The Structure of Larval Odonate Assemblages in the Enoree River Basin of South Carolina

Odonate larvae were collected at 127 sites in the Enoree River and nine of its tributaries in the summers of 1999 and 2000. Mean odonate abundance, species richness, and Simpson’s diversity were compared across tributaries and the main channel of the Enoree River with one-way ANOVA. These indices were significantly lower in Brushy Creek, Rocky Creek, and the Upper Enoree than in the other streams (Tukey multiple comparison test, p < 0.05). These three streams also differed from the others in species composition (MANOVA p < 0.0001), as measured by changes in the relative abundances of the five most abundant species: Progomphus obscurus, Boyeria vinosa, Macromia illinoiensis, Cordulegaster maculata, and Ophiogomphus mainensis. For example, O. mainensis was nearly absent from Brushy, Rocky, and the Upper Enoree, but was a significant component of the assemblages in other streams. Cordulegaster maculata was rare in Rocky Creek but dominated the Upper Enoree where other species were less abundant. Brushy, Rocky, and the Upper Enoree are areas of either rapid residential development or known industrial contamination. The different structure of odonate assemblages in these streams may reflect the impact of these local anthropogenic effects.