PARENT SESSION
Oral Session #47: Conservation Ecology: Aquatic.
Presiding: L. Stevens
Tuesday, August 6. 1:00 PM to 4:45 PM. Palo Verde Room, Radisson.

Regional Stream Classification Frameworks for the Midwest: An evaluation using landscape-scale patterns in fish communities.

Chapin, Bridgett^*,1, ¹ University of Kansas, Lawrence, KS

ABSTRACT- Regional stream classification frameworks represent spatial hypotheses of expected organism-environment interactions, and their development is still a work in progress. Much debate addresses whether more terrestrially focused or more aquatically focused frameworks better explain landscape-level ecological variation in streams. Also, the value of using watersheds (representing physical barriers to species dispersal) versus ecological regions (representing ecological barriers) to classify streams is at issue. This study addressed the issues posited above by comparing the classification strengths (CS) of nine a priori and a posteriori classification frameworks for Midwest streams. CS was based on fish community similarity (Sorenson and Bray-Curtis) within frameworks. The single non-regional and four regional a priori frameworks included: Strahler order; watersheds (USGS Hydrologic Unit Codes [HUCs]); two terrestrial approaches (Bailey and Omernik ecoregions), and one aquatic approach (Maxwell et al. 1995). The a posteriori frameworks included: non-spatial random groupings; geographic distance clusters; and both ecoregion schemes stratified by watershed. Results will identify connections between large-scale patterns in fish communities in the Midwest and causal mechanisms for those patterns. This study will also provide suggestions as to how the ecoregion concepts currently employed in the design of large scale aquatic monitoring frameworks may be fine tuned to more accurately reflect natural variation in lotic ecosystems.

KEY WORDS: ecoregions, stream classification, fish community ecology, landscape ecology