Trait-space disparity in fish communities spanning 380 million years from the Late Devonian to present

Abstract

AbstractThe diversity and distribution of traits in an ecological community determine how it functions. Modern fish communities conserve trait space across similar habitats. However, little is known about trait-space variation through deep time. We examined two Devonian fish communities — a tropical reef (Gogo, Australia) and a tropical estuary (Miguasha, Canada) — and compares them with six modern communities from diverse habitats. Trait-space metrics reflecting the amount of diversity found in each community (functional richness) and the similarity among species in each community (nearest neighbour) indicated Devonian communities had similar scores to modern communities, but were consistently less functionally rich than their closest modern analogues. Metrics describing location in trait space (specialisation, centroid distances, hypervolume overlap) also showed distinctions between Devonian and modern communities. Indeed, location in trait space of Devonian and modern communities differed on several axes associated with a range of traits largely confined to modern communities. Thus, modern fish communities are more functionally diverse in the traits we considered, potentially due to greater evolutionary lability. These results highlight the importance of evolutionary constraints in shaping community trait space and raise questions regarding whether differences between Devonian and modern communities indicate differences in community structure and function.