Roosting Ecology and the Evolution of Pelage Markings in Bats

Multiple lineages of bats have evolved striking facial and body pelage makings, including spots, stripes and countershading. Although researchers have hypothesized that these markings mainly evolved for crypsis, this idea has never been tested in a quantitative and comparative context. We present the first comparative study integrating data on roosting ecology (roost type and colony size) and pelage coloration patterns across bats, and explore the hypothesis that the evolution of bat pelage markings is associated with roosting ecologies that benefit from crypsis. We find that lineages that roost in the vegetation have evolved pelage markings, especially stripes and neck collars, which may function in crypsis through disruptive coloration and a type of countershading that might be unique to bats. We also demonstrate that lineages that live in larger colonies and are larger in size tend not to have pelage markings, possibly because of reduced predation pressures due to the predator dilution effect and a lower number of potential predators. Although social functions for pelage color patterns are also possible, our work provides strong support for the idea that roosting ecology has driven the evolution of pelage markings in bats

Auditory opportunity and visual constraint enabled the evolution of echolocation in bats

Substantial evidence now supports the hypothesis that the common ancestor of bats was nocturnal and capable of both powered flight and laryngeal echolocation. This scenario entails a parallel sensory and biomechanical transition from a nonvolant, vision-reliant mammal to one capable of sonar and flight. Here we consider anatomical constraints and opportunities that led to a sonar rather than vision-based solution. We show that bats' common ancestor had eyes too small to allow for successful aerial hawking of flying insects at night, but an auditory brain design sufficient to afford echolocation. Further, we find that among extant predatory bats (all of which use laryngeal echolocation), those with putatively less sophisticated biosonar have relatively larger eyes than do more sophisticated echolocators. We contend that signs of ancient trade-offs between vision and echolocation persist today, and that non-echolocating, phytophagous pteropodid bats may retain some of the necessary foundations for biosonar

All You Can Eat: High Performance Capacity and Plasticity in the Common Big-Eared Bat, Micronycteris microtis (Chiroptera: Phyllostomidae)

Ecological specialization and resource partitioning are expected to be particularly high in the species-rich communities of tropical vertebrates, yet many species have broader ecological niches than expected. In Neotropical ecosystems, Neotropical leaf-nosed bats (Phyllostomidae) are one of the most ecologically and functionally diverse vertebrate clades. Resource partitioning in phyllostomids might be achieved through differences in the ability to find and process food. We selected Micronycteris microtis, a very small (5–7 g) animalivorous phyllostomid, to explore whether broad resource use is associated with specific morphological, behavioral and performance traits within the phyllostomid radiation. We documented processing of natural prey and measured bite force in free-ranging M. microtis and other sympatric phyllostomids. We found that M. microtis had a remarkably broad diet for prey size and hardness. For the first time, we also report the consumption of vertebrates (lizards), which makes M. microtis the smallest carnivorous bat reported to date. Compared to other phyllostomids, M. microtis had the highest bite force for its size and cranial shape and high performance plasticity. Bite force and cranial shape appear to have evolved rapidly in the M. microtis lineage. High performance capacity and high efficiency in finding motionless prey might be key traits that allow M. microtis, and perhaps other species, to successfully co-exist with other gleaning bats

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

Data from: Quantifying the effect of gape and morphology on bite force: biomechanical modeling and in vivo measurements in bats

Maximum bite force is an important metric of feeding performance that defines the dietary ecology of many vertebrates. In mammals, theoretical analyses and empirical studies suggest a trade-off between maximum bite force and gape at behavioural and evolutionary scales; in vivo bite force is expected to decrease at wide gapes, and cranial morphologies that enable high mechanical advantage are thought to have a lower ability to generate high bite forces at wide gapes, and vice versa. However, very few studies have confirmed these relationships in free-ranging mammals. This study uses an ecologically diverse sample of bats to document the variation in bite force with respect to gape angle, and applies three-dimensional models of the feeding apparatus to identify the major morphological and biomechanical predictors of the gape-bite force relationship. In vivo and model data corroborated that bite force decreases significantly at wide gapes across species, but there is substantial intraspecific variation in the data obtained from live bats. Results from biomechanical models, analysed within a phylogenetic framework, revealed that species with larger temporalis muscles, higher temporalis stretch factors and high mechanical advantages experience a steeper reduction in bite force with increasing gape. These trends are illustrated by short-faced durophagous frugivores. The results from this study suggest that gape-mediated changes in bite force can be explained both by behavioural effects and cranial morphology, and that these links are relevant for functional analyses of mammal dietary ecology

The evolution of cranial morphology, feeding performance and behavior in neotropical leaf-nosed bats (Chiroptera: Phyllostomidae)

Morphology can play a major role in ecological diversification and adaptive radiation when it consistently enhances performance and behavior. Here I investigate how cranial and dental morphology, feeding performance and behavior relate to one another and to the dietary radiation in Neotropical leaf-nosed bats (Family Phyllostomidae). First, I build a 3D biomechanical model to investigate the mechanism connecting cranial morphology and bite performance (bite force) and how bats with different diets vary in biomechanical parameters predicting bite force. The model demonstrates that cranial morphology is a strong predictor of bite force variation, and that bats differ in biomechanical predictors of bite force when they are classified according to dietary hardness. Second, I investigate the relationship between biting behavior and bite force across phyllostomids. My results indicate that bats modulate their performance by changing their biting behaviors to maximize bite force when feeding on hard foods. Using phylogenetic correlations and ancestral state reconstructions, I provide evidence for correlated evolution of behavior and performance, and rapid evolution in these traits that coincided with the use of plant resources. Third, I investigate the trends in molar complexity, chewing behavior and efficiency in breaking down prey across phyllostomids with different diets. My results illustrate that frugivores exhibit a higher dental complexity than insectivores and omnivores, and that the latter groups achieve higher performance in insect breakdown through higher molar complexity and chewing behavior. Finally, I investigate if other behavioral traits relevant to fitness have shaped the evolution of the skull morphology, using roost excavation in Lophostoma silvicolum as a model system. Through finite element analysis, I provide support for the prediction that the skull of L. silvicolum presents adaptations for roost excavation, in the form of a stronger skull. When all my findings are considered there is evidence that, although morphology can strongly predict performance, behavior plays an important role in modulating performance, and selection on this ability could have contributed to the ecological diversification of phyllostomids. Overall, the dietary radiation of phyllostomids, in particular the use of plant resources, was associated with dramatic changes in cranial and dental morphology, feeding performance and behavior

Model and in vivo bite force data

Field measurements of bite forces at low and wide gapes for bats, and input and output data of 3D bite force models of bat skulls at low and wide gapes

Procustes coordinates and centroid sizes-Lateral view

Procustes coordinates and centroid sizes from the lateral view of Rhinolophus skull

Data from: Go big or go fish: morphological specializations in carnivorous bats

Specialized carnivory is relatively uncommon across mammals, and bats constitute one of the few groups in which this diet has evolved multiple times. While size and morphological adaptations for carnivory have been identified in other taxa, it is unclear what phenotypic traits characterize the relatively recent evolution of carnivory in bats. To address this gap, we apply geometric morphometric and phylogenetic comparative analyses to elucidate which characters are associated with ecological divergence of carnivorous bats from insectivorous ancestors, and if there is morphological convergence among independent origins of carnivory within bats, and with other carnivorous mammals.We find that carnivorous bats are larger and converged to occupy a subset of the insectivorous morphospace, characterized by skull shapes that enhance bite force at relatively wide gapes. Piscivorous bats are morphologically distinct, with cranial shapes that enable high bite force at narrow gapes, which is necessary for processing fish prey. All animal-eating species exhibit positive allometry in rostrum elongation with respect to skull size, which could allow larger bats to take relatively larger prey. The skull shapes of carnivorous bats share similarities with generalized carnivorans, but tend to be more suited for increased bite force production at the expense of gape, when compared with specialized carnivorans