What drives community dynamics?

Abstract

The search for general mechanisms of community assembly is a major focus of community ecology. The common practice so far has been to examine alternative assembly theories using dichotomist approaches of the form neutrality versus niche, or compensatory dynamics versus environmental forcing. In reality, all these mechanisms will be operating, albeit with different strengths. While there have been different approaches to community structure and dynamics, including neutrality and niche differentiation, less work has gone into separating out the temporal variation in species abundances into relative contributions from different components. Here we use a refined statistical machinery to decompose temporal fluctuations in species abundances into contributions from environmental stochasticity and inter-/intraspecific interactions, to see which ones dominate. We apply the methodology to community data from a range of taxa. Our results show that communities are largely driven by environmental fluctuations, and that member populations are, to different extents, regulated through intraspecific interactions, the effects of interspecific interactions remaining broadly minor. By decomposing the temporal variation in this way, we have been able to show directly what has been previously inferred indirectly: compensatory dynamics are in fact largely outweighed by environmental forcing, and the latter tends to synchronize the population dynamics.

Environmental change and declining resource availability for small‐mammal communities in the Great Basin

“…In fact, recent models and experiments show much variability in the responses of aggregate properties depending on the type, frequency, and time scale of disturbance (Vasseur and Fox 2007, Downing et al 2008, Keitt 2008. Furthermore, compensatory dynamics in natural communities may occur less frequently than previously thought (e.g., Houlahan et al 2007, Mutshinda et al 2009), and the diversitystability relationship may be multifaceted and dependent on the context of the perturbation (Ives and Carpenter 2007). As such, the presumed relative stability of aggregate community properties over time is equivocal (Micheli et al 1999).…”

Ecosystem assembly rules: the interplay of green and brown webs during salt marsh succession

“…In particular, can we identify ''ecosystem assembly rules'' based on variation in average traits among trophic groups that govern ecosystem development over time? Thereby, we expand on the current agenda of ''community assembly rules,'' which are based on variation in traits among species within trophic groups (Levin et al 2001, Mutshinda et al 2009). As mentioned, many have stressed the importance of the interactions between detritivores and herbivores in shaping the trophic structure of ecosystems, but how both the brown web (detritivore-based, sensu Moore et al 2004) and the green web (herbivore-based) interact over succession is still poorly understood.…”

Quantifying effects of abiotic and biotic drivers on community dynamics with multivariate autoregressive (MAR) models

“…Bayesian approaches have been less frequently used in MAR modeling (cf. Mutshinda et al 2009), though they can have some advantages. They more easily allow for non-Gaussian error structures or nonlinear process models, but depending on the circumstances, maximum likelihood may perform similarly to Bayesian approaches.…”

“…MAR modeling has been used to study lynx-hare dynamics (Vik et al 2008), to examine the effects of climate change on insect community dynamics (Yamamura et al 2006), and to compare the relative importance of environmental stochasticity vs. stochasticity driven by interspecific-intraspecific interactions in rodents (Mutshinda et al 2009). Given that trophic interactions and ecosystem stability are of similar interest across aquatic and terrestrial ecology, and that long-term data sets are available across systems, the scarcity of MAR use outside of freshwater ecology may be due to a lack of familiarity with MAR models and the ways in which they may be modified when data or questions do not conform with existing examples in the ecological literature.…”