Community structure of a Neotropical bat fauna as revealed by stable isotope analysis: Not all species fit neatly into predicted guilds

Abstract

Neotropical bat communities are among the most diverse mammal communities in the world, and a better understanding of these assemblages may permit inferences about how so many species coexist. While broad trophic guilds (e.g., frugivore, insectivore) of bats are recognized, details of diet and similarities among species remain largely unknown. We used stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) to characterize the community structure of a diverse Neotropical bat fauna from Belize to test predictions of niche theory and the competitive exclusion principle. We predicted that (1) interspecific variation in isotopic overlap would be greater within guilds than between guilds, and (2) no two sympatric populations would have isotopic niches that overlap completely, unless there is variation along some other axis (e.g., temporal, spatial). We additionally tested body size as an explanatory metric of potential overlap and predicted that larger‐bodied animals would have greater niche breadths. Results suggest that while guild‐level characterizations of communities are at least somewhat informative, there are multiple examples of intra‐ and inter‐guild species pairs with significantly overlapping isotopic niches, suggesting that, counter to predictions, they may compete for resources. Understanding the trophic structure of animal communities is fundamental to conservation and management of endangered species and ecosystems and important for evolutionary studies, and stable isotope analyses can provide key insights as well as informing hypotheses of the diet of species that are not well known. Abstract in Spanish is available with online material.

Foraging shifts and visual preadaptation in ecologically diverse bats

“…Despite the proposed association between phyllostomids and plants beginning at node E, dietary studies of phyllostomids highlight variation and flexibility in dietary niche breadth across certain species; for example, Phyllostominae have flexible diets that, to various degrees, include plant products (Clare et al., 2014; Oelbaum, Fenton, Simmons, & Broders, 2019; Rojas et al., 2018). Bayesian ancestral character reconstructions have previously been used to propose that predominant phytophagy (e.g., frugivory and nectarivory) evolved directly from insectivory in parallel lineages during the Miocene—placing them at later evolutionary time points than branch E (Rojas et al., 2011).…”

You Are More Than What You Eat: Differential Enrichment of Microbiome Functions Across Bat Dietary Guilds

“…The models were best at predicting insectivorous or primarily animalivorous species based on their gut metagenomes but were substantially worse at predicting frugivores and omnivores. It is important to note that many dietary specializations, including frugivory and nectarivory, are more labile than previously thought [27,74,75]. For instance, some species of Neotropical bats are known to occasionally take insects despite being considered "frugivores" [51], so rather than existing as discrete, closed niches, many bat species probably fall along a spectrum running from primarily plant-feeding, to omnivorous, to primarily animal-feeding.…”

Inter- and intra-specific variation in hair cortisol concentrations of Neotropical bats

“…Information on diet, foraging style, percentage of invertebrates in the diet, and fecundity was extracted from the Elton Traits, PanTHERIA, and Amniote Life History databases (Myhrvold et al, 2015; Wilman et 206 al., 2014). We collapsed variation in diet into two dietary niches: phytophagy (including nectarivores and frugivores) and animalivory (insectivores and carnivores) because many bat species in our study have diets that combine more than one food source within these categories (Fenton et al , 2001; Kunz and Fenton, 2005; Reid, 2009; Oelbaum et al , 2019). We also considered the percentage of invertebrates in the diet of the animalivorous bats, which can vary significantly among species.…”

“…From pilot analyses, we determined a minimum 1 amount of mg of hair was necessary to obtain values around 50% binding on the standard curve thereby accurately estimating cortisol concentration in the sample. 1 Oelbaum et al, 2019). We also considered the percentage of invertebrates in the diet of the animalivorous bats, which can vary significantly among species.…”

“…Hair cortisol levels are not likely affected by stress induced by capture and/or handling, which is one of the main limitations of blood GC analysis (Russell et al , 2012). A single sample of hair can also provide complementary and valuable information about ecology and behavior, including diet and movement (e.g., using stable isotope analyses; Fraser et al , 2010; Sullivan et al , 2012; Voigt et al , 2012; Oelbaum et al , 2019), condition (e.g. nutrition; Montillo et al , 2019), toxicant exposure (Hernout et al , 2016; Becker et al , 2018), and molecular identification (Magioli et al , 2019), opening possibilities for more integrative studies.…”