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Evolutionary suicide as a consequence of runaway selection for greater aggregation tendency
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
Department of Mathematics and Statistics, University of Turku, 20014 Turku, Finland.
Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Evolution and Ecology Program, International Institute for Applied Systems Analysis, 2361 Laxenburg, Austria.
2013 (English)In: Journal of Theoretical Biology, ISSN 0022-5193, E-ISSN 1095-8541, Vol. 317, 96-104 p.Article in journal (Refereed) Published
Abstract [en]

Aggregation of individuals is a common phenomenon in nature. By aggregating, individuals can reap benefits but may also be subject to associated costs from increased competition. The benefits of aggregation can depend on population density, which in turn can be affected by aggregation when it determines reproductive success of individuals. The Allee effect is often considered to be one of the factors that can explain the evolution of aggregation behavior. We investigated this hypothesis with a mathematical model which integrates population dynamics and evolution. Individuals gain synergistically from aggregation but suffer from scramble competition with aggregation tendency as an evolving trait. We found that aggregation behavior can stabilize the population dynamics and reduce population growth. The results show that the Allee effect alone is not sufficient for aggregative behavior to evolve as an evolutionarily stable strategy. We also found that weak local competition does not promote aggregation due to feedback from the population level: under low competition, the population can achieve high density such that aggregation becomes costly rather than beneficial. Our model instead exhibits an escalation of aggregation tendency, leading to the extinction of the population in a process known as evolutionary suicide. We conclude that for aggregation to evolve as an evolutionarily stable strategy we need to consider other factors such as inter-patch dispersal to new patches and avoidance of excessively large groups. 

Place, publisher, year, edition, pages
Elsevier, 2013. Vol. 317, 96-104 p.
Keyword [en]
Invasion fitness, Adaptive dynamics, Allee effect, Site-based model
National Category
Biological Sciences
URN: urn:nbn:se:umu:diva-66650DOI: 10.1016/j.jtbi.2012.09.033ISI: 000313758500011OAI: diva2:609357
Available from: 2013-03-05 Created: 2013-02-26 Last updated: 2014-04-08Bibliographically approved
In thesis
1. Evolutionary consequences of ecological interactions
Open this publication in new window or tab >>Evolutionary consequences of ecological interactions
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Eco-evolutionary dynamics integrates the reciprocal interactions betweenecology and evolution. These two branches of biology traditionally assumethe other as static for simplicity. However, increasing evidence shows thatthis simplification may not always hold because ecology and evolution canoperate in similar timescales. This thesis theoretically explores how thereciprocal interactions may influence ecological and evolutionary outcomesin four different eco-evolutionary contexts.Many species of non-social animals live in groups. Aggregating ingroups often has both benefits and costs that depend on group size. Thanksto the benefits of aggregation, population growth likely depends positivelyon population density when it is small. This phenomenon, the Allee effect,has been hypothesized to explain the evolution of aggregation behavior. Ifind that the Allee effect alone does not lead to the evolution whenpopulation dynamics is explicitly accounted for. Some other mechanisms,such as frequent needs for colonizing new patches or anti-aggregation,should be invoked to explain why aggregation behavior could evolve.Phenotypic plasticity is the ability of a genotype to express distinctphenotypes when exposed to different environments. Although it is oftenshown to be adaptive and not costly, highly plastic organisms are rare. Paststudies demonstrated some potential reasons. I test another possibility; costsmay arise from sexual selection because highly plastic individuals may beless preferred as a mate. I show that, even in the absence of the direct cost ofplasticity, the level of plasticity remained low at intermediate strengths ofassortative mating. This pattern is robust across wide ranges of parametervalues.Ecological speciation occurs when ecologically divergent selectionbetween environments causes reproductive isolation between divergingsubpopulations. Several verbal models of ecological speciation emphasizethe roles of phenotypic plasticity in promoting speciation. The complexprocesses involved in speciation, however, are difficult to be evaluated byverbal accounts. I quantitatively test the proposed idea in a mechanisticmodel of ecological speciation in the presence and absence of plasticity. Ifind conditions under which plasticity can promote or hinder ecologicalspeciation. Plasticity facilitates speciation by producing a gap in thedistributions of expressed phenotypes, which serves as a barrier to gene flowin an assortatively mating population.Ecosystem ecology and evolutionary biology are the least integratedfields in ecology and evolution. Natural selection operating at the individuallevels on traits governing ecosystem functions may affect ecosystemproperties, which may feedback to individuals. I reviewed this idea anddemonstrate the feedback loop by using a simple consumer-resource model.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2014. 24 p.
adaptive dynamics, eco-evolutionary dynamics, ecological speciation, ecosystem, individual based, population dynamics, phenotypic plasticity, predator-prey, sexual selection
National Category
urn:nbn:se:umu:diva-87734 (URN)978-91-7601-018-1 (ISBN)
Public defence
2014-04-29, Naturvetarhuset, N200, Umeå universitet, Umeå, 10:00 (English)
Available from: 2014-04-08 Created: 2014-04-07 Last updated: 2014-04-08Bibliographically approved

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Nonaka, EtsukoBrännström, Åke
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