Dataset Information

Post-Pleistocene range expansion of the recently imperiled eastern little brown bat (Myotis lucifugus lucifugus) from a single southern refugium.

ABSTRACT: Myotis lucifugus, once among the most widespread and common bats in North America, has been forecast to be extirpated east of the Rockies in as few as 16 years by the spread of white-nose syndrome. Recent genetic research has demonstrated that this species is paraphyletic and part of a broader species complex; however, only one lineage (Myotis lucifugus lucifugus [M. l. lucifugus]) is present in eastern North America. I used molecular tools and niche modeling to validate this and investigate the role that historical biogeography has played in the phylogenetic and population genetic structure of this species to determine if the eastern subspecies represents an evolutionarily distinct population.To establish the genetic structure within M. l. lucifugus, I densely sampled maternity colonies in Minnesota and sequenced 182 individuals for a portion of cytochrome b. Phylogenetic reconstruction and a haplotype network were used to infer the relationships among mitochondrial haplotypes. Population growth statistics were calculated to determine if there was evidence of significant expansion, and an environmental niche model (ENM) was constructed based on conditions during the last glacial maximum (LGM) to illustrate potential glacial refugia. All individuals derived from a single mitochondrial lineage. Genetic evidence points to population growth starting approximately 18 kya. ENM results show that there was likely a single large southern refugium extending across the southeastern United States and possibly several isolated refugia in western North America. Myotis lucifugus lucifugus likely maintained both a large range and a large population during the peaks of the glacial cycles, and its population appears to have expanded following the retreat of the Laurentide ice sheet. This imperiled lineage likely diverged in isolation from other members of the M. lucifugus/western long-eared Myotis during the Pleistocene.

SUBMITTER: Dixon MD

PROVIDER: S-EPMC3287298 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature

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Post-Pleistocene range expansion of the recently imperiled eastern little brown bat (Myotis lucifugus lucifugus) from a single southern refugium.

Dixon Michael D MD

Ecology and evolution 20111001 2

Myotis lucifugus, once among the most widespread and common bats in North America, has been forecast to be extirpated east of the Rockies in as few as 16 years by the spread of white-nose syndrome. Recent genetic research has demonstrated that this species is paraphyletic and part of a broader species complex; however, only one lineage (Myotis lucifugus lucifugus [M. l. lucifugus]) is present in eastern North America. I used molecular tools and niche modeling to validate this and investigate the ...[more]

PMID: 22393495

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Project description:White-nose syndrome (WNS) is an emerging infectious disease devastating hibernating North American bat populations that is caused by the psychrophilic fungus Geomyces destructans. Previous histopathological analysis demonstrated little evidence of inflammatory responses in infected bats, however few studies have compared other aspects of immune function between WNS-affected and unaffected bats. We collected bats from confirmed WNS-affected and unaffected sites during the winter of 2008-2009 and compared estimates of their circulating levels of total leukocytes, total immunoglobulins, cytokines and total antioxidants. Bats from affected and unaffected sites did not differ in their total circulating immunoglobulin levels, but significantly higher leukocyte counts were observed in bats from affected sites and particularly in affected bats with elevated body temperatures (above 20°C). Bats from WNS-affected sites exhibited significantly lower antioxidant activity and levels of interleukin-4 (IL-4), a cytokine that induces T cell differentiation. Within affected sites only, bats exhibiting visible fungal infections had significantly lower antioxidant activity and levels of IL-4 compared to bats without visible fungal infections. Overall, bats hibernating in WNS-affected sites showed immunological changes that may be evident of attempted defense against G. destructans. Observed changes, specifically elevated circulating leukocytes, may also be related to the documented changes in thermoregulatory behaviors of affected bats (i.e. increased frequencies in arousal from torpor). Alterations in immune function may reflect expensive energetic costs associated with these processes and intrinsic qualities of the immunocapability of hibernating bats to clear fungal infections. Additionally, lowered antioxidant activity indicates a possible imbalance in the pro- versus antioxidant system, may reflect oxidative tissue damage, and should be investigated as a contributor to WNS-associated morbidity and mortality.

Project description:The little brown bat (Myotis lucifugus) is one of the most widespread bat species in North America and is experiencing severe population declines because of an emerging fungal disease, white-nose syndrome (WNS). To manage and conserve this species effectively it is important to understand patterns of gene flow and population connectivity to identify possible barriers to disease transmission. However, little is known about the population genetic structure of little brown bats, and to date, no studies have investigated population structure across their entire range. We examined mitochondrial DNA and nuclear microsatellites in 637 little brown bats (including all currently recognized subspecific lineages) from 29 locations across North America, to assess levels of genetic variation and population differentiation across the range of the species, including areas affected by WNS and those currently unaffected. We identified considerable spatial variation in patterns of female dispersal and significant genetic variation between populations in eastern versus western portions of the range. Overall levels of nuclear genetic differentiation were low, and there is no evidence for any major barriers to gene flow across their range. However, patterns of mtDNA differentiation are highly variable, with high ΦST values between most sample pairs (including between all western samples, between western and eastern samples, and between some eastern samples), while low mitochondrial differentiation was observed within two groups of samples found in central and eastern regions of North America. Furthermore, the Alaskan population was highly differentiated from all others, and western populations were characterized by isolation by distance while eastern populations were not. These data raise the possibility that the current patterns of spread of WNS observed in eastern North America may not apply to the entire range and that there may be broad-scale spatial variation in the risk of WNS transmission and occurrence if the disease continues to spread west.

Project description:BackgroundWe address three key gaps in research on urban wildlife ecology: insufficient attention to (1) grassland biomes, (2) individual- and population-level effects, and (3) vertebrates other than birds. We hypothesized that urbanization in the North American Prairies, by increasing habitat complexity (via the proliferation of vertical structures such as trees and buildings), thereby enhancing the availability of day-roosts, tree cover, and insects, would benefit synanthropic bats, resulting in increased fitness among urban individuals.Methodology/principal findingsOver three years, we captured more than 1,600 little brown bats (Myotis lucifugus) in urban and non-urban riparian sites in and around Calgary, Alberta, Canada. This species dominated bat assemblages throughout our study area, but nowhere more so than in the city. Our data did not support most of our specific predictions. Increased numbers of urban bats did not reflect urbanization-related benefits such as enhanced body condition, reproductive rates, or successful production of juveniles. Instead, bats did best in the transition zone situated between strictly urban and rural areas.Conclusions/significanceWe reject our hypothesis and explore various explanations. One possibility is that urban and rural M. lucifugus exhibit increased use of anthropogenic roosts, as opposed to natural ones, leading to larger maternity colonies and higher population densities and, in turn, increased competition for insect prey. Other possibilities include increased stress, disease transmission and/or impacts of noise on urban bats. Whatever the proximate cause, the combination of greater bat population density with decreased body condition and production of juveniles indicates that Calgary does not represent a population source for Prairie bats. We studied a highly synanthropic species in a system where it could reasonably be expected to respond positively to urbanization, but failed to observe any apparent benefits at the individual level, leading us to propose that urban development may be universally detrimental to bats.

Dataset Information

Post-Pleistocene range expansion of the recently imperiled eastern little brown bat (Myotis lucifugus lucifugus) from a single southern refugium.

Publications

Post-Pleistocene range expansion of the recently imperiled eastern little brown bat (Myotis lucifugus lucifugus) from a single southern refugium.

Similar Datasets

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