Document: BEA-3-73-15

Partitioning of ecological variation amongst different levels of taxonomic resolution in Ohio fish assemblages.

DEWAARD, V.B.* and C.P.HAWKINS

Utah State University, Logan, UT 84322, USA ¹

Abstract:
Understanding patterns of ecological variation in space should allow better predictions of the taxa expected at unstudied sites and hence, the ability to assess effects of human disturbance. However, it is not clear what level of taxonomic resolution is needed for bioassessment purposes. Ideally, the level of taxonomic resolution used should represent a balance between obtaining ecological information detailed enough to detect human disturbance and the costs of obtaining that information. If the hypothesis that families represent the basic ecological units of adaptive radiation is true, then analyses relating variation in families to environmental variables should account for most of the variation at lower levels of taxonomic resolution. Furthermore, variation in regional variables should be more important at the family level, whereas local variables should be increasingly important at genus and species levels. In this study, we examined patterns of ecological radiation in Ohio stream fish assemblages to determine the level of taxonomic resolution at which most ecological variation occurs. We used data from 394 stream sites, which contained 20, 63 and 153 fish families, genera and species respectively. We clustered sites by their fish communities using flexible UPGMA at the family, genus and species levels to create groups of biologically similar sites and then related the resulting clusters to environmental variables with discriminant functions analysis. Our results were consistent with the hypothesis that much of the ecological variation present is captured at the family level of taxonomic resolution. The most important predictor variables at all levels of taxonomic resolution represented measures of stream size and temperature, which implies that families have different temperature optima and have specialized to occupy habitats associated with different sized streams. At higher levels of taxonomic resolution additional predictors represented factors associated with local habitat features, which implies that within a given temperature regime or size of stream, genera and species have evolved to occupy different microhabitats. These results suggest that sufficient information may exist at the family level to allow sensitive bioassessments.

Keywords: Fish, Streams, Adaptive Radiation, Taxonomic Resolution

This abstract is being presented at: 10:30 AM in session:
Poster Session #9: Fish, Lakes, Streams and Wetlands.