Genetic diversity, historic population size, and population structure in 2 North American tree bats (original) (raw)
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PeerJ, 2015
Documented fatalities of bats at wind turbines have raised serious concerns about the future impacts of increased wind power development on populations of migratory bat species. However, for most bat species we have no knowledge of the size of populations and their demographic trends, the degree of structuring into discrete subpopulations, and whether different subpopulations use spatially segregated migratory routes. Here, we utilize genetic data from eastern red bats (Lasiurus borealis), one of the species most highly affected by wind power development in North America, to (1) evaluate patterns of population structure across the landscape, (2) estimate effective population size (N e), and (3) assess signals of growth or decline in population size. Using data on both nuclear and mitochondrial DNA variation, we demonstrate that this species forms a single, panmictic population across their range with no evidence for the historical use of divergent migratory pathways by any portion of the population. Further, using coalescent estimates we estimate that the effective size of this population is in the hundreds of thousands to millions of individuals. The high levels of gene flow and connectivity across the population of eastern red bats indicate that monitoring and management of eastern red bats must integrate information across the range of this species.
PeerJ
There are increasing concerns regarding bat mortality at wind energy facilities, especially as installed capacity continues to grow. In North America, wind energy development has recently expanded into the Lower Rio Grande Valley in south Texas where bat species had not previously been exposed to wind turbines. Our study sought to characterize genetic diversity, population structure, and effective population size inDasypterus egaandD. intermedius, two tree-roosting yellow bats native to this region and for which little is known about their population biology and seasonal movements. There was no evidence of population substructure in either species. Genetic diversity at mitochondrial and microsatellite loci was lower in these yellow bat taxa than in previously studied migratory tree bat species in North America, which may be due to the non-migratory nature of these species at our study site, the fact that our study site is located at a geographic range end for both taxa, and possibly...
Acta Chiropterologica, 2012
Non-invasive population genetics has become a valuable tool in ecology and conservation biology, allowing genetic studies of wild populations without the need to catch, handle or even observe the study subjects directly. We address some of the concerns regarding the limitations of using non-invasive samples by comparing the quality of population genetic information gained through DNA extracted from faecal samples and biopsy samples of two elusive bat species, Myotis mystacinus and Myotis nattereri. We demonstrate that DNA extracted from faeces and tissue samples gives comparable results for frequency based population genetic analyses, despite the occurrence of genotyping errors when using faecal DNA. We conclude that non-invasive genetic sampling for population genetic analysis in bats is viable, and although more labour-intensive and expensive, it is an alternative to tissue sampling, which is particularly pertinent when specimens are rare, endangered or difficult to capture.
Acoustic and Genetic Approaches for Informing Population Status and Trends of Migratory Tree Bats
2021
Understanding the population structure and dynamics of bats is essential for assessing and mitigating risk and ensuring population viability. For many cave-roosting species, it is relatively easy to quantify and track populations because they congregate in large numbers during winter and can be monitored over time. However, for tree-roosting species, collecting and interpreting population data is challenging. These species do not aggregate in conspicuous locations but instead roost individually and are dispersed across the landscape, making it impractical for traditional surveys to provide estimates of census population sizes. Several species of bats are exposed to both natural and human-induced environmental stressors resulting in population declines. For cave-roosting species, White-nose Syndrome has decimated populations. Conversely, wind turbines represent a potential population-level threat for migratory bats, such as hoary bats (Lasiurus cinereus), eastern red bats (L. borealis), and silver-haired bats (Lasionycteris noctivagans), given their relatively low reproductive rates and the level of documented mortality across wind energy facilities in North America. Recent studies have assessed the potential population-level impact of wind energy facilities on hoary bats and given a set of assumptions for population growth rate and mortality rate from wind turbines, suggested a 38% reduction in turbine-related mortality is necessary to manage extinction risk for a starting population of 2.25 million bats. Reducing uncertainty in the model may not be immediately achievable as census data cannot be derived from existing methods. However, using a variety of techniques, including systematic acoustic sampling and genomic analysis, it is possible to build a weight of evidence on bat population trends and assess whether 1) mortality associated with wind turbines is sustainable, 2) minimal or substantial mitigation is required, and 3) mitigation measures are effective in ensuring population stability. Consistent, long-term data collection remains the most reasonable option for reducing uncertainty and offering clarity into population trends for migratory tree-roosting bats. Using statistically robust methods for collecting acoustic data through the North American Bat Monitoring Program (NABat) or estimating effective population size at repeated intervals may provide data points over time to show species trends. Although there are no options for shortterm actions that will result in significantly reducing uncertainty, there is opportunity for relatively short-term investments that can support long-term success of data collection efforts. For the wind energy industry, one option is to reallocate resources used for standard preconstruction acoustic monitoring to follow the NABat field methods and data submission protocols or provide funding support for NABat regional hubs in lieu of monitoring. Contributing to NABat will enable broad-scale inferences about bat populations. This approach has several additional benefits in that the data are not associated with a given wind energy project and the level of effort/cost, even for multiple years of data collection, may be equivalent to standard preconstruction acoustic surveys conducted in one year at a single wind energy project. There already is broad support for NABat, but the speed at which data are collected and available for analysis can be increased with support by the wind energy and wildlife community. Another option is to invest resources to collect genetic samples from bats collected at wind energy facilities during postconstruction mortality monitoring. This collection should be targeted vi
Genetic Approaches Are Necessary to Accurately Understand Bat-Wind Turbine Impacts
Diversity
Bats are killed at wind energy facilities worldwide and we must improve our understanding of why this is happening and implement effective strategies to minimize impacts. To this end, we need accurate assessments of which individuals from which bat species are being killed at individual wind projects and at regional and range-wide scales. Traditional fatality searches have relied on physical characteristics to ascertain species and sex of bat carcasses collected at wind turbines; however, the resulting data can be incomplete and inaccurate. In contrast, the use of readily available and low-cost molecular methods improves both the quality and quantity of available data. We applied such methods to a bat fatality dataset (n = 439 bats) from far-south Texas, USA. Using DNA barcoding, we increased accurate species identification from 83% to 97%, and discovered the presence of 2 bat species outside of their known geographic ranges. Using a PCR-based approach to determine sex, the number o...
PloS one, 2015
During late summer and early autumn, temperate bats migrate from their summering sites to swarming sites, where mating likely occurs. However, the extent to which individuals of a single summering site migrate to the same swarming site, and vice versa, is not known. We examined the migratory connectivity between summering and swarming sites in two temperate, North American, bat species, the little brown bat (Myotis lucifugus) and the northern long-eared bat (Myotis septentrionalis). Using mitochondrial and microsatellite DNA markers, we examined population structuring within and among summering and swarming sites. Both species exhibited moderate degrees of mitochondrial DNA differentiation (little brown bat: FST(SWARMING)= 0.093, FST(SWARMING)= 0.052; northern long-eared bat: FST(SWARMING)= 0.117, FST(SWARMING)= 0.043) and little microsatellite DNA differentiation among summering and among swarming sites. Haplotype diversity was significantly higher at swarming sites than summering ...
PLoS ONE, 2011
Observed patterns of genetic structure result from the interactions of demographic, physical, and historical influences on gene flow. The particular strength of various factors in governing gene flow, however, may differ between species in biologically relevant ways. We investigated the role of demographic factors (population size and sex-biased dispersal) and physical features (geographic distance, island size and climatological winds) on patterns of genetic structure and gene flow for two lineages of Greater Antillean bats. We used microsatellite genetic data to estimate demographic characteristics, infer population genetic structure, and estimate gene flow among island populations of Erophylla sezekorni/E. bombifrons and Macrotus waterhousii (Chiroptera: Phyllostomidae). Using a landscape genetics approach, we asked if geographic distance, island size, or climatological winds mediate historical gene flow in this system. Samples from 13 islands spanning Erophylla's range clustered into five genetically distinct populations. Samples of M. waterhousii from eight islands represented eight genetically distinct populations. While we found evidence that a majority of historical gene flow between genetic populations was asymmetric for both lineages, we were not able to entirely rule out incomplete lineage sorting in generating this pattern. We found no evidence of contemporary gene flow except between two genetic populations of Erophylla. Both lineages exhibited significant isolation by geographic distance. Patterns of genetic structure and gene flow, however, were not explained by differences in relative effective population sizes, island area, sex-biased dispersal (tested only for Erophylla), or surface-level climatological winds. Gene flow among islands appears to be highly restricted, particularly for M. waterhousii, and we suggest that this species deserves increased taxonomic attention and conservation concern.
Migration and dispersal patterns of bats and their influence on genetic structure
Mammal Review, 2013
Bats are important ecosystems service providers, make a significant contribution to biodiversity and can be important pests and disease vectors. In spite of this, information on their migration and dispersal patterns is limited. 2. In temperate bats, migration is most evident in females. This reflects seasonal differences in their habitat requirements, and the fact that seasonally suitable sites can be geographically distant. Tropical bats mainly migrate to track variation in food availability. 3. Little direct information is available on the patterns and drivers of bat dispersal, although drivers may include mate competition and inbreeding avoidance. In many temperate species, differential energy requirements and local resource competition among the sexes drive sexual segregation in the summer: females remain philopatric to their natal region, and frequently to their natal colony, while males disperse. In contrast, many tropical Pteropodidae form single-male/multifemale groups in which local resource defence contributes to female-biased or all-offspring dispersal from the natal site. 4. Population genetic studies are the most common source of evidence used to infer the spatial dynamics of bats. As expected, migratory species tend to have less genetically structured populations over large geographical scales due to mating outside of breeding areas, weak migratory connectivity and long-distance movements. In contrast and as expected, populations of sedentary species tend to be more differentiated at smaller geographical scales. 5. Despite this general pattern, a range of factors, including historical events, dispersal capabilities, and behavioural, ecological and geographical barriers, are implicated in the genetic partitioning of bat populations, irrespective of movement patterns. These factors limit the study of bat movements using only genetic methods. 6. Combining population genetics with other methods, such as mark-recapture, tracking or stable isotope analysis, should provide more insight into the movements of these ecologically and economically important species. bs_bs_banner
Journal of Mammalogy, 2007
Several geographically distinct mitochondrial DNA (mtDNA) lineages of the big brown bat (Eptesicus fuscus) have been documented in North America. Individuals from 2 of these lineages, an eastern and a western form, co-occur within maternity colonies in Colorado. The discovery of 2 divergent mtDNA lineages in sympatry prompted a set of questions regarding possible biological differences between haplotypes. We captured big brown bats at maternity roosts in Colorado and recorded data on body size, pelage color, litter size, roosting and overwintering behaviors, and local distributions. Wing biopsies were collected for genetic analysis. The ND2 region of the mtDNA molecule was used to determine lineage of the bats. In addition, nuclear DNA (nDNA) intron 1 of the b-globin gene was used to determine if mtDNA lineages are hybridizing. Eastern and western mtDNA lineages differed by 10.3% sequence divergence and examination of genetic data suggests recent population expansion for both lineages. Differences in distribution occur along the Colorado Front Range, with an increasing proportion of western haplotypes farther south. Results from nDNA analyses demonstrated hybridization between the 2 lineages. Additionally, no outstanding distinctiveness was found between the mtDNA lineages in natural history characters examined. We speculate that historical climate changes separated this species into isolated eastern and western populations, and that secondary contact with subsequent interbreeding was facilitated by European settlement.