Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 114, Issue 17, Pages 4447-4452Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1615338114
Keywords
dispersal limitation; McLaughlin Natural Reserve; metacommunity; seed addition; spatial scale
Categories
Funding
- National Sciences and Engineering Research Council (NSERC)'s Canada Graduate Scholarship
- Michael Smith Foreign Study Supplement
- Sigma Xi
- California Agricultural Experiment Station
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Ecological theory posits that dispersal among habitat patches links local communities and is a key regional process that maintains biological diversity. However, manipulations required to experimentally test regional processes are infeasible for most systems, and thus more work is needed to detect the scales at which regional processes manifest and their overall effect on diversity. In a Californian grassland, a hotspot for global biodiversity, we used a seed vacuum to increase dispersal at spatial scales varying from 1 m to 10 km while maintaining a realistic spatial structure of species pools and environmental conditions. We found that dispersal limitation has a profound influence on diversity; species richness increased with the spatial scale of seed mixing, doubling in plots that received seed from large (>= 5 km) compared with small (<= 5 m) scales. This increase in diversity corresponded to an increase in how well species distributions were explained by environmental conditions, from modest at small scales (R-2 = 0.34) to strong at large scales (R-2 = 0.52). Responses to the spatial scale of seed mixing were nonlinear, with no differences below 5 m or above 5 km. Non-linearities were explained by homogeneity of environmental conditions below 5 m and by a lack of additional variation in the species pool above 5 km. Our approach of manipulating natural communities at different spatial scales reveals (i) nonlinear transitions in the importance of environmental sorting and dispersal, and (ii) the negative effects of dispersal limitation on local diversity, consistent with previous research suggesting that large numbers of species are headed toward regional extinction.
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