apparently directed) female mobility during the days preceding estrus may serve as a means of shaping the pool of competing mates and is worthy of more attention in this and other, ecologically similar species.
The illegal harvest of natural resources (i.e., poaching) has the potential to threaten the persi... more The illegal harvest of natural resources (i.e., poaching) has the potential to threaten the persistence of many plant and animal species. In Michigan bobcats (Lynx rufus) are distributed throughout the Upper Peninsula (UP) and the northern half of the Lower Peninsula (LP) and are a biologically and economically important species. The popularity of bobcat hunting and trapping in Michigan, along with different harvest regulations between the 2 peninsulas, has created the need for a reliable method of identifying incidences of poaching. Because the bag limit is higher in the UP, we hypothesized that some bobcats harvested in the LP are being registered as originating from the UP. We used 8 polymorphic microsatellite markers and the statistical package STRUCTURE to assign individuals to the population in which they had the highest likelihood of occurrence based on their genotype. We evaluated the influence of using posterior probability threshold values from T . 0.9-0.999 on the number of animals classified as poached. Based on this range, STRUCTURE produced correct assignment rates of 53-82%. All instances of genetic re-assignment involved bobcats claimed as harvested in the UP but genetically assigned to the LP following the suspected method of bobcat poaching in Michigan. This approach provides a reliable method of determining the source population for bobcats harvested in the state and should provide enforcement agencies with a useful way of identifying potential poaching cases. (WILDLIFE SOCIETY BULLETIN 34(1):150-155; 2006)
Population genetics has fueled a substantial growth in studies of dispersal, a life-history trait... more Population genetics has fueled a substantial growth in studies of dispersal, a life-history trait that has important applications in ecology and evolution. Mammals typically exhibit male-biased gene flow, so this pattern often serves as a null hypothesis in empirical studies. Estimation of dispersal using population genetics is not without biases, so we utilized a combination of population genetic methods and simulations to evaluate gene flow within the American badger (Taxidea taxus (Schreber, 1777)), a highly elusive and poorly understood mustelid. A total of 132 badgers captured between 2001 and 2002 were genotyped at nine microsatellite loci to investigate fine-scale genetic structure consistent with philopatry in females and dispersal in males. Resultant genetic patterns were largely consistent with a panmictic population with little evidence for sex-biased dispersal, and simulations confirmed that our sampling scheme did not substantially impact our statistics. An overall deficiency of heterozygotes was observed across the Lower Peninsula, which indicates either a Wahlund effect, mixing of separate populations, or inbreeding. Our study emphasizes the importance in deciphering between actual behavioral mechanisms and sampling effects when interpreting genetic data to understand other factors that influence dispersal like population density and territoriality.
Historically, the Eastern Box Turtle (Terrapene c. carolina) was found in 31 counties in Michigan... more Historically, the Eastern Box Turtle (Terrapene c. carolina) was found in 31 counties in Michigan's Lower Peninsula, although it has been extirpated from 13 of those counties in the last ten years. One possible cause of the decline is roadbased habitat fragmentation with resulting demographic and genetic consequences. Accurately identifying population structure is necessary to determine conservation units and aid in the recovery of Terrapene c. carolina. We genotyped 163 turtles at eight microsatellite loci from three locations in southwestern Michigan covering 360 km 2 . We found high levels of genetic variation (H = 0.83; A = 16) and low levels of genetic differentiation (F ST = 0.006) in the system. The three areas exist as a single population and there was a low rate (11%) of misassignment across the sites. There was initial evidence of a genetic bottleneck in two of the three populations and the system as a whole. However, additional analysis failed to find a mode-shift in allele frequencies and did not detect any further evidence of a bottleneck in any of the populations. We conclude that the conflicting genetic indication of a bottleneck, despite the geographic evidence, is due to the long generation time of Terrapene c. carolina. Further, our study suggests that the retention of genetic variation despite population declines allows managers flexibility in dealing with the conservation of long-lived species.
We investigated population structure and genetic diversity for bobcats (Lynx rufus) in Michigan, ... more We investigated population structure and genetic diversity for bobcats (Lynx rufus) in Michigan, USA, which are distributed throughout the upper peninsula (UP) and the northern half of the lower peninsula (LP) of Michigan. Specifically, we assessed the influence of natural and artificial barriers to dispersal on the genetic population structure of the bobcat across Michigan, as well as in each peninsula. We used 5 microsatellite markers and the statistical package STRUCTURE to identify populations and assign individuals to their population of origin. STRUCTURE identified one population in each peninsula, indicating that the UP and LP are genetically isolated by the Straits of Mackinac which divide the UP and LP. Despite a greater density of roads in the LP, we found no evidence that they have led to intrapeninsular population structure. Our results suggest that, from a genetic standpoint, management agencies do not need to be concerned about the fragmenting effects of roads when producing management plans for bobcats. (JOURNAL OF WILDLIFE MANAGEMENT 71(1): 96-102; 2007)
The forage-selection hypothesis (FSH) explains sexual segregation in ungulates as a function of d... more The forage-selection hypothesis (FSH) explains sexual segregation in ungulates as a function of different dietary requirements producing different levels of habitat optimality, whereas the reproductive-strategy hypothesis (RSH) explains sexual segregation as a function of different survival strategies between the sexes. Based on observations of habitat use by elk (Cervus elaphus) in Yellowstone National Park, Wyoming with regard to varying levels of wolf encounter risk, we found that our determination of whether the RSH or FSH best applied to sexual segregation varied by the scale at which we were measuring habitat use. At broad spatial scales we found no significant avoidance of wolves by elk. At the habitat scale we found that habitat use by elk was consistent with predictions of the reproductive strategy in that female elk used habitats that offered a balance of forage and escape terrain for themselves and calves, and that the degree to which escape terrain was present was dependent upon the risk of wolf encounter. At the scale of the habitat patch we found that differences in forage availability likely drove the differences in habitat use. Our results highlight the importance of scale when investigating habitat use, nonlethal predation effects, and sexual segregation in ungulates.
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Papers by Brad Swanson