Spacial and temporal distributions of selected immature aquatic insect species collected in Sinking Creek, Virginia

Abstract

An investigation of the occurrence and distribution of portions of insect communities in selected riffles along the longitudinal gradient of Sinking Creek, Virginia was conducted over a twelve month period. Seasonal changes in total numbers of individuals and species were observed. Temporal changes in community dominance occurred throughout this study. Change in community composition was illustrated by variation in community dominance and in total numbers of individuals and species collected. The observed temporal and spatial distributions of thirty-six species were considered. Temporal distributions illustrate variations in the length of time individual species require to complete the aquatic portion of their life cycle, while differences in the observed longitudinal distribution of particular species indicate population responses to environmental change at points along the stream gradient. The spatial and/or temporal segregation of closely related organisms was indicated by seasonal and/or longitudinal differences in the relative abundance of particular species. Except for one family Hydropsychidae selected closely related species exhibited either spatial separations, temporal separations 1 or a combination of both spatial and temporal separations. Speculations on factors influencing the distributions of selected species are included. Baseline data indicate seasonal and longitudinal fluctuations. of physico-chemical parameters during this study. A discussion of these seasonal and longitudinal fluctuations is included.