Abstract
Physicochemical changes induced by long-term, landscape-scale disturbances such as agricultural clearing may affect stream invertebrate biodiversity and species' trait distributions. However, communities may be buffered from these impacts if generalist strategies (e.g. habitat flexibility and omnivory) are widespread, conferring greater resistance to disturbance. To determine whether such buffering occurs, we sampled sixteen low-order streams in southwestern Australia, assigned a priori to categories of high (> 30%, cleared, n = 8) or low (< 30%, uncleared, n = 8) clearing, collected invertebrates, and tested for physicochemical correlations. Invertebrate species were assigned traits related to streamflow and feeding according to existing literature. Taxonomic composition differed between high and low levels of catchment clearing, associated with differences in nutrient concentrations, conductivity, and depth. Differences in composition were associated with trait responses to land use, but feeding- and flow-related traits did not adequately predict responses to landscape clearing. Although categorical traits predicted responses to agricultural disturbance, they poorly predicted the prevalence of generalism (omnivory and habitat flexibility). Generalist modes of existence may be hidden within a lack of trait responses. Trait databases must find ways to define omnivory and habitat flexibility as fixed traits to obtain meaningful conclusions from trait analysis.
