A general framework for species‐abundance distributions: Linking traits and dispersal to explain commonness and rarity

Abstract

Species‐abundance distributions (SADs) describe the spectrum of commonness and rarity in a community. Beyond the universal observation that most species are rare and only a few common, more‐precise description of SAD shape is controversial. Furthermore, the mechanisms behind SADs and how they vary along environmental gradients remain unresolved. We lack a general, non‐neutral theory of SADs. Here, we develop a trait‐based framework, focusing on a local community coupled to the region by dispersal. The balance of immigration and exclusion determines abundances, which vary over orders‐of‐magnitude. The local trait‐abundance distribution (TAD) reflects a transformation of the regional TAD. The left‐tail of the SAD depends on scaling exponents of the exclusion function and the regional species pool. More‐complex local dynamics can lead to multimodal TADs and SADs. Connecting SADs with trait‐based ecological theory provides a way to generate more‐testable hypotheses on the controls over commonness and rarity in communities.

Functional traits and trait coordination change over the life of a leaf in a tropical fern species

“…The ability to use plant traits to make predictions about ecological processes is a cornerstone of modern ecological research (Violle et al, 2007; Ackerly and Monson, 2016; Funk et al, 2017; Koffel et al, 2022; Krieg and Chambers, 2022; McCulloh et al, 2022). Although numerous studies have shown that trait relationships with life history characteristics are strong at broad spatial and taxonomic scales, these relationships can break down at smaller taxonomic and ecological scales (e.g., variation within a species or individuals) (Mason et al, 2013; Anderegg et al, 2018).…”

The ecological causes of functional distinctiveness in communities

“…Negative growth in the sink locations arises because of a mismatch between species traits and local environmental conditions (Gibson et al, 1999; Grime, 1998; Keddy, 1992; Kraft, Adler, et al, 2015). A species can be consistently part of the community, even with a negative growth rate, if there is regular immigration of individuals from some source populations (Koffel et al, 2022; Mouquet & Loreau, 2003). Spatial sink populations have been a topic of study for decades in ecology.…”

“…Here, we build a conceptual framework that encompasses the major ecological drivers of functional distinctiveness to help organize and inspire work in this emerging area. As a foundation of the framework, we adopt a widespread conception of biodiversity dynamics in which a regional pool of organisms influences local community composition (Cornell & Harrison, 2014; Denelle et al, 2019; Keddy & Laughlin, 2021; Koffel et al, 2022; Ricklefs, 2008). As such, a species that is functionally distinct in one community may not be distinct in other communities where it occurs.…”

Understanding and predicting harmful algal blooms in a changing climate: A trait‐based framework

“…Mechanistic trait‐based models may predict a particular combination of traits that results in the highest fitness under given environmental conditions. It is possible that some range of trait combinations may have similar fitness, leading to the possibility of several species co‐occurring, especially if species with lower fitness are supported by immigration or changing selection regimes (Koffel et al 2022). Theoretical models may also predict more than one optimal trait value or trait combination (Litchman et al 2009; Kremer and Klausmeier 2017), which may make coexistence of different ecological strategies, possibly represented by different taxonomic groups, likely.…”