Species distributions across biogeographical regions of Malesia
For the second series of predictor variables, we quantified species’ distribution within and across the three bioregions of Malesia using a Venn diagram approach (see “predictor” and “symbol” column Table 1, Fig. 1; see Supporting information). For each family we estimated: 1)regional endemism, which we defined as species occurring strictly within one biogeographic region (\(A\cap\left(B\cap C\right)^{{}^{\prime}})\), and 2) regional overlapas being a non-exclusive term for species within a given region, expressed as (\(A\)), (\(B\)) or (\(C\)), with any given species having the potential to also occur within neighboring regions. Lastly, 3) A metric of cosmopolitanism, which we defined as species with distributions intersecting all three bioregions (\(A\cap B\cap C\)), which is the number of species shared by multiple regions (zeta-diversity or ζ). For each biogeographical metric, we divided the number of species matching said criteria by familial Malesian richness (\(A\cup B\cup C\)), being union of all bioregions, resulting in proportional values ranging from 0 - 1. We translated these metrics into colors, creating a unique CMYK hex code for each family, which we used for all figures. Color saturation was determined by the endemism metric (magenta – Sundaland; yellow – Wallacea; cyan - Sahul) and cosmopolitanism (black), adjusted to 25% transparency.