The spatial scales of species coexistence

Theory predicts that intraspecific competition should be stronger than interspecific competition for any pair of stably coexisting species, yet previous literature reviews found little support for this pattern. We screened over 5400 publications and identified 39 studies that quantified phenomenological intraspecific and interspecific interactions in terrestrial plant communities. Of the 67% of species pairs in which both intra- and interspecific effects were negative (competitive), intraspecific competition was, on average, four to five-fold stronger than interspecific competition. Of the remaining pairs, 93% featured intraspecific competition and interspecific facilitation, a situation that stabilises coexistence. The difference between intra- and interspecific effects tended to be larger in observational than experimental data sets, in field than greenhouse studies, and in studies that quantified population growth over the full life cycle rather than single fitness components. Our results imply that processes promoting stable coexistence at local scales are common and consequential across terrestrial plant communities.

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“…; Hart et al . ). Work on resource partitioning deserves equal treatment (e.g., Dybzinski & Tilman ).…”

Section: Discussionmentioning

confidence: 97%

Competition and coexistence in plant communities: intraspecific competition is stronger than interspecific competition

et al. 2018

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“…It will be exciting to disentangle these two components of the realized niche in future investigations. Repeating such analyses across large-scale environmental gradients should yield new insights into how trait spectra shape interspecific competition, niches and species coexistence at large spatial scales (Alexander, Diez, Hart, & Levine, 2016;Hart, Usinowicz, & Levine, 2017). Traits are known to affect how intraand interspecific competition alters individual demographic rates (e.g., basal area growth of individual trees; Kunstler et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

Functional traits explain the Hutchinsonian niches of plant species

Treurnicht

Pagel

Tonnabel

et al. 2019

Global Ecol Biogeogr

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Aim:The Hutchinsonian niche is a foundational concept in ecology and evolutionary biology that describes fundamental characteristics of any species: the global maximum population growth rate (r max ); the niche optimum (the environment for which r max is reached); and the niche width (the environmental range for which intrinsic population growth rates are positive). We examine whether these characteristics are related to inter-and intraspecific variation in functional traits.Location: Cape Floristic Region, South Africa. Time period: Present day.Major taxa studied: Twenty-six plant species (Proteaceae). Methods:We measured leaf, plant-architectural and seed traits across species geographical ranges. We then examined how species-mean traits are related to demographically derived niche characteristics of r max , in addition to niche optima and widths in five environmental dimensions, and how intraspecific trait variation is related to niche widths. Results:Interspecific trait variation generally exceeded range-wide intraspecific trait variation. Species-mean trait values were associated with variation in r max (R 2 = 0.27) but were more strongly related to niche optima (mean R 2 = 0.56). These relationships generally matched trait-environment associations described in the literature. Both species-mean traits and intraspecific trait variability were strongly related to niche widths (R 2 = 0.66 and 0.59, respectively). Moreover, niche widths increased with intraspecific trait variability. Overall, the different niche characteristics were associated with few, largely non-overlapping sets of traits. Main conclusions:Our study relating functional traits to Hutchinsonian niches demonstrates that key demographic properties of species relate to few traits with relatively strong effects. Our results further support the hypothesis that intraspecific trait variation increases species niche widths. Given that niche characteristics were related to distinct sets of traits, different aspects of environmental change might affect axes of trait variation independently. Trait-based studies of Hutchinsonian | 535 TREURNICHT ET al.

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“…Hart et al. () showed that selecting the correct spatial scale and accounting for environmental heterogeneity are critically important for being able to accurately detect coexistence using this approach. In this study, we have incorporated information on environmental heterogeneity (shade) and positive and higher‐order interactions.…”

Section: Discussionmentioning

confidence: 99%

Cyclic population dynamics and density‐dependent intransitivity as pathways to coexistence between co‐occurring annual plants

et al. 2018

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Recent studies have brought renewed attention to the importance of complex species interactions—notably intransitive interactions—to patterns of plant community diversity. One underappreciated avenue through which intransitivity can occur is through cyclic population dynamics. Although such cyclic intransitive relationships have been extensively studied in predator–prey systems, evidence of their importance in competitive communities, notably plant communities, is more limited. Most studies of coexistence in plant communities assume fixed‐point coexistence even while utilising models that allow for cyclic population dynamics. In this paper, we explore the potential for density‐dependent, cyclic population dynamics and intransitivity in a model for annual plants. We then examine how these density‐dependent cycles impact mutual invasibility and ultimately stable coexistence between plant species pairs. We do this using data collected from four co‐occurring annual plant species living in natural wildflower communities in SW Western Australia. To maximise the number of biologically plausible pathways by which coexistence mediated by density‐dependent cyclic intransitivity can occur, we use an annual plant model that allows for competitive direct interactions, facilitative direct interactions and higher‐order interactions between species. Results from our empirically parameterised model suggest that monocultures of all four focal species can have cyclic solutions with periodicity <1 under sunny (“open”) or shaded field conditions. Cyclic patterns drive variation in annual abundance patterns, with stable solutions for persistent monocultures and invasibility potential (the capacity of one population to invade another) common. Mutual invasibility in the face of cyclic population dynamics was found for just one of six species pairs, only under open environmental conditions. Our results illustrate the potential for cyclic intransitivity to both drive and prevent stable coexistence in environmentally heterogeneous biological communities. Synthesis. We provide analytical and empirical evidence that coexistence in competitive communities (annual plants) can be achieved under non‐equilibrium circumstances, through density‐dependent cyclic intransitivity. Our results suggest that cyclic population dynamics may be common and important for coexistence dynamics in some types of communities. In such communities, the exploration of stable coexistence should, therefore, include consideration of cyclic as well as fixed‐point equilibria for maximal accuracy.

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The spatial scales of species coexistence

Cited by 135 publications

References 74 publications

Competition and coexistence in plant communities: intraspecific competition is stronger than interspecific competition

Competition and coexistence in plant communities: intraspecific competition is stronger than interspecific competition

Functional traits explain the Hutchinsonian niches of plant species

Cyclic population dynamics and density‐dependent intransitivity as pathways to coexistence between co‐occurring annual plants

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