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  • 1.
    Cherif, Mehdi
    et al.
    Biogéochimie et Ecologie des Milieux Continentaux Laboratory, Unité Mixte de Recherche 7618, Ecole Normale Supérieure.
    Loreau, Michel
    Department of Biology, McGill University.
    Stoichiometric constraints on resource use, competitive interactions, and elemental cycling in microbial decomposers2007In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 169, no 6, p. 709-724Article in journal (Refereed)
    Abstract [en]

    Heterotrophic microbial decomposers, such as bacteria and fungi, immobilize or mineralize inorganic elements, depending on their elemental composition and that of their organic resource. This fact has major implications for their interactions with other consumers of inorganic elements. We combine the stoichiometric and resource-ratio approaches in a model describing the use by decomposers of an organic and an inorganic resource containing the same essential element, to study its consequences on decomposer interactions and their role in elemental cycling. Our model considers the elemental composition of organic matter and the principle of its homeostasis explicitly. New predictions emerge, in particular, ( 1) stoichiometric constraints generate a trade-off between the R* values of decomposers for the two resources; ( 2) they create favorable conditions for the coexistence of decomposers limited by different resources and with different elemental demands; ( 3) however, combined with conditions on species-specific equilibrium limitation, they draw decomposers toward colimitation by the organic and inorganic resources on an evolutionary time scale. Moreover, we derive the conditions under which decomposers switch from consumption to excretion of the inorganic resource. We expect our predictions to be useful in explaining the community structure of decomposers and their interactions with other consumers of inorganic resources, particularly primary producers.

  • 2. Claessen, David
    et al.
    Andersson, Jens
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    de Roos, André M
    The effect of population size and recombination on delayed evolution of polymorphism and speciation in sexual populations2008In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 172, no 1, p. E18-34Article in journal (Refereed)
    Abstract [en]

    Recent theory suggests that absolute population size may qualitatively influence the outcome of evolution under disruptive selection in asexual populations. Large populations are predicted to undergo rapid evolutionary branching; however, in small populations, the waiting time to branching increases steeply with decreasing abundance, and below a critical size, the population remains monomorphic indefinitely. Here, we (1) extend the theory to sexual populations and (2) confront its predictions with empirical data, testing statistically whether lake size affects the level of resource polymorphism in arctic char (Salvelinus alpinus) in 22 lakes of different sizes. For a given level of recombination, our model predicts qualitatively similar relations between population size and time to evolutionary branching (either speciation or evolution of genetic polymorphism) as the asexual model, while recombination further increases the delay to branching. The loss of polymorphism at certain loci, an inherent aspect of multilocus-trait evolution, may increase the delay to speciation, resulting in stable genetic polymorphism without speciation. The empirical analysis demonstrates that the occurrence of resource polymorphism depends on both lake size and the number of coexisting fish species. For a given number of coexisting species, the level of polymorphism increases significantly with lake size, thus confirming our model prediction.

  • 3. Cornforth, Daniel M
    et al.
    Sumpter, David J T
    Brown, Sam P
    Brännström, Åke
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Synergy and group size in microbial cooperation2012In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 180, no 3, p. 296-305Article in journal (Refereed)
    Abstract [en]

    Abstract Microbes produce many molecules that are important for their growth and development, and the exploitation of these secretions by nonproducers has recently become an important paradigm in microbial social evolution. Although the production of these public-goods molecules has been studied intensely, little is known of how the benefits accrued and the costs incurred depend on the quantity of public-goods molecules produced. We focus here on the relationship between the shape of the benefit curve and cellular density, using a model assuming three types of benefit functions: diminishing, accelerating, and sigmoidal (accelerating and then diminishing). We classify the latter two as being synergistic and argue that sigmoidal curves are common in microbial systems. Synergistic benefit curves interact with group sizes to give very different expected evolutionary dynamics. In particular, we show that whether and to what extent microbes evolve to produce public goods depends strongly on group size. We show that synergy can create an "evolutionary trap" that can stymie the establishment and maintenance of cooperation. By allowing density-dependent regulation of production (quorum sensing), we show how this trap may be avoided. We discuss the implications of our results on experimental design.

  • 4.
    Dahlgren, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Oksanen, Lauri
    Oksanen, Tarja
    Olofsson, Johan
    Trophic cascades and direct herbivore impacts in a low arctic scrublandIn: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323Article in journal (Other academic)
  • 5.
    de Roos, André M
    et al.
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Schellekens, Tim
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    van Kooten, Tobias
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    van de Wolfshaar, Karen
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Claessen, David
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Food-dependent growth leads to overcompensation in stage-specific biomass when mortality increases: the influence of maturation versus reproduction regulation2007In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 170, no 3, p. E59-E76Article in journal (Refereed)
  • 6.
    Diehl, Sebastian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lundberg, Peter A
    Gardfjell, Hans
    Oksanen, Lauri
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Daphnia-phytoplankton interactions in lakes: is there a need for ratio-dependent consumer-resource models?1993In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 142, no 6, p. 1052-1061Article in journal (Refereed)
  • 7. Hin, Vincent
    et al.
    Schellekens, Tim
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    de Roos, Andre M.
    Coexistence of Predator and Prey in Intraguild Predation Systems with Ontogenetic Niche Shifts2011In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 178, no 6, p. 701-714Article in journal (Refereed)
    Abstract [en]

    In basic intraguild predation (IGP) systems, predators and prey also compete for a shared resource. Theory predicts that persistence of these systems is possible when intraguild prey is superior in competition and productivity is not too high. IGP often results from ontogenetic niche shifts, in which the diet of intraguild predators changes as a result of growth in body size (life-history omnivory). As a juvenile, a life-history omnivore competes with the species that becomes its prey later in life. Competition can hence limit growth of young predators, while adult predators can suppress consumers and therewith neutralize negative effects of competition. We formulate and analyze a stage-structured model that captures both basic IGP and life-history omnivory. The model predicts increasing coexistence of predators and consumers when resource use of stage-structured predators becomes more stage specific. This coexistence depends on adult predators requiring consumer biomass for reproduction and is less likely when consumers outcompete juvenile predators, in contrast to basic IGP. Therefore, coexistence occurs when predation structures the community and competition is negligible. Consequently, equilibrium patterns over productivity resemble those of three-species food chains. Life-history omnivory thus provides a mechanism that allows intraguild predators and prey to coexist over a wide range of resource productivity.

  • 8. Härdling, Roger
    et al.
    Bergsten, Johannes
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Nonrandom Mating Preserves Intrasexual Polymorphism and Stops Population Differentiation in Sexual Conflict2006In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 167, p. 401-409Article in journal (Refereed)
    Abstract [en]

    Evolutionary conflict between the sexes is predicted to lead to sexual arms races in which male adaptations for acquiring mates (“offense” traits) are met by female counteradaptations—for example, to reduce mating rate (“defense” traits). Such coevolutionary chases may be perpetual. However, we show here that the coevolutionary process may also lead to a stable state in which multiple offense‐defense trait pairs are maintained. This type of polymorphism below the species level is a result of sexual conflict in combination with nonrandom mating. Our results show that if nonrandom mating occurs with respect to male and female conflict traits, genetic correlations will act to stabilize the trait frequencies so that all morphs are maintained. We discuss the results in special relation to the evolution of female polymorphism in diving beetles and argue that the process we describe may be a general force that maintains polymorphism in other taxa as well.

  • 9.
    Makoto, Kobayashi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Teshio Experimental Forest, Field Science Center for Northern Biosphere, Hokkaido University, Toikanbetsu, Horonobe, 098-2943, Hokkaido, Japan; and Graduate School of Environment and Information Sciences, Yokohama National University, Japan.
    Wilson, Scott D.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Biology, University of Regina, Regina, Canada.
    New Multicentury Evidence for Dispersal Limitation during Primary Succession2016In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 187, no 6, p. 804-811Article in journal (Refereed)
    Abstract [en]

    Primary succession is limited by both ecosystem development and plant dispersal, but the extent to which dispersal constrains succession over the long-term is unknown. We compared primary succession along two co-occurring arctic chronosequences with contrasting spatial scales: sorted circles that span a few meters and may have few dispersal constraints and glacial forelands that span several kilometers and may have greater dispersal constraints. Dispersal constraints slowed primary succession by centuries: plots were dominated by cryptogams after 20 years on circles but after 270 years on forelands; plots supported deciduous plants after 100 years on circles but after >400 years on forelands. Our study provides century-scale evidence suggesting that dispersal limitations constrain the rate of primary succession in glacial forelands.

  • 10. Mao, Jian-Feng
    et al.
    Wang, Xiao-Ru
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Distinct niche divergence characterizes the homoploid hybrid speciation of Pinus densata on the Tibetan Plateau2011In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 177, no 4, p. 424-439Article in journal (Refereed)
    Abstract [en]

    Ecological divergence and selection for novel adaptations to new habitats have been theoretically proposed to play important roles in promoting homoploid hybrid speciation (HHS). The successful establishment of Pinus densata on the Tibetan Plateau is one of the few known examples of HHS. In this study, we carried out extensive field expeditions to obtain representative coverage of occurrence sites of P. densata and its two putative parents. We then applied a series of geographic information system-based analyses to define the patterns of environmental variation within and among the three pine species, to remove potentially confounding effects of spatial autocorrelation in the environmental data due to allopatric ranges, and to build species distribution models. All results consistently indicated that the ecological preferences of P. densata and its parental species have diverged, and they identified candidate ecological factors associated with habitat-specific adaptation. Projections from niche modeling indicated that P. densata could extend across a vast range along the parallel valley systems of the southeastern Tibetan Plateau. Our findings provide evidence of a distinct niche shift in P. densata and support the hypothesis that local adaptation and geographic isolation help maintain and reinforce between-species differences and reproductive isolation in the species complex.

  • 11. McCauley, Shannon
    et al.
    Brodin, Tomas
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hammond, John
    Foraging rates of larval dragonfly colonists are positively related to habitat isolation: results from a landscape-level experiment2010In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 175, p. E66-E73Article in journal (Refereed)
    Abstract [en]

    There is increasing evidence of intraspecific variation in dispersal behavior. Individual differences in dispersal behavior may be correlated with other traits that determine the impact individuals have on patches they colonize. We established habitat patches—artificial pools—across a landscape, and these pools were naturally colonized by dragonfly larvae. Larvae were collected from pools at different levels of isolation and held under common lab conditions for 5 months. We then compared larval foraging rates. Foraging rate was positively related to habitat isolation, and colonists from the most isolated artificial pools had significantly higher foraging rates than individuals from the least isolated pools. Our results indicate that spatial patterns in colonist behavior can develop across a landscape independent of species‐level dispersal limitation. This finding suggests that studies of community structure across space should include an assessment of the distribution of phenotypes as well as species‐level dispersal limitation patterns.

  • 12.
    Monroe, Melanie J.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bokma, Folmer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Do speciation rates drive rates of body size evolution in mammals?2009In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 174, no 6, p. 912-918Article in journal (Refereed)
    Abstract [en]

    Recently, it has been shown with large data sets of extinct mammals that large‐bodied lineages experienced higher speciation and extinction rates; with extant mammals, it has been shown that body size evolution is accelerated during speciation. Therefore, it is interesting to investigate whether mammalian body size evolution is faster in large‐bodied lineages. Phylogenetic analysis assuming size‐independent speciation rates suggested that the rate of body size evolution increases with body size, whereas size differences in recent sister species (that are little affected by species turnover) appear to be independent of size. This supports the hypothesis that high rates of species turnover increase the rate at which interspecific differences accumulate in large‐bodied clades, whereas rates of evolution in single lineages are approximately size invariant. Similarly, these findings support the notion that mammalian body size evolution is indeed concentrated in speciation events.

  • 13.
    Nonaka, Etsuko
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Metapopulation Research Centre, Department of Biosciences, University of Helsinki, Helsinki, Finland.
    Svanbäck, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Ecology and Genetics/Limnology, Uppsala University.
    Thibert-Plante, Xavier
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Englund, Göran
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Brännström, Åke
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Evolution and Ecology Program, International Institute for Applied Systems Analysis, Laxenburg, Austria.
    Mechanisms by which phenotypic plasticity affects adaptive divergence and ecological speciation2015In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 186, no 5, p. E126-E143Article in journal (Refereed)
    Abstract [en]

    Phenotypic plasticity is the ability of one genotype to produce different phenotypes depending on environmental conditions. Several conceptual models emphasize the role of plasticity in promoting reproductive isolation and, ultimately, speciation in populations that forage on two or more resources. These models predict that plasticity plays a critical role in the early stages of speciation, prior to genetic divergence, by facilitating fast phenotypic divergence. The ability to plastically express alternative phenotypes may, however, interfere with the early phase of the formation of reproductive barriers, especially in the absence of geographic barriers. Here, we quantitatively investigate mechanisms under which plasticity can influence progress toward adaptive genetic diversification and ecological speciation. We use a stochastic, individual-based model of a predator-prey system incorporating sexual reproduction and mate choice in the predator. Our results show that evolving plasticity promotes the evolution of reproductive isolation under diversifying environments when individuals are able to correctly select a more profitable habitat with respect to their phenotypes (i.e., adaptive habitat choice) and to assortatively mate with relatively similar phenotypes. On the other hand, plasticity facilitates the evolution of plastic generalists when individuals have a limited capacity for adaptive habitat choice. We conclude that plasticity can accelerate the evolution of a reproductive barrier toward adaptive diversification and ecological speciation through enhanced phenotypic differentiation between diverging phenotypes.

  • 14. Ohlberger, Jan
    et al.
    Brännström, Åke
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Dieckmann, Ulf
    Adaptive phenotypic diversification along a temperature-depth gradient2013In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 182, no 3, p. 359-373Article in journal (Refereed)
  • 15. Ozgul, Arpat
    et al.
    Coulson, Tim
    Reynolds, Alan
    Cameron, Tom C.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. School of Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
    Benton, Tim G.
    Population Responses to Perturbations: The Importance of Trait-Based Analysis Illustrated through a Microcosm Experiment2012In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 179, no 5, p. 582-594Article in journal (Refereed)
    Abstract [en]

    Environmental change continually perturbs populations from a stable state, leading to transient dynamics that can last multiple generations. Several long-term studies have reported changes in trait distributions along with demographic response to environmental change. Here we conducted an experimental study on soil mites and investigated the interaction between demography and an individual trait over a period of nonstationary dynamics. By following individual fates and body sizes at each life-history stage, we investigated how body size and population density influenced demographic rates. By comparing the ability of two alternative approaches, a matrix projection model and an integral projection model, we investigated whether consideration of trait-based demography enhances our ability to predict transient dynamics. By utilizing a prospective perturbation analysis, we addressed which stage-specific demographic or trait-transition rate had the greatest influence on population dynamics. Both body size and population density had important effects on most rates; however, these effects differed substantially among life-history stages. Considering the observed trait-demography relationships resulted in better predictions of a population's response to perturbations, which highlights the role of phenotypic plasticity in transient dynamics. Although the perturbation analyses provided comparable predictions of stage-specific elasticities between the matrix and integral projection models, the order of importance of the life-history stages differed between the two analyses. In conclusion, we demonstrate how a trait-based demographic approach provides further insight into transient population dynamics.

  • 16.
    Schellekens, Tim
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    de Roos, Andre
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, the Netherlands.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ontogenetic Diet Shifts Result in Niche Partitioning between Two Consumer Species Irrespective of Competitive Abilities2010In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 176, no 5, p. 625-637Article in journal (Refereed)
    Abstract [en]

    Tilman's theory predicts the outcome of competition between two consumers sharing two resources on the basis of the shape of zero net-growth isoclines (ZNGIs). In his theory, intra-specific differences in resource use are not accounted for. Here we extend this theory to include situations where organisms undergo ontogenetic diet shifts, as these characterize the life histories of many species. In a situation that without diet shifts would lead to neutral coexistence of consumer species, we investigate whether ontogenetic diet shifts lead to niche partitioning. We analyze a model describing competition for two resources between two competitors with distinctive diets over ontogeny, using copepods (showing ontogenetic diet shifts) and daphnids (not showing ontogenetic diet shifts) as appropriate representatives. We show that an ontogenetic diet shift affects the shape of the ZNGI, changing it from reflecting perfectly substitutable resources to reflecting essential resources. Furthermore, we show that resource supply determines population stage structure and stage-dependent resource consumption in copepods and influences the competitive outcome with daphnids. In particular, we show that in itself, an ontogenetic diet shift can provide a competitive advantage if the supply of the adult resource is lower than the supply of the juvenile resource but that it always causes a disadvantage if the supply of the adult resource exceeds that of the juvenile resource.

  • 17.
    Scofield, Douglas G.
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Smouse, Peter E.
    Karubian, Jordan
    Sork, Victoria L.
    Use of Alpha, Beta, and Gamma Diversity Measures to Characterize Seed Dispersal by Animals2012In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 180, no 6, p. 719-732Article in journal (Refereed)
    Abstract [en]

    Seed dispersal shapes ecological and evolutionary dynamics of plant populations. Here, we extend classical diversity measures to study the impact of disperser behavior on seed dispersal. We begin by extending our previous diversity structure approach, which partitioned seed source diversity within and among dispersal sites, into the more general framework of traditional diversity measures. This statistical approach allows an assessment of the extent to which foraging behavior shapes alpha and gamma diversity, as well as the divergence in seed sources among dispersal sites, which we call delta. We also introduce tests to facilitate comparisons of diversity among dispersal sites and seed vectors and to compare overall diversity among sampled systems. We then apply these tools to investigate the diversity blend of parentage resulting from seed dispersal by two avian seed vectors with very different social and foraging behaviors: (1) acorn woodpeckers, transporting Quercus agrifolia acorns, and (2) long-wattled umbrellabirds, transporting Oenocarpus bataua palm nuts. Using these diversity and divergence measures, we test the hypothesis that different foraging behaviors generate distinctive diversity partitions for the two focal tree species. This approach provides a new tool for assessment of the impact of dispersal agents on the seed source structure of plant populations, which can be extended to include the impact of virtually any propagule vector for a range of systems.

  • 18. Stadler, Tanja
    et al.
    Rabosky, Daniel L.
    Ricklefs, Robert E.
    Bokma, Folmer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    On age and species richness of higher taxa2014In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 184, no 4, p. 447-455Article in journal (Refereed)
    Abstract [en]

    Many studies have tried to identify factors that explain differences in numbers of species between clades against the background assumption that older clades contain more species because they have had more time for diversity to accumulate. The finding in several recent studies that species richness of clades is decoupled from stem age has been interpreted as evidence for ecological limits to species richness. Here we demonstrate that the absence of a positive age-diversity relationship, or even a negative relationship, may also occur when taxa are defined based on time or some correlate of time such as genetic distance or perhaps morphological distinctness. Thus, inferring underlying processes from distributions of species across higher taxa requires caution concerning the way in which higher taxa are defined. When this definition is unclear, crown age is superior to stem age as a measure of clade age.

  • 19.
    Tibblin, Petter
    et al.
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Forsman, Anders
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Koch-Schmidt, Per
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Nordahl, Oscar
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Johannessen, Peter
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Nilsson, Jonas
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Larsson, Per
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Evolutionary divergence of adult body size and juvenile growth in sympatric subpopulations of a top predator in aquatic ecosystems2015In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 186, no 1, p. 98-110Article in journal (Refereed)
    Abstract [en]

    Evolutionary theory predicts that different selective regimes may contribute to divergent evolution of body size and growth rate among populations, but most studies have focused on allopatric populations. Here, we studied five sympatric subpopulations of anadromous northern pike (Esox lucius) in the Baltic Sea subjected to allopatric habitats for a short period of their life cycle due to homing behavior. We report differences in adult body size among subpopulations that were in part due to variation in growth rate. Body size of emigrating juveniles also differed among subpopulations, and differences remained when individuals were reared in a common environment, thus indicating evolutionary divergence among subpopulations. Furthermore, a QST-FST comparison indicated that differences had evolved due to divergent selection rather than genetic drift, possibly in response to differences in selective mortality among spawning habitats during the allopatric life stage. Adult and juvenile size were negatively correlated across subpopulations, and reconstruction of growth trajectories of adult fishes suggested that body size differences developed gradually and became accentuated throughout the first years of life. These results represent rare evidence that sympatric subpopulations can evolve differences in key life-history traits despite being subjected to allopatric habitats during only a very short fraction of their life.

  • 20. van Leeuwen, Anieke
    et al.
    Huss, Magnus
    Gardmark, Anna
    Casini, Michele
    Vitale, Francesca
    Hjelm, Joakim
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    de Roos, Andre M
    Predators with multiple ontogenetic niche shifts have limited potential for population growth and top-down control of their prey2013In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 182, no 1, p. 53-66Article in journal (Refereed)
    Abstract [en]

    Catastrophic collapses of top predators have revealed trophic cascades and community structuring by top-down control. When populations fail to recover after a collapse, this may indicate alternative stable states in the system. Overfishing has caused several of the most compelling cases of these dynamics, and in particular Atlantic cod stocks exemplify such lack of recovery. Often, competition between prey species and juvenile predators is hypothesized to explain the lack of recovery of predator populations. The predator is then considered to compete with its prey for one resource when small and to subsequently shift to piscivory. Yet predator life history is often more complex than that, including multiple ontogenetic diet shifts. Here we show that no alternative stable states occur when predators in an intermediate life stage feed on an additional resource (exclusive to the predator) before switching to piscivory, because predation and competition between prey and predator do not simultaneously structure community dynamics. We find top-down control by the predator only when there is no feedback from predator foraging on the additional resource. Otherwise, the predator population dynamics are governed by a bottleneck in individual growth occurring in the intermediate life stage. Therefore, additional resources for predators may be beneficial or detrimental for predator population growth and strongly influence the potential for top-down community control.

  • 21.
    Wickman, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Diehl, Sebastian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Blasius, Bernd
    Klausmeier, Christopher A.
    Ryabov, Alexey B.
    Brännström, Åke
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Determining Selection across Heterogeneous Landscapes: A Perturbation-Based Method and Its Application to Modeling Evolution in Space2017In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 189, no 4, p. 381-395Article in journal (Refereed)
    Abstract [en]

    Spatial structure can decisively influence the way evolutionary processes unfold. To date, several methods have been used to study evolution in spatial systems, including population genetics, quantitative genetics, moment-closure approximations, and individual-based models. Here we extend the study of spatial evolutionary dynamics to eco-evolutionary models based on reaction-diffusion equations and adaptive dynamics. Specifically, we derive expressions for the strength of directional and stabilizing/disruptive selection that apply both in continuous space and to metacommunities with symmetrical dispersal between patches. For directional selection on a quantitative trait, this yields a way to integrate local directional selection across space and determine whether the trait value will increase or decrease. The robustness of this prediction is validated against quantitative genetics. For stabilizing/disruptive selection, we show that spatial heterogeneity always contributes to disruptive selection and hence always promotes evolutionary branching. The expression for directional selection is numerically very efficient and hence lends itself to simulation studies of evolutionary community assembly. We illustrate the application and utility of the expressions for this purpose with two examples of the evolution of resource utilization. Finally, we outline the domain of applicability of reaction-diffusion equations as a modeling framework and discuss their limitations.

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