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Ranjan R, Koffel T, Klausmeier CA. The three-species problem: Incorporating competitive asymmetry and intransitivity in modern coexistence theory. Ecol Lett 2024; 27:e14426. [PMID: 38603592 DOI: 10.1111/ele.14426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 02/28/2024] [Accepted: 03/08/2024] [Indexed: 04/13/2024]
Abstract
While natural communities can contain hundreds of species, modern coexistence theory focuses primarily on species pairs. Alternatively, the structural stability approach considers the feasibility of equilibria, gaining scalability to larger communities but sacrificing information about dynamic stability. Three-species competitive communities are a bridge to more-diverse communities. They display novel phenomena while remaining amenable to mathematical analysis, but remain incompletely understood. Here, we combine these approaches to identify the key quantities that determine three-species competition outcomes. We show that pairwise niche overlap and fitness differences are insufficient to completely characterize competitive outcomes, which requires a strictly triplet-wise quantity: cyclic asymmetry, which underlies intransitivity. Low pairwise niche overlap stabilizes the triplet, while high fitness differences promote competitive exclusion. The effect of cyclic asymmetry on stability is complex and depends on pairwise niche overlap. In summary, we elucidate how pairwise niche overlap, fitness differences and cyclic asymmetry determine three-species competition outcomes.
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Affiliation(s)
- Ravi Ranjan
- W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan, USA
- Program in Ecology, Evolution and Behavior, Michigan State University, East Lansing, Michigan, USA
- Department of Plant Biology, Michigan State University, East Lansing, Michigan, USA
- Hanse-Wissenschaftskolleg Institute for Advanced Study, Delmenhorst, Germany
| | - Thomas Koffel
- W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan, USA
- Program in Ecology, Evolution and Behavior, Michigan State University, East Lansing, Michigan, USA
| | - Christopher A Klausmeier
- W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan, USA
- Program in Ecology, Evolution and Behavior, Michigan State University, East Lansing, Michigan, USA
- Department of Plant Biology, Michigan State University, East Lansing, Michigan, USA
- Department of Integrative Biology, Michigan State University, East Lansing, Michigan, USA
- Department of Global Ecology, Carnegie Institution for Science, Stanford, California, USA
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Huang Z, Li Y, Wang W, Li B, Luo W, Wang Y, Chu C. The unimodal intransitivity-fertility relationship is not mediated by demographic trade-offs in a subtropical forest. Ecology 2023; 104:e4172. [PMID: 37768319 DOI: 10.1002/ecy.4172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 08/25/2023] [Indexed: 09/29/2023]
Abstract
Intransitive competition has long been acknowledged as a potential mechanism favoring species coexistence. However, its prevalence, variance along environmental gradients, and possible underlying mechanisms (trade-offs) in plant communities (especially in forests) has seldom been examined. A recently developed "reverse-engineering" approach based on Markov Chain allowed us to estimate the competitive transition matrices and competitive intransitivity from observational abundance data. Using this approach, we estimated competitive intransitivity of five dominant species in a subtropical forest and then related it to soil fertility (soil organic matter and soil pH) and demographic trade-offs (growth-survival and stature-recruitment trade-offs). In our forest plot, intransitive competition was common among the dominant species and peaked at the intermediate level of soil organic matter. Neither the growth-survival trade-off nor the stature-recruitment trade-off was positively related to competitive intransitivity. Our study for the first time empirically supported the unimodal intransitivity-fertility relationship in forests, which, however, was not mediated by the two demographic trade-offs in our plot.
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Affiliation(s)
- Zhengliang Huang
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Yuanzhi Li
- State Key Laboratory of Biocontrol, School of Ecology, Shenzhen Campus of Sun Yat-sen University, Shenzhen, China
| | - Weitao Wang
- State Key Laboratory of Biocontrol, School of Ecology, Shenzhen Campus of Sun Yat-sen University, Shenzhen, China
| | - Buhang Li
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Wenqi Luo
- State Key Laboratory of Biocontrol, School of Ecology, Shenzhen Campus of Sun Yat-sen University, Shenzhen, China
| | - Youshi Wang
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Chengjin Chu
- State Key Laboratory of Biocontrol, School of Ecology, Shenzhen Campus of Sun Yat-sen University, Shenzhen, China
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Li Y, Bearup D, Liao J. Habitat loss alters effects of intransitive higher-order competition on biodiversity: a new metapopulation framework. Proc Biol Sci 2020; 287:20201571. [PMID: 33259756 DOI: 10.1098/rspb.2020.1571] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Recent studies have suggested that intransitive competition, as opposed to hierarchical competition, allows more species to coexist. Furthermore, it is recognized that the prevalent paradigm, which assumes that species interactions are exclusively pairwise, may be insufficient. More importantly, whether and how habitat loss, a key driver of biodiversity loss, can alter these complex competition structures (and therefore species coexistence) remain unclear. We thus present a new, simple yet comprehensive metapopulation framework that can account for any competition pattern and more complex higher-order interactions (HOIs) among species. We find that competitive intransitivity increases community diversity and that HOIs generally enhance this effect. Essentially, intransitivity promotes species richness by preventing the dominance of a few species, unlike the hierarchical competition, while HOIs facilitate species coexistence through stabilizing community fluctuations. However, variation in species' vital rates and habitat loss can weaken or even reverse such higher-order effects, as their interaction can lead to a more rapid decline in competitive intransitivity under HOIs. Thus, it is essential to correctly identify the most appropriate interaction model for a given system before models are used to inform conservation efforts. Overall, our simple model framework provides a more parsimonious explanation for biodiversity maintenance than the existing theory.
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Affiliation(s)
- Yinglin Li
- Ministry of Education's Key Laboratory of Poyang Lake Wetland and Watershed Research, School of Geography and Environment, Jiangxi Normal University, Ziyang Road 99, 330022 Nanchang, People's Republic of China
| | - Daniel Bearup
- Statistics and Actuarial Sciences, School of Mathematics, University of Kent, Parkwood Road, Canterbury, CT2 7FS, UK
| | - Jinbao Liao
- Ministry of Education's Key Laboratory of Poyang Lake Wetland and Watershed Research, School of Geography and Environment, Jiangxi Normal University, Ziyang Road 99, 330022 Nanchang, People's Republic of China
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Ulrich W, Puchałka R, Koprowski M, Strona G, Gotelli NJ. Ecological drift and competitive interactions predict unique patterns in temporal fluctuations of population size. Ecology 2019; 100:e02623. [PMID: 30644544 DOI: 10.1002/ecy.2623] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 12/07/2018] [Accepted: 12/20/2018] [Indexed: 11/08/2022]
Abstract
Recent studies have highlighted the importance of higher-order competitive interactions in stabilizing population dynamics in multi-species communities. But how does the structure of competitive hierarchies affect population dynamics and extinction processes? We tackled this important question by using spatially explicit simulations of ecological drift (10 species in a homogeneous landscape of 64 patches) in which birth rates were influenced by interspecific competition. Specifically, we examined how transitive (linear pecking orders) and intransitive (pecking orders with loops) competitive hierarchies affected extinction rates and population dynamics in simulated communities through time. In comparison to a pure neutral model, an ecological drift model including transitive competition increased extinction rates, caused synchronous density-dependent population fluctuations, and generated a white-noise distribution of population sizes. In contrast, the drift model with intransitive competitive interactions decreased extinctions rates, caused asynchronous (compensatory) density-dependent population fluctuations, and generated a brown noise distribution of population sizes. We also explored the effect on community stability of more complex patterns of competitive interactions in which pairwise competitive relationships were assigned probabilistically. These probabilistic competition models also generated density-dependent trajectories and a brown noise distribution of population sizes. However, extinction rates and the degree of population synchrony were comparable to those observed in purely neutral communities. Collectively, our results confirm that intransitive competition has a strong and stabilizing effect on local populations in species-poor communities. This effect wanes with increasing species richness. Empirical assemblages characterized by brown spectral noise, density-dependent regulation, and asynchronous (compensatory) population fluctuations may indicate a signature of intransitive competitive interactions.
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Affiliation(s)
- Werner Ulrich
- Department of Ecology and Biogeography, Nicolaus Copernicus University, Toruń, Poland
| | - Radosław Puchałka
- Department of Ecology and Biogeography, Nicolaus Copernicus University, Toruń, Poland
| | - Marcin Koprowski
- Department of Ecology and Biogeography, Nicolaus Copernicus University, Toruń, Poland
| | - Giovanni Strona
- Directorate D, Sustainable Resources, European Commission, Joint Research Centre, Ispra, Italy
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Godoy O, Stouffer DB, Kraft NJB, Levine JM. Intransitivity is infrequent and fails to promote annual plant coexistence without pairwise niche differences. Ecology 2017; 98:1193-1200. [PMID: 28241383 DOI: 10.1002/ecy.1782] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 02/08/2017] [Indexed: 11/09/2022]
Abstract
Intransitive competition is often projected to be a widespread mechanism of species coexistence in ecological communities. However, it is unknown how much of the coexistence we observe in nature results from this mechanism when species interactions are also stabilized by pairwise niche differences. We combined field-parameterized models of competition among 18 annual plant species with tools from network theory to quantify the prevalence of intransitive competitive relationships. We then analyzed the predicted outcome of competitive interactions with and without pairwise niche differences. Intransitive competition was found for just 15-19% of the 816 possible triplets, and this mechanism was never sufficient to stabilize the coexistence of the triplet when the pair-wise niche differences between competitors were removed. Of the transitive and intransitive triplets, only four were predicted to coexist and these were more similar in multidimensional trait space defined by 11 functional traits than non-coexisting triplets. Our results argue that intransitive competition may be less frequent than recently posed, and that even when it does operate, pairwise niche differences may be key to possible coexistence.
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Affiliation(s)
- Oscar Godoy
- Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Av. Reina Mercedes 10, E-41080, Sevilla, Spain
| | - Daniel B Stouffer
- Centre for Integrative Ecology, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand
| | - Nathan J B Kraft
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, 621 Charles E. Young Drive South, Los Angeles, California, 90095, USA
| | - Jonathan M Levine
- Institute of Integrative Biology, ETH Zurich, Universitaetstrasse 16, 8092, Zurich, Switzerland
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Abstract
Models describing the biotic drivers that create and maintain biological diversity within trophic levels have focused primarily on negative interactions (i.e. competition), leaving marginal room for positive interactions (i.e. facilitation). We show facilitation to be a ubiquitous driver of biodiversity by first noting that all species use resources and thus change the local biotic or abiotic conditions, altering the available multidimensional niches. This can cause a shift in local species composition, which can cause an increase in beta, and sometimes alpha, diversity. We show that these increases are ubiquitous across ecosystems. These positive effects on diversity occur via a broad host of disparate direct and indirect mechanisms. We identify and unify several of these facilitative mechanisms and discuss why it has been easy to underappreciate the importance of facilitation. We show that net positive effects have a long history of being considered ecologically or evolutionarily unstable, and we present recent evidence of its potential stability. Facilitation goes well beyond the common case of stress amelioration and it probably gains importance as community complexity increases. While biodiversity is, in part, created by species exploiting many niches, many niches are available to exploit only because species create them.
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Affiliation(s)
- Eliot J B McIntire
- Canadian Forest Service, Natural Resources Canada, 506 Burnside Road W., Victoria, BC, Canada, V8Z 1M5
- Canada Research Chair - Conservation Biology and Modeling, Département des sciences du bois et de la forêt, Université Laval, Québec, QC, Canada
| | - Alex Fajardo
- Centro de Investigación en Ecosistemas de la Patagonia (CIEP) Conicyt-Regional R10C1003, Universidad Austral de Chile, Ignacio Serrano 509, Coyhaique, Chile
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