Testing predictions of hydrological consequences for fish biodiversity at landscape scales (#83)
Rob Rolls
1
- University of New England, Armidale, NSW, QLD
- Ecohydrology and environmental flow management are increasingly considering the consequences of hydrological alteration (e.g. dams, extraction) and events (e.g. drought, floods) for the variability in ecological communities across landscapes. A useful concept for both topics is that spatial variation in hydrology positively affects the spatial variation among communities, with the specific prediction that increasingly similar hydrological regimes (caused by hydrological alteration) cause communities to become more similar within and among rivers. Yet these predictions have been seldom examined with real-world data.
- This study made use of two landscape-scale monitoring programs to explore (i) how spatial variation in hydrology has been altered by water resource development and major climate fluctuations, and (ii) corresponding consequences for fish biodiversity at multiple spatial scales.
- Water resource development increased spatial variation in hydrological regimes both among and within rivers, in contrast to predictions. Spatial variation in fish assemblages at both spatial scales was predominantly unrelated to spatial variation in modified flow regimes. In the context of climate fluctuations, spatial variation in hydrology showed minor and inconsistent changes across scales. Variation in fish assemblages showed inconsistent, river-specific changes among contrasting hydrological periods.
- Inconsistent hydrology-beta diversity patterns found here suggest that mechanisms and outcomes of drought, flooding, and water resource development for variation in fish assemblage composition are context-specific and not broadly generalisable. These findings fail to support predictions adopted by ecohydrological science that water resource development homogenises hydrological regimes, in turn causing biotic homogenisation in lowland rivers.
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