Veronica A. Brown

Population growth of Mexican free-tailed bats (Tadarida brasiliensis mexicana) predates human agricultural activity.

BackgroundHuman activities, such as agriculture, hunting, and habitat modification, exert a significant effect on native species. Although many species have suffered population declines, increased population fragmentation, or even extinction in connection with these human impacts, others seem to have benefitted from human modification of their habitat. Here we examine whether population growth in an insectivorous bat (Tadarida brasiliensis mexicana) can be attributed to the widespread expansion of agriculture in North America following European settlement. Colonies of T. b. mexicana are extremely large (~106 individuals) and, in the modern era, major agricultural insect pests form an important component of their food resource. It is thus hypothesized that the growth of these insectivorous bat populations was coupled to the expansion of agricultural land use in North America over the last few centuries.ResultsWe sequenced one haploid and one autosomal locus to determine the rate and time of onset of population growth in T. b. mexicana. Using an approximate Maximum Likelihood method, we have determined that T. b. mexicana populations began to grow ~220 kya from a relatively small ancestral effective population size before reaching the large effective population size observed today.ConclusionsOur analyses reject the hypothesis that T. b. mexicana populations grew in connection with the expansion of human agriculture in North America, and instead suggest that this growth commenced long before the arrival of humans. As T. brasiliensis is a subtropical species, we hypothesize that the observed signals of population growth may instead reflect range expansions of ancestral bat populations from southern glacial refugia during the tail end of the Pleistocene.

Genetic analysis of populations of the threatened bat Pteropus mariannus

The Mariana flying fox (Pteropus mariannus) has suffered substantial decline in recent years. Taxonomic classification of P. mariannus has been inconsistent, with subspecies designations based mainly on geography and morphological variation within small sample sizes. In this study, we examine relationships of P. mariannus across two island groups in the western Pacific Ocean. Microsatellite data and mitochondrial sequences, from D-loop, cytochrome oxidase I, and cytochrome b, suggest that the population on the islands of Palau is genetically isolated from the populations in the Mariana Islands. Our data confirm that the bats of Palau should be considered a separate conservation unit from the bats of the Mariana Islands, supporting the current subspecies separation of these two populations. Our results also suggest that there is gene flow among islands within the Mariana archipelago and that the bats on these islands, currently classified as two subspecies, should be managed as a single conservation unit, although we refrain from suggesting taxonomic revisions until genetic and morphological data become available from geographically intermediate populations.

Rapid range expansion of the Brazilian free-tailed bat in the southeastern United States, 2008–2016

Brazilian free-tailed bats (Tadarida brasiliensis) are one of the most widely distributed bat species in the Americas, often engaging in rapid, long-distance dispersals. Here, we document that, since ca. 2007, these bats have expanded their range into western North Carolina, eastern Tennessee, and Virginia. Reports from wildlife control professionals, wildlife rehabilitators, regional submissions of bats for rabies testing, acoustic monitoring, and the presence of T. brasiliensis in buildings and bat houses indicate that these bats are now established in year-round colonies in areas previously thought outside their range limits. The geographic distributions of many organisms are currently shifting to higher latitudes in response to changing climate. We hypothesize that a coldtolerant thermal physiology that allows these largely tropical bats to enter extended torpor contributes to the ability of T. brasiliensis to establish populations in formerly cooler regions, and propose that their rapid northward expansion is facilitated by climate change and their tendency to explore new habitats and use a wide diversity of roost sites. Because of their abundance and use of man-made structures, we anticipate that the range expansion of T. brasiliensis will have implications for public health, ecosystem services, and bat conservation.

Illuminating prey selection in an insectivorous bat community exposed to artificial light at night

1.Light pollution has been increasing around the globe and threatens to disturb natural rhythms of wildlife species. Artificial light impacts the behaviour of insectivorous bats in numerous ways, including foraging behaviour, which may in turn lead to altered prey selection. 2.In a manipulative field experiment, we collected faecal samples from six species of insectivorous bats in naturally dark and artificially lit conditions, and identified prey items using molecular methods to investigate effects of light pollution on prey selection. 3.Proportional differences of identified prey were not consistent and appeared to be species specific. Red bats, little brown bats, and gray bats exhibited expected increases in moths at lit sites. Beetle-specialist big brown bats had a sizeable increase in beetle consumption around lights, while tri-colored bats and evening bats showed little change in moth consumption between experimental conditions. Dietary overlap was high between experimental conditions within each species, and dietary breadth only changed significantly between experimental conditions in one species, the little brown bat. 4.Policy implications. Our results, building on others, demonstrate that bat-insect interactions may be more nuanced than the common assertion that moth consumption increases around lights. They highlight the need for a greater mechanistic understanding of bat-light interactions to predict which species will be most affected by light pollution. Given differences in bat and insect communities, we advocate biologists, land stewards, and civil planners work collaboratively to determine lighting solutions that minimize changes in foraging behaviour of species in the local bat community. Such efforts may allow stakeholders to more effectively craft management strategies to minimize unnatural shifts in prey selection caused by artificial lights. This article is protected by copyright. All rights reserved.

Identification of Southeastern Bat Species Using Noninvasive Genetic Sampling of Individual Guano Pellets

Abstract The impact of white-nose syndrome on North American bat populations may limit the effectiveness of traditional monitoring methods, including roost surveys, mist netting, and acoustic monitoring, and, in turn, determination of bat species occurrence. Genetic markers from deoxyribonucleic acid (DNA) extracted from feces (i.e., guano pellets) may provide an effective alternative method for assessing occurrence. We used an existing genetic marker from the 16S ribosomal subunit, mitochondrial DNA, to create a DNA sequence database for the 16 species of bats known to occur in Tennessee. We used our database to identify bat species from DNA extracted from 68 guano pellets collected from accumulations found in buildings of Great Smoky Mountains National Park from May to August 2015. No bats were directly observed at 19 roost buildings (55.9% of all identified roost buildings), where genetic analysis of guano was the only method available to determine species occurrence. Two of the species we detected roo...

Comparative Phylogeography of Pteropus samoensis and P. tonganus (Pteropodidae: Chiroptera) in the South Pacific

Pteropids are large, highly mobile bats that are distributed widely across islands of the Pacific and Indian Oceans, southern Asia, and Australia. Dispersal behaviors and colonization patterns of pteropid species among oceanic islands are poorly known. In the southern Pacific, Pteropus samoensis and P. tonganus have partially overlapping ranges, existing in sympatry on the Samoan and Fijian archipelagos. These species exhibit differences in morphology and roosting behavior, with P. samoensis being smaller and tending to roost solitarily or in small groups. Here, we use genetic data to explore whether these species also exhibit differences with regard to patterns of population genetic structure within and between these archipelagos. Phylogenetic analyses of mitochondrial DNA are consistent with earlier morphological recognition of different subspecies of P. samoensis on the Samoan vs. Fijian archipelagos. Patterns of mtDNA haplotype sharing suggest that P. tonganus experiences restricted gene flow between, but not within archipelagos, while P. samoensis shows significant structuring both between and within archipelagos. Species-level differences in patterns of population structure among islands within archipelagos may be due to interspecific differences in morphology, roosting ecology, and/or feeding ecology that can be affected by human influences. Our results directly bear on the conservation of these species, suggesting that (1) populations of both species from the archipelagos of Samoa and Fiji should each be considered as separate conservation units, (2) P. samoensis are much less likely than P. tonganus to naturally supplement local populations through inter-island dispersal, and (3) P. tonganus may experience more severe population bottlenecks during and following cyclones resulting in lower mitochondrial genetic diversity than in P. samoensis.

Disparities in second‐generation DNA metabarcoding results exposed with accessible and repeatable workflows

Different second‐generation sequencing technologies may have taxon‐specific biases when DNA metabarcoding prey in predator faeces. Our major objective was to examine differences in prey recovery from bat guano across two different sequencing workflows using the same faecal DNA extracts. We compared results between the Ion Torrent PGM and the Illumina MiSeq with similar library preparations and the same analysis pipeline. We focus on repeatability and provide an R Notebook in an effort towards transparency for future methodological improvements. Full documentation of each step enhances the accessibility of our analysis pipeline. We tagged DNA from insectivorous bat faecal samples, targeted the arthropod cytochrome c oxidase I minibarcode region and sequenced the product on both second‐generation sequencing platforms. We developed an analysis pipeline with a high operational taxonomic unit (OTU) clustering threshold (i.e., ≥98.5%) followed by copy number filtering to avoid merging rare but genetically similar prey into the same OTUs. With this workflow, we detected 297 unique prey taxa, of which 74% were identified at the species level. Of these, 104 (35%) prey OTUs were detected by both platforms, 176 (59%) OTUs were detected by the Illumina MiSeq system only, and 17 (6%) OTUs were detected using the Ion Torrent system only. Costs were similar between platforms but the Illumina MiSeq recovered six times more reads and four additional insect orders than did Ion Torrent. The considerations we outline are particularly important for long‐term ecological monitoring; a more standardized approach will facilitate comparisons between studies and allow faster recognition of changes within ecological communities.