Behavioural determinants of gene flow in the bat Miniopterus schreibersii

Context-specific variation and repeatability in behavioral traits of bent-wing bats

Animals may show consistent among-individual behavioral differences over time and in different contexts, and these tendencies may be correlated to one another and emerge as behavioral syndromes. The cross-context variation in these behavioral tendencies, however, is rarely explored with animals in contexts associated with different locomotion modes. This study assessed the variation and repeatability in behavioral traits of bent-wing bats Miniopterus fuliginosus in southern Taiwan, and the effects of contextual settings associated with locomotion mode. The bats were sampled in the dry winter season, and their behaviors were measured in hole-board box (HB) and tunnel box (TB) tests, both suited for quadrupedal movements of the bats, and flight-tent (FT) tests that allowed for flying behaviors. The bats in the FT tests showed more interindividual and between-trial behavioral variation than those in the HB and TB tests. Nearly all of the behaviors in the TB and FT tests, but only half of those in the HB tests, showed medium to high repeatability. These repeatable behaviors were grouped into distinct behavioral traits of boldness, activity, and exploration, which were correlated to one another across contexts. In addition, we observed a consistently higher correlation between behavioral categories across the HB and TB contexts than between either of these contexts and the FT context. The results indicate consistent among-individual behavioral differences across time and contexts in wildly caught bent-wing bats. The findings of behavioral repeatability and cross-context correlations also indicate context-dependent variation and suggest that test devices which allow for flight behaviors, such as flight tents or cages, may provide a more suitable setting for measuring the behaviors and animal personalities of bats, particularly for those species that display less or little quadrupedal movements.

Inferring genetic structure when there is little: population genetics versus genomics of the threatened bat Miniopterus schreibersii across Europe

Despite their paramount importance in molecular ecology and conservation, genetic diversity and structure remain challenging to quantify with traditional genotyping methods. Next-generation sequencing holds great promises, but this has not been properly tested in highly mobile species. In this article, we compared microsatellite and RAD-sequencing (RAD-seq) analyses to investigate population structure in the declining bent-winged bat (Miniopterus schreibersii) across Europe. Both markers retrieved general patterns of weak range-wide differentiation, little sex-biased dispersal, and strong isolation by distance that associated with significant genetic structure between the three Mediterranean Peninsulas, which could have acted as glacial refugia. Microsatellites proved uninformative in individual-based analyses, but the resolution offered by genomic SNPs illuminated on regional substructures within several countries, with colonies sharing migrators of distinct ancestry without admixture. This finding is consistent with a marked philopatry and spatial partitioning between mating and rearing grounds in the species, which was suspected from marked-recaptured data. Our study advocates that genomic data are necessary to properly unveil the genetic footprints left by biogeographic processes and social organization in long-distant flyers, which are otherwise rapidly blurred by their high levels of gene flow.

Sharing roosts but not ectoparasites: high host-specificity in bat flies and wing mites of Miniopterus schreibersii and Rhinolophus ferrumequinum (Mammalia: Chiroptera)

Schreiber’s bent-winged bat Miniopterus schreibersii and the greater horseshoe bat Rhinolophus ferrumequinum are widespread and common cavernicolous species across southern Europe that host numerous specialized ectoparasite species. The objective of this study was to characterize the species assemblage, genetic diversity, and host specificity of bat flies (Nycteribiidae, Diptera) and wing mites (Spinturnicidae, Acari) found on these bat hosts in Serbia and Bosnia and Herzegovina. Notably, while bat flies lay puparia on the cave walls and can thus be transmitted indirectly, wing mites require direct body contact for transmission. Morphological identification and sequencing of a 710-bp fragment of cytochrome oxidase I gene of 207 bat flies yielded 4 species, 3 on M. schreibersii and 1 on R. ferrumequinum. Sequencing of a 460-bp small subunit ribosomal RNA fragment, in all 190 collected wing mites revealed 2 species, 1 per host. In no case was a parasite associated with 1 host found on the other host. Species and genetic diversity of flies were higher in M. schreibersii, likely reflecting their host’s larger colony sizes and migratory potential. Mite species of both hosts showed similarly low diversity, likely due to their faster life history and lower winter survival. Our findings highlight a remarkably high host-specificity and segregation of ectoparasite species despite direct contact among their hosts in the roost, suggesting a defined host preference in the investigated ectoparasite species. Furthermore, the differences in ectoparasite genetic diversity exemplify the interplay between host and parasite life histories in shaping parasite population genetic structure.

Spillover of West Caucasian Bat Lyssavirus (WCBV) in a Domestic Cat and Westward Expansion in the Palearctic Region

In June 2020, a cat from Arezzo (Italy) that died from a neurological disease was diagnosed with West Caucasian Bat Lyssavirus (WCBV). The virus retained high identity across the whole-genome with the reference isolate found in 2002 from a Russian bent-winged bat. We applied control measures recommended by national regulations, investigated a possible interface between cats and bats using visual inspections, bioacoustics analyses and camera trapping and performed active and passive surveillance in bats to trace the source of infection. People that were exposed to the cat received full post-exposure prophylaxis while animals underwent six months of quarantine. One year later, they are all healthy. In a tunnel located near the cat’s house, we identified a group of bent-winged bats that showed virus-neutralizing antibodies to WCBV across four sampling occasions, but no virus in salivary swabs. Carcasses from other bat species were all negative. This description of WCBV in a non-flying mammal confirms that this virus can cause clinical rabies in the absence of preventive and therapeutic measures, and highlights the lack of international guidelines against divergent lyssaviruses. We detected bent-winged bats as the most probable source of infection, testifying the encroachment between these bats and pets/human in urban areas and confirming free-ranging cats as potential hazard for public health and conservation.

Hydrogen isotopes reveal evidence of migration of Miniopterus schreibersii in Europe

Background

The Schreiber’s bat, Miniopterus schreibersii, is adapted to long-distance flight, yet long distance movements have only been recorded sporadically using capture-mark-recapture. In this study, we used the hydrogen isotopic composition of 208 wing and 335 fur specimens from across the species' European range to test the hypothesis that the species migrates over long distances.

Results

After obtaining the hydrogen isotopic composition (δ²H) of each sample, we performed geographic assignment tests by comparing the δ²H of samples with the δ²H of sampling sites. We found that 95 bats out of 325 showed evidence of long-distance movement, based on the analysis of either fur or wing samples. The eastern European part of the species range (Greece, Bulgaria and Serbia) had the highest numbers of bats that had moved. The assignment tests also helped identify possible migratory routes, such as movement between the Alps and the Balkans.

Conclusions

This is the first continental-scale study to provide evidence of migratory behaviour of M. schreibersii throughout its European range. The work highlights the need for further investigation of this behaviour to provide appropriate conservation strategies.

Out of Africa: The origins of the protozoan blood parasites of the Trypanosoma cruzi clade found in bats from Africa

Understanding geographic patterns of interaction between hosts and parasites can provide useful insight into the evolutionary history of the organisms involved. However, poor taxon sampling often hinders meaningful phylogenetic descriptions of groups of parasites. Trypanosome parasites that constitute the Trypanosoma cruzi clade are worldwide distributed infecting several mammalian species, especially bats. Diversity in this clade has been recently expanded by newly discovered species, but the common ancestor and geographical origins of this group of blood parasites are still debated. We present here results based on the molecular characterization of trypanosome isolates obtained from 1493 bats representing 74 species and sampled over 16 countries across four continents. After estimating the appropriate number of hypothetical species in our data set using GMYC models in combination with Poisson Tree Processes (mPTP) and ABGD, the 18S rRNA and gGAPDH genes were used for phylogenetic analyses to infer the major evolutionary relationships in the T. cruzi clade. Then, biogeographical processes influencing the distribution of this cosmopolitan group of parasites was inferred using BioGeoBEARS. Results revealed a large lineages diversity and the presence of trypanosomes in all sampled regions which infected 344 individuals from 31 bat species. We found eight Trypanosoma species, including: five previously known; one subspecies of Trypanosoma livingstonei (Trypanosoma cf. livingstonei); and two undescribed taxa (Trypanosoma sp. 1, Trypanosoma sp. 2), which were found exclusively in bats of the genus Miniopterus from Europe and Africa. The new taxa discovered have both an unexpected position in the global phylogeny of the T. cruzi clade. Trypanosoma sp. 1 is a sister lineage of T. livingstonei which is located at the base of the tree, whereas Trypanosoma sp. 2 is a sister lineage of the Shizotrypanum subclade that contains T. c. cruzi and T. dionisii. Ancestral areas reconstruction provided evidence that trypanosomes of the T. cruzi clade have radiated from Africa through several dispersion events across the world. We discuss the impact of these findings on the biogeography and taxonomy of this important clade of parasites and question the role played by bats, especially those from the genus Miniopterus, on the dispersal of these protozoan parasites between continents.

A continent-scale study of the social structure and phylogeography of the bent-wing bat, Miniopterus schreibersii (Mammalia: Chiroptera), using new microsatellite data

Miniopterus schreibersii is a cave-dwelling bat species with a wide distribution in the western Palearctic spanning southern and central Europe, North Africa, Anatolia, the Middle East, and the Caucasus. We investigated the social structure and its effects on the genetic makeup of this species, using 10 nuclear microsatellite markers and a partial fragment of the mitochondrial cytochrome b gene. Samples were examined from the species' entire circum-Mediterranean range. Local structuring that was previously detected among populations of M. schreibersii using mitochondrial markers was not observed for microsatellite markers, indicating male-biased dispersal for the species. Some support was found for postglacial expansions in Europe, with Anatolia potentially acting as the primary refugium during the Last Glacial Maximum (LGM). However, support for this hypothesis is not as strong as that previously detected using mitochondrial DNA markers. This is likely due to the diminishing effect of male-mediated dispersal, replenishing the nuclear diversity faster than the mitochondrial diversity in regions that are relatively far from the glacial refugia.

Hyperparasitism in caves: Bats, bat flies and ectoparasitic fungus interaction

Bat flies (Diptera: Nycteribiinae) are highly specialized bloodsucking bat ectoparasites. Some of the ectoparasitic bat flies are themselves parasitized with an ectoparasitic fungus of the genus Arthrorhynchus (Laboulbeniales). Ascospores of the fungus attach to the cuticle of a bat fly and develop a haustorium that penetrates the host cuticle. This interaction defines the fungus as a hyperparasite. Both the fly and the fungus are obligate parasites and this peculiar case of hyperparasitism has remained largely unstudied. We studied the prevalence of Laboulbeniales, genus Arthrorhynchus, in natural populations of bat flies infesting the bat species Miniopterus schreibersii, Myotis bechsteinii, My. blythii, My. daubentonii, My. escalerai and My. myotis in Portuguese caves. Laboulbeniales were found infecting 10 of the 428 screened bat flies (2.3%) in natural populations, with fewer infections in winter. Images obtained with transmission electron microscopy show the fungal haustorium within the bat fly host tissue, from where it extracts nutrition.

Geographical variation in the echolocation calls of bent-winged bats, Miniopterus fuliginosus

Evolutionary biologists had a long-standing interest in the evolutionary forces underlying geographical variation in the acoustic signals of animals. However, the evolutionary forces driving acoustic variation are still unclear. In this study, we quantified the geographical variation in the peak frequencies of echolocation calls in eight Miniopterus fuliginosus bat colonies, and assessed the forces that drive acoustic divergence. Our results demonstrated that seven of the colonies had very similar peak frequencies, while only one colony was significantly higher than the others. This similarity in echolocation call frequency among the seven colonies was likely due to frequent dispersal and migration, leading to male-mediated infiltration of nuclear genes. This infiltration enhances gene flow and weakens ecological selection, and also increases interactions in the presence of conspecifics. Significant correlations were not observed between acoustic distances and morphological distances, climatic differences, geographic distances or mtDNA genetic distances. However, variation in acoustic distances was significantly positive correlated with nDNA genetic distance, even after controlling for geographic distance. Interestingly, the relationship between call divergence and genetic distance was no longer significant after excluding the colony with the highest call frequency, which may be due to the minimal genetic distance among the other seven colonies. The highest frequencies of echolocation calls observed in the one colony may be shaped by selection pressure due to loud background noise in the area. Taken together, these results suggest that geographic divergence of echolocation calls may not be subject to genetic drift, but rather, that the strong selective pressure induced by background noise may lead to acoustic and genetic differentiation between JXT and the other colonies.

Agriculture shapes the trophic niche of a bat preying on multiple pest arthropods across Europe: Evidence from DNA metabarcoding

The interaction between agricultural production and wildlife can shape, and even condition, the functioning of both systems. In this study, we i) explored the degree to which a widespread European bat, namely the common bent-wing bat Miniopterus schreibersii, consumes crop-damaging insects at a continental scale, and ii) tested whether its dietary niche is shaped by the extension and type of agricultural fields. We employed a dual-primer DNA metabarcoding approach to characterize arthropod 16S and COI DNA sequences within bat faecal pellets collected across 16 Southern European localities, to first characterize the bat species' dietary niche, second measure the incidence of agricultural pests across their ranges and third assess whether geographical dietary variation responds to climatic, landscape diversity, agriculture type and vegetation productivity factors. We detected 12 arthropod orders, among which lepidopterans were predominant. We identified >200 species, 44 of which are known to cause agricultural damage. Pest species were detected at all but one sampling site and in 94% of the analysed samples. Furthermore, the dietary diversity of M. schreibersii exhibited a negative linear relation with the area of intensive agricultural fields, thus suggesting crops restrict the dietary niche of bats to prey taxa associated with agricultural production within their foraging range. Overall, our results imply that M. schreibersii might be a valuable asset for biological pest suppression in a variety of agricultural productions and highlight the dynamic interplay between wildlife and agricultural systems.

Diversity, Host Specialization, and Geographic Structure of Filarial Nematodes Infecting Malagasy Bats

We investigated filarial infection in Malagasy bats to gain insights into the diversity of these parasites and explore the factors shaping their distribution. Samples were obtained from 947 individual bats collected from 52 sites on Madagascar and representing 31 of the 44 species currently recognized on the island. Samples were screened for the presence of micro- and macro-parasites through both molecular and morphological approaches. Phylogenetic analyses showed that filarial diversity in Malagasy bats formed three main groups, the most common represented by Litomosa spp. infecting Miniopterus spp. (Miniopteridae); a second group infecting Pipistrellus cf. hesperidus (Vespertilionidae) embedded within the Litomosoides cluster, which is recognized herein for the first time from Madagascar; and a third group composed of lineages with no clear genetic relationship to both previously described filarial nematodes and found in M. griveaudi, Myotis goudoti, Neoromicia matroka (Vespertilionidae), Otomops madagascariensis (Molossidae), and Paratriaenops furculus (Hipposideridae). We further analyzed the infection rates and distribution pattern of Litomosa spp., which was the most diverse and prevalent filarial taxon in our sample. Filarial infection was disproportionally more common in males than females in Miniopterus spp., which might be explained by some aspect of roosting behavior of these cave-dwelling bats. We also found marked geographic structure in the three Litomosa clades, mainly linked to bioclimatic conditions rather than host-parasite associations. While this study demonstrates distinct patterns of filarial nematode infection in Malagasy bats and highlights potential drivers of associated geographic distributions, future work should focus on their alpha taxonomy and characterize arthropod vectors.

How a haemosporidian parasite of bats gets around: the genetic structure of a parasite, vector and host compared

Parasite population structure is often thought to be largely shaped by that of its host. In the case of a parasite with a complex life cycle, two host species, each with their own patterns of demography and migration, spread the parasite. However, the population structure of the parasite is predicted to resemble only that of the most vagile host species. In this study, we tested this prediction in the context of a vector-transmitted parasite. We sampled the haemosporidian parasite Polychromophilus melanipherus across its European range, together with its bat fly vector Nycteribia schmidlii and its host, the bent-winged bat Miniopterus schreibersii. Based on microsatellite analyses, the wingless vector, and not the bat host, was identified as the least structured population and should therefore be considered the most vagile host. Genetic distance matrices were compared for all three species based on a mitochondrial DNA fragment. Both host and vector populations followed an isolation-by-distance pattern across the Mediterranean, but not the parasite. Mantel tests found no correlation between the parasite and either the host or vector populations. We therefore found no support for our hypothesis; the parasite population structure matched neither vector nor host. Instead, we propose a model where the parasite's gene flow is represented by the added effects of host and vector dispersal patterns.