The tropical forests of Borneo and Amazonia may each contain more tree species diversity in half a square kilometre than do all the temperate forests of Europe, North America, and Asia combined1. Biologists have long been fascinated by this disparity, using it to investigate potential drivers of biodiversity2. Latitudinal variation in many of these drivers is expected to create geographic differences in ecological2,3,4 and evolutionary processes4,5, and evidence increasingly shows that tropical ecosystems have higher rates of diversification, clade origination, and clade dispersal5,6. However, there is currently no evidence to link gradients in ecological processes within communities at a local scale directly to the geographic gradient in biodiversity. Here, we show geographic variation in the storage effect, an ecological mechanism that reduces the potential for competitive exclusion more strongly in the tropics than it does in temperate and boreal zones, decreasing the ratio of interspecific-to-intraspecific competition by 0.25% for each degree of latitude that an ecosystem is located closer to the Equator. Additionally, we find evidence that latitudinal variation in climate underpins these differences; longer growing seasons in the tropics reduce constraints on the seasonal timing of reproduction, permitting lower recruitment synchrony between species and thereby enhancing niche partitioning through the storage effect. Our results demonstrate that the strength of the storage effect, and therefore its impact on diversity within communities, varies latitudinally in association with climate. This finding highlights the importance of biotic interactions in shaping geographic diversity patterns, and emphasizes the need to understand the mechanisms underpinning ecological processes in greater detail than has previously been appreciated.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
We thank J. M. Levine, M. G. Turner, D. M. Waller, D. J. Mladenoff and J. Zhu for comments on the manuscript, and S.-H. Wu of the Taiwan Forestry Research Institute for plant identification. We acknowledge the following funding sources, which have been essential in the ongoing collection of long-term forest data (in alphabetical order): Andrew M. Mellon Foundation, Center for Tropical Forest Science, Environment Research and Technology Development Fund of the Japan Ministry of the Environment, JSPS KAKENHI, National Key Research and Development Program of China, National Natural Science Foundation of China, National Science Foundation of the United States (DDIG, IGERT, LTER, LTREB), Natural Environment Research Council of the UK, Natural History Museum of London, Smithsonian Tropical Research Institute, Taiwan Forestry Bureau, Taiwan Forestry Research Institute, Taiwan Ministry of Science and Technology, USDA Forest Service.
About this article
Patterns of Beta Diversity of Vascular Plants and Their Correspondence With Biome Boundaries Across North America
Frontiers in Ecology and Evolution (2018)