Ecological and biogeographical influences on stream community composition in Zoar Valley, New York

Abstract

Biotic communities in low order streams are influenced by multiple factors that may reflect both ecological conditions within individual watersheds, and also biogeographic considerations such as spatial proximity among streams and organism dispersal abilities. Our aim was to assess benthic invertebrate community composition in 23first -third order streams in Zoar Valley, NY, across a gradient in habitat quality, and to further explore the role of local biogeography. Replicate Surber samples were collected from each stream on three dates during April-September 2006. One hundred and thirty-seven taxa were collected, representing fifty-five families, dominated by juvenile insects. Additionally we quantified ecological variables such as stream order, watershed area, habitat quality indices, and land cover, and we generated a spatial distance matrix to quantify geographic separation among streams. Similarity/dissimilarity among stream communities was quantified by multivariate ordination of genus/species distributions by Non-metric Multi-dimensional Scaling. Dipterans (true flies) tended to be a cohesive group, and loaded towards lower-order streams, whereas taxa of Ephemeroptera (mayflies) and Plecoptera (stoneflies) were more variable in distribution across stream orders and watershed sizes. Separate ordination of the thirty-one encountered genera/species of Chironomidae suggested specificity towards individual streams. Regression of distances in ordination space on geographic distances was non-significant, indicating these streams represented individual geographic units, apparently with little overlap among them. Give the high degree of disturbance inherent in many small woodland streams, these quantitative studies of the high integrity steam systems surrounding Zoar Valley canyon should prove valuable to conservation and restoration strategies.