Metrics of family-level species richness, evolutionary age, and spatial distributions
We estimated metrics of the distribution of richness, evolutionary age, and boundaries of occurrence on elevational and latitudinal gradients at the family level (see “predictor” and “symbol” column in Table 1). Our metrics are as follows: 1) Malesian richness ; is defined as the total number of species (gamma diversity or γ) of a given family occurring within Malesia, also referred to as the union (rather than intersection) of three biogeographic regions (\(A\cup B\cup C\)). Note, Malesian richness may have fewer species than expected from literature because of our ≥ 2 record criteria, thus excluding rare species. 2) Localized richness ratio ; is a proportional metric calculated as richness within a single elevation bin (α) divided byMalesian richness (γ); comparable to beta-diversity. 3)Elevation with peak in richness ; is based on distribution curves for each family (see Supporting information) using polynomial regression to predict richness in one meter increments; used to infer the habitat optimum or point of origin. Metrics 4), 5), and 6) are the elevational boundaries of familial distribution. 4) Familial elevational extent ; was calculated as the maximum upper-most limit minus the minimum lower-most limit of any species within a given family; used to infer familial expansion across habitat types. 5) Average lower elevation limit and 6) Average higher elevation limit were calculated separately using species’ average lower or upper most elevation of occurrence. We regarded average lower elevation limits as an indicator of biotic competition based boundaries, whereasaverage upper elevation limits as indicative of tolerance to abiotic stressors. Metrics 7) evolutionary age and 8)latitudinal extent , are based on data by Hawkins et al. , 2011.