Regional Influences on Local Species Composition

Abstract

Regional influences on local species composition are considered within the context of ‘species pools’, representing sets of species that are potentially capable of coexisting in a particular community. Accumulating evidence shows that many ecological communities are not saturated with species, indicating that in addition to local biotic interactions such as predation, symbiosis and competition, regional processes such as dispersal, speciation and extinction are the important drivers of local community composition. Although current studies have been unable to reconcile completely two important difficulties – the filtering of species lists and the study of nonindependent variables – it is evident that much of the observed local variation in plant and animal diversity can be attributed to the differing sizes of species pools evolved under particular habitat conditions and to the probabilities with which the species may arrive in particular local communities. Key Concepts: Local species composition is the result of complex interactions of small‐scale and regional processes. Empirical relationships between diversity at local and regional scales provide an indication of the relative roles of local processes (e.g. biotic interactions) and regional processes (e.g. dispersal, speciation) in structuring ecological communities. Existing evidence suggests that many ecological communities are unsaturated by species and that new species may immigrate to the community by crossing dispersal barriers. Uncertainty remains with respect to methodology. Estimation of regional species pools lacks a definitive approach; both empirical and theoretical methods exist. The interpretation of local and regional species richness suffers from unresolved statistical controversy. More case studies are needed to overcome these problems and provide community ecology with further empirical evidence.

Congruence across taxa and spatial scales: Are we asking too much of species data?

“…The strong effect of spatial scale on species richness is probably attributable to the different contribution of processes operating in forest ecosystems at the plot, site and continental scales from those related to the fine-scale pattern of forest structural components to those depending on site characteristics such as biomass accumulation and broad biogeographical factors. Large-scale processes, such as speciation, migration and dispersal, determine regional species pools, whereas local diversity is governed by filtering of abiotic and biotic factors (Zobel, Szava-Kovats, & Pärtel, 2011 , & Sitzia, 2017). In contrast, other taxa, whose activity is mostly limited to a small extent (i.e.…”

“…The patterns observed when shifting from the local to the regional scale are marked by local ecological processes being replaced by biogeographical ones (Zobel et al, ). Therefore, by increasing the extent from site to continental, it is likely that broad‐scale factors (e.g., climatic and biogeographical patterns) are more decisive in determining congruence patterns in species richness and composition when compared with the effect of those fine‐scale determinants directly or indirectly related to forest structure (e.g., microclimatic conditions, occurrence of specific elements).…”

Concordance in wetland physicochemical conditions, vegetation, and surrounding land cover is robust to data extraction approach

“…Regional biogeographical processes, local landscape composition and in situ physicochemical conditions and biotic interactions may all serve as important controls on community assembly [17]. However, these factors operate at different spatial scales, and their relative influence on community composition varies according to the region, ecosystem and taxa under consideration e.g., [18].…”