Identifying physical and ecological boundaries that limit where species can occur is important for predicting how those species will respond to global change. The island of Borneo encompasses a wide range of habitats that support some of the highest richness on Earth, making it an ideal location for investigating ecological mechanisms underlying broad patterns of species distribution. We tested variation in richness and range-size in relation to edaphic specialization and vegetation zone boundaries using 3060 plant species from 193 families centered around the elevational gradient of Mt. Kinabalu, Borneo. Across species, average range-size increased with elevation, consistent with Rapoport’s rule. However, plants associated with ultramafic soil, which is low in nutrient and water availability and often has high concentrations of heavy metals, had larger range-sizes and greater richness than expected along the elevational gradient, as compared to a null model with randomization of edaphic association. In ... : This dataset includes summary information on elevational range-sizes and edaphic associations for 3060 vascular plant species in Nothern Borneo, Malaysia, with an emphasis on the Mount Kinabalu region. Data was compiled from multiple sources, including the Sabah Parks herbarium data, GBIF, and botanical monographs. Efforts were made to standardize nomenclature used for "Family", "Genus", and "Species" dataset columns. Species occurance along an elevational gradient was summarized in columns for the number of observations ("obs" column, which is used as a metric of rarity), elevation minimum ("elev.min" column), elevation maximum ("elev.max" column), and elevational range-size ("extent" column, which is the values of elev.max minus elev.min). All elevation values refer to meters above sea-level (m a.s.l). Edaphic association ("edaphic.association" column) is the qualtiative interpretation of the frequency of occurance for species on ultramafic soil, with three categories used (ultramafic specialist, ...