Ecology Of Bats Research Articles

Home ranges, directionality and the influence of moon phases on the movement ecology of Indian flying fox males in southern India.

Flying foxes of the genus Pteropus are amongst the largest fruit bats and potential long-range pollinators and seed dispersers in the paleotropics. Pteropus giganteus (currently P. medius) is the only flying fox that is distributed throughout the Indian mainland, including in urban and rural areas. Using GPS telemetry, we mapped the home ranges and examined flight patterns in P. giganteus males across moon phases in a semi-urban landscape in southern India. Home range differed between the tracked males (n=4), likely due to differences in their experience in the landscape. We found that nightly time spent outside the roost, distance commuted and the number of sites visited by tracked individuals did not differ significantly between moon phases. In 61% of total tracked nights across bats, the first foraging site was within 45˚ of the emergence direction. At the colony-level, scan-based observations showed emergence flights were mostly in the northeast (27%), west (22%) and southwest (19%) directions that could potentially be related to the distribution of foraging resources. The movement ecology of fruit bats in relation to the pollination and seed dispersal services they provide requires to be investigated in future studies. This article has an associated First Person interview with the first author of the paper.

First person – Baheerathan Murugavel

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping researchers promote themselves alongside their papers. Baheerathan Murugavel is first author on ‘ Home ranges, directionality and the influence of moon phases on the movement ecology of Indian flying fox males in southern India’, published in BiO. Baheerathan is a PhD Student in the lab of Professor Hema Somanathan at School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, India, investigating the behaviour, sensory, and movement ecology of bats.

Seasonal differences in day-roost selection by Northern long-eared bats (Myotis septentrionalis) in Louisiana and a meta-analytical comparison across North America

Resting-site selection involves some of the most important decisions made by organisms. For forest-dwelling bats, where to roost influences not only resting but also many other activities that affect fitness such as raising young, thermoregulation, communication, and evasion of predators. Across much of North America, many bats roost in trees during summer and hibernate in caves during winter and as such, most of the focus on roosting ecology and forest management has been during summer. Along much of the Atlantic and Gulf coastal plains in the southern portion of North America, winters are relatively warm, few caves exist, and many bat species are active. Herein, we described the tree-roosting ecology of Northern long-eared bats (Myotis septentrionalis) in Louisiana in both summer and winter, examined roost selection, compared selection seasonally, and compared various aspects of roosting ecology in Louisiana to other areas across North America. We found that in Louisiana M. septentrionalis roosted primarily in pine trees and found no significant differences in roosting characteristics between sexes. Year-round, bats preferred roosts in trees in more advanced stages of decay than available trees. In summer, bats selected for plot level characteristics such as higher density of trees that were large and in more advanced stages of decay. In contrast, in winter, bats selected for tree characteristics such as those with taller, greater diameter and with more exfoliating bark. Comparisons with 21 other studies across North America indicated variation in selected roost characteristics among regions. These results highlight variability in roost selection through space and time and suggest that management strategies that are tailored to specific sites may be most effective for enhancing roosting opportunities of M. septentrionalis and ultimately the conservation of this species.

Ecological and physiological parameters of Myotis dasycneme (Mammalia: Chiroptera: Vespertilionidae) in the Urals

Understanding the evolution of bat homeostasis and the formation of an adaptive strategy of animals to climatic fluctuations and pathogens determine the need for further laboratory and modelling studies devoted to the ecology and physiology of bats. This study was aimed to assess the hematological and biochemical parameters of homeostasis of Myotis dasycneme, a protected endemic bat species of the Urals. Animals (n = 65) were caught in the zone of mass habitation of bats in the Southern Urals (Chelyabinsk Region) and the Middle Urals (Sverdlovsk Region). We used samples from M. dasycneme populations in the Ilmensky State Nature Reserve (Russia). Multivariate non-parametric analysis of variance has shown no significant sex differences in red blood parameters in bats (p > 0.05). The blood of bats was characterised by high levels of hemoglobin (167.9–187.2 g/L), hematocrit (47.2–51.5%), erythrocytes (9.6–11.5 × 1012/L), platelets (136.8–271.3 × 109/L). In the autumn-winter period of hibernation, under hypoxic load on the body and prolonged exposure to low positive and near-zero temperatures, an increased content of agranulocytes (50.6–53.6%) was noted in the blood of females and males. The spring process of awakening and exit from deep hypothermia is accompanied by the reactivity of the innate immune system in males and females (granulocytes: 53.2–54.2%). During the winter period of hypobiosis in bats, the basal metabolism increases and the concentration of glucose in the blood increases to 4.7 ± 0.5 mmol/L (p < 0.05). The absence of statistically significant sex differences in the content of glucose and triglycerides (p > 0.05) in the blood plasma of animals has been noted. This ensures metabolic processes (carbohydrate and lipid metabolism) in all seasonal periods of their annual life cycle. The amino acid fund of blood plasma of bats is represented by 22 amino acids. In the blood plasma of males and females, the fund of free amino acids decreases during the year in the following direction: summer ≥ autumn ≥ winter > spring (p < 0.05). There were no sex differences (p > 0.05) in the content of amino acid metabolic groups, namely glycogenic (GGAA), non-essential (NEAA), branched carbon chain (BCCA). A significant accumulation of metabolically active glucoplastic alanine in autumn (3.1 times) and winter (2.3 times) in the blood of females, and in autumn and winter (2.0 and 1.9 times) in males indicates its role as a low-temperature adaptogen. Under conditions of low positive temperatures, in the blood plasma of M. dasycneme, the disappearance of the essential amino acid tryptophan was observed (p < 0.05). This suggests a high demand for serotonin synthesis as one of triggers actively involved in maintaining hypothermia and hypometabolism in bats. Thus, the biochemical and immunohematological parameters, obtained in the course of the study, make it possible to expand and systematise the available information on the mechanisms of participation of the blood system in the regulatory processes in bats. They can be used for long-term monitoring in solving problems of conservation and abundance of healthy populations of bats that adapt both to seasonal modulations and biotic factors, and to stressors of zoonotic significance.

Characterising diel activity patterns to design conservation measures: Case study of European bat species

Although diel activity time is a major axis of species' niche space, very few conservation measures focus on preserving daily periods free of anthropogenic pressures. While the spatial ecology of bats has received much attention, less is known about their temporal ecology, the knowledge being dispersed in studies of limited taxonomical, spatial and temporal range. We used data from the French bat monitoring program based on citizen science and standardised acoustic recordings (4409 sites monitored and 9807 nights monitored from 2014 to 2020) to characterise the diel activity patterns of 20 bat species so that their consideration in mitigation measures can help conservation. We designed a method to extract times of key descriptors and describe bat activity distribution throughout the night. We found that bat species could be separated in three functional groups characterised by a crepuscular activity, an activity that occurs when it is completely dark or an intermediate activity. We showed variations of diel activity patterns depending on season. We argue that accounting for these complex diel activity patterns would help design efficient mitigation measures, for instance to reduce the exposure of bats to light pollution or wind turbines. Overall, we advocate multi-taxa approaches to design conservation policies adapted to both the temporal and spatial distributions of species.

EcoCountHelper: an R package and analytical pipeline for the analysis of ecological count data using GLMMs, and a case study of bats in Grand Teton National Park.

Here we detail the use of an R package, 'EcoCountHelper', and an associated analytical pipeline aimed at making generalized linear mixed-effects model (GLMM)-based analysis of ecological count data more accessible. We recommend a GLMM-based analysis workflow that allows the user to (1) employ selection of distributional forms (Poisson vs negative binomial) and zero-inflation (ZIP and ZINB, respectively) using AIC and variance-mean plots, (2) examine models for goodness-of-fit using simulated residual diagnostics, (3) interpret model results via easy to understand outputs of changes in predicted responses, and (4) compare the magnitude of predictor variable effects via effects plots. Our package uses a series of easy-to-use functions that can accept both wide- and long-form multi-taxa count data without the need for programming experience. To demonstrate the utility of this approach, we use our package to model acoustic bat activity data relative to multiple landscape characteristics in a protected area (Grand Teton National Park), which is threatened by encroaching disease-white nose syndrome. Global threats to bat conservation such as disease and deforestation have prompted extensive research to better understand bat ecology. Notwithstanding these efforts, managers operating on lands crucial to the persistence of bat populations are often equipped with too little information regarding local bat activity to make informed land-management decisions. In our case study in the Tetons, we found that an increased prevalence of porous buildings increases activity levels of Eptesicus fuscus and Myotis volans; Myotis lucifugus activity decreases as distance to water increases; and Myotis volans activity increases with the amount of forested area. By using GLMMs in tandem with 'EcoCountHelper', managers without advanced programmatic or statistical expertise can assess the effects of landscape characteristics on wildlife in a statistically-robust framework.

Comment on Dunbar et al. (2022) “Webslinger vs. Dark Knight: First record of a false widow spider Steatoda nobilis preying on a pipistrelle bat in Britain”

Abstract. A recent publication in Ecosphere claimed to report the first case of a predation event by a theridiid spider on a bat globally and the first case of a member of the genus Steatoda preying on a mammal globally, and the paper concludes with possible implications for public health. Predation is typically understood to mean “capture, kill, and eat”. However, none of these aspects had been observed. Moreover, key aspects of bat biology were not taken into account, including that the bat in question was a flightless newborn, the capture of which would require some explanation. We revisit this interesting observation considering both bat and spider ecology.

Mapping the Spatiotemporal Distribution of Bovine Rabies in Colombia, 2005-2019.

Introduction: Rabies is caused by a virus belonging to the genus Lyssavirus and family Rhabdoviridae, which can infect any mammal including humans. Hematophagous, fructivorous, and insectivorous bats have become the main reservoir of sylvatic rabies in Latin America. In the sylvatic cycle, hematophagous bats are usually the main reservoir. In contrast, dogs and cats fulfil this critical role in the urban cycle. However, in rural areas, the most affected animals are bovines. They show clinical signs such as behavioural changes, hypersalivation, muscle tremors, spasms caused by extensive damage to the central nervous system, and death from respiratory paralysis. Objective: To describe the spatiotemporal distribution of bovine rabies in Colombia from 2005 to 2019. Methods: Retrospective cross-sectional descriptive observational study, based on the monthly reports of the Colombian Agricultural Institute (ICA) on the surveillance of bovine rabies in Colombia from 2005 to 2019, retrieved from its official website. The data were converted to databases in Microsoft Access 365®. Multiple epidemiological maps were developed with the GIS software Kosmo RC1® 3.0 coupled to the shape files (.shp) of all the country’s municipalities. Results: During the study period, 4888 cases of rabies were confirmed in cattle, ranging from a peak of 542 cases (11.1%) in 2014 to 43 in 2019 (0.88%). From 2014 to 2019, there has been a significant reduction in the annual national number of cases (r2 = 0.9509, p < 0.05). In 2019, 32.6% of the cases occurred in January, and 48.8% occurred in the department of Sucre. In 2009, the maximum number of spatial clusters (13) occurred in the Orinoquia region, where other clusters were also identified in 2005, 2006 and 2008. In 2018, 98 outbreaks were identified that led to the death of cattle and other animals, 28.6% of them in the department of Sucre. In the first half of 2019, of 38 outbreaks, 55.2% were identified in Sucre. Conclusions: It is necessary to review the current national program for the prevention and control of rabies in cattle, incorporating concepts from the ecology of bats, as well as the prediction of contagion waves of geographical and temporal spread in the context of the OneHealth Approach. Sylvatic rabies remains a threat in Colombia that requires further study.

Effect of forest areas configuration on the community of insectivorous bats in agroforestry landscapes

AbstractIn Chile, many aspects of the ecology of bats and their distribution are unknown, despite their ecological and economic importance. This situation does not allow a correct implementation of conservation efforts even when they are legally recognized as beneficial animals for agriculture. Here, we studied the bats' activity and community in two agricultural landscape types (homogeneous vs. heterogeneous) in a hotspot of biodiversity in the centre‐south of Chile. We monitored four transects of 10 km per landscape type with 10 listening points separated by 1 km. These transects were repeated 5 times, once per month. We evaluated the bats activity according to the forest cover type (native, mixed and plantations) and the isolated trees density. Our results showed that the heterogeneous landscape was dominated by T. brasiliensis while the homogeneous landscape was by Lasiurus spp. However, only the species T. brasiliensis was affected by the landscape type. In the heterogeneous landscape, only the forest cover variables had significance in the activity of the bat species, where Lasiurus spp. and M. chiloensis had a positive response for native and mixed forest, as well as Lasiurus spp. had a negative response for plantations. The density of isolated trees had a negative effect on the activity of T. brasiliensis and Lasiurus spp. in the homogeneous landscape type. Our results showed the importance of considering the forest elements in agroforestry landscape to conserve bat communities.

Pathogen spillover driven by rapid changes in bat ecology

During recent decades, pathogens that originated in bats have become an increasing public health concern. A major challenge is to identify how those pathogens spill over into human populations to generate a pandemic threat1. Many correlational studies associate spillover with changes in land use or other anthropogenic stressors2,3, although the mechanisms underlying the observed correlations have not been identified4. One limitation is the lack of spatially and temporally explicit data on multiple spillovers, and on the connections among spillovers, reservoir host ecology and behaviour and viral dynamics. We present 25 years of data on land-use change, bat behaviour and spillover of Hendra virus from Pteropodid bats to horses in subtropical Australia. These data show that bats are responding to environmental change by persistently adopting behaviours that were previously transient responses to nutritional stress. Interactions between land-use change and climate now lead to persistent bat residency in agricultural areas, where periodic food shortages drive clusters of spillovers. Pulses of winter flowering of trees in remnant forests appeared to prevent spillover. We developed integrative Bayesian network models based on these phenomena that accurately predicted the presence or absence of clusters of spillovers in each of the 25 years. Our long-term study identifies the mechanistic connections between habitat loss, climate and increased spillover risk. It provides a framework for examining causes of bat virus spillover and for developing ecological countermeasures to prevent pandemics.

Opportunities and Limitations of Molecular Methods for Studying Bat-Associated Pathogens.

Bats have been identified as reservoirs of zoonotic and potentially zoonotic pathogens. Significant progress was made in the field of molecular biology with regard to infectious diseases, especially those that infect more than one species. Molecular methods, sequencing and bioinformatics have recently become irreplaceable tools in emerging infectious diseases research and even outbreak prediction. Modern methods in the molecular biology field have shed more light on the unique relationship between bats and viruses. Here we provide readers with a concise summary of the potential and limitations of molecular methods for studying the ecology of bats and bat-related pathogens and microorganisms.

Ecological determinants of rabies virus dynamics in vampire bats and spillover to livestock.

The pathogen transmission dynamics in bat reservoirs underpin efforts to reduce risks to human health and enhance bat conservation, but are notoriously challenging to resolve. For vampire bat rabies, the geographical scale of enzootic cycles, whether environmental factors modulate baseline risk, and how within-host processes affect population-level dynamics remain unresolved. We studied patterns of rabies exposure using an 11-year, spatially replicated sero-survey of 3709 Peruvian vampire bats and co-occurring outbreaks in livestock. Seroprevalence was correlated among nearby sites but fluctuated asynchronously at larger distances. A generalized additive mixed model confirmed spatially compartmentalized transmission cycles, but no effects of bat demography or environmental context on seroprevalence. Among 427 recaptured bats, we observed long-term survival following rabies exposure and antibody waning, supporting hypotheses that immunological mechanisms influence viral maintenance. Finally, seroprevalence in bats was only weakly correlated with outbreaks in livestock, reinforcing the challenge of spillover prediction even with extensive data. Together our results suggest that rabies maintenance requires transmission among multiple, nearby bat colonies which may be facilitated by waning of protective immunity. However, the likelihood of incursions and dynamics of transmission within bat colonies appear largely independent of bat ecology. The implications of these results for spillover anticipation and controlling transmission at the source are discussed.

Landscape and age dynamics of immune cells in the Egyptian rousette bat.

Bats harbor high-impact zoonotic viruses often in the absence of disease manifestation. This restriction and disease tolerance possibly rely on specific immunological features. In-depth molecular characterization of cellular immunity and imprinting of age on leukocyte compartments remained unexplored in bats. We employ single-cell RNA sequencing (scRNA-seq) and establish immunostaining panels to characterize the immune cell landscape in juvenile, subadult, and adult Egyptian rousette bats (ERBs). Transcriptomic and flow cytometry data reveal conserved subsets and substantial enrichments of CD79a+ B cells and CD11b+ Tcells in juvenile animals, whereas neutrophils, CD206+ myeloid cells, and CD3+ Tcells dominate as bats reach adulthood. Despite differing frequencies, phagocytosis of circulating and tissue-resident myeloid cells and proliferation of peripheral and splenic lymphocytes are analogous in juvenile and adult ERBs. We provide a comprehensive map of the immune landscape in ERBs and show age-imprinted resilience progression and find that variability in cellular immunity only partly recapitulates mammalian archetypes.

Seasonal and Nightly Activity Patterns of Migrating Silver-Haired Bats (Lasionycteris noctivagans) Compared to Non-Migrating Big Brown Bats (Eptesicus fuscus) at a Fall Migration Stopover Site

Migrating temperate bats travel hundreds and perhaps thousands of kilometers, which necessitates making use of stopover sites. Migratory birds use stopover sites to rest and refuel for subsequent migratory flights, but it isn't clear what bats do during their comparatively brief stopovers. We used acoustic monitoring to compare activity patterns of migrating silver-haired bats (Lasionycteris noctivagans) and resident big brown bats (Eptesicus fuscus) at Long Point, Ontario, Canada. From September 1 to October 31 2020 we recorded 4,333 echolocation passes from our two focal species and quatified feeding buzzes in those recordings. Migratory L. noctivagans passed through in two waves, one of which had been identified by previous study, and a second suggesting that the migratory period may be longer than previously identified. Eptesicus fuscus was primarily active only in the early and late parts of the night, in contrast to the activity pattern of L. noctivagans which were similarly active and foraging at dusk and dawn, but also during the middle parts of the night. Our acoustic monitoring data complement previous data collected from bat captures and radiotelemetry to provide further insight into stopover behaviors and ecology of temperate migratory bats.

Bioclimatic Envelopes for Two Bat Species from a Tropical Island: Insights on Current and Future Distribution from Ecological Niche Modeling

Bats perform critical ecosystem functions, including the pollination, seed dispersal, and regulation of invertebrate populations. Yet, bat populations are declining worldwide primarily due to habitat loss and other anthropogenic stressors. Thus, studies on bat ecology, particularly on environmental determinants of bat occupancy, are paramount to their conservation. High mobility, nocturnal behavior, and roosting site selection of bats make conventional surveys challenging. Moreover, little is known about geographic distribution, habitat suitability, and responses to climate change among tropical bat species. To bridge these research gaps, we applied ecological niche modeling to two Ceylonese bat species, Kerivoula malpasi and Kerivoula picta, to map their geographic distribution. Seasonal variations in temperature and precipitation were critical environmental predictors of bat distribution in general. Southwestern lowland forests contained the most optimal habitats for the relatively wide-ranging Kerivoula picta, while the central highlands provided the most suitable habitats for the narrow-ranging Kerivoula malpasi. No tangible changes in the highly suitable habitats were evident in response to projected climate change for either species. Yet, the optimal ranges of K. malpasi can become fragmented in the future, whereas the most optimal habitats for K. picta are likely to become spatially contiguous in the future. Habitat availability or fundamental niche alone is insufficient to reliably forecast species persistence, thus we caution against considering these two bat species as resilient to climate change. Our findings will enable the conservation authorities to initiate preemptive conservation strategies, such as the establishment of landscape-scale habitat connectivity and management of buffer zones around conservation lands. We also encourage conservation authorities to employ ecological niche models to map potential species distributions and to forecast range shifts due to climate change.

Uncertainty and ignored information in the analysis of bat ultrasound: Bayesian approximation to the rescue

Bat ultrasound analysis has been around for several decades and it is one of the most important tools in studies of bat ecology. Discrimination between species is based on intra-specific features of echolocation calls. Identification of species and genera in audio files can be attempted either manually or through software which performs a fully automated discrimination between species. However, significant overlap in various features (e.g. frequencies of calls) exists between species and even genera. Species ID is therefore often not an absolute conclusion, but rather an opinion or best guess, as opposed to DNA tests or measurements on external characters of captured bats. To make things even worse, the probability of actually observing a bat of a given species in space and time is ignored when performing bat ultrasound analysis. This study introduces Bayesian approximation through a new method we have named Alternative Bayesian Bat Analysis (ABBA). We show, through a simple proof-of-concept example, the importance of adding information about the local composition of the bat community, hence making informed decisions regarding which species is most likely present in audio files. The superior performance of ABBA is also shown through an example using R code. Here, we use simulated data for three Pipistrellus spp., a genus with significant overlap in frequencies, but the code can easily be adapted to other bat species and genera worldwide. ABBA outperformed the non-Bayesian approach for all three species. The rare species in the simulated data set was super-inflated when using the non-Bayesian method. Further the results show, contrarily to common belief, that the frequency dominated by a given species in a data set, depends on the composition of the bat fauna and not just means and SDs reported in the literature. ABBA allows researchers to include all observations in statistical modeling, rather than excluding observations, an approach which can affect the reliability of studies. This study also, to a great extent, explains the poor performance of software attempting automated bat ID. Implementing Bayesian algorithms, and thereby allowing users to interact with the software, should significantly improve their performance.

Social Communication in Big Brown Bats

Bats are social mammals that display a wide array of social communication calls. Among them, it is common for most bats species to emit distress, agonistic, appeasement and infant isolation calls. Big brown bats (Eptesicus fuscus) are no different: They are gregarious animals living in colonies that can comprise hundreds of individuals. These bats live in North America and, typically found roosting in man-made structures like barns and attics, are considered common. They are insectivorous laryngeal echolocators, and while their calls and associated brain mechanisms in echolocation are well-documented, much less is known about their neural systems for analyzing social vocalizations. In this work we review what we know about the social lives of big brown bats and propose how to consolidate the nomenclature used to describe their social vocalizations. Furthermore, we discuss the next steps in the characterization of the social structure of this species and how these studies will advance both research in neuroethology and ecology of big brown bats.

Trematodes of Genera Gyrabascus and Parabascus from Bats in European Russia: Morphology and Molecular Phylogeny.

Simple SummaryThe ecology of bats determines their unique parasitic fauna. Most species of worms from bats are highly specialized parasites. We studied parasitic worms of bats that died of natural causes, using classical morphological and molecular phylogenetic approaches. Original drawings, descriptions, and results of molecular phylogenetic analysis for five species of trematodes were provided. We established a broad morphological variability in the studied trematode species, which means that the identification of closely related species may be problematic for researchers. We proposed a taxonomic key for the reliable identification of the studied trematode species. The results of our study contribute to the knowledge of bat helminths and host-parasite relationships in general.Morphological variability of trematodes from bats (Chiroptera) is poorly studied. Since the variability of adult digenean specimens may be rather high, morphological features are often insufficient for the identification of closely related species, and confirmation with the use of molecular data is required. The aim of our study was to combine the morphological and molecular phylogenetic analyses of several bat trematodes from the genera Gyrabascus and Parabascus (Pleurogenidae): Gyrabascus amphoraeformis, Gyrabascus oppositus, Parabascus lepidotus, Parabascus duboisi, and Parabascus semisquamosus, of which G. amphoraeformis and G. oppositus are little known in European Russia. We made detailed morphological descriptions of these trematodes from several definitive hosts, analyzed morphometric features, and generated new partial sequences of the 28S rRNA gene. A broad variability of trematodes of the genera Gyrabascus and Parabascus was revealed both from various host species and from specimens of the same host species. We propose a new taxonomic key for the identification of the studied species. Certain host specificity of these trematodes was revealed.

Bats (Mammalia, Chiroptera) from a cave area in NW Italy

Caves play an important role in bat ecology, offering natural roosting and wintering sites. In the reproductive period, bats need to find an effective foraging environment away from the cave entrance, but only few studies have considered the use of foraging habitats in the immediate proximity of the caves. We provide a list of 18 bat species and 5 bat acoustic groups observed in a system of 81 caves in NW Italy. Winter censuses carried out during 17 years showed an increase of the Greater Horseshoe bat, a species of conservation concern. In the summer period this rare species was also observed foraging in nearby areas. Recording of bat calls in the summer period was performed both at cave entrances and in three foraging habitats present in the area surrounding the cave (woods, agricultural mosaic with artificial light, dark mosaic). Light mosaics and woods showed the highest foraging activity (160.3 and 72.0 pass/hour), while woods and cave entrances were accessed by the largest number of bat species. Our survey improves the inventory of bat species in a poorly sampled area, and we recommend a reduced tourism access, thereby promoting preservation of bats.

Positively selected genes in the hoary bat (Lasiurus cinereus) lineage: prominence of thymus expression, immune and metabolic function, and regions of ancient synteny.

BackgroundBats of the genus Lasiurus occur throughout the Americas and have diversified into at least 20 species among three subgenera. The hoary bat (Lasiurus cinereus) is highly migratory and ranges farther across North America than any other wild mammal. Despite the ecological importance of this species as a major insect predator, and the particular susceptibility of lasiurine bats to wind turbine strikes, our understanding of hoary bat ecology, physiology, and behavior remains poor.MethodsTo better understand adaptive evolution in this lineage, we used whole-genome sequencing to identify protein-coding sequence and explore signatures of positive selection. Gene models were predicted with Maker and compared to seven well-annotated and phylogenetically representative species. Evolutionary rate analysis was performed with PAML.ResultsOf 9,447 single-copy orthologous groups that met evaluation criteria, 150 genes had a significant excess of nonsynonymous substitutions along the L. cinereus branch (P < 0.001 after manual review of alignments). Selected genes as a group had biased expression, most strongly in thymus tissue. We identified 23 selected genes with reported immune functions as well as a divergent paralog of Steep1 within suborder Yangochiroptera. Seventeen genes had roles in lipid and glucose metabolic pathways, partially overlapping with 15 mitochondrion-associated genes; these adaptations may reflect the metabolic challenges of hibernation, long-distance migration, and seasonal variation in prey abundance. The genomic distribution of positively selected genes differed significantly from background expectation by discrete Kolmogorov–Smirnov test (P < 0.001). Remarkably, the top three physical clusters all coincided with islands of conserved synteny predating Mammalia, the largest of which shares synteny with the human cat-eye critical region (CECR) on 22q11. This observation coupled with the expansion of a novel Tbx1-like gene family may indicate evolutionary innovation during pharyngeal arch development: both the CECR and Tbx1 cause dosage-dependent congenital abnormalities in thymus, heart, and head, and craniodysmorphy is associated with human orthologs of other positively selected genes as well.