Variáveis ambientais influenciam a ocorrência de anuros em lagoas de uma planície alagável tropical no início da estação reprodutiva

Abstract

The occurrence of species is determined by the specific relationship between life history characteristics and habitat conditions. This relationship is well documented in stable systems, however in systems that undergo sudden seasonal changes, such as flood plains, this relationship can be difficult to detect. Here, we test whether species that share similar life history characteristics are linked to a specific set of environmental conditions. In a location in the Pantanal, at the beginning of the rainy season, we installed autonomous recorders in 44 lagoons in order to detect the presence and absence of frogs for three consecutive nights. In addition, we collected three important environmental variables, lagoon area covered by emerging aquatic vegetation, hydroperiod and lagoon area, and one landscape, distance from the lagoon to the nearest forest formation. To test our hypothesis, we used multi-species hierarchical models (which distinguished the non-detection of true absences) to assess the occurrence of anurans (with their different characteristics of life history) in relation to environmental and landscape variables. Few species were influenced by environmental variables. When the occurrence was related to an abiotic filter, species with totally different life history characteristics had the same relationship with habitat conditions, while anurans with the same characteristics were antagonically related to the same variable. The lack of specificity and the absence of a relationship between environmental variables and the occurrence of frogs may be due to the period of sampling. We capture the beginning of the migratory process, when, possibly, the frogs have not yet reached the reproductive sites that have ideal conditions for reproduction. Another possible explanation would be that migration to reproductive sites occurs at random, not respecting the specific ecological requirements of each species. Thus, we can say that at the beginning of the reproductive period of anurans, the processes linked to the niche are not responsible for their distribution in the Pantanal.