Trophic structure and natural history of bat guano invertebrate communities, with special reference to Brazilian caves

Mapping global conservation priorities and habitat vulnerabilities for cave-dwelling bats in a changing world

Research and media attention is disproportionately focused on taxa and ecosystems perceived as charismatic, while other equally diverse systems such as caves and subterranean ecosystems are often neglected in biodiversity assessments and prioritisations. Highlighting the urgent need for protection, an especially large fraction of cave endemic species may be undescribed. Yet these more challenging systems are also vulnerable, with karsts for example losing a considerable proportion of their area each year. Bats are keystone to cave ecosystems making them potential surrogates to understand cave diversity patterns and identify conservation priorities. On a global scale, almost half (48 %) of known bat species use caves for parts of their life histories, with 32 % endemic to a single country, and 15 % currently threatened. We combined global analysis of cave bats from the IUCN spatial data with site-specific analysis of 1930 bat caves from 46 countries to develop global priorities for the conservation of the most vulnerable subterranean ecosystems. Globally, 28 % of caves showed high bat diversity and were highly threatened. The highest regional concentration of conservation priority caves was in the Palearctic and tropical regions (except the Afrotropical, which requires more intensive cave data sampling). Our results further highlight the importance of prioritising bat caves by incorporating locally collected data and optimising parameter selection (i.e., appropriate landscape features and threats). Finally, to protect and conserve these ecosystems it is crucial that we use frameworks such as this to identify priorities in species and habitat-level and map vulnerable underground habitats with the highest biodiversity and distinctiveness.

DarkCideS 1.0, a global database for bats in karsts and caves

Understanding biodiversity patterns as well as drivers of population declines, and range losses provides crucial baselines for monitoring and conservation. However, the information needed to evaluate such trends remains unstandardised and sparsely available for many taxonomic groups and habitats, including the cave-dwelling bats and cave ecosystems. We developed the DarkCideS 1.0 (https://darkcides.org/), a global database of bat caves and species synthesised from publicly available information and datasets. The DarkCideS 1.0 is by far the largest database for cave-dwelling bats, which contains information for geographical location, ecological status, species traits, and parasites and hyperparasites for 679 bat species are known to occur in caves or use caves in part of their life histories. The database currently contains 6746 georeferenced occurrences for 402 cave-dwelling bat species from 2002 cave sites in 46 countries and 12 terrestrial biomes. The database has been developed to be collaborative and open-access, allowing continuous data-sharing among the community of bat researchers and conservation biologists to advance bat research and comparative monitoring and prioritisation for conservation.

Measurement(s)	spatial region
Technology Type(s)	occurrent
Sample Characteristic - Organism	Mammalia • Chiroptera sp. BOLD:AAA2524
Sample Characteristic - Environment	cave system • karst cave
Sample Characteristic - Location	Global

Chthonius kirghisicus (Pseudoscorpiones, Chthoniidae), a new cave-dwelling species from Kyrgyzstan

A new pseudoscorpion species, Chthonius kirghisicussp. nov., is described. It can be distinguished from the other species of the genus mainly by the number and shape of chelal teeth, the number of coxae setae, the arrangement of carapacal setae, and its measurements. This new species represents the first record for the genus in Kyrgyzstan. We also provide recommendations for future research on this species.

Collecting eco-evolutionary data in the dark: Impediments to subterranean research and how to overcome them

Caves and other subterranean habitats fulfill the requirements of experimental model systems to address general questions in ecology and evolution. Yet, the harsh working conditions of these environments and the uniqueness of the subterranean organisms have challenged most attempts to pursuit standardized research.Two main obstacles have synergistically hampered previous attempts. First, there is a habitat impediment related to the objective difficulties of exploring subterranean habitats and our inability to access the network of fissures that represents the elective habitat for the so-called "cave species." Second, there is a biological impediment illustrated by the rarity of most subterranean species and their low physiological tolerance, often limiting sample size and complicating laboratory experiments.We explore the advantages and disadvantages of four general experimental setups (in situ, quasi in situ, ex situ, and in silico) in the light of habitat and biological impediments. We also discuss the potential of indirect approaches to research. Furthermore, using bibliometric data, we provide a quantitative overview of the model organisms that scientists have exploited in the study of subterranean life.Our over-arching goal is to promote caves as model systems where one can perform standardized scientific research. This is important not only to achieve an in-depth understanding of the functioning of subterranean ecosystems but also to fully exploit their long-discussed potential in addressing general scientific questions with implications beyond the boundaries of this discipline.

Optimizing speleological monitoring efforts: insights from long-term data for tropical iron caves

Understanding the factors underpinning species abundance patterns in space and time is essential to implement effective cave conservation actions. Yet, the methods employed to monitor cave biodiversity still lack standardization, and no quantitative assessment has yet tried to optimize the amount and type of information required to efficiently identify disturbances in cave ecosystems. Using a comprehensive monitoring dataset for tropical iron caves, comprising abundance measurements for 33 target taxa surveyed across 95 caves along four years, here we provide the first evidence-based recommendations to optimize monitoring programs seeking to follow target species abundance through time. We found that seasonality did not influence the ability to detect temporal abundance trends. However, in most species, abundance estimates assessed during the dry season resulted in a more accurate detection of temporal abundance trends, and at least three surveys were required to identify global temporal abundance trends. Finally, we identified a subset of species that could potentially serve as short-term disturbance indicators. Results suggest that iron cave monitoring programs implemented in our study region could focus sampling efforts in the dry season, where detectability of target species is higher, while assuring data collection for at least three years. More generally, our study reveals the importance of long-term cave monitoring programs for detecting possible disturbances in subterranean ecosystems, and for using the generated information to optimize future monitoring efforts.

Hypogean Communities as Cybernetic Systems: Implications for the Evolution of Cave Biotas

Ramón Margalef proposed in 1968 that ecosystems could be better understood if they were viewed as cybernetic systems. I tested this hypothesis in the case of hypogean ecosystems using available pieces of evidence. I looked on how information on feedbacks, stability, succession, organization, diversity, and energy flows in the hypogean environment fit the cybernetics hypothesis. The results were that there are convincing arguments that the application of the concept of cybernetics in biospeleology can be beneficial to broadening our understanding of cave biota in terms of their structure. I also make the case that this approach can provide more clarity about how cave biota has evolved through time and the implications for their conservation.

Cave Communities: From the Surface Border to the Deep Darkness

The discipline of subterranean biology has provided us incredible information on the diversity, ecology and evolution of species living in different typologies of subterranean habitats. However, a general lack of information on the relationships between cave species still exists, leaving uncertainty regarding the dynamics that hold together cave communities and the roles of specific organisms (from the least to the most adapted species) for the community, as well as the entire ecosystem. This Special Issue aims to stimulate and gather studies which are focusing on cave communities belonging to all different typologies of subterranean habitats, with the overarching goal to corroborate the key role of the subterranean biology in ecological and evolutionary studies.

Notes on the predation of an assassin bug by a spider in a Neotropical cave

Intraguild predation have rarely been documented in scientific literature, even though this type of interaction can affect population dynamics and competition. In this study we present an intraguild predation event that occurred at different times, but in the same cave, where we observed spiders of the species Enoploctenus cyclotorax preying on specimens of assassin bug Zelurus diasi. Inside the studied caves, food resources are scarce and populations can be fairly small in size. It is possible, therefore, that these events are the result of ecological pressures imposed by the hypogean environment.

Variation in Bat Guano Bacterial Community Composition With Depth

Bats are known to be reservoirs for a variety of mammalian pathogens, including viruses, fungi, and bacteria. Many of the studies examining the microbial community inhabiting bats have investigated bacterial taxa found within specific bat tissues and isolated bat guano pellets, but relatively few studies have explored bacterial diversity within bat guano piles. In large bat caves, bat guano can accumulate over time, creating piles several meters deep and forming complex interactions with coprophagous organisms in a habitat with low light and oxygen. As the guano decays, the nutrient composition changes, but the bacterial communities deep within the pile have not been characterized. Here, we assess the bacterial communities across varying depths within the guano pile using both culture-independent and culture-dependent methods. We found that although similar taxa are found throughout the guano pile, the relative abundances of taxa within the pile shift, allowing certain taxa to dominate the bacterial community at varying depths. We also identified potential bacterial functions being performed within the bat guano as various depths within the pile and found little variation in terms of the dominant predicted functions, suggesting that although the relative abundances of bacterial taxa are changing, the functions being performed are similar. Additionally, we cultured 15 different bacterial species, including 2 not present in our culture-independent analysis, and discuss the pathogenicity potential of these taxa. This study represents the first characterization of the bacterial community from the extreme environment within a bat guano pile and demonstrates the potential for bat caves as resources for identifying new bacterial species.

Conserving relics from ancient underground worlds: assessing the influence of cave and landscape features on obligate iron cave dwellers from the Eastern Amazon

The degradation of subterranean habitats is believed to represent a serious threat for the conservation of obligate subterranean dwellers (troglobites), many of which are short-range endemics. However, while the factors influencing cave biodiversity remain largely unknown, the influence of the surrounding landscape and patterns of subterranean connectivity of terrestrial troglobitic communities have never been systematically assessed. Using spatial statistics to analyze the most comprehensive speleological database yet available for tropical caves, we first assess the influence of iron cave characteristics and the surrounding landscape on troglobitic communities from the Eastern Amazon. We then determine the spatial pattern of troglobitic community composition, species richness, phylogenetic diversity, and the occurrence of frequent troglobitic species, and finally quantify how different landscape features influence the connectivity between caves. Our results reveal the key importance of habitat amount, guano, water, lithology, geomorphology, and elevation in shaping iron cave troglobitic communities. While mining within 250 m from the caves influenced species composition, increasing agricultural land cover within 50 m from the caves reduced species richness and phylogenetic diversity. Troglobitic species composition, species richness, phylogenetic diversity, and the occurrence of frequent troglobites showed spatial autocorrelation for up to 40 km. Finally, our results suggest that the conservation of cave clusters should be prioritized, as geographic distance was the main factor determining connectivity between troglobitic communities. Overall, our work sheds important light onto one of the most overlooked terrestrial ecosystems, and highlights the need to shift conservation efforts from individual caves to subterranean habitats as a whole.

Repellent Effect of Volatile Fatty Acids on Lesser Mealworm (Alphitobius diaperinus)

Volatile fatty acids (VFAs) are a group of common metabolites and semiochemicals mediating information transfer between higher organisms and bacteria, either from microbiome or external environment. VFAs commonly occur among various insect orders. There are numerous studies exploring their influence on the behavior of different insect species. In relation to the papers published by J. E. McFarlane in 1985, we assessed the effects of formic, acetic, propionic, butyric and valeric acids on the spatial preference of the lesser mealworm (Alphitobius diaperinus), a common pest of stored food grain products and the poultry industry. The main aim of the presented study was to provide new angles in VFA research, recreating the classical study both with new methods and on economically significant pest species. This paper presents a novel method of continuous, simultaneous assessment of site preference and the travelled distance in a constant-flow olfactometer. All the tested VFAs, except valeric acid, had a significant repellent effect, with formic acid being effective even at the lowest used concentration. Additionally, the VFAs significantly altered the distance travelled by the insects. The obtained results indicate a potential role for VFAs in the olfactory guided behavior of A. diaperinus. It is suspected that the reaction to the presence of VFAs may deviate from the specificity of species’ original habitat.

Reconciling Mining with the Conservation of Cave Biodiversity: A Quantitative Baseline to Help Establish Conservation Priorities

Caves pose significant challenges for mining projects, since they harbor many endemic and threatened species, and must therefore be protected. Recent discussions between academia, environmental protection agencies, and industry partners, have highlighted problems with the current Brazilian legislation for the protection of caves. While the licensing process is long, complex and cumbersome, the criteria used to assign caves into conservation relevance categories are often subjective, with relevance being mainly determined by the presence of obligate cave dwellers (troglobites) and their presumed rarity. However, the rarity of these troglobitic species is questionable, as most remain unidentified to the species level and their habitats and distribution ranges are poorly known. Using data from 844 iron caves retrieved from different speleology reports for the Carajás region (South-Eastern Amazon, Brazil), one of the world's largest deposits of high-grade iron ore, we assess the influence of different cave characteristics on four biodiversity proxies (species richness, presence of troglobites, presence of rare troglobites, and presence of resident bat populations). We then examine how the current relevance classification scheme ranks caves with different biodiversity indicators. Large caves were found to be important reservoirs of biodiversity, so they should be prioritized in conservation programs. Our results also reveal spatial autocorrelation in all the biodiversity proxies assessed, indicating that iron caves should be treated as components of a cave network immersed in the karst landscape. Finally, we show that by prioritizing the conservation of rare troglobites, the current relevance classification scheme is undermining overall cave biodiversity and leaving ecologically important caves unprotected. We argue that conservation efforts should target subterranean habitats as a whole and propose an alternative relevance ranking scheme, which could help simplify the assessment process and channel more resources to the effective protection of overall cave biodiversity.