Composição e padrões de diversidade de morcegos em cavernas de Conceição do Mato Dentro, Minas Gerais, Brasil

Abstract

The extent of human influence and its impact on the environment has reached unprecedented levels on a global scale, leading to a drastic reduction in biodiversity, both in terrestrial and marine ecosystems. These anthropogenic activities have resulted in habitat loss and fragmentation, which are two of the main consequences of land-use changes in anthropogenic landscapes. Bats emerge as a good model for studying the impacts of habitat loss due to their high diversity, with 186 known species in Brazil and equally high diversity in the Neotropical region. Caves are the primary shelter used by various bat species; in return, bats are essential for the functioning of cave ecosystems, especially through guano and carcasses, which support other subterranean organisms. Anthropogenic activities and mineral exploitation in karst regions threaten the caves in these areas, the entire subterranean ecosystem, and the bat species that inhabit them. Therefore, the objectives of this study were to evaluate whether and how the type and intensity of human activities and the size of caves influence the richness and composition of bat species in cave shelters, as well as to assess, in the case of variation in species composition, which process is responsible for beta diversity. The study was conducted in the municipality of Conceição do Mato Dentro, in the central region of the state of Minas Gerais, Brazil. Ninety-one caves were sampled in three areas: Serra da Ferrugem (SFE), Serra do Cangueiro (SCA), and Serra de Santo Antônio (SSA). The areas were categorized according to different anthropogenic activities and land uses within a 5 km radius circular buffer. Two bat sampling campaigns were conducted per year, in each cave, from 2018 to 2022, and one campaign in 2023, through daytime incursions to capture the specimens using hand nets. Species richness was assessed to investigate possible variations in this parameter among the sampled areas, within each cavity of the respective areas, and in relation to the cave’s horizontal projection. Spatial beta diversity partitioning was used to determine which process drives compositional changes in bats between the sampled locations. Four land-use classes were identified: natural, pasture, eucalyptus, and urban. Bats were recorded in 61 of the 91 sampled caves, totaling 439 records of 14 species, all from the Phyllostomidae family. There is no difference in bat species richness in caves among the three locations, but PERMANOVA analysis revealed a difference in community structure in SFE compared to SCA and SSA. The species that contributed most to dissimilarity are Glossophaga soricina, Mimon bennetti, Chrotopterus auritus, and Micronycteris microtis. The composition of bat communities in cavities differs between areas with different anthropogenic land uses; additionally, we found a positive correlation between species richness and occurrence of bat species in relation to the horizontal projection of the caves. Species turnover is the main component of spatial beta diversity partitioning that generates differences in the composition of bat assemblages. This study demonstrated that bat assemblages respond both to cave size and to the landscapes of the locations where shelters are found. The present study highlights the importance of evaluating not only structural and abiotic characteristics, such as area, size, and microclimate, but also considering the context of the caves' insertion in the landscape, through the quantitative characterization of habitat attributes and the composition of these locations.