Wing morphology predicts individual niche specialization in Pteronotus mesoamericanus (Mammalia: Chiroptera)

A metabarcoding assessment of the diet of the insectivorous bats of Madeira Island, Macaronesia

Understanding the trophic structure of species assemblages is crucial in order to comprehend how syntropic species coexist in space and time. Bats are the second most taxonomically diverse group of mammals and display a wide range of dietary strategies. Due to their ability to disperse over water, ca. 60% of all extant bat species occur on islands and for the most part their interspecific ecological interactions are poorly known. Using DNA metabarcoding, this study offers the first insights into the diet of Macaronesian bats by providing a holistic overview of prey consumed by all 3 bat species found on Madeira Island (Pipistrellus maderensis, Nyctalus leisleri verrucosus, and Plecotus austriacus) and investigating both interspecific (between P. maderensis and N. l. verrucosus) and intraspecific (between female and male N. l. verrucosus) dietary differences. We identified a total of 110 species of arthropod prey in the diet of the 3 bat species, including multiple agriculture and forestry pest species, a human disease-relevant species, and numerous taxa not previously recorded on the island. Lepidoptera was the primary prey order for all 3 bat species. The diet composition of P. maderensis and N. l. verrucosus differed significantly, with P. maderensis consuming more Diptera and multiple prey taxa not found in the diet of N. l. verucosus. Moreover, male N. l. verrucosus exhibited a broader niche breadth than females. This study is among the first to use DNA metabarcoding to evaluate the diet of insular bats and thus greatly advances knowledge regarding the trophic ecology and pest suppression services of these poorly-known mammals.

Living with voracious roommates: Factors that explain isotopic niche variation in a mixed colony of insectivorous bats

Theory predicts that in resource-limited environments, coexisting species may overlap their niche dimensions but must differ in at least one to avoid competitive exclusion. Specifically, it has been suggested that the coexistence of competing species within a guild, could be sustained with mechanisms of resource partitioning, such as segregation along a trophic dimension. Among the most gregarious mammals are bats, which present diversification in their diet based on habitat choice and body size. Despite differences that could explain specialization in prey selection, there are insufficient studies that explore food overlap in mixed bat colonies and the factors that determine the selection of prey, both at intra- and inter-specific levels. To fill this gap, we analyzed the isotope signal (δ13C and δ15N) in feces collected in a mixed colony of Tadarida brasiliensis and Myotis chiloensis. To understand how several factors could influence these isotopic signals, intrinsic explanatory variables were analyzed, including body mass, body length, age, and sex. Also, extrinsic variables were analyzed, including monthly temporality and moonlight intensity. Our findings support age-dependent specialization in M. chiloensis, with a significant role of moonlight intensity and sex on δ15N. In T. brasiliensis, we identified a significant effect of size, sex, and ear length on δ15N. Our analysis indicates that both species of bats experience diverse degrees of overlap through austral summer months, affected by several factors that explain the variability in their fecal isotopic signals.

River zebrafish combine behavioral plasticity and generalized morphology with specialized sensory and metabolic physiology to survive in a challenging environment

Phenotypes that allow animals to detect, weather, and predict changes efficiently are essential for survival in fluctuating environments. Some phenotypes may remain specialized to suit an environment perfectly, while others become more plastic or generalized, shifting flexibly to match current context or adopting a form that can utilize a wide range of contexts. Here, we tested the differences in behavior, morphology, sensory and metabolic physiology between wild zebrafish (Danio rerio) in highly variable fast-flowing rivers and still-water sites. We found that river zebrafish moved at higher velocities than did still-water fish, had lower oxygen demands, and responded less vigorously to small changes in flow rate, as we might expect for fish that are well-suited to high-flow environments. River zebrafish also had less streamlined bodies and were more behaviorally plastic than were still-water zebrafish, both features that may make them better-suited to a transitional lifestyle. Our results suggest that zebrafish use distinct sensory mechanisms and metabolic physiology to reduce energetic costs of living in fast-flowing water while relying on morphology and behavior to create flexible solutions to a challenging habitat. Insights on animals' reliance on traits with different outcomes provide a framework to better understand their survival in future environmental fluctuations.

Wing morphology is related to niche specialization and interaction networks in stenodermatine bats (Chiroptera: Phyllostomidae)

Plant–animal interactions constitute some of the most important ecological processes for the maintenance of tropical forests. Bats are the only group of mammals capable of true flight and have been recognized as important dispersers of pioneer and secondary successional plant species. Although progress has been made in the study of Neotropical bats, morphological variation of the wing and its influence on niche separation between species is unknown. We evaluated relationships among habitat structures of selected Colombian tropical dry forest patches, the diet through interaction networks, and wing morphology of 11 species of bats in the Stenodermatinae subfamily (297 individuals) using geometric morphometry in a phylogenetic context. The results indicate that the phylogenetic signal for wing size is greater than for wing shape, thus providing some evidence for evolutionary convergence. Wing shape variation was associated primarily with the distal anatomical tip of the third finger and the joint between the humerus and the radius and ulna. Species with wide, short wings, as in the genus Artibeus had generalist diets and less nested positions within the interaction networks. In contrast, species with elongated and pointed wings, such as Sturnira and Platyrrhinus, had specialized diets and more nested positions within the interaction networks. We argue that wing shape variation may play an important role as a source of interspecific variation leading to food specialization within tropical bat communities.

Selective Logging Shows No Impact on the Dietary Breadth of a Generalist Bat Species: The Fawn Leaf-Nosed Bat (Hipposideros cervinus)

Logging activities degrade forest habitats across large areas of the tropics, but the impacts on trophic interactions that underpin forest ecosystems are poorly understood. DNA metabarcoding provides an invaluable tool to investigate such interactions, allowing analysis at a far greater scale and resolution than has previously been possible. We analysed the diet of the insectivorous fawn leaf-nosed bat Hipposideros cervinus across a forest disturbance gradient in Borneo, using a dataset of ecological interactions from an unprecedented number of bat-derived faecal samples. Bats predominantly consumed insects from the orders Lepidoptera, Diptera, Blattodea, and Coleoptera, and the taxonomic composition of their diet remained relatively consistent across sites regardless of logging disturbance. There was little difference in the richness of prey consumed per-bat in each logging treatment, indicating potential resilience of this species to habitat degradation. In fact, bats consumed a high richness of prey items, and intensive sampling is needed to reliably compare feeding ecology over multiple sites. Multiple bioinformatic parameters were used, to assess how they altered our perception of sampling completeness. While parameter choice altered estimates of completeness, a very high sampling effort was always required to detect the entire prey community.

Ecological Morphology of Neotropical Bat Wing Structures

Morphology has a direct influence on animal fitness. Studies addressing the identification of patterns and variations across several guilds are fundamental in ecomorphological research. Wings are the core of ecological morphology in bats; nevertheless, individual bones and structures that support the wing, including metacarpals, phalanges and the length of digits, have rarely been the subject of comprehensive research when studying wing morphology. Here, I analyzed morphological variations of wing structures across 11 bat guilds and how individual bone structures are correlated to diet, foraging mode and habitat use. I obtained wing measurements from 1512 voucher specimens of 97 species. All the specimens analyzed came from the Mammalian Collection at the Museo Javeriano de Historia Natural of Pontificia Universidad Javeriana (MPUJ-MAMM) (Bogotá, Colombia). Positive correlations between size and the length of the third and fifth digit were detected. Bat guilds that capture their preys using aerial strategy in uncluttered habitats had longer third digits but short fifth digits compared to guilds that rely on gleaning strategy and forage in highly cluttered space. Although terminal phalanges were shown to be important structures for guild classification, metacarpals were strongly related to aerial foragers from uncluttered habitats because of their potential role in flight performance and ecological adaptations. Results show that habitat use, as well as foraging mode, are reflected in wing structures. Different wing traits to those evaluated in this study should be considered to better understand the ecological interactions, foraging strategy, wing adaptations, and flight performance in Neotropical bats.

Molecular diet analysis of neotropical bats based on fecal DNA metabarcoding

Bat communities in the Neotropics are some of the most speciose assemblages of mammals on Earth, with regions supporting more than 100 sympatric species with diverse feeding ecologies. Because bats are small, nocturnal, and volant, it is difficult to directly observe their feeding habits, which has resulted in their classification into broadly defined dietary guilds (e.g., insectivores, carnivores, and frugivores). Apart from these broad guilds, we lack detailed dietary information for many species and therefore have only a limited understanding of interaction networks linking bats and their diet items. In this study, we used DNA metabarcoding of plants, arthropods, and vertebrates to investigate the diets of 25 bat species from the tropical dry forests of Lamanai, Belize. Our results report some of the first detection of diet items for the focal bat taxa, adding rich and novel natural history information to the field of bat ecology. This study represents a comprehensive first effort to apply DNA metabarcoding to bat diets at Lamanai and provides a useful methodological framework for future studies testing hypotheses about coexistence and niche differentiation in the context of modern high-throughput molecular data.

In situ novel environment assay reveals acoustic exploration as a repeatable behavioral response in migratory bats

Integrating information on species-specific sensory perception with spatial activity provides a high-resolution understanding of how animals explore environments, yet frequently used exploration assays commonly ignore sensory acquisition as a measure for exploration. Echolocation is an active sensing system used by hundreds of mammal species, primarily bats. As echolocation call activity can be reliably quantified, bats present an excellent model system to investigate intraspecific variation in environmental cue sampling. Here, we developed an in situ roost-like novel environment assay for tree-roosting bats. We repeatedly tested 52 individuals of the migratory bat species, Pipistrellus nathusii, across 24 h, to examine the role of echolocation when crawling through a maze-type arena and test for consistent intraspecific variation in sensory-based exploration. We reveal a strong correlation between echolocation call activity and spatial activity. Moreover, we show that during the exploration of the maze, individuals consistently differed in spatial activity as well as echolocation call activity, given their spatial activity, a behavioral response we term 'acoustic exploration'. Acoustic exploration was correlated with other exploratory behaviors, but not with emergence latency. We here present a relevant new measure for exploration behavior and provide evidence for consistent (short-term) intra-specific variation in the level at which wild bats collect information from a novel environment.