The latitudinal gradient in plant community assembly processes: A meta‐analysis

• Published in: Ecology letters Vol. 25; no. 7; pp. 1711 - 1724
• Main Authors: Nishizawa, Keita, Shinohara, Naoto, Cadotte, Marc W., Mori, Akira S., Chase, Jonathan
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.07.2022
• Subjects: Assembly; Biodiversity; community assembly; Community composition; Composition; Dispersal; dispersal limitation; environmental filtering; latitudinal gradient; Meta-analysis; Plant communities; Plant populations; Plants; Sampling; Signal processing; Species composition; Statistical analysis; Variation; variation partitioning; vascular plant; β‐diversity; vascular plant; dispersal limitation; variation partitioning; environmental filtering; meta-analysis; latitudinal gradient; community assembly; β-diversity
• ISSN: 1461-023X; 1461-0248
• DOI: 10.1111/ele.14019

Beta(β)‐diversity, or site‐to‐site variation in species composition, generally decreases with increasing latitude, and the underlying processes driving this pattern have been challenging to elucidate because the signals of community assembly processes are scale‐dependent. In this meta‐analysis, by synthesising the results of 103 studies that were distributed globally and conducted at various spatial scales, we revealed a latitudinal gradient in the detectable assembly processes of vascular plant communities. Variations in plant community composition at low and high latitudes were mainly explained by geographic variables, suggesting that distance decay and dispersal limitations causing spatial aggregation are influential in these regions. In contrast, variation in species composition correlated most strongly with environmental variables at mid‐latitudes (20–30°), reflecting the importance of environmental filtering, although this unimodal pattern was not statistically significant. Importantly, our analysis revealed the effects of different spatial scales, such that the correlation with spatial variables was stronger at smaller sampling extents, and environmental variables were more influential at larger sampling extents. We concluded that plant communities are driven by different community assembly processes in distinct biogeographical regions, suggesting that the latitudinal gradient of biodiversity is created by a combination of multiple processes that vary with environmental and species size differences. We found a clear unimodal latitudinal trend in the relative importance of the community assembly processes; that is, spatial processes were more important in lower and higher latitudes, whereas environmental processes were most influential in the mid‐latitudinal regions.