Distributions of macroinvertebrates downstream from a beaver dam: applying island biogeography theory to a stream setting.

Abstract

In this study, macroinvertebrate populations on submerged pieces of wood were examined in relation to the surface area of the wood and its distance from a beaver dam. The study was conducted on the east branch of the Maple River just north of Lake Kathleen, Emmet County, Michigan. It was hypothesized that species richness would decrease as distance from the dam increased. The dam was assumed to be a source of invertebrates and the pieces of wood as habitat islands. A negative trend in macroinvertebrate numbers and taxa was observed as distance from the dam increased. Weak correlations were also observed between surface area of the wood and numbers of taxa. There was no observable trend in macroinvertebrate species diversity, however. The study was inconclusive; however, there is some evidence that island biogeography theory may be playing a role in distributions of invertebrates in streams.