Trophic niche flexibility inGlossophaga soricina: how a nectar seeker sneaks an insect snack

Calibrated microphone array recordings reveal that a gleaning bat emits low-intensity echolocation calls even in open-space habitat

Echolocating bats use ultrasound for orientation and prey capture in darkness. Ultrasound is strongly attenuated in air. Consequently, aerial-hawking bats generally emit very intense echolocation calls to maximize detection range. However, call levels vary more than tenfold (>20 dB) between species and are tightly linked to the foraging strategy. The brown long-eared bat (Plecotus auritus) is a primarily gleaning, low-amplitude species that may occasionally hawk airborne prey. We used state-of-the-art calibrated acoustic 3D-localization and automated call analysis to measure P. auritus' source levels. Plecotus auritus emits echolocation calls of low amplitude (92 dB rmsSPL re. 20 µPa at 10 cm) even while flying in open-space. While P. auritus thus probably benefits from delayed evasive manoeuvres of eared insects, we propose that low-amplitude echolocation did not evolve as an adaptive countermeasure, but is limited by morphological constraints.

Trophic structure and foraging strategies in a bat community in northern Pantanal, Brazil

The influence of the landscape mosaic on the composition of the bat fauna regarding its trophic guild in a ranch area of northern Pantanal was evaluated. Seven trophic categories and five foraging strategies were found, composing 11 guild associations. Cluster analysis and non-metric multidimensional scaling (NMDS) revealed the structure of the data and enabled a broader understanding of resource exploitation. The similarity between sites for the presence of guilds was moderate, with the presence of aerial insectivores and trawling insectivores occurring in most of them, mainly in pasture areas and in the cambará forest. Gleaning sedentary frugivores, gleaning nomadic frugivores, and gleaning nectarivores were present in almost all sites, most often in dense acuri palm forest. Frugivores were the most numerous at the individual level, followed by trawling insectivores and hematophagous. The similarities between groups ranged from low to moderate. Some subgroups identified in the analyzes showed high similarity, with strong congruences between sites. The areas used by cattle do not seem to restrict the use by some species of bats, especially those already proven to be associated with degraded areas. However, information is still lacking to predict which level of alteration is acceptable for the conservation of each guild and foraging strategy of bat species.

You are more than what you eat: potentially adaptive enrichment of microbiome functions across bat dietary niches

BACKGROUND

Animals evolved in a microbial world, and their gut microbial symbionts have played a role in their ecological diversification. While many recent studies report patterns of phylosymbiosis between hosts and their gut bacteria, fewer studies examine the potentially adaptive functional contributions of these microbes to the dietary habits of their hosts. In this study, we examined predicted metabolic pathways in the gut bacteria of more than 500 individual bats belonging to 60 species and compare the enrichment of these functions across hosts with distinct dietary ecologies.

RESULTS

We found that predicted microbiome functions were differentially enriched across hosts with different diets. Using a machine-learning approach, we also found that inferred microbiome functions could be used to predict specialized host diets with reasonable accuracy. We detected a relationship between both host phylogeny and diet with respect to microbiome functional repertoires. Because many predicted functions could potentially fill nutritional gaps for bats with specialized diets, we considered pathways discriminating dietary niches as traits of the host and fit them to comparative phylogenetic models of evolution. Our results suggest that some, but not all, predicted microbiome functions may evolve toward adaptive optima and thus be visible to the forces of natural selection operating on hosts over evolutionary time.

CONCLUSIONS

Our results suggest that bats with specialized diets may partially rely on their gut microbes to fulfill or augment critical nutritional pathways, including essential amino acid synthesis, fatty acid biosynthesis, and the generation of cofactors and vitamins essential for proper nutrition. Our work adds to a growing body of literature suggesting that animal microbiomes are structured by a combination of ecological and evolutionary processes and sets the stage for future metagenomic and metabolic characterization of the bat microbiome to explore links between bacterial metabolism and host nutrition.

Functional differences in echolocation call design in an adaptive radiation of bats

All organisms have specialized systems to sense their environment. Most bat species use echolocation for navigation and foraging, but which and how ecological factors shaped echolocation call diversity remains unclear for the most diverse clades, including the adaptive radiation of neotropical leaf-nosed bats (Phyllostomidae). This is because phyllostomids emit low-intensity echolocation calls and many inhabit dense forests, leading to low representation in acoustic surveys. We present a field-collected, echolocation call dataset spanning 35 species and all phyllostomid dietary guilds. We analyze these data under a phylogenetic framework to test the hypothesis that echolocation call design and parameters are specialized for the acoustic demands of different diets, and investigate the contributions of phylogeny and body size to echolocation call diversity. We further link call parameters to dietary ecology by contrasting minimum detectable prey size estimates (MDPSE) across species. We find phylogeny and body size explain a substantial proportion of echolocation call parameter diversity, but most species can be correctly assigned to taxonomic (61%) or functional (77%) dietary guilds based on call parameters. This suggests a degree of acoustic ecological specialization, albeit with interspecific similarities in call structure. Theoretical MDPSE are greatest for omnivores and smallest for insectivores. Omnivores significantly differ from other dietary guilds in MDPSE when phylogeny is not considered, but there are no differences among taxonomic dietary guilds within a phylogenetic context. Similarly, predators of non-mobile/non-evasive prey and predators of mobile/evasive prey differ in estimated MDPSE when phylogeny is not considered. Phyllostomid echolocation call structure may be primarily specialized for overcoming acoustic challenges of foraging in dense habitats, and then secondarily specialized for the detection of food items according to functional dietary guilds. Our results give insight into the possible ecological mechanisms shaping the diversity of sensory systems, and their reciprocal influence on resource use.

Agricultural Fast Food: Bats Feeding in Banana Monocultures Are Heavier but Have Less Diverse Gut Microbiota

Habitat alteration for agriculture can negatively affect wildlife physiology and health by decreasing diet diversity and increasing exposure to agrochemicals for animals foraging in altered landscapes. Such negative effects may be mediated by the disruption of the gut microbiota (termed dysbiosis), yet evidence for associations between habitat alteration, wildlife health, and the gut microbiota remains scarce. We examine the association between management intensity of banana plantations and both the body condition and gut microbiota composition of nectar-feeding bats Glossophaga soricina, which commonly forage within banana plantations across Latin America. We captured and measured 196 bats across conventional monocultures, organic plantations, and natural forests in Costa Rica, and quantified gut microbiome bacterial phylogenetic diversity using 16S rRNA amplicon sequencing. We found that gut microbiota from bats foraging in conventional monocultures were overall less phylogenetically diverse than those from bats foraging in organic plantations or natural forests, both of which were characterized by diverse bacterial assemblages and individualized microbiota. Despite lower diversity, co-occurrence network complexity was higher in conventional monocultures, potentially indicating altered microbial interactions in agricultural landscapes. Bats from both organic and conventional plantations tended to be larger and heavier than their forest counterparts, reflecting the higher food supply. Overall, our study reveals that whilst both conventional monocultures and organic plantations provide a reliable food source for bats, conventional monocultures are associated with less diverse and potentially dysbiotic microbiota, whilst organic plantations promote diverse and individualized gut microbiota akin to their natural forest-foraging counterparts. Whilst the long-term negative effects of anthropogenically-altered microbiota are unclear, our study provides further evidence from a novel perspective that organic agricultural practices are beneficial for wildlife health.

Dietary Diversification and Specialization in Neotropical Bats Facilitated by Early Molecular Evolution

Dietary adaptation is a major feature of phenotypic and ecological diversification, yet the genetic basis of dietary shifts is poorly understood. Among mammals, Neotropical leaf-nosed bats (family Phyllostomidae) show unmatched diversity in diet; from a putative insectivorous ancestor, phyllostomids have radiated to specialize on diverse food sources including blood, nectar, and fruit. To assess whether dietary diversification in this group was accompanied by molecular adaptations for changing metabolic demands, we sequenced 89 transcriptomes across 58 species and combined these with published data to compare ∼13,000 protein coding genes across 66 species. We tested for positive selection on focal lineages, including those inferred to have undergone dietary shifts. Unexpectedly, we found a broad signature of positive selection in the ancestral phyllostomid branch, spanning genes implicated in the metabolism of all major macronutrients, yet few positively selected genes at the inferred switch to plantivory. Branches corresponding to blood- and nectar-based diets showed selection in loci underpinning nitrogenous waste excretion and glycolysis, respectively. Intriguingly, patterns of selection in metabolism genes were mirrored by those in loci implicated in craniofacial remodeling, a trait previously linked to phyllostomid dietary specialization. Finally, we show that the null model of the widely-used branch-site test is likely to be misspecified, with the implication that the test is too conservative and probably under-reports true cases of positive selection. Our findings point to a complex picture of adaptive radiation, in which the evolution of new dietary specializations has been facilitated by early adaptations combined with the generation of new genetic variation.

Cryptic species in Glossophaga soricina (Chiroptera: Phyllostomidae): do morphological data support molecular evidence?

Cryptic species, defined as those that are morphologically indistinguishable but phylogenetically distinct, are common in bats and correspond to the majority of newly described species. Such seems to be the case of Glossophaga soricina, a generalist, glossophagine bat that is broadly distributed throughout the Neotropics. Several studies have found high levels of molecular variation within G. soricina, suggesting that it could be a cryptic species complex. Here, we explore data derived from two-dimensional geometric morphometric analyses of cranial characters and their covariation with environmental variables, aiming to test the existence of more than one species grouped within it and to contribute to the knowledge of its variation and evolutionary history. Variation in shape and size of skull and mandible supports the two main mitochondrial lineages reported in previous studies, one corresponding to the east side of the Andes (subspecies G. s. soricina) and the other one corresponding to populations from Mesoamerica and the west side of the Andes, in turn composed of at least three monophyletic and morphologically differentiated taxa. Environmental variables correlate with shape variation and might be responsible for convergences in shape and size between the species with the smallest distributions. Based on the evidence we present in this work we elevate four subspecies to the taxonomic level of species. The correct names for the species of the analyzed complex are: G. soricina (Pallas 1766), G. mutica Merriam 1898, G. antillarum Rehn 1902, and G. valens Miller 1913.

Morcegos urbanos de Guarulhos: alta riqueza de espécies e dominância de espécies ecologicamente flexíveis reveladas a partir de dados de monitoramento da raiva

RESUMO Urbanização afeta a composição e funções ecossistêmicas das comunidades de morcegos em várias regiões do planeta. Entretanto, este ainda é um tema pouco explorado no Neotrópico. No Brasil, embora poucas cidades apresentem inventários de quirópteros, órgãos municipais de saúde pública (e.g., Centro de Controle de Zoonoses) realizam a vigilância passiva dos morcegos infectados pelo vírus da raiva. Estas instituições fazem a identificação dos espécimes oriundos principalmente de áreas urbanas e coletam dados biológicos importantes para o manejo ambiental, controle populacional, ecologia e conservação das espécies. O presente estudo analisou os dados de recebimento de morcegos, de 2001 a 2017, oriundos da cidade de Guarulhos, comparando as taxas de recebimento, frequência, riqueza e dominância das espécies com estudos prévios conduzidos em cidades brasileiras. Os dados da vigilância em saúde pública demonstraram uma alta riqueza de espécies (n = 29), representadas por três famílias mais comuns em áreas urbanas brasileiras (Phyllostomidae, Molossidae e Vespertilionidae). Molossus molossus (Pallas, 1766), Glossophaga soricina (Pallas, 1766) e Myotis nigricans (Schinz, 1821) representaram a maioria (70%) dos dados da quiropterofauna de Guarulhos. Esta dominância pode estar relacionada com a flexibilidade da dieta dessas espécies (insetívoras e nectarívoras não obrigatórias) e abrigos diurnos em edificações, recursos estes altamente disponíveis nas cidades brasileiras. Assim, para mitigar os efeitos da urbanização sobre a rica quiropterofauna regional, recomenda-se que o planejamento ambiental das cidades considere suas diretrizes urbanísticas e florísticas como uma ferramenta ao manejo integrado da fauna silvestre e saúde pública, além de implantar estratégias para aumentar o potencial de conservação da biodiversidade nestes ambientes.

Differential cellular proliferation underlies heterochronic generation of cranial diversity in phyllostomid bats

Background

Skull diversity in the neotropical leaf-nosed bats (Phyllostomidae) evolved through a heterochronic process called peramorphosis, with underlying causes varying by subfamily. The nectar-eating (subfamily Glossophaginae) and blood-eating (subfamily Desmondontinae) groups originate from insect-eating ancestors and generate their uniquely shaped faces and skulls by extending the ancestral ontogenetic program, appending new developmental stages and demonstrating peramorphosis by hypermorphosis. However, the fruit-eating phyllostomids (subfamilies Carollinae and Stenodermatinae) adjust their craniofacial development by speeding up certain developmental processes, displaying peramorphosis by acceleration. We hypothesized that these two forms of peramorphosis detected by our morphometric studies could be explained by differential growth and investigated cell proliferation during craniofacial morphogenesis.

Results

We obtained cranial tissues from four wild-caught bat species representing a range of facial diversity and labeled mitotic cells using immunohistochemistry. During craniofacial development, all bats display a conserved spatiotemporal distribution of proliferative cells with distinguishable zones of elevated mitosis. These areas were identified as modules by the spatial distribution analysis. Ancestral state reconstruction of proliferation rates and patterns in the facial module between species provided support, and a degree of explanation, for the developmental mechanisms underlying the two models of peramorphosis. In the long-faced species, Glossophaga soricina, whose facial shape evolved by hypermorphosis, cell proliferation rate is maintained at lower levels and for a longer period of time compared to the outgroup species Miniopterus natalensis. In both species of studied short-faced fruit bats, Carollia perspicillata and Artibeus jamaicensis, which evolved under the acceleration model, cell proliferation rate is increased compared to the outgroup.

Conclusions

This is the first study which links differential cellular proliferation and developmental modularity with heterochronic developmental changes, leading to the evolution of adaptive cranial diversity in an important group of mammals.

Foraging shifts and visual preadaptation in ecologically diverse bats

Changes in behaviour may initiate shifts to new adaptive zones, with physical adaptations for novel environments evolving later. While new mutations are commonly considered engines of adaptive change, sensory evolution enabling access to new resources might also arise from standing genetic diversity, and even gene loss. We examine the relative contribution of molecular adaptations, measured by positive and relaxed selection, acting on eye-expressed genes associated with shifts to new adaptive zones in ecologically diverse bats from the superfamily Noctilionoidea. Collectively, noctilionoids display remarkable ecological breadth, from highly divergent echolocation to flight strategies linked to specialized insectivory, the parallel evolution of diverse plant-based diets (e.g., nectar, pollen and fruit) from ancestral insectivory, and-unusually for echolocating bats-often have large, well-developed eyes. We report contrasting levels of positive selection in genes associated with the development, maintenance and scope of visual function, tracing back to the origins of noctilionoids and Phyllostomidae (the bat family with most dietary diversity), instead of during shifts to novel diets. Generalized plant visiting was not associated with exceptional molecular adaptation, and exploration of these novel niches took place in an ancestral phyllostomid genetic background. In contrast, evidence for positive selection in vision genes was found at subsequent shifts to either nectarivory or frugivory. Thus, neotropical noctilionoids that use visual cues for identifying food and roosts, as well as for orientation, were effectively preadapted, with subsequent molecular adaptations in nectar-feeding lineages and the subfamily Stenodermatinae of fig-eating bats fine-tuning pre-existing visual adaptations for specialized purposes.

Peramorphosis, an evolutionary developmental mechanism in neotropical bat skull diversity

BACKGROUND

The neotropical leaf-nosed bats (Chiroptera, Phyllostomidae) are an ecologically diverse group of mammals with distinctive morphological adaptations associated with specialized modes of feeding. The dramatic skull shape changes between related species result from changes in the craniofacial development process, which brings into focus the nature of the underlying evolutionary developmental processes.

RESULTS

In this study, we use three-dimensional geometric morphometrics to describe, quantify, and compare morphological modifications unfolding during evolution and development of phyllostomid bats. We examine how changes in development of the cranium may contribute to the evolution of the bat craniofacial skeleton. Comparisons of ontogenetic trajectories to evolutionary trajectories reveal two separate evolutionary developmental growth processes contributing to modifications in skull morphogenesis: acceleration and hypermorphosis.

CONCLUSION

These findings are consistent with a role for peramorphosis, a form of heterochrony, in the evolution of bat dietary specialists.

Habitat fragmentation is associated with dietary shifts and microbiota variability in common vampire bats

Host ecological factors and external environmental factors are known to influence the structure of gut microbial communities, but few studies have examined the impacts of environmental changes on microbiotas in free-ranging animals. Rapid land-use change has the potential to shift gut microbial communities in wildlife through exposure to novel bacteria and/or by changing the availability or quality of local food resources. The consequences of such changes to host health and fitness remain unknown and may have important implications for pathogen spillover between humans and wildlife. To better understand the consequences of land-use change on wildlife microbiotas, we analyzed long-term dietary trends, gut microbiota composition, and innate immune function in common vampire bats (Desmodus rotundus) in two nearby sites in Belize that vary in landscape structure. We found that vampire bats living in a small forest fragment had more homogenous diets indicative of feeding on livestock and shifts in microbiota heterogeneity, but not overall composition, compared to those living in an intact forest reserve. We also found that irrespective of sampling site, vampire bats which consumed relatively more livestock showed shifts in some core bacteria compared with vampire bats which consumed relatively less livestock. The relative abundance of some core microbiota members was associated with innate immune function, suggesting that future research should consider the role of the host microbiota in immune defense and its relationship to zoonotic infection dynamics. We suggest that subsequent homogenization of diet and habitat loss through livestock rearing in the Neotropics may lead to disruption to the microbiota that could have downstream impacts on host immunity and cross-species pathogen transmission.

Approaches to integrating genetic data into ecological networks

As molecular tools for assessing trophic interactions become common, research is increasingly focused on the construction of interaction networks. Here, we demonstrate three key methods for incorporating DNA data into network ecology and discuss analytical considerations using a model consisting of plants, insects, bats and their parasites from the Costa Rica dry forest. The simplest method involves the use of Sanger sequencing to acquire long sequences to validate or refine field identifications, for example of bats and their parasites, where one specimen yields one sequence and one identification. This method can be fully quantified and resolved and these data resemble traditional ecological networks. For more complex taxonomic identifications, we target multiple DNA loci, for example from a seed or fruit pulp sample in faeces. These networks are also well resolved but gene targets vary in resolution and quantification is difficult. Finally, for mixed templates such as faecal contents of insectivorous bats, we use DNA metabarcoding targeting two sequence lengths (157 and 407 bp) of one gene region and a MOTU, BLAST and BIN association approach to resolve nodes. This network type is complex to generate and analyse, and we discuss the implications of this type of resolution on network analysis. Using these data, we construct the first molecular-based network of networks containing 3,304 interactions between 762 nodes of eight trophic functions and involving parasitic, mutualistic and predatory interactions. We provide a comparison of the relative strengths and weaknesses of these data types in network ecology.

In Cold Blood: Compositional Bias and Positive Selection Drive the High Evolutionary Rate of Vampire Bats Mitochondrial Genomes

Mitochondrial genomes of animals have long been considered to evolve under the action of purifying selection. Nevertheless, there is increasing evidence that they can also undergo episodes of positive selection in response to shifts in physiological or environmental demands. Vampire bats experienced such a shift, as they are the only mammals feeding exclusively on blood and possessing anatomical adaptations to deal with the associated physiological requirements (e.g., ingestion of high amounts of liquid water and iron). We sequenced eight new chiropteran mitogenomes including two species of vampire bats, five representatives of other lineages of phyllostomids and one close outgroup. Conducting detailed comparative mitogenomic analyses, we found evidence for accelerated evolutionary rates at the nucleotide and amino acid levels in vampires. Moreover, the mitogenomes of vampire bats are characterized by an increased cytosine (C) content mirrored by a decrease in thymine (T) compared with other chiropterans. Proteins encoded by the vampire bat mitogenomes also exhibit a significant increase in threonine (Thr) and slight reductions in frequency of the hydrophobic residues isoleucine (Ile), valine (Val), methionine (Met), and phenylalanine (Phe). We show that these peculiar substitution patterns can be explained by the co-occurrence of both neutral (mutational bias) and adaptive (positive selection) processes. We propose that vampire bat mitogenomes may have been impacted by selection on mitochondrial proteins to accommodate the metabolism and nutritional qualities of blood meals.

Comparing Microbiome Sampling Methods in a Wild Mammal: Fecal and Intestinal Samples Record Different Signals of Host Ecology, Evolution

The gut microbiome is a community of host-associated symbiotic microbes that fulfills multiple key roles in host metabolism, immune function, and tissue development. Given the ability of the microbiome to impact host fitness, there is increasing interest in studying the microbiome of wild animals to better understand these communities in the context of host ecology and evolution. Human microbiome research protocols are well established, but wildlife microbiome research is still a developing field. Currently, there is no standardized set of best practices guiding the collection of microbiome samples from wildlife. Gut microflora are typically sampled either by fecal collection, rectal swabbing, or by destructively sampling the intestinal contents of the host animal. Studies rarely include more than one sampling technique and no comparison of these methods currently exists for a wild mammal. Although some studies have hypothesized that the fecal microbiome is a nested subset of the intestinal microbiome, this hypothesis has not been formally tested. To address these issues, we examined guano (feces) and distal intestinal mucosa from 19 species of free-ranging bats from Lamanai, Belize, using 16S rRNA amplicon sequencing to compare microbial communities across sample types. We found that the diversity and composition of intestine and guano samples differed substantially. In addition, we conclude that signatures of host evolution are retained by studying gut microbiomes based on mucosal tissue samples, but not fecal samples. Conversely, fecal samples retained more signal of host diet than intestinal samples. These results suggest that fecal and intestinal sampling methods are not interchangeable, and that these two microbiotas record different information about the host from which they are isolated.

Mercury bioaccumulation in bats reflects dietary connectivity to aquatic food webs

Mercury (Hg) is a persistent and widespread heavy metal with neurotoxic effects in wildlife. While bioaccumulation of Hg has historically been studied in aquatic food webs, terrestrial consumers can become contaminated with Hg when they feed on aquatic organisms (e.g., emergent aquatic insects, fish, and amphibians). However, the extent to which dietary connectivity to aquatic ecosystems can explain patterns of Hg bioaccumulation in terrestrial consumers has not been well studied. Bats (Order: Chiroptera) can serve as a model system for illuminating the trophic transfer of Hg given their high dietary diversity and foraging links to both aquatic and terrestrial food webs. Here we quantitatively characterize the dietary correlates of long-term exposure to Hg across a diverse local assemblage of bats in Belize and more globally across bat species from around the world with a comparative analysis of hair samples. Our data demonstrate considerable interspecific variation in hair total Hg concentrations in bats that span three orders of magnitude across species, ranging from 0.04 mg/kg in frugivorous bats (Artibeus spp.) to 145.27 mg/kg in the piscivorous Noctilio leporinus. Hg concentrations showed strong phylogenetic signal and were best explained by dietary connectivity of bat species to aquatic food webs. Our results highlight that phylogeny can be predictive of Hg concentrations through similarity in diet and how interspecific variation in feeding strategies influences chronic exposure to Hg and enables movement of contaminants from aquatic to terrestrial ecosystems.

Trophic position and dietary breadth of bats revealed by nitrogen isotopic composition of amino acids

Bats perform important ecosystem services, but it remains difficult to quantify their dietary strategies and trophic position (TP) in situ. We conducted measurements of nitrogen isotopes of individual amino acids (δ 15NAA) and bulk-tissue carbon (δ 13Cbulk) and nitrogen (δ 15Nbulk) isotopes for nine bat species from different feeding guilds (nectarivory, frugivory, sanguivory, piscivory, carnivory, and insectivory). Our objective was to assess the precision of δ 15NAA-based estimates of TP relative to other approaches. TPs calculated from δ 15N values of glutamic acid and phenylalanine, which range from 8.3-33.1‰ and 0.7-15.4‰ respectively, varied between 1.8 and 3.8 for individuals of each species and were generally within the ranges of those anticipated based on qualitative dietary information. The δ 15NAA approach reveals variation in TP within and among species that is not apparent from δ 15Nbulk data, and δ 15NAA data suggest that two insectivorous species (Lasiurus noctivagans and Lasiurus cinereus) are more omnivorous than previously thought. These results indicate that bats exhibit a trophic discrimination factor (TDF) similar to other terrestrial organisms and that δ 15NAA provides a reliable approach for addressing questions about variation in the TP of bats that have heretofore proven elusive.

Bayesian hierarchical models suggest oldest known plant-visiting bat was omnivorous

The earliest record of plant visiting in bats dates to the Middle Miocene of La Venta, the world's most diverse tropical palaeocommunity. Palynephyllum antimaster is known from molars that indicate nectarivory. Skull length, an important indicator of key traits such as body size, bite force and trophic specialization, remains unknown. We developed Bayesian models to infer skull length based on dental measurements. These models account for variation within and between species, variation between clades, and phylogenetic error structure. Models relating skull length to trophic level for nectarivorous bats were then used to infer the diet of the fossil. The skull length estimate for Palynephyllum places it among the larger lonchophylline bats. The inferred diet suggests Palynephyllum fed on nectar and insects, similar to its living relatives. Omnivory has persisted since the mid-Miocene. This is the first study to corroborate with fossil data that highly specialized nectarivory in bats requires an omnivorous transition.

Simplifying a wing: diversity and functional consequences of digital joint reduction in bat wings

Bat wings, like other mammalian forelimbs, contain many joints within the digits. These joints collectively affect dynamic three-dimensional (3D) wing shape, thereby affecting the amount of aerodynamic force a wing can generate. Bats are a speciose group, and show substantial variation in the number of wing joints. Additionally, some bat species have joints with extensor but no flexor muscles. While several studies have examined the diversity in number of joints and presence of muscles, musculoskeletal variation in the digits has not been interpreted in phylogenetic, functional or ecological contexts. To provide this context, the number of joints and the presence/absence of muscles are quantified for 44 bat species, and are mapped phylogenetically. It is shown that, relative to the ancestral state, joints and muscles were lost multiple times from different digits and in many lineages. It is also shown that joints lacking flexors undergo cyclical flexion and extension, in a manner similar to that observed in joints with both flexors and extensors. Comparison of species with contrasting feeding ecologies demonstrates that species that feed primarily on non-mobile food (e.g. fruit) have fewer fully active joints than species that catch mobile prey (e.g. insects). It is hypothesized that there is a functional trade-off between energetic savings and maneuverability. Having fewer joints and muscles reduces the mass of the wing, thereby reducing the energetic requirements of flapping flight, and having more joints increases the assortment of possible 3D wing shapes, thereby enhancing the range and fine control of aerodynamic force production and thus maneuverability.

The use of DNA barcodes in food web construction-terrestrial and aquatic ecologists unite!

By depicting who eats whom, food webs offer descriptions of how groupings in nature (typically species or populations) are linked to each other. For asking questions on how food webs are built and work, we need descriptions of food webs at different levels of resolution. DNA techniques provide opportunities for highly resolved webs. In this paper, we offer an exposé of how DNA-based techniques, and DNA barcodes in particular, have recently been used to construct food web structure in both terrestrial and aquatic systems. We highlight how such techniques can be applied to simultaneously improve the taxonomic resolution of the nodes of the web (i.e., the species), and the links between them (i.e., who eats whom). We end by proposing how DNA barcodes and DNA information may allow new approaches to the construction of larger interaction webs, and overcome some hurdles to achieving adequate sample size. Most importantly, we propose that the joint adoption and development of these techniques may serve to unite approaches to food web studies in aquatic and terrestrial systems-revealing the extent to which food webs in these environments are structured similarly to or differently from each other, and how they are linked by dispersal.

Molecular detection of trophic interactions: emerging trends, distinct advantages, significant considerations and conservation applications

The emerging field of ecological genomics contains several broad research areas. Comparative genomic and conservation genetic analyses are providing great insight into adaptive processes, species bottlenecks, population dynamics and areas of conservation priority. Now the same technological advances in high-throughput sequencing, coupled with taxonomically broad sequence repositories, are providing greater resolution and fundamentally new insights into functional ecology. In particular, we now have the capacity in some systems to rapidly identify thousands of species-level interactions using non-invasive methods based on the detection of trace DNA. This represents a powerful tool for conservation biology, for example allowing the identification of species with particularly inflexible niches and the investigation of food-webs or interaction networks with unusual or vulnerable dynamics. As they develop, these analyses will no doubt provide significant advances in the field of restoration ecology and the identification of appropriate locations for species reintroduction, as well as highlighting species at ecological risk. Here, I describe emerging patterns that have come from the various initial model systems, the advantages and limitations of the technique and key areas where these methods may significantly advance our empirical and applied conservation practices.