Our goal was to interrogate the idea that “mountain passes are higher in the tropics” by investigating ecological and biogeographic drivers of elevational range-sizes patterns among equatorial flora. We used herbarium records for sixty species-rich plant families, representing 18535 species total, to estimate distributions over a 4500 m elevational gradient. For each family, we estimated the change in average range-sizes with increasing elevation (i.e. Rapoport’s rule, abbreviated as ERR) and quantified 15 metrics of familial richness distribution, evolutionary age, and biogeographic affiliation. We visualized covariation across families using phylogenetic principal components analysis (pPCA). We then evaluated how family-level ERR slopes correlated with each metric individually, as well as when using multivariate techniques to reduce dimensionality. We hypothesized that if long term climate stability over millions of years promotes habitat specialization, then among taxa with longer-term tropical affiliations, we would expect smaller range-sizes within lowland forests, with greater range-size expansion towards higher elevations, expressed as a positive ERR slope. Conversely, variation in growing conditions should promote larger, relatively consistent, range-sizes at all sections of an elevational gradient, expressed as a neutral ERR slope. Our results support this corollary because of the dichotomy of ERR slopes observed in relation to the elevational distribution of richness and historical biogeographic positioning. We found that families with greater Sundaland endemism, or richness that was restricted to tropical lowland forests, had positive ERR slopes. Families with stronger Sahul affiliation, or montane centered richness, had shallower, neutral, or negative ERR slopes, as did clades with temperate origins. Families with Wallacea affiliation, broader latitudinal or elevational distributions, cosmopolitanism, greater richness, or older evolutionary age had mixed results. We conclude that the relative steepness of an ERR slope is an indicator of a taxonomic group’s tolerance of habitat variation and vulnerability to contemporary climate change.

This dataset includes species-level elevational ranges and occurrence distribution summaries for >31k plant species from Malesia, which includes the Malay Peninsula and islands of Sumatra, Borneo, Philippines, Java, Lesser Sunda Isles, Sulawesi, Maluki, and New Guinea (excluding the Bismarck archipelago). 

For details on methods, data-sources, data standardization practices, or nomencalture used for “Biogeographic history and centers of richness define elevational range-size patterns for Malesian flora” refer to main document and Supporting information. The data used in the main manuscript is a subset of this Dryad file, selecting only species with two or more observations and from a species-rich family.

Note, the original sources of data included more than a half-million entries from multiple data-sources, most origininating from GBIF.org. The Dryad data file does not include herbarium entries that were excluded due to being flagged as erroneous, non-relevant, or with information that we found to be lacking or conflicting. Elevation data is shown as meters above sea-level (m a.s.l); manually interpreted and converted from feet if necessary. In some instances, nomenclature used for family names has been adjusted to match the phylogenetic mega tree.

Extensive quality control efforts were made to prevent errors with elevation, location, or nomenclature entries, but there is always potential for improvement. This file is provided as-is. Refer to the corresponding author for additional information if needed.