Roosting ecology of Stenodermatinae bats (Phyllostomidae): evolution of foliage roosting and correlated phenotypes

Seasonal variation and host sex affect bat-bat fly interaction networks in the Amazonian savannahs

Bats are the second-most diverse group of mammals in the world, and bat flies are their main parasites. However, significant knowledge gaps remain regarding these antagonistic interactions, especially since diverse factors such as seasonality and host sex can affect their network structures. Here, we explore the influence of such factors by comparing species richness and composition of bat flies on host bats, as well as specialization and modularity of bat-bat fly interaction networks between seasons and adult host sexes. We captured bats and collected their ectoparasitic flies at 10 sampling sites in the savannahs of Amapá State, northeastern region of the Brazilian Amazon. Despite female bats being more parasitized and recording greater bat fly species richness in the wet season, neither relationship was statistically significant. The pooled network could be divided into 15 compartments with 54 links, and all subnetworks comprised >12 compartments. The total number of links ranged from 27 to 48 (for the dry and wet seasons, respectively), and female and male subnetworks had 44 and 41 links, respectively. Connectance values were very low for the pooled network and for all subnetworks. Our results revealed higher bat fly species richness and abundance in the wet season, whereas specialization and modularity were higher in the dry season. Moreover, the subnetwork for female bats displayed higher specialization and modularity than the male subnetwork. Therefore, both seasonality and host sex contribute in different ways to bat-bat fly network structure. Future studies should consider these factors when evaluating bat-bat fly interaction networks.

Roost making in bats

Structures created by animals can serve many purposes. Spiders weave intricate webs to trap prey; beavers engineer complex networks of dams to alter waterways; male bower birds construct and decorate elaborate bowers to attract mates. Animal architecture ranges widely in function, but by far the most common use is shelter. Animals can spend a large amount of time in their shelters, and this is often where they both sleep and rear young, two of the most vulnerable states in animal lives. To optimize the safety and suitability of refuges available to them, many animals have become architects and create their own shelters, ranging from simple holes in the ground to the large complex nests of some social insects.

Review of studies about bat-fly interactions inside roosts, with observations on partnership patterns for publications

Pressures from anthropogenic disturbances have triggered a wealth of studies focusing on the assessment and mitigation of the negative impacts of these disturbances on inter and intraspecific ecological interactions, including bats and bat flies in their roosts. The heterogeneity of research methods employed for these studies and the scientific imbalance between countries may constrain advances and the consolidation of the knowledge on this subject. We reviewed the literature regarding bat and bat-ectoparasite interactions in roosts assessing global research trends and patterns of author collaborative work to be able to identify key questions for future studies and potential initiatives to improve the knowledge on this subject. Current information available has mostly come from the Americas and is predominantly focused on the recognition and description of parasite-host interactions between bats and bat flies. Our findings suggest the value of increasing collaboration for future research, as several countries with largely diverse environments and high organismal richness are disconnected from the countries that produce the most publications in this area, and/or have low records of publications. These regions are in the Global South, mostly in South American and African countries. We suggest that more collaborative networks may increase scientific production in the area, and that investing in local research development and enhancing partnerships for publications may strengthen the field. These research programs and collaborations are key for the development of conservation strategies for bats and bat flies, for their roosts, and for understanding bat and bat-ectoparasite interactions.

Wings of fringed fruit-eating bats (Artibeus fimbriatus) are highly integrated biological aerofoils from perspectives of secondary sexual dimorphism, allometry and modularity

Phenotypic variability is ubiquitous. This is especially true in bats, where families such as Phyllostomidae encompass as much phenotypic variability as some entire orders of mammals. Typically, phenotypic variability is characterized based on cranial morphology, with studies of other functionally important aspects of the phenotype, such as legs, feet and wings, being less frequent. We examined patterns of secondary sexual dimorphism and allometry of wing elements of the fringed fruit-eating bat (Artibeus fimbriatus) and examined, for the first time, the modularity of bat wings. Patterns were based on 13 wing measurements taken from 21 females and 15 males from eastern Paraguay. From a multivariate perspective, A. fimbriatus exhibited significant secondary sexual dimorphism. Females were larger than males for all 13 wing characteristics, with significant differences involving the last phalanx of the fourth and fifth digits. Female wings were also relatively larger than male wings from a multivariate perspective, as was the last phalanx of the fourth and fifth digits, after adjusting for wing size based on forearm length. Wing elements were highly variable regarding allometric relationships, with some exhibiting no allometric patterns and others exhibiting isometry or hyperallometry, depending on the element. Wings exhibited significant modularity, with metacarpals, proximal phalanges and distal phalanges each representing a discrete module. The wings of A. fimbriatus exhibit substantive patterns of dimorphism, allometry and modularity. Although the big mother hypothesis is a strong theoretical construct to explain wing dimorphism, there is not yet any sound theoretical basis for the patterns of allometry and modularity of the wing. Further investigation is required to understand the determinants of variation in wing morphology.

From island biogeography to landscape and metacommunity ecology: A macroecological perspective of bat communities

The equilibrium theory of island biogeography and its quantitative consideration of origination and extinction dynamics as they relate to island area and distance from source populations have evolved over time and enriched theory related to many disciplines in spatial ecology. Indeed, the island focus was catalytic to the emergence of landscape ecology and macroecology in the late 20th century. We integrate concepts and perspectives of island biogeography, landscape ecology, macroecology, and metacommunity ecology, and show how these disciplines have advanced the understanding of variation in abundance, biodiversity, and composition of bat communities. We leverage the well-studied bat fauna of the islands in the Caribbean to illustrate the complex interplay of ecological, biogeographical, and evolutionary processes in molding local biodiversity and system-wide structure. Thereafter, we highlight the role of habitat loss and fragmentation, which is increasing at an accelerating rate during the Anthropocene, on the structure of local bat communities and regional metacommunities across landscapes. Bat species richness increases with the amount of available habitat, often forming nested subsets along gradients of patch or island area. Similarly, the distance to and identity of sources of colonization influence the richness, composition, and metacommunity structure of islands and landscape networks.

New architecture of leaf-tents in American oil palms (Elaeis oleifera) used by Pacific tent-making bat (Uroderma convexum) in Panama

In this study, we report for the first time the use of the American oil palm (Elaeis oleifera) as roost by the Neotropical Pacific tent-making bat (Uroderma convexum). Palms with tent roosts consisting of modified leaves were found within the semi-deciduous lowland rainforest in Panama. We present detailed information on a new style of leaf modifications and compare these to tent architectures in other palm species used by U. convexum.

Evolution of litter size in bats and its influence on longevity and roosting ecology

Litter size varies in mammals, with about half of the species producing at least two offspring per gestation (polytocy). In bats, however, the modal litter size is one (monotocy), and polytocy is restricted to family Vespertilionidae. Here, we reconstruct the evolutionary history of polytocy in chiropterans and use phylogenetically informed regressions to investigate its relationship to roost type, longevity and group size. Our phylogenetic reconstructions suggested that production of multiple offspring was the ancestral condition in family Vespertilionidae. The distribution of monotocy/polytocy in Chiroptera was best explained by a minimum of two evolutionary transitions from monotocy to polytocy and by ≥ 18 transitions from polytocy to monotocy. The regression models showed that longevity and roost type explained the variation in litter size, whereas group size did not. Our analyses also revealed a greater diversity of polytocous bats in the Northern Hemisphere, in both temperate and tropical regions. We suggest that the high resource allocation to reproduction in polytocous bats limited their lifespan. The absence of a relationship between polytocy and group size indicates that the benefits of cooperative breeding surpass the costs of intrasexual competition in bats.

Relative contributions of ecological drift and selection on bat community structure in interior Atlantic Forest of Paraguay

Despite extensive focus on numerous mechanisms that potentially structure Neotropical bat communities, understanding of the relative importance of any is still illusive. Recently, it has been demonstrated that all mechanisms used to explain community organization can be conceptualized as one or a combination of the few higher-level processes of dispersal, drift, selection and speciation. These four higher-level processes have not been addressed equally by Neotropical bat community ecologists. In particular, predictions formulated from a hypothesis of ecological drift have not been tested for any Neotropical bat community. Herein we contrast efficacy of predictions based on the higher-level processes of drift and selection in describing community structure of bats in the Atlantic Forest of eastern Paraguay. Predictions apply to species-environment interactions, patterns of trait variation and beta-diversity, predictability of dominant competitors and responses to seasonality. At best, there was inconsistent support for the operation of either drift or selection within this bat community. Selection, however, had more various forms of support including strong species-environment relationships, predictable patterns of dominant competitors and strong responses to seasonality. Despite stronger support for selection, a number of predictions of drift were supported as well. It is likely that a combination of both of these processes operates across the variable environments experienced in Atlantic Forest. Predictions of both processes are difficult to make operational. Support for drift often comes from failure to demonstrate a significant pattern and should not be considered strong support of a prediction. Similarly, many predictions of selection predict phenotypic patterns among species without specifying a particular trait. This is problematic because the phenotype is multifaceted and a lack of pattern in one measured trait might mask a strong pattern in some other unmeasured trait. Distilling mechanisms of community organization into four higher level processes is a substantial innovation in community ecology. Nonetheless, efforts need to be made to develop a suite of mutually exclusive and falsifiable predictions to facilitate future and more rapid understanding of community organization.

New tent architecture roost by Dermanura phaeotis (Miller, 1902) (Chiroptera: Phyllostomidae) in southeastern Mexico

Some phyllostomid bats modify leaves of certain plant species in order to build tents as daytime roosts. Most tent-roosting members of the Artibeus and Dermanura genus have a widespread geographic distribution; nevertheless, there are few reports regarding roost architecture. This is the first report in Mexico of boat/apical tents built by the pygmy fruit-eating bat Dermanura phaeotis.

Bat flies aggregation on Artibeus planirostris hosts in the Pantanal floodplain and surrounding plateaus

For parasites in natural systems, the most common pattern of spatial distribution is aggregation among hosts. The main causes of such aggregation are variable exposure of hosts to parasites and heterogeneity in host susceptibility. The objective of this study was to determine if there are differences in the aggregation pattern of two species of ectoparasitic flies between the Pantanal and Cerrado regions of Brazil on the bat Artibeus planirostris. We collected the ectoparasites from bats captured between 2002 and 2017 with mist nets in 21 sites in the Pantanal and 15 sites in the surrounding plateaus. The results showed that the aggregation of ectoparasitic flies in Pantanal was more pronounced than in Cerrado. The discrepancy aggregation index (D) of the bat fly Megistopoda aranea was 0.877 in Pantanal and 0.724 in Cerrado. The D values of Aspidoptera phyllostomatis was even higher, with 0.916 and 0.848 in the Pantanal and Cerrado, respectively. Differences in the shelters used may be the main factor shaping variation in aggregation, since the Pantanal does not have rock formations, with only foliage, crowns and hollow tree trunks. These differences likely affect host exposure to the parasites, leading to an increase in parasite aggregation.

Specialized landing maneuvers in Spix's disk-winged bats (Thyroptera tricolor) reveal linkage between roosting ecology and landing biomechanics

Disk-winged bats (Thyroptera spp.) are the only mammals that use suction to cling to smooth surfaces, having evolved suction cups at the bases of the thumbs and feet that facilitate attachment to specialized roosts: the protective funnels of ephemeral furled leaves. We predicted that this combination of specialized morphology and roosting ecology is coupled with concomitantly specialized landing maneuvers. We tested this prediction by investigating landings in Thyroptera tricolor using high-speed videography and a force-measuring landing pad disguised within a furled leaf analogue. We found that their landing maneuvers are distinct among all bats observed to date. Landings comprised three phases: 1) approach, 2) ballistic descent, and 3) adhesion. During approach, bats adjusted trajectory until centered in front of and above the landing site, typically the leaf's protruding apex. Bats initiated ballistic descent by arresting the wingbeat cycle and tucking their wings to descend toward the leaf, simultaneously extending the thumb-disks cranially. Adhesion commenced when the thumb-disks contacted the landing site. Significant body reorientation occurred only during adhesion, and only after contact, when the thumb-disks acted as fulcra about which the bats pitched 75.02±26.17° (mean±s.d.) to swing the foot-disks into contact. Landings imposed 6.98±1.89 bodyweights of peak impact force. These landing mechanics are likely influenced by the orientation, spatial constraints, and compliance of furled leaf roosts. Roosting ecology influences critical aspects of bat biology, and taken as a case-study, this work suggests that roosting habits and landing mechanics could be functionally linked across bats.

Multifactorial processes underlie parallel opsin loss in neotropical bats

The loss of previously adaptive traits is typically linked to relaxation in selection, yet the molecular steps leading to such repeated losses are rarely known. Molecular studies of loss have tended to focus on gene sequences alone, but overlooking other aspects of protein expression might underestimate phenotypic diversity. Insights based almost solely on opsin gene evolution, for instance, have made mammalian color vision a textbook example of phenotypic loss. We address this gap by investigating retention and loss of opsin genes, transcripts, and proteins across ecologically diverse noctilionoid bats. We find multiple, independent losses of short-wave-sensitive opsins. Mismatches between putatively functional DNA sequences, mRNA transcripts, and proteins implicate transcriptional and post-transcriptional processes in the ongoing loss of S-opsins in some noctilionoid bats. Our results provide a snapshot of evolution in progress during phenotypic trait loss, and suggest vertebrate visual phenotypes cannot always be predicted from genotypes alone.

Bats are famous for using their hearing to explore their environments, yet fewer people are aware that these flying mammals have both good night and daylight vision. Some bats can even see in color thanks to two light-sensitive proteins at the back of their eyes: S-opsin which detects blue and ultraviolet light and L-opsin which detects green and red light. Many species of bat, however, are missing one of these proteins and cannot distinguish any colors; in other words, they are completely color-blind.

Some bat species found in Central and South America have independently lost their ability to see blue-ultraviolet light and have thus also lost their color vision. These bats have diverse diets – ranging from insects to fruits and even blood – and being able to distinguish color may offer an advantage in many of their activities, including hunting or foraging. The vision genes in these bats, therefore, give scientists an opportunity to explore how a seemingly important trait can be lost at the molecular level.

Sadier, Davies et al. now report that S-opsin has been lost more than a dozen times during the evolutionary history of these Central and South American bats. The analysis used samples from 55 species, including animals caught from the wild and specimens from museums. As with other proteins, the instructions encoded in the gene sequence for S opsin need to be copied into a molecule of RNA before they can be translated into protein. As expected, S-opsin was lost several times because of changes in the gene sequence that disrupted the formation of the protein. However, at several points in these bats’ evolutionary history, additional changes have taken place that affected the production of the RNA or the protein, without an obvious change to the gene itself. This finding suggests that other studies that rely purely on DNA to understand evolution may underestimate how often traits may be lost. By capturing ‘evolution in action’, these results also provide a more complete picture of the molecular targets of evolution in a diverse set of bats.

Laboulbeniales hyperparasites (Fungi, Ascomycota) of bat flies: Independent origins and host associations

The aim of this study was to explore the diversity of ectoparasitic fungi (Ascomycota, Laboulbeniales) that use bat flies (Diptera, Hippoboscoidea) as hosts. Bat flies themselves live as ectoparasites on the fur and wing membranes of bats (Mammalia, Chiroptera); hence this is a tripartite parasite system. Here, we collected bats, bat flies, and Laboulbeniales, and conducted phylogenetic analyses of Laboulbeniales to contrast morphology with ribosomal sequence data. Parasitism of bat flies by Laboulbeniales arose at least three times independently, once in the Eastern Hemisphere (Arthrorhynchus) and twice in the Western Hemisphere (Gloeandromyces, Nycteromyces). We hypothesize that the genera Arthrorhynchus and Nycteromyces evolved independently from lineages of ectoparasites of true bugs (Hemiptera). We assessed phylogenetic diversity of the genus Gloeandromyces by considering the LSU rDNA region. Phenotypic plasticity and position-induced morphological adaptations go hand in hand. Different morphotypes belong to the same phylogenetic species. Two species, G. pageanus and G. streblae, show divergence by host utilization. In our assessment of coevolution, we only observe congruence between the Old World clades of bat flies and Laboulbeniales. The other associations are the result of the roosting ecology of the bat hosts. This study has considerably increased our knowledge about bats and their associated ectoparasites and shown the necessity of including molecular data in Laboulbeniales taxonomy.