Papers in the Biological Sciences


Edaphic specialization and vegetation zones define elevational range-sizes for Mt Kinabalu regional flora

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Whitman, M., Beaman, R.S., Repin, R., Kitayama, K., Aiba, S.-I. and Russo, S.E. (2021), Edaphic specialization and vegetation zones define elevational range-sizes for Mt Kinabalu regional flora. Ecography, 44: 1698-1709.


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 rich- ness 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, consis- tent 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 gradi- ent, as compared to a null model with randomization of edaphic association. In con- trast, non-ultramafic species had smaller range-sizes and lower richness than expected. These results suggest that tolerance of resource limitation may be associated with wider range-sizes, whereas species intolerant of edaphic stress may have narrower range-sizes, possibly owing to more intense competition in favorable soil types. Using elevation as a predictor of average range-sizes, we found that piece-wise models with breakpoints at vegetation zone transitions explained species distributions better than models that did not incorporate ecological boundaries. The greatest relative increases in range-size with respect to elevation occurred mid-elevation, within the montane cloud forest vegeta- tion zone. Expansion of average range-size across an area without physical boundar- ies may indicate a shift in ecological strategy and importance of biotic versus abiotic stressors. Our results indicate that elevational range-size patterns are structured by ecological constraints such as species’ edaphic association, which may limit the ability of species to migrate up or down mountains in response to climate change.