Brigitte Sommer (1), Eugenia Sampayo (2), Peter L. Harrison (3), Russ C. Babcock (4), Maria Beger (5), John M. Pandolfi (6)
1 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,
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 Marine Ecology Research Centre, Southern Cross University, Lismore NSW 2480 Australia, firstname.lastname@example.org,
4 CSIRO Marine and Atmospheric Research, Dutton Park QLD 4102 Australia, email@example.com,
5 Centre for Biodiversity and Conservation Science, The University of Queensland, Brisbane, QLD 4072, firstname.lastname@example.org, @mariabeger
6 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, @JohnPandolfi
Understanding the relative importance of environmental filtering and species interactions in shaping the organisation of biological communities is a prerequisite to predicting how they may respond to climate change. At species ranges, strong environmental pressures may mask the signature of competitive processes and phylogenetic community ecology approaches can help disentangle their relative importance. Here we integrate species abundance, functional, phylogenetic and environmental data for scleractinian corals in the tropical-to-temperate transition zone in eastern Australia to investigate the mechanisms that drive the origin and maintenance of coral biodiversity patterns at their high-latitude range margins. We identify a phylogenetic signal in ecologically relevant functional traits, indicating conserved trait evolution and functional similarity of closely related species. Tests for phylogenetic structure show that coral species found on high-latitude reefs are a non-random subset of the Great Barrier Reef species pool, as species are more closely related than expected. While this supports the predominant role of environmental filtering at the regional scale, patterns in phylogenetic diversity along gradients of latitude and species richness reveal that the relative influence of species interactions and environmental filtering varies in the region. Our results indicate growing influence of competitive processes at lower latitude, where co-occurring species are more distantly related at the tips of the phylogeny, a pattern consistent with niche differentiation. Conservatism of tested traits indicates that corals will likely track their niches with climate change, and species-specific relationships with environmental parameters suggest that range expansions will likely be heterogeneous among species.