A targeted phylogenetic approach helps explain New World functional diversity patterns of two eudicot lineages

Abstract

AimLarge‐scale functional diversity studies typically examine isolated traits, often without phylogenetic context. Here, we integrate data from five life‐history traits with phylogeny and occurrence records to assess: (a) correlated latitudinal gradients of trait combinations; (b) which traits show phylogenetic conservatism and (c) quantitative, clade‐specific differences in trait syndromes, illustrating the phylogenetic scale of observable variation in ecological strategies.LocationThe Americas.TaxonEricales (Asterids) and Fabales (Rosids).MethodsWe used publicly available trait data sets on height, seed mass, wood density, leaf mass per area (LMA) and growth form, an open‐source phylogeny, and georeferenced occurrence records to investigate functional diversity patterns. We employed phylogenetic generalized least squares and phylogenetic principal components analyses (pPCA) to assess correlated trait evolution and quantify the trait syndrome, respectively. We employed the InfoMap Ecoregions web app to cluster species by bioregions. We used standard statistical tests and randomization simulations to assess statistical significance of results.ResultsEricales and Fabales exhibited a biogeographically consistent, phylogenetically conserved trait syndrome. Moving poleward, species exhibited progressively smaller trait values and more herbaceous and shrubby growth forms (except for LMA, which showed no consistent pattern). We quantified latitudinal variation in this trait syndrome using pPCA, and provide evidence for correlated trait evolution.Main conclusionsWe demonstrate a functional trait syndrome involving height, seed mass, wood density and growth form, but not LMA. Functional trait values showed consistent latitudinal patterns and evidence of correlated evolution, suggesting an underlying ecological strategy. Furthermore, the two clades showed quantitative differences in the manifestation of this trait syndrome. Variation in the syndrome was best observed among species from con‐ordinal families. We interpret this trait syndrome as a strategy of resource acquisition in which habitats with relatively greater soil nutrient content and a shorter growing season favour shorter stature, lower seed mass and wood density, and shrubby or herbaceous growth form.