Comparisons of macroinvertebrate traits with empirically defined environmental preferences

Analytical approaches that use empirically-derived environmental optima to infer ecological conditions are commonly used in ecology.  Similarly, analytical approaches that consider the functional characteristics of biota, such as life-history and habitat preference, are receiving renewed attention in community ecology.  Species traits are often used to describe these characteristics because they link functional roles of biota with environmental factors.  In contrast to the empirical estimates of optima, trait characterizations are often assigned based on best professional judgment.  We use information for benthic invertebrate assemblages in streams to consider whether trait characterizations correspond with empirically-estimated optimum values.  Trait characterizations were summarized from a compiled database of benthic invertebrate traits for North America.  Optimum values were estimated from invertebrate assemblage and environmental data from the Western United Sates.  Our results indicate that traits and optima show significant patterns of agreement.  Temperature optima are low (12 C) for cold-water biota and significantly higher (27 C) for warm-water biota.  Sediment optima are low for fast-water biota and high for slow-water biota.  These preliminary results suggest that both empirical and trait-based approaches may be useful for developing inferences about environmental conditions in streams.