Maria Beger (1), Brigitte Sommer (2), John M Pandolfi (3)
1 Centre for Biodiversity and Conservation Science, The University of Queensland, Brisbane, QLD 4072, firstname.lastname@example.org, @mariabeger
2 Australian Research Council Centre of Excellence for Coral Reef Studies, School of Biological Sciences, The University of Queensland, Brisbane QLD 4072 Australia, email@example.com
3 Australian Research Council Centre of Excellence for Coral Reef Studies, School of Biological Sciences, The University of Queensland, Brisbane QLD 4072 Australia, firstname.lastname@example.org, @JohnPandolfi
Understanding the drivers of fish community assembly on subtropical reefs is an important prerequisite to predict how temperate and subtropical reef ecosystems may be affected by climate change. While declines in fish species richness towards higher latitudes have been documented, the spatial dynamics of abundance and biomass, and the biological traits and environmental variables that drive them, are still unknown. Here we investigate drivers of fish community assembly along the tropical-to-temperate transition zone in eastern Australia. We examine patterns of trait association with latitude and environmental drivers, considering trophic group, thermal affiliation, pelagic larval duration and maximum length. We show that the degree of overlap among fishes with different thermal capacity varies with temperature, distance from shore and season. While the relative abundance of tropical fishes decreases with higher latitudes, relative abundances of subtropical and temperate fishes show the opposite pattern. Moreover, the proportion of fishes displaying different traits changes in the transition zone. For example, the proportion of fishes with larger maximum size and longer pelagic larval duration increases towards higher latitudes. Trophic groups, such as corallivores, predators and herbivores exhibit declines, increases and non-linear relationships with latitude, respectively. In summary, dynamics of fish communities in the tropical-to-temperate transition zone respond to environmental drivers and are mediated by specific life history traits. This enables us to predict which types of fishes are more likely to invade south, and which species are more likely to be adversely affected by tropicalisation.