RESUMO
Our objective was to estimate and analyze the body-size distribution parameters of terrestrial mammal assemblages at different spatial scales, and to determine whether these parameters are controlled by local ecological processes or by larger-scale ones. Based on 93 local assemblages, plus the complete mammal assemblage from three continents (Africa, North, and South America), we estimated three key distribution parameters (diversity/size slope, skewness, and modal size) and compared the values to those expected if size distributions are mainly controlled by local interactions. Mammal diversity decreased much faster as body size increased than predicted by fractal niche theory, both at continental and at local scales, with continental distributions showing steeper slopes than the localities within them. South America showed a steeper slope (after controlling for species diversity), compared to Africa and North America, at local and continental scales. We also found that skewness and modal body size can show strikingly different correlations with predictor variables, such as species richness and median size, depending on the use of untransformed versus log-transformed data, due to changes in the distribution density generated by log-transformation. The main differences in slope, skewness, and modal size between local and continental scales appear to arise from the same biogeographical process, where small-sized species increase in diversity much faster (due to higher spatial turnover rates) than large-sized species. This process, which can operate even in the absence of competitive saturation at local scales, generates continental assemblages with steeper slopes, smaller modal sizes, and higher right skewness (toward small-sized species) compared to local communities. In addition, historical factors can also affect the size distribution slopes, which are significantly steeper, in South American mammal assemblages (probably due to stronger megafauna extinction events in South America) than those in North America and Africa.
RESUMO
Inventories are the basis of every work with biodiversity, with increased importance due to the current environmental crisis. Bats are one of the most diverse groups of mammals, with high ecologic versatility and are good bioindicators to monitor environmental impacts. We performed a two-stage survey at an Atlantic Forest reserve in the State of Paraíba, the first stage registering 187 individuals of 24 species and the second stage, 1073 individuals of 11 species; the second stage's richness being a subset of the first as pointed by the Mann-Whitney test. The second stage was more efficient in accumulating individuals, while the first accumulated species more efficiently. The diversity estimation (Chao 1) pointed that the survey was efficient in registering 93.75% of the species richness predicted for the area, and that diversity estimators are more reliable to evaluate sampling efficiency than methods based in number of captures. The inventory survey registered over 42% of the species richness registered for the State of Paraíba, as well as included a new register, Natalus stramineus, pointing that the bat richness for the state is yet to be sufficiently studied.
Inventários são a base de qualquer trabalho com biodiversidade, com sua importância exacerbada dada a crise ambiental atual. Morcegos são um dos grupos de mamíferos mais diversos, com alta versatilidade ecológica, e se apresentam como bons bioindicadores para monitorar impactos ambientais. O presente trabalho é um inventário de morcegos em longo prazo, dividido em duas etapas, numa reserva biológica de Floresta Atlântica no Estado da Paraíba, Brasil. A primeira etapa capturou 187 indivíduos de 24 espécies, o segundo registrou 1073 indivíduos de 11 espécies, sendo a diversidade deste um subgrupo da diversidade do primeiro, como apontado pelo teste de Mann-Whitney. O segundo estágio foi mais eficaz em acumular indivíduos, enquanto o primeiro acumulou espécies mais eficientemente. O estimador de diversidade Chao 1 apontou que o inventário foi eficiente em registrar 93,75% da riqueza de espécies prevista para a área, e que estimadores de diversidade são mais confiáveis para avaliar suficiência amostral que métodos baseados em número mínimo de capturas. O inventário registrou cerca de 42% da riqueza de espécies conhecida para o Estado da Paraíba, assim como incluiu um novo registro, Natalus stramineus, ressaltando que a riqueza de espécies de morcegos no estado está por ser suficientemente estudada.