Dietary overlap and seasonality in three species of mormoopid bats from a tropical dry forest.

Competing hypotheses explaining species' use of resources have been advanced. Resource limitations in habitat and/or food are factors that affect assemblages of species. These limitations could drive the evolution of morphological and/or behavioural specialization, permitting the coexistence of closely related species through resource partitioning and niche differentiation. Alternatively, when resources are unlimited, fluctuations in resources availability will cause concomitant shifts in resource use regardless of species identity. Here, we used next-generation sequencing to test these hypotheses and characterize the diversity, overlap and seasonal variation in the diet of three species of insectivorous bats of the genus Pteronotus. We identified 465 prey (MOTUs) in the guano of 192 individuals. Lepidoptera and Diptera represented the most consumed insect orders. Diet of bats exhibited a moderate level of overlap, with the highest value between Pteronotus parnellii and Pteronotus personatus in the wet season. We found higher dietary overlap between species during the same seasons than within any single species across seasons. This suggests that diets of the three species are driven more by prey availability than by any particular predator-specific characteristic. P. davyi and P. personatus increased their dietary breadth during the dry season, whereas P. parnellii diet was broader and had the highest effective number of prey species in all seasons. This supports the existence of dietary flexibility in generalist bats and dietary niche overlapping among groups of closely related species in highly seasonal ecosystems. Moreover, the abundance and availability of insect prey may drive the diet of insectivores.

Micronucleus Test Reveals Genotoxic Effects in Bats Associated with Agricultural Activity.

Bats play a vital role in our ecosystems and economies as natural pest-control agents, seed dispersers, and pollinators. Agricultural intensification, however, can impact bats foraging near crops, affecting the ecosystem services they provide. Exposure to pesticides, for example, may induce chromosome breakage or missegregation that can result in micronucleus formation. Detection of micronuclei is a simple, inexpensive, and relatively minimally invasive technique commonly used to evaluate chemical genotoxicity but rarely applied to assess wildlife genotoxic effects. We evaluated the suitability of the micronucleus test as a biomarker of genotoxicity for biomonitoring field studies in bats. We collected blood samples from insectivorous bats roosting in caves surrounded by different levels of disturbance (agriculture, human settlements) in Colima and Jalisco, west central Mexico. Then, we examined the frequency of micronucleus inclusions in erythrocytes using differentially stained blood smears. Bats from caves surrounded by proportionately more (53%) land used for agriculture and irrigated year-round had higher micronucleus frequency than bats from a less disturbed site (15% agriculture). We conclude that the micronucleus test is a sensitive method to evaluate genotoxic effects in free-ranging bats and could provide a useful biomarker for evaluating risk of exposure in wild populations. Environ Toxicol Chem 2021;40:202-207. © 2020 SETAC.

The role of the gut microbiota in the dietary niche expansion of fishing bats.

BACKGROUND: Due to its central role in animal nutrition, the gut microbiota is likely a relevant factor shaping dietary niche shifts. We analysed both the impact and contribution of the gut microbiota to the dietary niche expansion of the only four bat species that have incorporated fish into their primarily arthropodophage diet. RESULTS: We first compared the taxonomic and functional features of the gut microbiota of the four piscivorous bats to that of 11 strictly arthropodophagous species using 16S rRNA targeted amplicon sequencing. Second, we increased the resolution of our analyses for one of the piscivorous bat species, namely Myotis capaccinii, and analysed multiple populations combining targeted approaches with shotgun sequencing. To better understand the origin of gut microorganisms, we also analysed the gut microbiota of their fish prey (Gambusia holbrooki). Our analyses showed that piscivorous bats carry a characteristic gut microbiota that differs from that of their strict arthropodophagous counterparts, in which the most relevant bacteria have been directly acquired from their fish prey. This characteristic microbiota exhibits enrichment of genes involved in vitamin biosynthesis, as well as complex carbohydrate and lipid metabolism, likely providing their hosts with an enhanced capacity to metabolise the glycosphingolipids and long-chain fatty acids that are particularly abundant in fish. CONCLUSIONS: Our results depict the gut microbiota as a relevant element in facilitating the dietary transition from arthropodophagy to piscivory.