Drought mediates the importance of stochastic community assembly

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 104; no. 44; pp. 17430 - 17434
• Main Author: Chase, Jonathan M
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 30.10.2007; National Acad Sciences
• Subjects: Biodiversity; Biological Sciences; Biological variation; Community composition; Community structure; death; Disasters; Drought; Ecological niches; Ecology; Environmental conditions; environmental factors; Extinct species; extinction; Freshwater ecology; Niches; Ponds; Population ecology; Species; Species composition; Species diversity; Species extinction; Stochastic Processes; Sustainable communities; Synecology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0704350104

Historically, the biodiversity and composition of species in a locality was thought to be influenced primarily by deterministic factors. In such cases, species' niches create differential responses to environmental conditions and interspecific interactions, which combine to determine that locality's biodiversity and species composition. More recently, proponents of the neutral theory have placed a premium on how stochastic factors, such as birth, death, colonization, and extinction (termed "ecological drift") influence diversity and species composition in a locality independent of their niches. Here, I develop the hypothesis that the relative importance of stochastic ecological drift and/or priority effects depend on the harshness of the ecological filter in those habitats. I established long-term experimental ponds to explore the relative importance of community assembly history and drought on patterns of community compositional similarity among ponds that were otherwise similar in their environmental conditions. I show considerable site-to-site variation in pond community composition in the absence of drought that likely resulted from a combination of stochastic ecological drift and priority effects. However, in ponds that experienced drought, I found much higher similarity among communities that likely resulted from niche-selection filtering out species from the regional pool that could not tolerate such environmental harshness. These results implicate the critical role for understanding the processes of community assembly when examining patterns of biodiversity at different spatial scales.