Body size determines key behavioral and life history traits across species, as well as interactions between individuals within and between species. Therefore, variation in sizes of immigrants, by exerting variation in trophic interaction strengths, may drive the trajectory and outcomes of community assembly. Here, I study the effects of size variation in the immigration pool on assembly dynamics and equilibrium distributions of sizes and consumer-resource size-ratios using a general mathematical model. I find that because small sizes both, improve the ability to invade and destabilize the community, invasibility and stability pull body size distributions in opposite directions, favoring an increase in both size and size-ratios during assembly, and ultimately yielding a right-skewed size and a symmetric size-ratio distribution. In many scenarios, the result at equilibrium is a systematic increase in body sizes and size-ratios with trophic level. Thus these patterns in size structure are 'signatures' of dynamically constrained, non-neutral community assembly. I also show that for empirically feasible distributions of body sizes in the immigration pool, immigration bias in body sizes cannot counteract dynamical constraints during assembly and thus signatures emerge consistently. I test the theoretical predictions using data from nine terrestrial and aquatic communities and find strong evidence that natural communities do indeed exhibit such signatures of dynamically constrained assembly. Overall, the results provide new measures to detect general, non-neutral patterns in community assembly dynamics, and show that in general, body size is dominant trait that strongly influences assembly and recovery of natural communities and ecosystems.
Pawar, S. (2015). The Role of Body Size Variation in Community Assembly. In Advances in Ecological Research (Vol. 52, pp. 201–248). Academic Press Inc. https://doi.org/10.1016/bs.aecr.2015.02.003