Intra-specific trait variation across a hydrological gradient

Trait-based models of ecological communities and ecosystem functioning often fail to account for intraspecific variation in functional traits, assuming that intraspecific variability is negligible compared with interspecific variability. However, this assumption remains poorly tested across vertebrate animals where past studies routinely describe species according to mean trait values without explicit consideration of individual trait variability. We assessed nine functional traits for 4254 individuals belonging to 15 freshwater fish species from 11 families in northern Australia, including body elongation, body shape, caudal peduncle throttle, eye size, eye position, gape shape, gape size, mouth position, and pectoral fin length. We quantified the extent and geography of intraspecific trait variability and its relationship with riverine hydrologic regimes. We demonstrate that intraspecific trait variability can contribute up to 70% of the total trait variability depending on the attribute considered and averaged 31% across all traits. The magnitude of intraspecific trait variability also varied across the hydrological permanency gradient. Our study provides the first evidence of intraspecific trait variability driven by a disturbance gradient for an animal group and points to the need for additional research into the functional importance of intraspecific variability in animal ecology.

Luiz, O.J., Olden, J.D., Kennard, M.J., Crook, D.A., Douglas, M.M., Saunders, T.M., and A.J. King. 2022. Substantial intra-specific trait variation across a hydrological gradient in northern Australian fishes. Ecosphere 13: e4169. Article