1
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Miller ZR, Clenet M, Della Libera K, Massol F, Allesina S. Coexistence of many species under a random competition-colonization trade-off. Proc Natl Acad Sci U S A 2024; 121:e2314215121. [PMID: 38261621 PMCID: PMC10835059 DOI: 10.1073/pnas.2314215121] [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: 08/17/2023] [Accepted: 12/14/2023] [Indexed: 01/25/2024] Open
Abstract
The competition-colonization (CC) trade-off is a well-studied coexistence mechanism for metacommunities. In this setting, it is believed that the coexistence of all species requires their traits to satisfy restrictive conditions limiting their similarity. To investigate whether diverse metacommunities can assemble in a CC trade-off model, we study their assembly from a probabilistic perspective. From a pool of species with parameters (corresponding to traits) sampled at random, we compute the probability that any number of species coexist and characterize the set of species that emerges through assembly. Remarkably, almost exactly half of the species in a large pool typically coexist, with no saturation as the size of the pool grows, and with little dependence on the underlying distribution of traits. Through a mix of analytical results and simulations, we show that this unlimited niche packing emerges as assembly actively moves communities toward overdispersed configurations in niche space. Our findings also apply to a realistic assembly scenario where species invade one at a time from a fixed regional pool. When diversity arises de novo in the metacommunity, richness still grows without bound, but more slowly. Together, our results suggest that the CC trade-off can support the robust emergence of diverse communities, even when coexistence of the full species pool is exceedingly unlikely.
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Affiliation(s)
- Zachary R Miller
- Department of Ecology & Evolution, University of Chicago, Chicago, IL 60637
- Department of Plant Biology, University of Illinois, Urbana, IL, 61801
| | - Maxime Clenet
- Laboratoire d'Informatique Gaspard-Monge, UMR 8049, CNRS, Université Gustave Eiffel, Marne-la-Vallée 77454, France
| | - Katja Della Libera
- Department of Ecology & Evolution, University of Chicago, Chicago, IL 60637
| | - François Massol
- Université Lille, CNRS, INSERM, CHU Lille, Institut Pasteur de Lille, U1019-UMR 9017-Center for Infection and Immunity of Lille, Lille F-59000, France
| | - Stefano Allesina
- Department of Ecology & Evolution, University of Chicago, Chicago, IL 60637
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2
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Svensson O, Woodhouse K, Smith A, Seehausen O, Turner GF. Sympatry and parapatry among rocky reef cichlids of Lake Victoria explained by female mating preferences. J Evol Biol 2024; 37:51-61. [PMID: 38285657 DOI: 10.1093/jeb/voad006] [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: 04/19/2023] [Revised: 09/15/2023] [Accepted: 11/06/2023] [Indexed: 01/31/2024]
Abstract
Work on the Lake Victoria cichlids Pundamilia nyererei (red dorsum males, deeper water), Pundamilia pundamilia (blue males, shallower water) and related species pairs has provided insights into processes of speciation. Here, we investigate the female mating behaviour of 5 Pundamilia species and 4 of their F1 hybrids through mate choice trials and paternity testing. Complete assortative mating was observed among all sympatric species. Parapatric species with similar depth habitat distributions interbred whereas other parapatric and allopatric species showed complete assortative mating. F1 hybrids mated exclusively with species accepted by females of the parental species. The existence of complete assortative mating among some currently allopatric species suggests that pre-existing mating barriers could be sufficient to explain current patterns of co-existence, although, of course, many other factors may be involved. Regardless of the mechanism, mating preferences may influence species distribution in potentially hybridizing taxa, such as in the adaptive radiation of cichlid fish. We suggest that this at least partly explains why some species fail to establish breeding populations in locations where they are occasionally recorded. Our results support the notion that the mating preferences of potentially cross-breeding species ought to be included in coexistence theory.
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Affiliation(s)
- Ola Svensson
- Department of Educational Work, University of Borås, Borås, Sweden
- The Linnaeus Centre for Marine Evolutionary Biology, University of Gothenburg, Gothenburg, Sweden
- Department of Biology, School of Natural Sciences, University of Hull, Hull, United Kingdom
| | - Katie Woodhouse
- Department of Biology, School of Natural Sciences, University of Hull, Hull, United Kingdom
| | - Alan Smith
- Department of Biology, School of Natural Sciences, University of Hull, Hull, United Kingdom
| | - Ole Seehausen
- Department of Fish Ecology and Evolution, Center for Ecology, Evolution and Biogeochemistry, Eawag-Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
- Division of Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| | - George F Turner
- School of Natural and Environmental Sciences, Bangor University, Bangor, United Kingdom
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3
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Rynne N, Birtles G, Bell J, Pau Duhlian MS, McNeil S, Mehrpooya A, Noske B, Vakeesan Y, Bode M. Complex patch geometry promotes species coexistence through a reverse competition-colonization trade-off. Proc Biol Sci 2023; 290:20231554. [PMID: 37909079 PMCID: PMC10618891 DOI: 10.1098/rspb.2023.1554] [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] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 09/28/2023] [Indexed: 11/02/2023] Open
Abstract
Explaining the maintenance of diverse species assemblages is a central goal of ecology and conservation. Recent coexistence mechanisms highlight the role of dispersal as a source of the differences that allow similar species to coexist. Here, we propose a new mechanism for species coexistence that is based on dispersal differences, and on the geometry of the habitat patch. In a finite habitat patch with complex boundaries, species with different dispersal abilities will arrange themselves in stable, concentric patterns of dominance. Species with superior competitive and dispersal abilities will dominate the interior of the patch, with inferior species at the periphery. We demonstrate and explain the mechanism on a simple one-dimensional domain, and then on two-dimensional habitat patches with realistic geometries. Finally, we use metrics from landscape ecology to demonstrate that habitat patches with more complex geometries can more easily support coexistence. The factors that underpin this new coexistence mechanism-different dispersal abilities and habitat patches with complex geometries-are common to many marine and terrestrial ecosystems, and it is therefore possible that the mechanism is a common factor supporting diverse species assemblages.
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Affiliation(s)
- Nina Rynne
- School of Mathematical Sciences, Queensland University of Technology, 4 George Street, Brisbane, Queensland 4000, Australia
| | - Geneva Birtles
- School of Mathematical Sciences, Queensland University of Technology, 4 George Street, Brisbane, Queensland 4000, Australia
| | - Jamie Bell
- School of Mathematics and Applied Statistics, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Mung Suan Pau Duhlian
- School of Science, Royal Melbourne Institute of Technology, Melbourne, Victoria 3001, Australia
| | - Samuel McNeil
- College of Engineering, Science and Environment, The University of Newcastle, Newcastle, New South Wales 2300, Australia
| | - Adel Mehrpooya
- School of Mathematical Sciences, Queensland University of Technology, 4 George Street, Brisbane, Queensland 4000, Australia
| | - Blake Noske
- School of Science, Royal Melbourne Institute of Technology, Melbourne, Victoria 3001, Australia
| | - Yadursha Vakeesan
- School of Science, Royal Melbourne Institute of Technology, Melbourne, Victoria 3001, Australia
| | - Michael Bode
- School of Mathematical Sciences, Queensland University of Technology, 4 George Street, Brisbane, Queensland 4000, Australia
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4
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Miller ZR, Allesina S. Habitat Heterogeneity, Environmental Feedbacks, and Species Coexistence across Timescales. Am Nat 2023; 202:E53-E64. [PMID: 37531282 DOI: 10.1086/724821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/04/2023]
Abstract
AbstractClassic ecological theory explains species coexistence in variable environments. While spatial variation is often treated as an intrinsic feature of a landscape, it may be shaped and even generated by the resident community. All species modify their local environment to some extent, driving changes that can feed back to affect the composition and coexistence of the community, potentially over timescales very different from population dynamics. We introduce a simple nested modeling framework for community dynamics in heterogeneous environments, including the possible evolution of heterogeneity over time due to community-environment feedbacks. We use this model to derive analytical conditions for species coexistence in environments where heterogeneity is either fixed or shaped by feedbacks. Among other results, our approach reveals how dispersal and environmental specialization interact to shape realized patterns of habitat association and demonstrates that environmental feedbacks can tune landscape conditions to allow the stable coexistence of any number of species. Our flexible modeling framework helps explain feedback dynamics that arise in a wide range of ecosystems and offers a generic platform for exploring the interplay between species and landscape diversity.
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5
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Lyu S, Alexander JM. Compensatory responses of vital rates attenuate impacts of competition on population growth and promote coexistence. Ecol Lett 2023; 26:437-447. [PMID: 36708049 DOI: 10.1111/ele.14167] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 12/16/2022] [Accepted: 12/19/2022] [Indexed: 01/29/2023]
Abstract
Competition is among the most important factors regulating plant population and community dynamics, but we know little about how different vital rates respond to competition and jointly determine population growth and species coexistence. We conducted a field experiment and parameterised integral projection models to model the population growth of 14 herbaceous plant species in the absence and presence of neighbours across an elevation gradient (284 interspecific pairs). We found that suppressed individual growth and seedling establishment contributed the most to competition-induced declines in population growth, although vital rate contributions varied greatly between species and with elevation. In contrast, size-specific survival and flowering probability and seed production were frequently enhanced under competition. These compensatory vital rate responses were nearly ubiquitous (occurred in 92% of species pairs) and significantly reduced niche overlap and stabilised coexistence. Our study highlights the importance of demographic processes for regulating population and community dynamics, which has often been neglected by classic coexistence theories.
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Affiliation(s)
- Shengman Lyu
- Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland
| | - Jake M Alexander
- Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland
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6
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Terui A, Urabe H, Senzaki M, Nishizawa B. Intentional release of native species undermines ecological stability. Proc Natl Acad Sci U S A 2023; 120:e2218044120. [PMID: 36749724 DOI: 10.1073/pnas.2218044120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The massive release of captive-bred native species ("intentional release") is a pervasive method to enhance wild populations of commercial and recreational species. However, such external inputs may disrupt the sensitive species interactions that allow competing species to coexist, potentially compromising long-term community stability. Here, we use theory and long-term data of stream fish communities to show that intentional release destabilizes community dynamics with limited demographic benefit to the enhanced species. Our theory predicted that intentional release intensifies interspecific competition, facilitating the competitive exclusion of unenhanced species that otherwise stably coexist. In parallel, the excessive input of captive-bred individuals suppressed the natural recruitment of the enhanced species via intensified within-species competition. Consequently, the ecological community with the intentional release is predicted to show reduced community density with unstable temporal dynamics. Consistent with this prediction, stream fish communities showed greater temporal fluctuations and fewer taxonomic richness in rivers with the intensive release of hatchery salmon-a major fishery resource worldwide. Our findings alarm that the current overreliance on intentional release may accelerate global biodiversity loss with undesired consequences for the provisioning of ecosystem services.
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7
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Smith DJB. The functional form of specialised predation affects whether Janzen-Connell effects can prevent competitive exclusion. Ecol Lett 2022; 25:1458-1470. [PMID: 35474601 PMCID: PMC9324109 DOI: 10.1111/ele.14014] [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] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 01/31/2022] [Accepted: 03/24/2022] [Indexed: 11/29/2022]
Abstract
Janzen–Connell effects (JCEs), specialised predation of seeds and seedlings near conspecific trees, are hypothesised to maintain species richness. While previous studies show JCEs can maintain high richness relative to neutral communities, recent theoretical work indicates JCEs may weakly inhibit competitive exclusion when species exhibit interspecific fitness variation. However, recent models make somewhat restrictive assumptions about the functional form of specialised predation—that JCEs occur at a fixed rate when offspring are within a fixed distance of a conspecific tree. Using a theoretical model, I show that the functional form of JCEs largely impacts their ability to maintain coexistence. If predation pressure increases additively with adult tree density and decays exponentially with distance, JCEs maintain considerably higher species richness than predicted by recent models. Loosely parameterising the model with data from a Panamanian tree community, I elucidate the conditions under which JCEs are capable of maintaining high species richness.
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Affiliation(s)
- Daniel J B Smith
- Committee on Evolutionary Biology, University of Chicago, Chicago, Illinois, USA
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8
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Usinowicz J, Levine JM. Climate-driven range shifts reduce persistence of competitors in a perennial plant community. Glob Chang Biol 2021; 27:1890-1903. [PMID: 33432781 DOI: 10.1111/gcb.15517] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 11/18/2020] [Accepted: 12/17/2020] [Indexed: 06/12/2023]
Abstract
Forecasting the impacts of climate change on species persistence in diverse natural communities requires a way to account for indirect effects mediated through species interactions. In particular, we expect species to experience major changes in competition as they track favorable climates. Here, we combine experimental data with a recently developed theoretical framework based on coexistence theory to measure the impact of climate-driven range shifts on alpine plant persistence under climate change. We transplanted three co-dominant alpine perennial species to five elevations, creating a maximum of 5°C increase in average growing-season temperature. We statistically modeled species' demographic rates in response to the environment and interpolated species' intrinsic ranges-the environmental mapping of reproduction in the absence of competition. We used low-density population growth rates-species' initial rate of invasion into an established community-as a metric of persistence. Further analysis of low-density growth rates (LGRs) allowed us to parse the direct impacts of climate change from indirect impacts mediated by shifting competition. Our models predict qualitatively different range shifts for each species based on the climate conditions under which growth rates are maximized and where they are zero. Overall, climate change is predicted to increase the intrinsic (competition free) growth rates of all species, as warmer and wetter conditions increase the favorability of alpine habitat. However, these benefits are entirely negated by increased competition arising from greater overlap between competitors in their intrinsic ranges. Species were highly dispersal limited, which can prevent species from tracking shifting intrinsic ranges by reducing population spread rates. Yet dispersal limitation also promoted species' persistence because it promotes persistence mechanisms. Our study demonstrates the complex pathways by which climate change impacts species' persistence by altering their competitive environment, and highlights how a persistence framework based on LGRs can help disentangle impacts.
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Affiliation(s)
- Jacob Usinowicz
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Jonathan M Levine
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
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9
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Gómez-Llano M, Germain RM, Kyogoku D, McPeek MA, Siepielski AM. When Ecology Fails: How Reproductive Interactions Promote Species Coexistence. Trends Ecol Evol 2021; 36:610-622. [PMID: 33785182 DOI: 10.1016/j.tree.2021.03.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 03/09/2021] [Accepted: 03/10/2021] [Indexed: 11/19/2022]
Abstract
That species must differ ecologically is often viewed as a fundamental condition for their stable coexistence in biological communities. Yet, recent work has shown that ecologically equivalent species can coexist when reproductive interactions and sexual selection regulate population growth. Here, we review theoretical models and highlight empirical studies supporting a role for reproductive interactions in maintaining species diversity. We place reproductive interactions research within a burgeoning conceptual framework of coexistence theory, identify four key mechanisms in intra- and interspecific interactions within and between sexes, speculate on novel mechanisms, and suggest future research. Given the preponderance of sexual reproduction in nature, our review suggests that this is a neglected path towards explaining species diversity when traditional ecological explanations have failed.
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Affiliation(s)
- Miguel Gómez-Llano
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
| | - Rachel M Germain
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Biodiversity Research Centre, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Daisuke Kyogoku
- The Museum of Nature and Human Activities, Hyogo 669-1546, Japan
| | - Mark A McPeek
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Adam M Siepielski
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA
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10
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Abstract
Mutualisms are ubiquitous in nature and are thought to play important roles in the maintenance of biodiversity. For biodiversity to be maintained, however, species must coexist in the face of competitive exclusion. Chesson's coexistence theory provides a mechanistic framework for evaluating coexistence, yet mutualisms are conspicuously absent from coexistence theory and there are no comparable frameworks for evaluating how mutualisms affect the coexistence of competiting species. To address this conceptual gap, I develop theory predicting how multitrophic mutualisms mediate the coexistence of species competing for mutualistic commodities and other limiting resources using the niche and fitness difference concepts of coexistence theory. I demonstrate that failing to account for mutualisms can lead to erroneous conclusions. For example, species might appear to coexist on resources alone, when the simultaneous incorporation of mutualisms actually drives competitive exclusion, or competitive exclusion might occur under resource competition, when in fact, the incorporation of mutualisms generates coexistence. Existing coexistence theory cannot therefore be applied to mutualisms without explicitly considering the underlying biology of the interactions. By discussing how the metrics derived from coexistence theory can be quantified empirically, I show how this theory can be operationalized to evaluate the coexistence consequences of mutualism in natural communities.
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Affiliation(s)
- Christopher A Johnson
- Department of Ecology and Evolutionary Biology, Princeton University, 106A Guyot Hall, Princeton, New Jersey, 08544, USA.,Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH) Zürich, Universitäetstrasse 16, Zürich, 8092, Switzerland
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11
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Germain RM, Hart SP, Turcotte MM, Otto SP, Sakarchi J, Rolland J, Usui T, Angert AL, Schluter D, Bassar RD, Waters MT, Henao-Diaz F, Siepielski AM. On the Origin of Coexisting Species. Trends Ecol Evol 2021; 36:284-93. [PMID: 33353727 DOI: 10.1016/j.tree.2020.11.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 11/07/2020] [Accepted: 11/13/2020] [Indexed: 11/22/2022]
Abstract
Speciation is frequently initiated but rarely completed, a phenomenon hypothesized to arise due to the failure of nascent lineages to persist. Although a failure to persist often has ecological causes, key gaps exist between ecological and evolutionary theories that, if filled, would clarify when and why speciation succeeds or fails. Here, we apply ecological coexistence theory to show how the alignment between different forms of niche opportunity and niche use shape the initiation, progression, and completion of speciation. Niche evolution may drive coexistence or competitive exclusion, and an ability to coexist ecologically may help or hinder speciation. Our perspective allows progress towards unifying the origin and maintenance of species diversity across the tree of life.
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12
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Hülsmann L, Chisholm RA, Hartig F. Is Variation in Conspecific Negative Density Dependence Driving Tree Diversity Patterns at Large Scales? Trends Ecol Evol 2020; 36:151-163. [PMID: 33589047 DOI: 10.1016/j.tree.2020.10.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 09/28/2020] [Accepted: 10/01/2020] [Indexed: 02/06/2023]
Abstract
Half a century ago, Janzen and Connell hypothesized that the high tree species diversity in tropical forests is maintained by specialized natural enemies. Along with other mechanisms, these can cause conspecific negative density dependence (CNDD) and thus maintain species diversity. Numerous studies have measured proxies of CNDD worldwide, but doubt about its relative importance remains. We find ample evidence for CNDD in local populations, but methodological limitations make it difficult to assess if CNDD scales up to control community diversity and thereby local and global biodiversity patterns. A combination of more robust statistical methods, new study designs, and eco-evolutionary models are needed to provide a more definite evaluation of the importance of CNDD for geographic variation in plant species diversity.
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Affiliation(s)
- Lisa Hülsmann
- Theoretical Ecology, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
| | - Ryan A Chisholm
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Florian Hartig
- Theoretical Ecology, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany
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13
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Bernhardt JR, Kratina P, Pereira AL, Tamminen M, Thomas MK, Narwani A. The evolution of competitive ability for essential resources. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190247. [PMID: 32200736 PMCID: PMC7133530 DOI: 10.1098/rstb.2019.0247] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/04/2020] [Indexed: 02/01/2023] Open
Abstract
Competition for limiting resources is among the most fundamental ecological interactions and has long been considered a key driver of species coexistence and biodiversity. Species' minimum resource requirements, their R*s, are key traits that link individual physiological demands to the outcome of competition. However, a major question remains unanswered-to what extent are species' competitive traits able to evolve in response to resource limitation? To address this knowledge gap, we performed an evolution experiment in which we exposed Chlamydomonas reinhardtii for approximately 285 generations to seven environments in chemostats that differed in resource supply ratios (including nitrogen, phosphorus and light limitation) and salt stress. We then grew the ancestors and descendants in a common garden and quantified their competitive abilities for essential resources. We investigated constraints on trait evolution by testing whether changes in resource requirements for different resources were correlated. Competitive abilities for phosphorus improved in all populations, while competitive abilities for nitrogen and light increased in some populations and decreased in others. In contrast to the common assumption that there are trade-offs between competitive abilities for different resources, we found that improvements in competitive ability for a resource came at no detectable cost. Instead, improvements in competitive ability for multiple resources were either positively correlated or not significantly correlated. Using resource competition theory, we then demonstrated that rapid adaptation in competitive traits altered the predicted outcomes of competition. These results highlight the need to incorporate contemporary evolutionary change into predictions of competitive community dynamics over environmental gradients. This article is part of the theme issue 'Conceptual challenges in microbial community ecology'.
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Affiliation(s)
- Joey R. Bernhardt
- Aquatic Ecology Department, Eawag, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland
| | - Pavel Kratina
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Aaron Louis Pereira
- Aquatic Ecology Department, Eawag, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland
| | - Manu Tamminen
- Department of Biology, University of Turku, Natura, University Hill, 20014 Turku, Finland
| | - Mridul K. Thomas
- Centre for Ocean Life, DTU Aqua, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Anita Narwani
- Aquatic Ecology Department, Eawag, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland
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14
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Shoemaker LG, Barner AK, Bittleston LS, Teufel AI. Quantifying the relative importance of variation in predation and the environment for species coexistence. Ecol Lett 2020; 23:939-950. [PMID: 32255558 DOI: 10.1111/ele.13482] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 11/20/2019] [Accepted: 01/19/2020] [Indexed: 12/25/2022]
Abstract
Coexistence and food web theory are two cornerstones of the long-standing effort to understand how species coexist. Although competition and predation are known to act simultaneously in communities, theory and empirical study of these processes continue to be developed largely independently. Here, we integrate modern coexistence theory and food web theory to simultaneously quantify the relative importance of predation and environmental fluctuations for species coexistence. We first examine coexistence in a theoretical, multitrophic model, adding complexity to the food web using machine learning approaches. We then apply our framework to a stochastic model of the rocky intertidal food web, partitioning empirical coexistence dynamics. We find the main effects of both environmental fluctuations and variation in predator abundances contribute substantially to species coexistence. Unexpectedly, their interaction tends to destabilise coexistence, leading to new insights about the role of bottom-up vs. top-down forces in both theory and the rocky intertidal ecosystem.
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Affiliation(s)
| | - Allison K Barner
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA, 94720, USA.,Department of Biology, Colby College, Waterville, ME, 04901, USA
| | - Leonora S Bittleston
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.,Department of Biological Sciences, Boise State University, Boise, ID, 83725, USA
| | - Ashley I Teufel
- Santa Fe Institute, Santa Fe, NM, 87501, USA.,Department of Integrative Biology, The University of Texas at Austin, Austin, TX, 78712, USA
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15
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Pásztor L, Barabás G, Meszéna G. Competitive Exclusion and Evolution: Convergence Almost Never Produces Ecologically Equivalent Species: (A Comment on McPeek, "Limiting Similarity? The Ecological Dynamics of Natural Selection among Resources and Consumers Caused by Both Apparent and Resource Competition"). Am Nat 2020; 195:E112-E117. [PMID: 32216672 DOI: 10.1086/707610] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
In a recent modeling study ("Limiting Similarity? The Ecological Dynamics of Natural Selection among Resources and Consumers Caused by Both Apparent and Resource Competition") that appeared in the April 2019 issue of The American Naturalist, Mark A. McPeek argued that ecologically equivalent species may emerge via competition-induced trait convergence, in conflict with naive expectations based on the limiting similarity principle. Although the emphasis on the possibility of the convergence of competitors is very timely, here we show that the proposed mechanism will only lead to actual coexistence in the converged state for specially chosen fine-tuned parameter settings. It is therefore not a robust mechanism for the evolution of ecologically equivalent species. We conclude that invoking trait convergence as an explanation for the co-occurrence of seemingly fully equivalent species in nature would be premature.
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16
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Bergamo PJ, Susin Streher N, Traveset A, Wolowski M, Sazima M. Pollination outcomes reveal negative density-dependence coupled with interspecific facilitation among plants. Ecol Lett 2019; 23:129-139. [PMID: 31650660 DOI: 10.1111/ele.13415] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/07/2019] [Accepted: 10/03/2019] [Indexed: 01/27/2023]
Abstract
Pollination is thought to be under positive density-dependence, destabilising plant coexistence by conferring fitness disadvantages to rare species. Such disadvantage is exacerbated by interspecific competition but can be mitigated by facilitation and intraspecific competition. However, pollinator scarcity should enhance intraspecific plant competition and impose disadvantage on common over rare species (negative density-dependence, NDD). We assessed pollination proxies (visitation rate, pollen receipt, pollen tubes) in a generalised plant community and related them to conspecific and heterospecific density, expecting NDD and interspecific facilitation due to the natural pollinator scarcity. Contrary to usual expectations, all proxies indicated strong intraspecific competition for common plants. Moreover interspecific facilitation prevailed and was stronger for rare than for common plants. Both NDD and interspecific facilitation were modulated by specialisation, floral display and pollinator group. The combination of intraspecific competition and interspecific facilitation fosters plant coexistence, suggesting that pollination can be a niche axis maintaining plant diversity.
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Affiliation(s)
- Pedro J Bergamo
- Graduate Program in Ecology, University of Campinas, Monteiro Lobato St., 255, Campinas, PO Box 13083-862, Brazil.,Mediterranean Institute for Advanced Studies, CSIC-UIB, Miquel Marqués St., 21, Esporles, Mallorca, PO Box 07190, Spain
| | - Nathália Susin Streher
- Graduate Program in Plant Biology, University of Campinas, Monteiro Lobato St., 255, Campinas, PO Box 13083-862, Brazil
| | - Anna Traveset
- Mediterranean Institute for Advanced Studies, CSIC-UIB, Miquel Marqués St., 21, Esporles, Mallorca, PO Box 07190, Spain
| | - Marina Wolowski
- Institute of Natural Sciences, Federal University of Alfenas, Gabriel Monteiro da Silva St., 700, Alfenas, PO Box 37130-000, Brazil
| | - Marlies Sazima
- Department of Plant Biology, Institute of Biology, University of Campinas, Monteiro Lobato St., 255, Campinas, PO Box 13083-862, Brazil
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Abstract
Protective mutualisms, where a symbiont reduces the negative effects of another species on a shared host, represent a common type of species interaction in natural communities, yet it is still unclear what ecological conditions might favor their emergence. Studies suggest that the initial evolution of protective mutualists might involve closely related pathogenic variants with similar life histories, but different competitive abilities and impacts on host fitness. We derive a model to evaluate this hypothesis and show that, in general, a protective variant cannot spread from rarity or exclude a more pathogenic strain. While the conditions allowing mutualist invasion are more likely with increased environmental productivity, they still depend on initial densities in the invaded patch exceeding a threshold, highlighting the likely importance of spatial structure and demographic stochasticity. Using a numerical simulation approach, we show that regional coexistence is in fact possible in an explicitly spatial system and that, under some circumstances, the mutualist population can exclude the enemy. More broadly, the establishment of protective mutualists may be favored when there are other life-history differences from more pathogenic symbionts, such as vertical transmission or additional direct benefits to hosts.
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Affiliation(s)
- Timothée Poisot
- Université Montpellier II, Institut des Sciences de l'Evolution, UMR 5554Place Eugène Bataillon, 34095, Montpellier, CEDEX 05, France
- Département de Biologie, Université du Québec à Rimouski300 Allée des Ursulines, Rimouski, Quebec, G5L 3A1, Canada
- Québec Centre for Biodiversity SciencesMontréal (QC), Canada
- School of Biological Sciences, University of CanterburyPrivate Bag, 4800, Christchurch, 8140, New Zealand
| | - James D Bever
- Department of Biology, Indiana UniversityBloomington, Indiana, 47405
| | - Peter H Thrall
- CSIRO Plant IndustryGPO Box 1600, Canberra, Australian Capital Territory, 2601, Australia
| | - Michael E Hochberg
- Université Montpellier II, Institut des Sciences de l'Evolution, UMR 5554Place Eugène Bataillon, 34095, Montpellier, CEDEX 05, France
- Santa Fe InstituteSanta Fe, New Mexico, 87501
- Wissenschaftskolleg zu BerlinBerlin, 14193, Germany
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