Cave physical attributes influencing the structure of terrestrial invertebrate communities in Neotropics

Abstract

The stability of temperature and humidity in caves is well known. However, little is known if higher or lower cave environmental stability (temperature, humidity, light and others) implies changes in the structure of the biological communities. Number, position and size of entrances, then size, depth, host rock and extent of the cave, the amount and type of food resources are all factors that can have strong influence on the cave biological communities. The objective of the present study was to evaluate the correlation between the presence of water bodies, size of entrances and the linear development of caves with the terrestrial invertebrate richness and species composition in 55 limestone caves located in the Brazilian Savannah, sampled from 2000 to 2011. Invertebrates were sampled by active search throughout the caves, prioritizing micro-habitats (sites under rocks) and organic resources (litter, twigs, feces and bat guano). We recorded 1,451 invertebrate species. Species richness was positively correlated with presence of cave streams, width of entrances and linear development of the caves. The richness of troglomorphic species was positively correlated to the presence of perennial pools and linear development of the caves. The presence of cave streams was a decisive factor for determining the community structure, increasing the number and the similarity of troglophile species among the caves. Flood pulses can cause disturbances that eventually select the same species besides importing resources. However, for the terrestrial troglomorphic species the disturbance caused by cave streams may decrease the number of species.