Format: ORAL

R.A Folk1, M.W. Belitz2,3, C.M. Siniscalchi1, H.R. Kates2, D.E. Soltis2,3,4,5, P.S. Soltis2,4,5, R.P. Guralnick2,5, L.M. Borges6

1 Department of Biological Sciences, Mississippi State University, Mississippi State, MS, USA 2 Florida Museum, University of Florida, Gainesville, FL, USA 3 Department of Biology, University of Florida, Gainesville, FL, USA 4 Genetics Institute, University of Florida, Gainesville, FL, USA 5 Biodiversity Institute, University of Florida, Gainesville, FL, USA 6 Universidade Federal de São Carlos, São Carlos, SP, Brazil

Among the most vexing questions in legume biogeography is why non-nodulating and facultatively nodulating legumes, i.e., those that do not or need not engage in RNS with rhizobia, are preponderant in the tropics, whereas extratropical areas have almost entirely nodulating legumes. Understanding the environments associated with loss of symbiosis would yield more precise insight into the ecological function that nodulation confers in natural ecosystems. Here we determine centers of species richness (SR), relative phylogenetic diversity (RPD) and centers of paleo- and neo-endemism, and regionalizations of phylogenetic diversity in the mimosoid clade of the legumes to understand the distribution and environmental associates of mimosoids lacking RNS (root nodule symbiosis). We built a phylogenetic tree of 1313 species and high-quality species distribution models for 1128 species representing the phylogenetic breadth of the mimosoid clade to identify the geographic distribution of RNS. Centers of significant RPD and endemism were identified using a randomization approach, the latter using CANAPE. Phylogenetic regionalization used a distance-based phylogenetic beta-diversity approach. We recognized nine areas of contiguous high SR as distinct SR hotspots. Non-RNS species occur mainly outside hotspots but are closely correlated with high RPD. Absence of RNS was best predicted by high precipitation, and represents multiple independent phylogenetic assemblages in different biogeographic areas. SR hotspots are partly incongruent with centers of RPD and phylogenetic endemism. Lineages lacking RNS, likely to represent loss of symbiosis, are distributed in SR hotspots in Africa and the Americas, belong to biogeographically separate species assemblages, and are, in most cases, associated with relatively moist tropical environments with low temperature seasonality and high available soil nitrogen.