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.