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

Stouffer, Daniel B.; Wainwright, Claire E.; Flanagan, Thomas C.; Mayfield, Margaret M.

doi:10.1111/1365-2745.12960

Cited by 29 publications

(46 citation statements)

References 42 publications

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“…The relative dynamic treatment effect was generally similar to, but smaller on average than, the magnitude to ambient change (Figure 4a). (Fuhlendorf & Smeins, 1997;Foster & Gross, 1998;Ostfeld & Keesing, 2000;De Mazancourt et al, 2013;Stouffer et al, 2018). By this estimate, treatment effects on the average species were equivalent to only 4.3 years of ambient change in species abundance.…”

Section: (B)mentioning

confidence: 91%

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Ambient changes exceed treatment effects on plant species abundance in global change experiments

Langley

Chapman

Pierre

et al. 2018

Global Change Biology

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The responses of species to environmental changes will determine future community composition and ecosystem function. Many syntheses of global change experiments examine the magnitude of treatment effect sizes, but we lack an understanding of how plant responses to treatments compare to ongoing changes in the unmanipulated (ambient or background) system. We used a database of long‐term global change studies manipulating CO2, nutrients, water, and temperature to answer three questions: (a) How do changes in plant species abundance in ambient plots relate to those in treated plots? (b) How does the magnitude of ambient change in species‐level abundance over time relate to responsiveness to global change treatments? (c) Does the direction of species‐level responses to global change treatments differ from the direction of ambient change? We estimated temporal trends in plant abundance for 791 plant species in ambient and treated plots across 16 long‐term global change experiments yielding 2,116 experiment–species–treatment combinations. Surprisingly, for most species (57%) the magnitude of ambient change was greater than the magnitude of treatment effects. However, the direction of ambient change, whether a species was increasing or decreasing in abundance under ambient conditions, had no bearing on the direction of treatment effects. Although ambient communities are inherently dynamic, there is now widespread evidence that anthropogenic drivers are directionally altering plant communities in many ecosystems. Thus, global change treatment effects must be interpreted in the context of plant species trajectories that are likely driven by ongoing environmental changes.

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Section: (B)mentioning

confidence: 91%

“…We propose that sustained, directional shifts in plant responses provide a signal of the longer-term species trajectories rather than shorter-term changes that could be cyclical (Stouffer, Wainwright, Flanagan, & Mayfield, 2018). We focused on sustained, directional change in abundances.…”

Section: Introductionmentioning

confidence: 99%

Ambient changes exceed treatment effects on plant species abundance in global change experiments

Langley

Chapman

Pierre

et al. 2018

Global Change Biology

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“…Then, we targeted which of the feasible assemblages were also stable by computing whether the maximal eigenvalues (in absolute value terms) of the Jacobian matrix for the annual plant model was less than one. One limitation of these techniques is that they allow the evaluation of coexistence under a fixed equilibrium point but they do not capture potential coexistence promoted by intransitive structures with heteroclinic cycles (see Stouffer, Wainwright, Flanagan, & Mayfield, for recent developed methods). To partially solve this limitation, we took another approach in which we evaluated whether transitive and intransitive triplets differed in the time to which the first species become extinct, starting from a population of 10,000 seeds.…”

Section: Methodsmentioning

confidence: 99%

An experimental extreme drought reduces the likelihood of species to coexist despite increasing intransitivity in competitive networks

et al. 2018

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Very little is known about how variation in environmental conditions alters the strength and the structure of competitive networks and what are the consequences of this for species coexistence. We performed a competition experiment with 10 annual plant species to parameterise a population model describing species’ dynamics according to their vital rates and pairwise competitive coefficients. Seeds from all species were sown under two different climatic scenarios: (1) right before the first major storm of the growing season and (2) after an imposed fall drought of 2 months simulating an extreme climatic event of intense aridity. Species’ demography and competitive responses were used to estimate pairwise stabilising niche differences and average fitness differences. In addition, we used tools from network theory to characterise the structure of multispecies competition from the determinants of species coexistence. Specifically, we evaluated changes in competitive dominance between species pairs, and the prevalence of intransitive competitive relationships for 120 triplets between these two climatic events. The experimental extreme event significantly reduced fitness differences between species pairs. Such an equalising mechanism promotes coexistence. However, niche differences were also reduced in such a way that the number of species pairs whose niche differences overcame their fitness differences was reduced from six to two. Contrary to our expectations, the extreme event did not increase the hierarchy of competitive dominance. Instead, and depending on the technique used, the prevalence of intransitivity remained marginally similar (17% to 22%) or significantly increased from 19.4% to 29.8%. This pattern was likely a consequence of the significant changes in competitive dominance between species pairs (26 changes out of 45; 58%). Although fitness differences were equalised and intransitive competition promoted, our model predicted a lower likelihood of coexistence under the extreme event for both species pairs and triplets, mainly because competitive interactions did not promote enough niche differences to balance the observed fitness asymmetries in our competitive networks. Synthesis. We empirically proved that an extreme climate results in communities with reduced niche and fitness differences in which species are less likely to coexist despite the increasing prevalence of intransitive competition.

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“…Matías et al. () and Stouffer, Wainwright, Flanagan, and Mayfield () are among the first studies to do so. Matías et al.…”

Section: How Does Intransitive Competition Affect Coexistence?mentioning

confidence: 99%

Everything you always wanted to know about intransitive competition but were afraid to ask

Soliveres

Allan

2018

Journal of Ecology

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Over 40 years after the introduction of the concept into ecology, intransitive (i.e. non‐hierarchical) competition remains overlooked by ecological theory, despite theoretical work showing it could be a major driver of species coexistence. This special feature presents six studies, including models, reviews, experimental studies and large‐scale observational studies. Collectively, these studies help to (i) link intransitive competition with short‐ and long‐term coexistence and with other ecological patterns, (ii) evaluate the conditions under which intransitivity is more common and (iii) determine how best to quantify the degree of intransitivity. The studies in this special feature show the generality of intransitive competition in nature, explore interactions between intransitivity and other coexistence mechanisms, and illustrate the effect of environmental conditions (drought, shade, fertility) on intransitivity and coexistence. They also show which metrics best quantify intransitivity and highlight the importance of adopting a more continuous view of competition as varying from strongly transitive to strongly intransitive. The studies also examine relationships between intransitivity and functional diversity and explore the evolution of intransitivity over time. Synthesis. The studies presented here advance the field by integrating intransitive competition into species coexistence and general ecological theory. We also highlight important research gaps that will hopefully inspire the next generation of studies in this topic.

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

Cited by 29 publications

References 42 publications

Ambient changes exceed treatment effects on plant species abundance in global change experiments

Ambient changes exceed treatment effects on plant species abundance in global change experiments

An experimental extreme drought reduces the likelihood of species to coexist despite increasing intransitivity in competitive networks

Everything you always wanted to know about intransitive competition but were afraid to ask

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