DOCSLIB.ORG

Criticality and Scaling in Evolutionary Ecology

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Criticality and Scaling in Evolutionary Ecology PERSPECTIVES Is there any particular situation where such complex structures emerge? The Criticality and scaling in answer is yes. In physics, fractal struc- tures in space and time were known to evolutionary ecology emerge in the proximity of some types of phase transition10,11. The classic example is a magnetic material. A small piece of Ricard V. Solé iron can tug on a paper clip at room tem- Susanna C. Manrubia perature, but if we heat it to a high tem- perature T, no magnetic power is ob- Michael Benton served. We say the magnetization M is Stuart Kauffman zero. The atoms that form the iron are themselves like small magnets. Each atom Per Bak only interacts with its nearest neighbors and their natural tendency is to align Fluctuations in ecological systems are known to involve a wide range of spatial and spontaneously into small domains with temporal scales, often displaying self-similar (fractal) properties. Recent theoretical the same orientation. At high T the cou- approaches are trying to shed light on the nature of these complex dynamics. The pling between nearest atoms breaks results suggest that complexity in ecology and evolution comes from the network-like down because of thermal perturbations structure of multispecies communities that are close to instability. If true, these ideas and, therefore, the atoms can have any might change our understanding of how complexity emerges in the biosphere and how polarity (up or down) and M 5 0. But sud- macroevolutionary events could be decoupled from microevolutionary ones. denly, when the material is cooled down, order spontaneously shows up. There is a critical temperature at which global Ricard Solé is at the CSRG-Dept of Physics, FEN, Universitat Politècnica de Catalunya, M. Campus Nord Mòdul B4, 08034 Barcelona, Spain ([email protected]; magnetization appears ( 0) and both Susanna Manrubia is at the Fritz-Haber Institut der Max-Planck Gesellschaft, Faradeyweg 4–6, fractal-spatial and fractal-temporal fea- 14195 Berlin, Germany ([email protected]); Michael Benton is at the tures arise. These transitions are de- Dept of Geology, University of Bristol, Bristol, UK BS8 1RJ ([email protected]); scribed by an ‘order parameter’ (here M), Stuart Kauffman is at the Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA which is zero at the disordered phase ([email protected]); Per Bak is at the Bohr Institute, Biegdamsvej 17, DK-2100 Copenhagen, and positive otherwise. Denmark ([email protected]). Self-similarity is a defining character- istic of the critical state. The surprise came when physicists realized that very ractals are widespread in nature1,2 and t.0 is a given exponent, often called the different systems behaved exactly the Fhave features that look the same when critical exponent. The reason why these same when close to critical transition there is a change in scale: they are called laws are characteristic of fractal objects points6,10,11. Surprisingly, extremely sim- ‘self-similar’. In biology, self-similar pat- is that they are the only functions dis- ple models of these systems provided an terns are known to occur at many levels1–4 playing invariance under scale change. If exact description. This is a consequence (Box 1). But fractals are also present in we look at a larger or smaller scale – that of the so-called ‘universality’. Universal- time: the fluctuations of a given quantity is, if we take s9 5 gs – it is not difficult to ity means that systems sharing a small can appear the same when observed at see that N(s9) 5 C9N(s) or, in other words, number of basic features behave identi- different temporal resolutions (Fig. 1a). a change of scale does not modify the cally at the critical point. Are there also This is the case for heartbeat intervals5, basic statistical behavior. universal principles behind apparently epidemics in small islands6, breeding bird The same argument can be employed different biological phenomena? populations7 or the fossil record8. for a time series (Fig. 1b). If self-similar Because fractals involve long-range behavior is present, then the time corre- From RNA viruses to epidemics correlations, they also reflect some key lations should decay in a power-law fash- Starting at the molecular level, an features of how living systems are or- ion9. This is something that has been example of a critical point in biological ganized and how they evolve in time. The widely observed and is known as ‘1/f- systems can be exemplified by the dy- implications for evolution are very im- noise’6,8,9. A 1/f-like signal looks like a namics of RNA viruses12. The under- portant, because cooperative effects mountain landscape in time, rather than standing of how these entities evolve and emerging from the interactions can lead to space. The self-similarity is described by adapt must take into account their ex- new, sometimes counterintuitive, results. the power spectrum P(f ), which measures treme variability, caused by the error- A consequence of this is that order could the contribution of each frequency to the prone RNA polymerase activity and the be generated through evolution by a syn- overall time series6. The 1/f noise is defined lack of proofreading mechanisms13. In- ergy between natural selection and self- as P(f ) < f-b being the exponent 0,b,2. stead of a given single sequence, we have organizing processes. Scaling and power laws The common feature of self-similar be- Box 1. Fractals everywhere havior is the presence of scaling laws4 The patterns displayed by many natural systems do not allow for a simple description using Euclidean (also known as power laws). Given the fre- geometry: they present scale-invariance; that is, no characteristic length measure can be obtained from them. Therefore, when observed at different resolutions, they display the same pattern. This is the case quency distribution N(s) of some quantity of river networks and mountains1, tree branching and blood vessels3 or forest spatial structures2,4. Even s (number of species, size, lifetime, etc.) at the molecular level, fractals can be observed: if we analyse the linear distribution of nucleotides in a it is said that it follows a power law if DNA chain, a self-similar pattern can also be detected5. These structures – the so-called fractals – share N(s) 5 Cs2t (Fig. 1a). Let us assume that s the presence of long-range correlations. stands for size. Here C is a constant and 156 0169-5347/99/$ – see front matter © 1999 Elsevier Science. All rights reserved. PII: S0169-5347(98)01518-3 TREE vol. 14, no. 4 April 1999 PERSPECTIVES (a) Box 2. Recipe for a catastrophe: the error catastrophe 4 10 A population of strings is simulated to explore how the ‘master’ sequence population behaves when the mutation rate is changed (a). Here, N 5 100 strings of size n 5 15. Each string is defined by a sequence e S1S2…Sn where Si {0,1}. At each time step, we choose a string and make a copy of it after removing 103 5 5 another randomly chosen string. This replication takes place with probability P 1 if Si 1 for all units (this is the master sequence) and with probability P 5 0.05 for any other string16. The copy process involves a mutation rate m, which means that the probability of error per unit and per replication cycle is 102 m for each string. Starting from a random population, we repeat the same rules over 13104 steps and at Frequency the end we look into the system to see if there is any copy of the master sequence. Here the master sequence is the string 1111…11; that is, the one with the highest replication rate. This is averaged over 101 3 2 1 10 trials and for each mutation rate we compute how many of these replicas (Pm) have at least one master sequence. Although our intuition would expect a smooth, continuous decay of this probability, 100 101 102 there is actually a sharp decay close to a given critical mutation rate (i.e. Pm acts as an order parameter Avalanche size for this transition). This phenomenon is known as the ‘error catastrophe’. It describes the breakdown of heredity and the transition from a localized set of mutant sequences (localized around the master sequence in sequence space) towards a random set of strings17. The inset graphs show the evolution (b) of relative population sizes of strings when (b) m 5 0.05 and (c) m 5 0.12. The master sequence is indicated by the unbroken line in these two graphs. 30 (a) 20 1.0 10 Extinction rate (c) 0 40 0 200 400 600 0.8 Geological time (million years) 30 20 0.6 10 (c) Frequency (b) 60 0 0 100 200 0.4 40 Time Order parameter 20 Frequency 0.2 0 0 100 200 Time 0.0 0.00 0.10 0.20 Mutation rate (Online: Fig. I ) a cloud of mutants around the so-called theoretical19 work show that critical ‘master’ sequence. This cloud is known points could play a very important role in as a quasispecies, a term first coined by the evolution of quasispecies. Manfred Eigen in 1971 (Refs 14,15). These transitions are well known in Fig. 1. Scaling and self-similarity. (a) Power RNA viruses adapt to a changing the dynamics of infectious diseases20 and law: in a log–log plot, a power law distribution, 21 defined as N(s) < s2a gives a straight line. environment by making use of their in some habitat fragmentation models .
Load more

Recommended publications
  • Predators As Agents of Selection and Diversification
    diversity Review Predators as Agents of Selection and Diversification Jerald B. Johnson * and Mark C. Belk Evolutionary Ecology Laboratories, Department of Biology, Brigham Young University, Provo, UT 84602, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-801-422-4502 Received: 6 October 2020; Accepted: 29 October 2020; Published: 31 October 2020 Abstract: Predation is ubiquitous in nature and can be an important component of both ecological and evolutionary interactions. One of the most striking features of predators is how often they cause evolutionary diversification in natural systems. Here, we review several ways that this can occur, exploring empirical evidence and suggesting promising areas for future work. We also introduce several papers recently accepted in Diversity that demonstrate just how important and varied predation can be as an agent of natural selection. We conclude that there is still much to be done in this field, especially in areas where multiple predator species prey upon common prey, in certain taxonomic groups where we still know very little, and in an overall effort to actually quantify mortality rates and the strength of natural selection in the wild. Keywords: adaptation; mortality rates; natural selection; predation; prey 1. Introduction In the history of life, a key evolutionary innovation was the ability of some organisms to acquire energy and nutrients by killing and consuming other organisms [1–3]. This phenomenon of predation has evolved independently, multiple times across all known major lineages of life, both extinct and extant [1,2,4]. Quite simply, predators are ubiquitous agents of natural selection. Not surprisingly, prey species have evolved a variety of traits to avoid predation, including traits to avoid detection [4–6], to escape from predators [4,7], to withstand harm from attack [4], to deter predators [4,8], and to confuse or deceive predators [4,8].
    [Show full text]
  • Read Evolutionary Ecology
    Evolutionary Ecology Eric R. Pianka For this generation who must confront the shortsightness of their ancestors Citation Classic, Book Review Sixth Edition out of print but available used Seventh Edition - eBook available from Google Read On Line Here (use Safari --(other browsers may not work): Chapter 1 - Background Definitions and Groundwork, anthropocentrism, the importance of wild organisms in pristine natural environments, scaling and the hierarchical structure of biology, levels of approach in biology, domain of ecology, the scientific method, models, simple versus multiple causality, environment, limiting factors, tolerance limits, the principle of allocation, natural selection, self-replicating molecular assemblages, levels of selection, the urgency of basic ecological research Chapter 2 - Classical Biogeography Self-replicating molecular assemblages, geological past, classical biogeography, plate tectonics and continental drift Chapter 3 - Meteorology Major determinants of climate, local perturbations, variations in time and space, global weather modification Chapter 4 - Climate and Vegetation Plant life forms and biomes, microclimate, primary production and evapotranspiration, soil formation and primary succession, ecotones, classification of natural communities, interface between climate and vegetation, aquatic systems Chapter 5 - Resource Acquisition and Allocation Limiting factors, physiological optima and tolerance curves, energetics of metabolism and movement, resource and energy budgets, the principle of allocation, leaf
    [Show full text]
  • Niche Evolution ­ Evolutionary Biology ­ Oxford Bibliographies
    8/23/2016 Niche Evolution ­ Evolutionary Biology ­ Oxford Bibliographies Niche Evolution Alex Pyron LAST MODIFIED: 26 MAY 2016 DOI: 10.1093/OBO/9780199941728­0075 Introduction The evolution of species’ niches is a process that is fundamental to investigations in numerous fields of biology, including speciation, community assembly, and long­term regional and global diversification processes. It forms the nexus between ecological and evolutionary questions. Topics as diverse as ecological speciation, niche conservatism, species coexistence, and historical biogeography all rely on interpreting patterns and drivers of species’ niches through time and across landscapes. Despite this importance, a distinct research agenda concerning niche evolution as a discrete topic of inquiry has yet to emerge. Niche evolution is often considered as a sidebar or of secondary importance when addressing questions such as “how did two species diverge?” Basic questions such as “what is a niche,” “what is the biological basis of niche evolution,” “at what scale should we evaluate niche evolution,” and “how can we observe niche evolution at different timescales” have rarely been addressed directly, or not at all in some systems. However, various intellectual threads connecting these ideas are evident in a number of recent and historical publications, giving some semblance of form to a framework for interpreting and evaluating niche evolution, and outlining major areas for future research from an evolutionary perspective. There is a reverse perspective from the macroecological scale as well, with questions involving coexistence, distributions and ranges, food webs, and other organismal attributes. General Overview Niche evolution has rarely, if ever, been addressed in depth as a standalone topic.
    [Show full text]
  • Dr. Michael L. Rosenzweig the Man the Scientist the Legend
    BIOL 7083 Community Ecologist Presentation Dr. Michael L. Rosenzweig The Man The Scientist The Legend Michael Rosenzweigs Biographical Information Born in 1941 Jewish Parents wanted him to be a physician Ph.D. University of Pennsylvania, 1966 Advisor: Robert H. MacArthur, Ph.D. Married for over 40 years to Carole Ruth Citron Together they have three children, and several grandchildren Biographical Information Known to be an innovator Founded the Department of Ecology & Evolutionary Biology at the University of Arizona in 1975, and was its first head In 1987 he founded the scientific journal Evolutionary Ecology In 1998, when prices for journals began to rise, he founded a competitor, Evolutionary Ecology Research Honor and Awards Ecological Society of America Eminent Ecologist Award for 2008 Faculty of Sci, Univ Arizona, Career Teaching Award, 2001 Ninth Lukacs Symp: Twentieth Century Distinguished Service Award, 1999 International Ecological Soc: Distinguished Statistical Ecologist, 1998 Udall Center for Studies in Public Policy, Univ Arizona: Fellow, 1997±8 Mountain Research Center, Montana State Univ: Distinguished Lecturer, 1997 Univ Umeå, Sweden: Distinguished Visiting Scholar, 1997 Univ Miami: Distinguished Visiting Professor, 1996±7 Univ British Columbia: Dennis Chitty Lecturer, 1995±6 Iowa State Univ: 30th Paul L. Errington Memorial Lecturer, 1994 Michigan State Univ, Kellogg Biological Station: Eminent Ecologist, 1992 Honor and Awards Ben-Gurion Univ of the Negev, Israel: Jacob Blaustein Scholar, 1992
    [Show full text]
  • Can More K-Selected Species Be Better Invaders?
    Diversity and Distributions, (Diversity Distrib.) (2007) 13, 535–543 Blackwell Publishing Ltd BIODIVERSITY Can more K-selected species be better RESEARCH invaders? A case study of fruit flies in La Réunion Pierre-François Duyck1*, Patrice David2 and Serge Quilici1 1UMR 53 Ӷ Peuplements Végétaux et ABSTRACT Bio-agresseurs en Milieu Tropical ӷ CIRAD Invasive species are often said to be r-selected. However, invaders must sometimes Pôle de Protection des Plantes (3P), 7 chemin de l’IRAT, 97410 St Pierre, La Réunion, France, compete with related resident species. In this case invaders should present combina- 2UMR 5175, CNRS Centre d’Ecologie tions of life-history traits that give them higher competitive ability than residents, Fonctionnelle et Evolutive (CEFE), 1919 route de even at the expense of lower colonization ability. We test this prediction by compar- Mende, 34293 Montpellier Cedex, France ing life-history traits among four fruit fly species, one endemic and three successive invaders, in La Réunion Island. Recent invaders tend to produce fewer, but larger, juveniles, delay the onset but increase the duration of reproduction, survive longer, and senesce more slowly than earlier ones. These traits are associated with higher ranks in a competitive hierarchy established in a previous study. However, the endemic species, now nearly extinct in the island, is inferior to the other three with respect to both competition and colonization traits, violating the trade-off assumption. Our results overall suggest that the key traits for invasion in this system were those that *Correspondence: Pierre-François Duyck, favoured competition rather than colonization. CIRAD 3P, 7, chemin de l’IRAT, 97410, Keywords St Pierre, La Réunion Island, France.
    [Show full text]
  • Interpretation of Models of Fundamental Ecological Niches and Species’ Distributional Areas
    Biodiversity Informatics, 2, 2005, pp. 1-10 INTERPRETATION OF MODELS OF FUNDAMENTAL ECOLOGICAL NICHES AND SPECIES’ DISTRIBUTIONAL AREAS JORGE SOBERÓN Comisión Nacional de Biodiversidad, México, and Instituto de Ecología, UNAM, México AND A. TOWNSEND PETERSON Natural History Museum and Biodiversity Research Center, University of Kansas, Lawrence, Kansas 66045 USA Abstract.—Estimation of the dimensions of fundamental ecological niches of species to predict their geographic distributions is increasingly being attempted in systematics, ecology, conservation, public health, etc. This technique is often (of necessity) based on data comprising records of presences only. In recent years, modeling approaches have been devised to estimate these interrelated expressions of a species’ ecology, distributional biology, and evolutionary history—nevertheless, a formal basis in ecological and evolutionary theory has largely been lacking. In this paper, we outline such a formal basis to clarify the use of techniques applied to the challenge of estimating ‘ecological niches;’ we analyze example situations that can be modeled using these techniques, and clarify interpretation of results. Key words.—ecological niche, fundamental niche, realizad niche, geographic distribution The fact that, at certain scales, climatic and occurrences with data sets summarizing climatic, physical factors affect profoundly the distributions topographic, edaphic, and other ‘ecological’ of species has been known for a very long time. In dimensions (in the form of GIS layers); the last two decades, mathematical techniques combinations of environmental variables most designed to estimate the geographic extent of the closely associated with observed presences of “fundamental ecological niche” (FN), or subsets of species can then be identified and projected onto it, defined mostly in coarse-scale climatic landscapes to identify appropriate regions, as dimensions [the “bioclimatic envelope” or climatic above.
    [Show full text]
  • Density-Dependent Selection in Evolutionary Genetics: a Lottery Model of Grime’S Triangle
    bioRxiv preprint doi: https://doi.org/10.1101/102087; this version posted February 7, 2017. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. Density-dependent selection in evolutionary genetics: a lottery model of Grime's triangle J Bertram1 and J Masel1 1Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721 February 7, 2017 Corresponding author; e-mail: [email protected]. 1 bioRxiv preprint doi: https://doi.org/10.1101/102087; this version posted February 7, 2017. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. Abstract Fitness is typically represented in heavily simplified terms in evolutionary genetics, often using constant selection coefficients. This excludes fundamental ecological factors such as dynamic population size or density-dependence from the most genetically-realistic treatments of evolution, a problem that inspired MacArthur's influential but problematic r/K theory. Following in the spirit of r/K-selection as a general-purpose theory of density-dependent se- lection, but grounding ourselves empirically in \primary strategy" trait classification schemes like Grime's triangle, we develop a new model of density-dependent selection which revolves around territorial contests. To do so, we generalize the classic lottery model of territorial acquisition, which has primarily been used for studying species co-existence questions, to accommodate arbitrary densities.
    [Show full text]
  • Limits to Species Richness in a Continuum of Habitat Heterogeneity: an ESS Approach
    Evolutionary Ecology Research, 2000, 2: 293–316 Limits to species richness in a continuum of habitat heterogeneity: An ESS approach William A. Mitchell* Department of Zoology, University of Wisconsin, Madison, WI 53706, USA ABSTRACT I use a co-evolutionary model to investigate the co-existence of species in ecological and evolutionary time in an environment that comprises a continuum of habitat heterogeneity. The model considers the ecology and evolution of communities organized by a trade-off in foraging costs over the environmental continuum. I assume that foragers use an optimal patch departure rule for depleting environments, where the rule itself depends on both the habitat and the forager’s phenotype, which is a heritable evolutionary strategy. I consider the effects of three variables on co-evolutionarily stable co-existence: (1) travel cost, (2) maintenance and replace- ment cost, and (3) the range of habitat heterogeneity. When travel cost is positive, it, as well as the other two variables, affects species richness. Increasing either travel cost or maintenance cost results in a decrease in richness. Increasing habitat heterogeneity can increase species richness. Keywords: co-evolution, evolutionarily stable strategy, habitat selection, species richness, travel cost. INTRODUCTION Species richness results from a combination of processes occurring at different spatial scales. At the provincial scale, immigration, dispersal and source–sink dynamics influence richness (Holt, 1985, 1993; Ricklefs, 1987, Pulliam, 1988). At the local scale, species inter- actions such as competition may be important (Rosenzweig, 1981; Tilman, 1982). To pre- dict species richness and how it is expected to change with environmental conditions requires an understanding of the importance and relative contributions of both types of processes (Holt, 1993).
    [Show full text]
  • Number of Censuses Required for Demographic Estimation of Effective Population Size
    Society for Conservation Biology 1XPEHURI&HQVXVHV5HTXLUHGIRU'HPRJUDSKLF(VWLPDWLRQRI(IIHFWLYH3RSXODWLRQ6L]H $XWKRU V -RKQ$9XFHWLFKDQG7KRPDV$:DLWH 5HYLHZHGZRUN V 6RXUFH&RQVHUYDWLRQ%LRORJ\9RO1R 2FW SS 3XEOLVKHGE\Blackwell PublishingIRUSociety for Conservation Biology 6WDEOH85/http://www.jstor.org/stable/2387576 . $FFHVVHG Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Blackwell Publishing and Society for Conservation Biology are collaborating with JSTOR to digitize, preserve and extend access to Conservation Biology. http://www.jstor.org Number of Censuses Required for Demographic Estimation of Effective Population Size JOHN A. VUCETICH*AND THOMAS A. WAITEt *School of Forestry, Michigan Technological University, Houghton, MI 49931, U.S.A., email [email protected] tDepartment of Zoology, Ohio State University, Columbus, OH 43210-1293, U.S.A., email waite.l@?osu.edu Abstract: Adequate population viability assessment may require estimation of effective population size (Ne). Butfailure to take into account the effect of temporalfluctuation in population size (FPS) on Ne may routinely lead to unrealistically optimistic viability assessments. We thus evaluate a technique that accounts for the effect of FPS on Ne. Using time series of annual counts of 48free-ranging animal populations, we show that Ne is dependent on timescale: as more census records are incorporated, estimates of FPS tend to increase, and thus estimates of N tend to decrease.
    [Show full text]
  • Evolutionary Ecology, Biogeography and Conservation of Water Beetles in Mediterranean Saline Ecosystems
    Limnetica, 29 (2): x-xx (2011) Limnetica, 34 (2): 481-494 (2015). DOI: 10.23818/limn.34.36 c Asociación Ibérica de Limnología, Madrid. Spain. ISSN: 0213-8409 Evolutionary ecology, biogeography and conservation of water beetles in Mediterranean saline ecosystems Paula Arribas1,2,∗, Pedro Abellán3, Josefa Velasco4 and Andrés Millán4 1 Department of Life Sciences, Natural History Museum London, United Kingdom. 2 Department of Life Sciences, Imperial College London, United Kingdom. 3 Department of Biology, Queens College, City University of New York, USA. 4 Department of Ecology and Hydrology, University of Murcia, Spain. ∗ Corresponding author: [email protected] 2 Received: 05/02/2015 Accepted: 04/06/2015 ABSTRACT Evolutionary ecology, biogeography and conservation of water beetles in Mediterranean saline ecosystems Among the variety of Mediterranean aquatic habitats, inland saline ecosystems are considered particularly rare and have been much less studied than other freshwater systems. Previous research has emphasised the ecological and evolutionary singularity of these environments and their great conservation value, as they are extremely endangered and also include a highly specialised biota with a high degree of endemism and genetic diversity. However, until recently, our knowledge about the biogeographical patterns and evolutionary processes of the lineages inhabiting these particular systems has been very sparse. This paper is a compilation and summary of the principal results obtained from various recent studies that were developed in the framework of the PhD thesis of the first author and focused on the water beetle diversity of the Mediterranean inland saline waters. The evolution of salinity tolerance, the main factors driving diversification on saline lineages and the application of all this information to provide relevant data for the conservation of aquatic saline biodiversity are addressed.
    [Show full text]
  • Trade-Off Between R-Selection and K-Selection in Drosophila Populations (Population Dynamics/Density-Dependent Selection/Evolution/Drosophila Melanogaster) LAURENCE D
    Proc. Natl Acad. Sci. USA Vol. 78, No. 2, pp. 1303-1305, February 1981 Population Biology Trade-off between r-selection and K-selection in Drosophila populations (population dynamics/density-dependent selection/evolution/Drosophila melanogaster) LAURENCE D. MUELLERt AND FRANCISCO J. AYALA Department ofGenetics, University ofCalifornia, Davis, California 95616 Contributed by Franciscoj. Ayala, October 17, 1980 ABSTRACT Density-dependent genetic evolution was tested that show a trade-off-i.e., genotypes with high rs have low Ks in experimental populations of Drosophila melanogaster subject and vice versa-the outcome of evolution in Roughgarden's for eight generations to natural selection under high (K-selection) model is dependent on the environment. In stable environ- or low (r-selection) population density regimes. The test consisted of determining at high and at low densities the per capita rate of ments, the population reaches its carrying capacity and the gen- population growth of the selected populations. At high densities, otype with the largest value ofK ultimately becomes established the K-selected populations showed a higher per capita rate ofpop- and all others are eliminated. When the population is often be- ulation growth than did the r-selected populations, but the reverse low its carrying capacity owing to frequent episodes ofdensity- was true at lowdensities.These results corroborate the predictions independent mortality, the genotype with the highest r is fa- derived from formal models ofdensity-dependent selection. How- vored. Thus, according to this model evolution favors the gen- ever, no evidence of a trade-off in per capita rate of growth was observed in 25 populations ofD.
    [Show full text]
  • Ecological Effects on Estimates of Effective Population Size in an Annual Plant
    Biological Conservation 143 (2010) 946–951 Contents lists available at ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon Ecological effects on estimates of effective population size in an annual plant E.K. Espeland a,*, K.J. Rice b a USDA ARS Pest Management Research Unit, 1500 N. Central Avenue, Sidney, MT 59270, USA b Ecology Graduate Group, Department of Plant Sciences, Mail Stop 1, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA article info abstract Article history: Effective population size (Ne) is a critical indicator of the vulnerability of a population to allele loss via Received 13 April 2009 genetic drift, and it can also be used to assess the evolutionary potential of a population. While some Received in revised form 28 December 2009 plant conservation plans have focused on outcrossing through cross-pollination as a way to increase esti- Accepted 3 January 2010 mated N , variance in reproductive output determined by ecological factors such as competition can also Available online 25 January 2010 e strongly affect estimated Ne. We examined the effects of intraspecific and interspecific competition, stressful soils, and local adaptation on estimates of Ne in an annual plant species. While ecological influ- Keywords: ences on plant growth rate variance have been predicted to influence estimates of N /N, we found a sig- Abiotic stress e nificant effect on the estimate of N /N, but no significant ecological effects on growth rate variance. Lower Competition e Effective population size survivorship on stressful soil was the most important effect reducing estimates of Ne/N.
    [Show full text]