Ecological interactions shape the evolution of flower colour in communities across a temperate biodiversity hotspot

Processes driving the divergence of floral traits may be integral to the extraordinary richness of flowering plants and the assembly of diverse plant communities. Several models of pollinator-mediated floral evolution have been proposed; floral divergence may (i) be directly involved in driving speciation or may occur after speciation driven by (ii) drift or local adaptation in allopatry or (iii) negative interactions between species in sympatry. Here, we generate predictions for patterns of trait divergence and community assembly expected under these three models, and test these predictions in Hakea (Proteaceae), a diverse genus in the Southwest Australian biodiversity hotspot. We quantified functional richness for two key floral traits (pistil length and flower colour), as well as the phylogenetic distance between species and across communities, and compared these patterns to null models of community assembly. We estimated the statistical relationship between rates of trait evolution and lineage diversification across the phylogeny. Patterns of community assembly suggest that flower colour, but not floral phenology or morphology, or phylogenetic relatedness, is more divergent in communities than expected. Rates of lineage diversification and flower colour evolution were negatively correlated across the phylogeny. These results support a role for diversity-dependent species interactions driving floral divergence during the Hakea radiation, contributing to the development of the extraordinary species richness of southwest Australia.
Methods
"Hakea_trait_data.csv" & "Hakea_flowering_times_overlap_matrix.csv" = Morphological and Phenological data from the Flora of Australia vol. 17B and Skeels, A., and M. Cardillo. 2019a. Equilibrium and non-equilibrium phases in the radiation of Hakea and the drivers of diversity in Mediterranean-Type Ecosystems. Evolution 73:1392–1410.

"Hakea_phylogeny.newick" = Phylogenetic data from Cardillo, M., P. H. Weston, Z. K. M. Reynolds, P. M. Olde, A. R. Mast, E. M. Lemmon, A. R. Lemmon, and L. Bromham. 2017. The phylogeny and biogeography of Hakea (Proteaceae) reveals the role of biome shifts in a continental plant radiation. Evolution 71:1928–1943.

"Hakea_presence_absence_matrix" & "site_coordinates.csv" = Community survey data from Gibson, N., G. Keighery, M. Lyons, and A. Webb. 2004. Terrestrial flora and vegetation of the Western Australian wheatbelt. Rec. West. Aust. Museum Suppl. 67:139–189.

"RGB_histogram_for_colordistance.rds" & "Hakea_RGB_measurements" = Flower colour data from this study and methods explained in the main text and Appendix S1.

"Hakea_macroevolutionary_rates_by_branch.csv" = ClaDS and RRPhylo analyses, methods in main text.

"FD_and_mpd_on_null_models" folder = simulated communities under two different null models (independant swap and dispersal null models) methods in main text.