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Roads fragment ecosystems around the globe, but the effects of this fragmentation on biodiversity remain poorly understood. Wolverines (Gulo gulo) are snow-dependent carnivores that occur at low densities and they exhibit low genetic diversity at the southern extent of their range where they are snow-limited and fragmented by human development. Therefore, understanding the effect of roads and transportation infrastructure on population connectivity in protected strongholds such as national parks is crucial to effective wolverine management in a changing climate. We assessed whether the Trans-Canada Highway, Canada's largest east-west transportation corridor, affects wolverine gene flow in the Rocky Mountains. We used noninvasive genetic sampling methods (i.e., hair traps, backtracking) to collect DNA samples (i.e. hair, scat) from an 8000 km2 area of Banff, Kootenay, and Yoho National Parks and provincial lands and then used population and individual-based genetic analyses (e.g., assignment tests, principal coordinates analysis) to examine genetic structure across the highway in the national parks complex. We collected 2586 DNA samples between 2010 and 2013 from which we identified 49 unique individuals (29 males, 20 females). We detected weak population structure in males and relatively strong genetic differentiation in females spanning the highway with complementary nuclear and mitochondrial DNA analyses. Our results demonstrate that sex-biased dispersal across a major highway can lead to genetic isolation and demographic fragmentation in a protected carnivore population, highlighting the urgent need to maintain connectivity for wildlife over an expanding global road network in the face of climate change, landscape degradation, and loss of biodiversity.

The management of rare species is a conservation priority worldwide, but this task is made difficult by detection errors in population surveys. Both false positive (misidentification) and false negative (missed detection) errors are prevalent in surveys for rare species and can affect resulting inferences about their population status or distribution. Environmental DNA (eDNA)—DNA shed from an organism in its environment—coupled with quantitative PCR (qPCR) analyses, has become a reliable and extremely sensitive mean for identifying rare species in aquatic systems. Due to the demonstrated effectiveness of these methods, we tested their efficacy in surveys for rare species in terrestrial settings to reduce detection errors for three rare forest carnivores of conservation concern: Canada lynx (Lynx canadensis), fisher (Pekania pennanti), and wolverine (Gulo gulo). We specifically investigated our ability to reliably: 1) identify species directly from snow samples collected within tracks; 2) identify species by collecting snow in locations where an animal had been photographed; and 3) identify species from hair samples collected during the summer after being deployed throughout the winter (i.e., overwinter surveys). Our findings indicated that qPCR assays can effectively detect DNA of all three species, including from snow-track surveys, snow collected at camera stations, and overwinter samples that failed to amplify with conventional PCR techniques. All results indicate that the sources of targeted DNA collection provided adequate quantities of DNA for robust species detection. We suggest that using qPCR methods to detect DNA has the potential to revolutionize winter surveys for rare species in terrestrial settings by reducing or eliminating misidentifications and missed detections.

Cave-hibernating bats are widespread in North America but are facing precipitous population declines due to the impacts of white-nose syndrome (WNS). It is in winter hibernacula that bats are most vulnerable to the fungus that causes WNS, but the locations of over-wintering sites in western North America are largely unknown. This poses a significant challenge for bat monitoring, disease surveillance, and management efforts at the disease front. To advance initiatives to locate bats on the landscape, we developed real-time PCR assays to detect big brown bats (Eptesicus fuscus) from environmental DNA samples (eDNA). Three assays were designed, one each for eastern, western, and southern North America, to account for the high intra-specific genetic variability within big brown bats. We demonstrate that these assays can detect bat DNA in environmental samples, including air, water, and soil, and are able to detect target DNA at concentrations as low as 2 copies per reaction. Although the assays are highly sensitive, detections from samples collected in field samples were modest. Our findings suggest that eDNA may provide a much-needed, non-invasive alternative to conventional tools used to detect bats on the landscape but require further research to optimize their field application.

Environmental DNA sampling (eDNA) has emerged as a powerful tool for detecting aquatic animals. Previous research suggests that eDNA methods are substantially more sensitive than traditional sampling. However, the factors influencing eDNA detection and the resulting sampling costs are still not well understood. Here we use multiple experiments to derive independent estimates of eDNA production rates and downstream persistence from brook trout ( Salvelinus fontinalis ) in streams. We use these estimates to parameterize models comparing the false negative detection rates of eDNA sampling and traditional backpack electrofishing. We find that using the protocols in this study eDNA had reasonable detection probabilities at extremely low animal densities (e.g., probability of detection 0.18 at densities of one fish per stream kilometer) and very high detection probabilities at population-level densities (e.g., probability of detection > 0.99 at densities of ≥ 3 fish per 100 m). This is substantially more sensitive than traditional electrofishing for determining the presence of brook trout and may translate into important cost savings when animals are rare. Our findings are consistent with a growing body of literature showing that eDNA sampling is a powerful tool for the detection of aquatic species, particularly those that are rare and difficult to sample using traditional methods.

Climate change impacts many species through shifts in habitat. The intensity of this impact will depend on the dispersal rates of the species, the patchiness of the environment, and the velocity of habitat change. Here we examine how dispersal affects projected future habitat availability for a threatened carnivore, the fisher (Pekania [Martes] pennanti). We used non-invasive genetic sampling to detect fisher across their historical distribution in Montana and Idaho. This survey included 4846 non-invasive hair snares, of which 288 identified fishers through mitochondrial DNA analysis. We modeled the distribution of fisher across western Montana and northern Idaho using a suite of vegetative, topographic, and climatic variables. We modeled future distribution using a global climate model and two climate change scenarios (high emissions [A2] or reduced emissions [B2]) and three time steps (2030, 2060, and 2090). We incorporated the effects of dispersal ability and habitat patch size into our model by varying the distance and enforcing a minimum patch size at which newly created habitat could be colonized. We found that the probability of current fisher occurrence was highest given the presence of mesic forest types with tall trees, high annual precipitation, and mid-range winter temperatures. Future predictions show an increase in area of high-probability habitat under most dispersal assumptions. Interestingly, we found a large contrast in results when minimum patch size and species dispersal capabilities were considered. Our distribution model with full dispersal and no limits on patch size predicted a 24.5% increase in fisher habitat by 2090, whereas a dispersal limit of 1 km through non-habitat (agricultural fields and urban zones) and a minimum patch size yielded a loss of 25.8% of fisher habitat under this same scenario. Varying dispersal appears to limit habitat availability more than minimum patch size under most scenarios.

Loss of genetic variation through genetic drift can reduce population viability. However, relatively little is known about loss of variation caused by the combination of fluctuating population size and variance in reproductive success in age structured populations. We built an individual-based computer simulation model to examine how actual culling and hunting strategies influence the effective population size (Ne) and allelic diversity in Yellowstone bison over 200 years (∼28 generations). The Ne for simulated populations ranged from 746 in stable populations of size 2000 up to 1165 in fluctuating populations whose census size fluctuates between 3000 and 3500 individuals. Simulations suggested that ∼93% of allelic diversity, for loci with five alleles will be maintained over 200 years if the population census size remains well above ∼2000 bison (and if variance in male reproductive success is high). However for loci with 20 alleles, only 83% of allelic diversity will be maintained over 200 years. Removal of only juveniles (calves and yearlings) resulted in longer generation intervals which led to higher maintenance of allelic diversity (96%) after 200 years compared to the culling of adults (94%) when the mean census size was 3250 (for loci with five alleles). These simulations suggest that fluctuations in population census size do not necessarily accelerate the loss of genetic variation, at least for the relatively large census size and growing populations such as in Yellowstone bison. They also suggest that the conservation of high allelic diversity (>95%) at loci with many alleles (e.g., ⩾5) will require maintenance of a populations size greater than approximately 3250 and removal of mainly or only juveniles.

We test the ability of gene flow to alleviate the deleterious effects of inbreeding in a small mammal, the deer mouse ( Peromyscus maniculatus ). After three generations of sib–sib mating, individuals from three lines of mice were either subject to further inbreeding or were mated with an outbred individual. Subsequently, these mice, plus a control line, which were first generation (F 1 ) mice from unrelated individuals kept in captivity for the same duration as the treatment lines, were released into isolated pens in a forest in western Montana. Survival of individual mice was recorded. Survival models that allowed variation in breeding treatments were well supported, whereas models explaining variation in line, or release location were not well supported. Survival was highest for offspring of the outcross group, intermediate for the inbred animals, and lowest for the control group. This suggests that the introduction of migrants can reduce inbreeding depression, as theory predicts. We also show limited evidence for purging of deleterious recessive alleles that can cause inbreeding depression. While purging may have occurred, the demographic cost was non-trivial as 5 of 8 of our inbred mouse lines went extinct during the inbreeding process.

Population trends play a large role in species risk assessments and conservation planning, and species are often considered threatened if their recent rate of decline meets certain thresholds, regardless how large the population is. But how reliable an indicator of extinction risk is a single estimate of population trend? Given the integral role this decline-based approach has played in setting conservation priorities, it is surprising that it has undergone little empirical scrutiny. We compile an extensive global dataset of time series of abundance data for over 1300 vertebrate populations to provide the first major test of the predictability of population growth rates in nature. We divided each time series into assessment and response periods and examined the correlation between growth rates in the two time periods. In birds, population declines tended to be followed by further declines, but mammals, salmon, and other bony fishes showed the opposite pattern: past declines were associated with subsequent population increases, and vice versa. Furthermore, in these taxa subsequent growth rates were higher when initial declines were more severe. These patterns agreed with data simulated under a null model for a dynamically stable population experiencing density dependence. However, this type of result could also occur if conservation actions positively affected the population following initial declines—a scenario that our data were too limited to rigorously evaluate. This ambiguity emphasizes the importance of understanding the underlying causes of population trajectories in drawing inferences about rates of decline in abundance.