Changes in the Arthropod Community along an Elevational Transect in the Venezuelan Andes

Abstract

Sweep samples of insects at 200, 1600, 3550, and 3600 m elevation in secondary vegetation in the Venezuelan Andes near Merida show that the greatest number of insect species and dry weight occurs at the intermediate elevation, that the species richness of Diptera and parasitic Hymenoptera is not as proportionately reduced by elevation as is the species richness of other insect groups, that at higher elevations there are a reduced number of species and an increasingly unequal distribution of the individuals among the species, and that large insects are much less abundant at high than low elevations. These results confirm trends first indicated in an earlier elevational transect of Costa Rican insects. WE REPORT the results of sweep sampling the insect community at 3600 m, 3550 m, 1600 m, and 200 m elevation in the Venezuelan Andes near Merida, and at 3380 m in Costa Rica. The study is a continuation of the examination of large scale heterogeneity in tropical insect community structure that was initiated by Janzen (1973a,b). Here, we ask how sweep samples of low secondary vegetation differ at elevations characterized by paramo, mid-elevation evergreen forest which is generally converted to coffee and sugar cane plantations in Venezuela, and lowland (tierra caliente) evergreen forest, which is generally converted to cattle pasture and sugar cane in Venezuela.