Abundance and distribution within a guild of benthic stream fishes: Local processes and regional patterns

1. Spatial patterns at regional and local scales were examined for evidence that species interactions can influence distribution and abundance within a guild of benthic fishes in upland streams of Oklahoma, U.S.A. Three groups of community patterns were examined: the species-area relationship, species-habitat associations, and interspecific associations. 2. The species-area relationship for riffle habitats was compared to a null species-area model based on random placement. The observed species-area curve was steeper resulting in less species per unit area in small streams than predicted by the null model. 3. Small, species-poor streams had summed fish densities at least as high as larger, species-rich streams, suggesting density compensation. 4. Several significant patterns of negative covariation were found among species at the regional scale, before and after statistically accounting for effects due to measured habitat variables. 5. For two of these negatively covarying taxa (Cottus carolinae and Etheostoma spectabile), the influence of each species on the distribution of the other was evaluated experimentally in field enclosures varying in depth and current velocity. The sculpin C. carolinae caused a shift in habitat use by the darter E. spectabile, but no reciprocal shift was found. 6. These results indicate an agreement between local and regional patterns of distribution for C. carolinae and E. spectabile and suggest that biotic interactions can influence regional patterns of distribution for species within this guild.