Forest ecosystems are frequently disturbed by wind, fire, or herbivores. Disturbance regimes vary greatly in nature and intensity, depending on the disturbance mechanism, as well as the spatial and climatic environment of the disturbed vegetation landscape. Although it is straightforward to measure the direct impact of disturbances on vegetation by reporting the affected areas where most individuals have died, it remains a challenge to uncover the consequences that different disturbance regimes have on forest demography and evolution. Field studies are constrained by the often relatively long times needed for observing demographic change, and, for the same reason, empirical studies of adaptive evolution often have to build on comparative evidence between regions. These limitations have promoted theoretical research on modeling forest dynamics. Building on recent advances by Falster et al., who in a previous YSSP project have studied a size-structured metapopulation model for the adaptive evolution of two salient plant functional traits, I will develop an individual-based, spatially-explicit forest model in which the demographic and evolutionary consequences of different disturbance regimes will be explored. The present effort will therefore reveal how results by Falster et al. are affected by considering explicit space and finite population size. Details

For Darwin, the origin of species was the “mystery of mysteries,” and it remains poorly understood even today. Speciation, as the process that generated much of the biodiversity in the world today, is fundamental to the nature of life; it is thus clearly worthy of study in its own right. A better understanding of speciation also has consequences for conservation biology and for the mitigation of anthropogenic ecological disturbances. It has previously been shown that adaptation to a local environment and local competition for resources can promote speciation. This project will investigate the effects of spatial environmental variation and dispersal distance on speciation dynamics and the resultant biodiversity patterns. Time permitting, temporal environmental variation and the evolution of dispersal and mate choice may also be explored within this framework. This research will be conducted using an individual-based evolutionary model, building on previous work in IIASA’s Evolution and Ecology Program. Details

The evolution and maintenance of cooperation among unrelated individuals have been a major focus of evolutionary studies over the last decades. Models of this kind are traditionally cast in the framework of game theory. In cooperation games, individuals accumulate payoff according to their and their partners’ strategies. One of the most well-studied cooperation games, the Prisoner’s Dilemma, describes the interaction between just two players. Most biological situations, however, involve larger groups of individuals, resulting in situations that can be described by an n-person analogue of the Prisoner’s Dilemma, known as the Public Goods Game. In this study, we will extend the Public Goods Game from one to several public goods (multi-public-good game). This extension allows for more realistic social and biological situations: a community consisting of n individuals, might require several different public goods, with each individual contributing to none, some, or all of these. During the YSSP, a simple baseline model and some of its socially or biologically relevant extensions will be investigated in detail. Details

According to the Food and Agriculture Organization of the United Nations, the catch of anchovy reached its peak in the 1970s, dramatically decreased in the 1980s, and recovered to the previous level in the 1990s. In contrast, the catch of sardine began to grow in the 1970s, reached its peak in the 1980s, and has dropped sharply in the 1990s. This oscillatory phenomenon is known as sardine-anchovy cycles. Both anchovy and sardine serve as major food resources around the globe, so their cycling strongly impacts seafood supplies, fisheries economics, and coastal communities. Recent studies discovered that fluctuations in air temperature and ocean temperature were similar, in terms of phase and duration, to the oscillatory catches, suggesting that sardine-anchovy cycles are primarily driven by climatic changes. In addition, interactions among these species, and also among cohorts within each species, have been suggested to contribute to the cycles. In general, however, the causal origin of sardine-anchovy cycles remains open, and no model exists yet to describe these cycles. My research will therefore focus on developing a simple life-history model of the two species that can reproduce this globally observed phenomenon. In this model, I will consider the following factors: (1) climatic change, (2) interspecific interactions, (3) intraspecific cohort dynamics, (4) life-history evolution, and – time permitting – (5) spatial range dynamics. In collaboration with the Korean National Fisheries Research and Development Institute, I will calibrate the developed model with empirical data and with other information available in the literature. It is hoped that this work will help to reveal the mechanisms that are causing the observed long-term cycles, and thus contribute to a better understanding of factors influencing the sustainable exploitation of living marine resources. Details

Rapid evolution and diversification plays an essential role in the formation of biodiversity and in the response of species and ecosystems to anthropogenic forces such as climate change, harvesting, invasions by introduced species, or treatment with pesticides or antibiotics. A particularly important evolutionary response involves biological diversification, causing an existing lineage to split into new forms or species. Traditional approaches to describing such evolutionary branching assume that fluctuating ecological conditions can be approximated by their equilibrium values when considering dynamics over longer evolutionary timescales. However, the fluctuations in natural populations due to demographic and environmental factors can have a significant impact upon their evolution. On the short timescales characteristic of anthropogenic evolution, the impacts of these fluctuations will be even more pronounced. The goal of this project is to devise a theoretical framework for understanding the impacts of demographic and environmental variation on evolutionary branching. We will develop numerical simulations and analytic approximations to quantify these impacts and determine under what conditions such fluctuations promote, frustrate, or forever prevent evolutionary branching. Details

A group’s public goods require costly investments by individual group members while benefiting all group members irrespective of their investments. This leads to a so-called social dilemma: as non-contributors cannot be excluded from the benefits of the public good, there is a strong incentive for free riding. Much research in the last decade has focused on public-goods games and on mechanisms that maintain cooperation, such as punishment of non-contributors or voluntary participation. However, important examples of public goods contain the strategic element of time, which has largely been neglected by both experimental studies and theoretical analysis to date. Without explicitly incorporating a temporal dimension, important features of several public goods are not adequately captured. Real-world examples, including investments into the prevention of climate change or effort levels in joint projects, suggest that the strategy “wait and see” plays a key role. Both examples are characterized by time pressure: joint projects usually have a deadline, and actions against climate change are more effective the earlier they are implemented. In order to incorporate temporal effects into the analysis of public-goods games, we consider an evolutionary model in which each individual determines not only the amount but also the timing of its investments. We include time pressure by assuming that the effectiveness of contributions to, or the benefits derived from, the public good change over time. The resultant evolution of strategies will be explored using analytical adaptive-dynamics techniques and agent-based simulations. Details

Most epidemiological models focus on infection dynamics at the level of individual hosts or a population of hosts, without addressing the evolution of the infectious agent. Yet, disease evolution can significantly alter infection dynamics, at both the individual and the population level. The evolution of the virulence of an infectious agent is often analyzed in terms of a trade-off between the agent’s needs for achieving intense transmission between hosts while keeping hosts alive to prolong such transmission. Most research has therefore concentrated on the effects of virulence on classical epidemiological parameters, such as transmission rate or the length of the infectious period. Our aim in this project is to extend understanding of virulence evolution to host populations that are fragmented in space, forming patchy structures. This will require us to study, in addition, the effects of virulence on the spatial demography of hosts, including impacts on their residence time within patches, distance of movement between patches, and their chance of surviving such movement. We will use a stochastic model of a disease that is directly transmitted in continuous time in a host population that is patchy in space. The spread of the disease within and between patches will be modelled based on SIS-type dynamics excluding super-infection. The connectivity structure of the patchy host population is an important topic in this research, and different options will be studied; for example, all patches can be equally connected, or there can be a maximum movement distance for hosts. Details

One of the most intriguing questions in biology is why there is such a high diversity of species. In a tropical rain forest, thousands of species of trees can coexist on only a few square kilometers of land as the result of a long process of evolutionary diversification. The general aim of my project is to develop a better understanding of the ecological mechanisms and principles underlying diversification in tree architecture. Using simple eco-evolutionary models, we will first determine tree architectures that maximize the seed production of a solitary tree, so that there is no influence of other trees. Second, we will analyze monomorphic or polymorphic outcomes of architecture evolution of trees in stands, in which competition for light, the risk of wind breakage, and the pattern of grazing a tree experiences depend on other trees in its stand. As a first approximation, trees will be assumed to have simple geometric shapes consisting of a spheroidal crown, whose top is attached to the tip of a conical trunk. Each tree will be characterized by three evolving traits: the trunk’s apex angle, the relation of crown width to crown height, and the amount of available energy invested into the crown relative to the trunk. In a horizontally well mixed stand, the effects of wind, grazing, and light competition depend on the stand’s vertical biomass distribution, and thereby on the architectures of all trees in the stand, rendering selection on trees in stands frequency-dependent. We will consider stands of trees that occasionally are destroyed through fires and then re-established from similar stands through global random seed dispersal. Details

According to life-history theory, the strong and size-selective mortalities imposed by modern fishing are supposed to induce evolution in life-history traits such as growth, age and size at maturation, and reproductive investment. In accordance with this expectation, many field studies have revealed altered growth rates, earlier maturation at smaller size, and higher reproductive effort in harvested populations. Experiments have corroborated these results, showing that surprisingly rapid adaptive evolution is possible in response to harvesting. Unfortunately, genes coding for detailed aspects of fish life histories have not been identified so far, which precludes validating the genetic nature of observed phenotypic trends. Genetic analyses of fish stocks have instead focused on neutral genetic markers such as microsatellites. This allowed studying the neutral evolution of genetic diversity, which has been shown to decline in some harvested populations. Life-history traits and neutral genetic markers are indeed subject to neutral evolution through genetic drift, i.e., through purely random processes affecting allele frequencies that are the more pronounced the smaller a population’s size. The aim of this project is to develop a generic model for studying the interplay between neutral and adaptive evolution in the context of fishing. For this purpose, an individual-based model will be devised that includes neutral genetic markers as well as quantitative life-history traits, and that accounts for the complex ecology of exploited fish stocks. Our model analyses are planned to address three objectives. First, we will explore whether we can identify relationships between fisheries-induced changes in the distributions of neutral genetic markers and changes in demographic stock characteristics such as population size, spawning stock biomass, and recruitment. Second, we will analyze the relative contribution of genetic drift and adaptive evolution in the responses of life-history traits to fishing. Third, we will investigate potential patterns linking neutral and adaptive genetic changes. If such a correlation were found, neutral markers, which are much easier to analyse empirically, could be used to establish early-warning signals for fisheries-induced evolutionary changes in exploited stocks. Details

The evolution of species interactions is central to understanding the structure and functioning of ecosystems. Improved insights into the underlying processes will shed light on how nature maintains its magnificent diversity of coexisting organisms. Although there are many types of interactions between species, trophic interactions between predators and their prey have particularly important evolutionary consequences, as these not only determine the viability of prey, but also affect interference and resource competition among predators. In this project, I will focus on the evolution of trophic interactions in multivariate niche spaces. The emerging properties of the resultant food webs, such as species number, connectance, as well as several other empirically measurable topological features of natural trophic networks will be studied. An individual-based model will be developed in which individuals are characterized by heritable multivariate traits describing the niches in which they are available as prey and in which they act as predators. Daisuke will also numerically analyze this model and compare the predicted evolutionary outcomes with empirical food-web statistics. Details

Seaweeds offer ideal habitats for many plants and animals in coastal ecosystems. In particular kelp beds are important spawning and feeding grounds, and provide refuges for many fish species and other aquatic organisms. After kelp plants die, they are decomposed by bacteria and microorganisms in the water. This raises the level of nutrients in the ecosystem, leading to increased productivity of phytoplankton and zooplankton, which are key resources for juvenile fishes and mussels inhabiting the kelp-bed ecosystem. Using the modeling framework ‘Ecopath with Ecosim’, this project will integrate recent survey data and published information from the literature into a foodweb model describing the trophic structure and energy flows of the kelp-bed ecosystem at Gouqi Island in the East China Sea. As Gouqi Island is one of the main mussel-cultivation areas in China, our research will focus on the potential interactions between mussel cultivation and kelp beds. We hope that this will provide new insights into the trophic ecology of this particular ecosystem and allow us to develop ideas pertinent to other instances of this unique kind of aquatic ecosystem. We aim to quantify the maximum carrying capacity for mussel production in the area around Gouqi Island. This would not only be useful for increasing the economic benefits and other services such an ecosystem can provide, but may provide managers with sustainable options for mariculture exploitation while minimizing the environmental degradation caused by mussel production. Details

A key issue in ecology is to understand mechanisms and processes causing speciation and extinction. Earlier theoretical studies have been based either on (i) physiologically unstructured populations of individuals characterized by one or more evolving traits or on (ii) continuously sizestructured populations of individuals characterized by their maximally attainable size as the single evolving trait. While these models prioritize evolutionary or ecological realism, respectively, they suffer from complementary limitations: models (i) oversimplify individual life histories, while models (ii) are unable to explain the coexistence of ecologically different species with comparable asymptotic body size. A natural way of overcoming these limitations is to synthesize the two model types, by considering an evolving trait describing an individual’s ecological niche in addition to one describing its asymptotic size. Hence, the first goal of this project is to develop and implement a continuously size-structured population model with two evolving traits describing asymptotic size and ecological niche. We will then explore conditions under which species can diversify in these traits and examine the resultant multi-species communities. Technically, our model will use the canonical equation of adaptive dynamics theory together with numerical solutions of continuously size-structured population models to simulate the dynamics of evolutionary community assembly. Details

Studies of fisheries-induced maturation evolution have revealed shifts towards smaller sizes and younger ages at maturation. In this context, probabilistic maturation reaction norms (PMRNs) serve as a new statistical tool that helps to disentangle phenotypic plasticity and evolutionary responses by describing the probability of individuals to mature as a function of their age and size. This perspective overcomes the otherwise confounding effects of changes in growth and survival on observed patterns of maturation. Chum salmon are semelparous fish in the North Pacific that spawn in freshwater and reproduce only once during their lifetime. I plan to calculate PMRNs for age and size at maturation of the chum salmon population spawning in the Namdae River in Korea, which constitutes the southern boundary of the natural range of chum salmon in the North Pacific. The estimation of PMRNs could make it possible to comprehend the effects of varied environmental conditions and size-selective fishing pressures on the life history of chum salmon. Therefore, my study will concentrate not only on environmental variability in life-history traits, but also on the effects of fisheries-induced evolution compared with environmentally induced changes on age and size at maturation. Details

Speciation in sympatry has received considerable attention because, unlike speciation in allopatry, the lack of population subdivision means that reproductive isolation must be achieved in the presence of persistent gene flow. One mechanism that is thought to be capable of creating reproductive isolation in sympatry is frequency-dependent disruptive selection, i.e., selection against intermediate phenotypes resulting from the frequency-dependent interactions between individuals. The focus of this research project will be to investigate how frequency-dependent mobility, mortality, and fecundity – mechanisms that may induce the spatial self-structuring of populations – influence the long-term evolution of assortative mating in heterogeneous environments and thus potentially lead to adaptive speciation through sexual selection. For this purpose, we will develop and investigate both stochastic individual-based models and deterministic analytical models. We will start by reproducing results already present in the literature, before extending the underlying models to allow for more complex heterogeneous environments. In this manner we hope to achieve a more comprehensive understanding of the relative importance of environmentally imposed and dynamically generated spatial heterogeneity for the emergence and stable persistence of reproductively isolated populations. Details

In most existing models of adaptive speciation, ecological specialization via resource partitioning is the predominant driving force for the evolution of reproductive isolation. One conclusion from these theoretical studies is that adaptive speciation is a theoretically plausible process, especially along environmental gradients. However, empirically motivated and data-based speciation models including ecologically derived parameter assumptions are needed to better evaluate the potential for such processes to occur in nature. Freshwater fish occupying postglacial environments are commonly used model systems for studying adaptive diversification in evolutionary ecology. Several taxa of freshwater fish have generated species and ecological diversity in a manner consistent with the theory of adaptive speciation. Specifically, there is increasing evidence that ecological opportunity and competition for resources promote adaptive divergence in coregonid fish, which feature sympatric forms of phenotypically divergent and reproductively isolated populations throughout the northern hemisphere. A sympatric pair of coregonids exists also in the northern German Lake Stechlin. Here, evidence suggests that the two existing species have segregated along the temperature-depth gradient in terms of divergent metabolic temperature adaptations. The goal of this research project is to develop a model for this ecological diversification as a first step towards understanding the adaptive speciation of fish populations along the environmental gradient of water temperature. We will start with a spatially structured single-trait model under the adaptive dynamics assumptions of asexual reproduction with small and rare mutations. If time allows, we will extend the model to size-structured and/or sexually reproducing populations. Details

Size-selective mortality due to fishing can impose strong selection on harvested fish populations, causing evolutionary changes in key life-history traits such as size at maturation. Understanding and predicting harvest-induced evolutionary change is crucial for the long-term maintenance of sustainable fisheries. I will investigate optimal management strategies for an evolutionarily sustainable fishery of the lacustrine brook charr (Salvelinus fontinalis) in southern Canada. Brook charr inhabit a series of lakes, some of which are harvested and some are not. This provides an ideal model system for investigating harvest-induced evolutionary changes and management strategies that mitigate such changes. I have previously developed an individual-based model of the effects of harvesting on life-history variation in brook charr populations, which I plan to parameterize with data provided by my collaborators, the Research Group on Aquatic Ecosystems at l’Université du Québec à Trois-Rivières. The important next step will be to elucidate optimal management strategies for the brook charr populations. In particular, I will investigate two types of management strategies, with the first aiming to minimize future evolutionary change by managing fishing effort and the second aiming to curtail ongoing evolutionary change by translocating individuals with late-maturing genes from unharvested to harvested lakes. To optimize these two strategies, I will employ genetic algorithms for evolving management strategies in the individualbased model. I will examine whether, especially when implemented together, the two optimal management strategies can slow down or reverse ongoing evolutionary changes resulting from past fishing practices and minimize future changes by improving these fishing practices. Details

Dispersal is a topic of paramount importance in theoretical ecology, influencing species abundances and distributions, population dynamics, genetic diversity, and the evolution of reproductive isolation. While dispersal is costly, theoretical investigations have demonstrated its selective advantage in numerous situations, e.g., to avoid kin competition and inbreeding, and to escape local catastrophes in temporally or spatially varying environments. The majority of these theoretical models assume unconditional dispersal, such that dispersal is characterized by a single global variable, typically defined as the dispersal rate or dispersal probability during a generation. While unconditional dispersal may occur in some cases, there is ample empirical evidence that dispersal is conditional in many species. In particular, the probability of an individual emigrating from its current patch may be contingent upon the local density of conspecifics. In models of conditional dispersal, the functional form describing the dependence of dispersal on density is often assumed a priori, such that only a few parameters controlling the shape of such a function are allowed to evolve. Another common assumption is topological regularity, with subpopulations often being arranged as cells on a two-dimensional lattice. The focus of this research is to relax these two simplifying assumptions and to analyze the resulting evolutionary dynamics of conditional dispersal strategies. Dispersal strategies will be represented as function-valued traits, thus allowing for a fuller exploration of the space of strategies, and pertinent topological properties of population structure, such as assortativity and hierarchical organization, will be systematically varied. Two salient research questions are: (i) Does the representation of conditional dispersal as a function-valued trait lead to the evolution of dispersal functions not found in previous studies? and (ii) How do the topological properties of complex population structures affect the evolution of conditional dispersal? Details

In modern societies, individuals often have a large degree of freedom and anonymity. This allows them to get away not only with free-riding on the efforts of others, but also with opting out from participating in cooperative enterprises altogether. While many studies in the biological and social sciences have contributed to understanding the enduring conundrum of how cooperation can emerge and be maintained in the presence of free-riders, only a handful of studies have studied the role of voluntary participation. These studies investigated a classical Public Goods game in which individuals could cooperate, defect, or opt not to participate in the game altogether. The evolutionary dynamics of these three pure strategies can resemble the “rock-scissors-paper” cycle known from evolutionary game theory, and thus prevent populations from ending up with 100% defection. While this can explain why a significant number of cooperators may be present in a population, it does not explain how the three pure strategies under consideration emerged in the first place. To overcome this limitation, we will consider a model in which individuals are characterized by two continuously varying traits describing their cooperative investment and participation rate in a Public Goods game in which payoffs depend nonlinearly on a group’s total cooperative investment. The resultant coevolutionary dynamics, including the potential for evolutionary branching in two or three directions, will be explored using adaptive dynamics techniques and through an individual-based model in which many of the otherwise needed simplifying assumptions can be relaxed. Details

While mutually beneficial interactions are common in nature, their persistence poses numerous theoretical problems. Mutualistic partnerships involve reciprocal cooperative actions between species that imply a cost for the actor and a benefit for the receiver. In principle, cooperators can easily become exploited by cheaters that accept cooperative acts without returning them. Such exploitation can be avoided when cooperators can identify cheaters and either forego or exit such partnerships, which is facilitated by interactions occurring on a local scale. Another mechanism is for cooperators to choose among potential partners according to their “offers”, just like goods are offered and chosen on a marketplace. These two mechanisms are known as partner fidelity and partner choice, respectively, and frequently occur together. My plan is to work out and study a model of mutualism evolution incorporating these combined effects. In particular, the formation of mutualistic partnerships (with participation of two or more individuals) will be driven by potential partners choosing others according to their initial offers or signs. The persistence of mutualistic partnerships will also depend on the level of “satisfaction” of the participants regarding the benefits they have received, in accordance with a “win stay-lose shift” strategy. Individuals can differ in their potential to find partners, in their cost of maintaining partnerships of different quality, and in their ability to sanction cheaters. Partner fidelity and partner choice lead to a diverse and rapidly changing interaction topology. My aim is to investigate how such a setup can favor the evolution and maintenance of high levels of mutualistic interactions by suppressing the spread of cheaters. Details

Current deficiencies in fisheries management within the EU are the lack of a formal framework for drafting and ranking specific stakeholder objectives, in conjunction with the lack of a transparent and communicable approach to management. The aim of this research is to work towards the development of such a framework. To achieve this, I will derive harvest control rules (HCRs) using models representing generic fish stocks that reflect the trade-offs between different objectives of fisheries management. I will maximize utility functions and use discount theory to help quantify and rank different biological, social, or economic objectives in order to derive objectives for an HCR. The objective-derived HCRs will then be applied and updated in stochastic population models to finally assess its performance in relation to the original objectives. This process outlines how HCRs can formally be tailored to facilitate communication and support a higher level of transparency to promote stakeholder consensus, incentives, and success in fishery management. Details

Humans can influence life history traits of domesticated and wild animals through selective processes. Fishing is often deliberately size-selective for economic and biological reasons. Size-selective fishing mortality has been associated with directional selection and changes in life history traits such as age and size at maturity. Norms of reaction show the ranges of potential phenotypes, such as different ages and sizes at maturation, that a given genotype could develop if an individual is exposed to different environmental conditions. Selection, due to many causes, may act on age and size at maturation and cause the reaction norm of an individual or population to change in position or shape. Maturation reaction norms may help to disentangle phenotypic plasticity associated with different growth and mortality conditions from genetic effects that influence maturation as a result of reaction norm evolution. Thus, they may reveal changes in maturation schedules associated with size-selective fishing. Bristol Bay, Alaska has some of the most diverse and abundant sockeye salmon (Oncorhynchus nerka) populations in the world. A large commercial gillnet fishery has exerted strong, size-selective fishing pressure on these salmon since 1884. I will use data from 1946-present to calculate probabilistic maturation reaction norms (PMRNs) for length and age at maturation of locally adapted sockeye spawning populations of the Wood River system of Bristol Bay. While PMRNs have been developed for a number of fish species who spawn multiple times, little work has been done understanding reaction norms for semelparous species, such as Pacific salmon, who spawn only once before dying. With these PMRNs, in the future I can understand changes in these life history traits over time and will evaluate if this fishery selection has the potential to cause life history evolution. Details

Selective exploitation of fish is increasingly recognized to drive evolution of life history traits and tools have been developed to detect changes in single traits. Eco-genetic individual based models are a powerful tool to study possible outcomes of evolution with multiple traits. However, in most applications the sexes are assumed to be equal whereas in fish they are often dimorphic at least in size. We will develop a case specific eco-genetic individual based model for North Sea plaice incorporating the sexual size dimorphism to study the evolution of plaice over the last century and in particular the different responses in males and females. In a first step we have to calibrate the model for males and females such that the model predictions match the observations. We then assume that differences in growth, onset of reproduction and reproductive investment between males and females arise from different mortality regimes that plaice males and females experience in particular during reproduction. We then use the model to test this hypothesis and to find a mechanistic explanation for different sex specific evolutionary responses. Details

Changes in life-history traits, particularly in age and size at maturation, have been reported in a number of commercially exploited fish stocks. Many studies have found fisheries-induced evolution to be a plausible explanation for the observed trends. Evidence for the existence of adaptive variation and local populations within several cod stocks has been found. One such stock is Icelandic cod for which spawning, life-history characteristics, condition and abundance vary spatially, and there is also evidence of genetic structure. Furthermore, fishing mortality of the Icelandic cod stock is unevenly distributed on the Icelandic shelf. Preliminary investigations suggest that age and size at maturation in this stock has declined over the last few decades. In line with the majority of fish stocks, Icelandic cod is currently managed as a single homogenous unit. However, failure to recognise or account for stock diversity could produce misleading results or even potentially severe ecological consequences. In this project, my aim is to investigate the development and subsequent dynamics of structure in a stock such as Icelandic cod and its influence on the rate, detection, and management of fisheries-induced evolution, with additional consideration of the role of variable fishing pressure on individual stock components. The development of an individual-based eco-genetic model will help tackle these research questions where empirical analysis would fail due to the limitations imposed by data availability. Details

Many case studies have shown that local communities are capable of managing natural renewable resources like fish, forests or grazing lands in a highly sustainable and profitable way by making informal agreements on the managing strategies. There are, however, situations in which these rules break down or do not evolve in the first place, leading to a situation often referred to as a tragedy of the commons. Many field studies indicate that social norms play a key role in this process. This research will take this factor into account explicitly by defining social norms as a rule of how to behave in a certain situation. Besides, there is no guarantee that the established norm will be the most efficient one, since once established, norms are very hard to replace. Therefore, social norms are an example par excellence for frequency-dependent selection. While evolutionary game theory is the most prominent method for explaining the evolution of harvesting rules, it has important limitations. These shortcomings can be overcome by using methods from the field of adaptive dynamics instead. This approach is appealing, as social norms can be, analogously to function-valued traits, defined as rules of behaviour. Besides, non-linear fitness functions can explain why certain norms that seem to be rather ineffective are not always replaced by more efficient ones. A model will be developed, in which agents will base their decisions on (i) monetary profits, (ii) actions of other agents, (iii) and the state of the resource. Social norms will be the mapping that translates this information into actions. Details

Bränström et al. have developed an evolutionary food web model based on body size of individual species as the evolving trait. However, although this model is capable of producing food webs with three to four trophic levels, there is a certain regularity in the resulting food webs with, typically, equal spacing in body size on a logarithmic scale. During the summer program we would concentrate on extending this evolutionary food web model so that two ecologically different species with approximately the same body size can coexist. The approach would be to add an abstract “niche trait” representing the ecological niche that a species occupies. The ability of a predator to forage on a prey would then be determined by both relative difference in body size and the distance between the individuals in niche space. The evolutionary process will be analyzed following the small mutational steps and using a second degree approximation of the fitness landscape around the resident trait value. To track the evolution of the traits, we would adopt the canonical equation of adaptive dynamics. Along with the analytical techniques, we would employ suitable numerical simulations using software such as MATLAB. Details

When coupled systems become synchronized, the courses of events in each system are strongly correlated. In a great number of ecological systems, this applies to changes in the abundances of the same species in different spatial patches. This form of demographic synchrony has traditionally been explained by two independent synchronizing mechanisms: coupling of patches through migration between patches, and dependence of population dynamics in different patches on fluctuating common environmental factors. Given the plethora of populations with wild local dynamics but synchronized global behavior encountered in nature, also Darwinian evolution may contribute to synchrony. The purpose of my project is to investigate this conjecture through the analysis of different dynamic ecological models of coupled populations subject to evolution. Details

While all plants use the common resources of light, water, and nutrients for growth, there is great diversity among species in rates of use and mix of inputs. Much of this diversity is thought to reflect the evolutionary diversification of a few key traits in response to frequency-dependent resource competition. The aim of this project is to investigate how competition for light leads to such evolution, diversification, and coexistence of a range of growth strategies in environments with repeated disturbance. Plant growth will be modeled based on well understood physiology, with competition between individuals giving a fitness advantage to strategies able to pre-empt light availability through height growth. The phenotypic evolution of two traits, growth rate and height at reproductive maturity, will then be explored. In particular, I will investigate: (1) whether an initially monomorphic population undergoes evolutionary branching, (2) if multiple strategies can coexist at the evolutionarily endpoint, and (3) whether the dynamics lead to correlated evolutionary divergences of traits across species. Details

Explaining the origin and development of species diversity is one of the greatest challenges in biology. To meet this challenge, it is necessary to achieve a better understanding of speciation processes. Past research has highlighted the importance of spatial population structure for the eco-evolutionary processes underlying speciation. The central role of geographic isolation in classical speciation theories illustrates this point. Recently it has also been shown in natural populations that non-random dispersal results in the genetic differentiation of fitness-related traits. In this project I will examine an individual-based, spatially and genetically explicit model of organisms with sexual reproduction. Focusing on sympatric conditions and uniform environments, I will investigate how conditions for evolutionary branching are influenced by spatial population structure. In particular, I will analyze the influence of the spatial ranges for competitive interaction, mate choice, and offspring dispersal. Details

In this project, I will focus on the ecological and evolutionary effects of size-selective fishing on stocks with female mating preferences. In particular, I will examine (i) if the maladaptation of female preferences can reduce the yield, stability, or recovery potential of exploited stocks, (ii) if size-selective fishing is likely to cause evolutionary changes in the mating strategies adopted by females, and (iii) how trajectories and outcomes of female preference evolution depend on harvesting regimes, natural ecological conditions, life-history traits, and the initial preference of females. To address these questions, I will develop an individual-based eco-genetic model describing an iteroparous species, in which both mate choice and harvesting are size-dependent. Populations will be structured with respect to age, size, and sex, and individual females will be characterized by their mate preference. Female preferences for male size will be directional, implying preferences increasing with the size of males, or matching, implying size-assortative mating. Harvesting strategies will either correspond to a minimum-size limit or to a size-slot prescription. Details

We use an adaptive dynamics model to study how the body size of a predator and its preference for a certain prey size jointly evolve. In particular, we investigate how the corresponding evolutionary patterns and outcomes depend on environmental parameters such as food availability and on ecological parameters such as encounter rate and handling time. Results could provide insights into the factors that determine the structure of natural communities and may explain some of the predator-prey patterns observed in nature. Details