This blog post on ‘Community structure’ is part of the BES ‘Key Concepts in Ecology‘ series, designed to help ecologists in learning the key topics in ecology! Take a look at the full blog series for a list of key topics you might typically find in an ecology textbook, each providing a quick introduction to the topic, and a list of suggested papers for students to refer to.
Community structure is defined by the number of species and their abundance in the community, which both derive from community assembly processes. Community assembly is governed by three main filters that allow species from a regional species pool to enter a community. Species should first be able to reach an environment through selection, drift, speciation, and dispersal, then adapt to abiotic factors (i.e., local environmental conditions) and finally survive and persist against biotic factors (e.g., species interactions such as competition, predation, herbivory etc.). Understanding community assembly can provide important insights on multiple ecological mechanisms including parasitism (Brian & Aldridge 2021) and biodiversity loss (Si et al. 2017), as well as on anthropogenic impacts that drive biodiversity changes (Zhang et al. 2021).
Well-established communities generally include two types of species which are foundation and keystone species. Foundation species are generally the dominant species within a community, and they change the environment where other species live, modifying it to benefit the organisms that live there. Changes in the identity and abundance of foundation species due to perturbations can have strong detrimental impacts on facilitative interactions that maintain community stability, with subsequent consequences for ecosystem functioning (Smale et al. 2023). Keystone species maintain community diversity and dynamics, as well as key ecosystem functions, and tend to be disproportionately important across multiple niche dimensions regardless of species abundance, interaction outcome, or community species richness (Timóteo et al. 2022).
Predicting species abundance and biodiversity in communities has been a long-standing research topic. While ecological systems are complex, a recent study demonstrated that simple models including only intra and interspecific interaction coefficients can be sufficient for estimating species-level abundances across a wide range of contexts (Clark et al. 2019). With the development of biodiversity research, new concepts emerged in the past decades, focusing more on functional and phylogenetical diversity than on species richness per se to assess community structure. Including analysis of functional alpha and beta diversity allowed ecologists to gain better insights on the assessment of biodiversity at different scales (Si et al. 2015) and on its impacts on ecosystem functioning (Magnago et al. 2013), with strong implications for conservation strategies.
Despite community assembly processes selecting for a set of species adapted to local conditions, community structure can change over time as it remains dependent on these abiotic factors. Fluctuations in environmental conditions modify species richness and abundance of plants, animals, and micro-organisms, both in terrestrial and aquatic communities with strong consequences for community structure. For example, climate change-induced drought (Sarremejane et al. 2020) or agricultural practices (Sreekar et al. 2021) are strong drivers of community change with generally negative impacts on biodiversity and associated ecosystem functions. Nevertheless, environmental stressors including temperature and precipitation, geographic isolation or soil pH can also have positive impacts on biodiversity by promoting higher rate of diversification (Buira et al. 2020).
Introduction written by Pierre Mariotte (Associate Editor, Journal of Ecology). Reading list curated by the BES journal Editors.
References and suggested reading
Describing communities
- Brian, J.I. et al. (2021), Abundance data applied to a novel model invertebrate host shed new light on parasite community assembly in nature. Journal of Animal Ecology, 90: 1096–1108.
- Si, X. et al. (2017), Functional and phylogenetic structure of island bird communities. Journal of Animal Ecology, 86: 532-542.
- Zhang, C. et al. (2021), Scale-dependent shifts in functional and phylogenetic structure of Mediterranean island plant communities over two centuries. Journal of Ecology, 109: 3513–3523.
- Smale, D. A. et al. (2022), Climate-driven substitution of foundation species causes breakdown of a facilitation cascade with potential implications for higher trophic levels. Journal of Ecology, 110: 2132–2144.
- Timóteo, S. et al. (2023), Tripartite networks show that keystone species can multitask. Functional Ecology, 37: 274–286.
Rank-abundance plots
Kinds of diversity – alpha, beta, gamma diversity
Drivers of local diversity – disturbance, resources, interactions
- Sarremejane, R. et al. (2021), Stochastic processes and ecological connectivity drive stream invertebrate community responses to short-term drought. Journal of Animal Ecology, 90: 886–898.
- Sreekar, R., et al. (2021), Land use and elevation interact to shape bird functional and phylogenetic diversity and structure: Implications for designing optimal agriculture landscapes. Journal of Applied Ecology, 58: 1738–1748.
- Buira, A. et al. (2021), The contribution of the edaphic factor as a driver of recent plant diversification in a Mediterranean biodiversity hotspot. Journal of Ecology, 109: 987–999.
