Notes on the faumstic complexity of cicadas (Homoptera; Cicadidae) in northern Costa Rica

Abstract

The geographical, habitat, and seasonal distributions of neotropical cicadas were studied at twelve localities on a northeast-southwest transect across northern Costa Rica Geographical regions sampled are: lowland tropical rain forest, montane wet forest, and seasonal forest (highland and lowland). Habitat associations (primary, secondary, and forest remnants; cultivated lands) are where cicada nymphal casts are found. There are about 23 species with highest faunal complexity (genera and species) in lowland tropical rain forest. Faunas of the Caribbean and Pacific slopes of the Cordillera Central are very distinct. The present-day fauna of the Meseta Central is similar to that of wet regions, with infiltration of a few seasonal forest species. In lowland dry forest, the fauna is greatly impoverished, probably due to past destruction of the original vegetation cover. Small pockets of persisting forest here support cicadas not found in disturbed habitats (pastures). The original fauna of the Meseta Central very likely contained more of the species found today in wet regions, but these became extinct when the vegetation was cleared. Faunal complexity here remains high owing to several species thriving in small forest refugia along streams, coupled with some living in cultivated habitats. High impoverishment occurs in a montane region of secondary forest. Faunal complexity of inontane primary wet forest is only slightly lower than that of lowland rain forest, presumably as a result of increased climatic instability and other factors. Throughout Costa Rica, many species emerge during the dry season, and timing of emergences during both seasons correlates well with seasonality of rainfall. The geographical complexity of Costa Rica, regional climatic and vegetation variations over short distances, and the existence of many secondary forests and cultivated lands, are the major determinants of the faunal diversity of cicadas. As more lowland tropical rain forest is cleared for cultivation and lumbering, many species of cicadas will likely become extinct, especially if no forest refugia are left behind.