Temporal dynamics of aquatic insects and oligochaetes in tropical springs

Seasonality and predictability of rainfall and air temperature can influence the temporal dynamics of aquatic insects and oligochaetes, especially in areas of eucalyptus monoculture because of its lower vegetation diversity and canopy structure. To date, however, few studies have been conducted in tropical springs. The 12 springs in this study, 5 located in forested areas and 7 in areas used for eucalyptus cultivation, were sampled over 3 years during the dry and rainy periods. Seasonality and predictability were high for both climate variables: accumulated rainfall and average air temperature. We found a greater abundance of macroinvertebrates in the dry period, mostly due to the increase in aquatic insects following a decrease in the abundance of oligochaetes. No difference was found in richness between the periods. Although the temporal beta diversity was high and the community composition was structured mainly by the replacement component, we found no significant difference between the periods in forest and eucalyptus springs. In addition, no homogeneity was found in the abiotic variables between the different periods. Our results help elucidate the temporal dynamics of macroinvertebrate communities in these tropical ecosystems.