Evolutionary Ecology

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We conduct evolutionary behavioural ecology research, asking questions about the adaptive evolution of behavioural strategies, and their genetic architectures, within an ecological context. Our research is motivated by behavioural ecology, life-history, and quantitative genetics theory, and seeks to test predictions and assumptions of adaptive theory using observational and experimental approaches in the laboratory and the wild.

We monitor 12 nest box populations of a passerine bird model (the great tit) south of Munich since 2010, providing unique longitudinal data of breeders and their offspring with respect to various key life-history and behavioural traits. We can thus uniquely study the action of selection and why it may favour a modular trait structure, such as represented by the integration between life-history and behavioural strategies (‘pace-of-life syndromes’) in the wild.

We focus on behaviours mediating the trade-off between current and future reproduction, such as aggressiveness and exploratory tendency, and use large-scale population-level environmental manipulations (predation risk, resource availability) to study how the interaction between ecological and population-level processes shape the adaptive evolution of trait integration in the wild. We use genetic pedigrees to estimate parameters key in testing evolutionary theory in the wild, while laboratory studies of pedigreed insect models (field crickets) further allow us to study how the interaction between genes and environment (e.g. diet, competitive regimes) shaped the genetic architecture of life-history behaviour.

Our group is further at the forefront of the development of statistical tools to quantify multi-level and multi-variate variation. For example, we have developed with a team of international collaborators an educational software package entitled SQUID (Statistical Quantification of Individual Differences) that enables self-teaching and research into mixed-effects modelling analyses and optimal sampling designs.

Evolutionary ecology of behavioural stability in natural bird populations

Funded by the German Science Foundation, PhD-students Alexander Hutfluss and Alexia Mouchet

Recent studies have provided compelling evidence for the existence of individuality in average behaviour (animal personality), responsiveness to environmental change (individual plasticity) and within-individual variability (behavioural stability). While research has thoroughly investigated the evolutionary ecological causes and consequences of personality and individual plasticity, this is not so for individuality in behavioural stability. Theory postulates that stable phenotypes are costly to produce (thus under sexual selection), or affect predation risk (thus under natural selection). The overarching objective of this DFG-project is to study the proximate and ultimate mechanisms shaping (the integration between) individual variation in personality, behavioural plasticity, and behavioural stability in the wild. Our specific objective is to study how the expression of within- and among-individual variance in each of these three types of behavioural characteristics, as well as their associations with key fitness components, vary with competitive regimes. We are focusing on stability in bird song, using pedigreed wild populations of great tits as a perfect model system. We are executing large-scale manipulations of competitive regimes (population density in particular) to test its role in causing heterogeneous selection acting on behavioural stability in bird song and its hypothesized correlates (key behaviours: aggressiveness and exploratory tendency). Our setup (12 nest box plots with 50 boxes each) is ideal for performing large-scale manipulations, with which we have ample experience.
We study proximate and ultimate perspectives in conjunction. We are identifying the sources of variation in behavioural stability, and determine (i) whether stability in bird song varies plastically within individuals as a function of the perceived amount of competition for resources, and (ii) whether stability in bird song shows long-term repeatability and heritability, and whether it is correlated with other key behaviours. We also focus on how selection acts on this variation, and determine (iii) the direct and indirect pathways by which selection acts on behavioural stability (e.g., via within- or extra-pair paternity, or survival), (iv) whether selection on behavioural stability fluctuates spatiotemporally (e.g., as a function of food availability and breeding density), and (v) whether fluctuating selection on correlated traits helps maintain individual variation in behavioural stability. We thereby forcefully combine proximate and ultimate viewpoints in studies of the adaptive integration of personality, individual plasticity, and behavioural stability in wild populations.top

How social environments affect the selection on animal behavioural types

Funded by the Alexander von Humboldt Foundation and the German Science Foundation, Postdoc Petri T. Niemelä, Advisor: N.J. Dingemanse

The social environment, i.e. interactions between conspecifics, represents one of the most dynamic environmental forces that individuals face, because the individual’s own behaviour as well as conspecifics’ behaviours jointly defines the frequency and intensity of the interactions. Overall fitness of an individual is expected to depend not only on its own behavioural type, but also on the interaction between its own behavioural type and the composition of behavioural types in the population (i.e. its social environment). Differences between behavioural types in time budget conflicts (i.e. activity in one context is adaptive while in other context it is maladaptive) are suggested as one of the main mechanisms mitigating fitness differences between behavioural types in nature and may depend on the social environment. However, despite its role in competition, co-operation and mating, the ecological and evolutionary implications of the social environment have largely been neglected in animal personality studies. In this project, I study 1) whether behavioural plasticity is a function of behavioural type and the social environment and if 2) differences in life-time reproduction success depend on the interaction between behavioural type and social environment. As a model species, I use native field cricket species, Gryllus campestris.top


The role of pre- and post-mating sexual selection on trait evolution: from ejaculates to behaviour

Funded by the DFG to Dr. Cristina Tuni

Understanding how pre- and post-mating sexual selection interact to shape the evolutionary diversification of reproductive traits remains a challenge in sexual selection research. Despite being fundamentally linked, these two episodes of selection have been traditionally studied apart. By making use of the field cricket (Gryllus bimaculatus) as an insect model system this project aims to understand how sexual selection shapes complex phenotypes by quantifying the relative contribution of pre- and post-mating selection to male reproductive fitness and key reproductive traits (behaviour, morphology, and ejaculates). It will examine whether their contribution is altered across social environments varying in the opportunity and strength for selection, and uncover correlated evolution and/or evolutionary trade-offs between pre- and post-mating traits.

The evolutionary ecology of social responsiveness in a wild insect

Funded by the DFG, Postdoc Petri T. Niemelä, Advisor: N.J. Dingemanse

Social evolution theory has been developed in the field of quantitative genetics, where the effects of social interactions on evolutionary processes are of main interest. Social evolution is also increasingly studied in behavioral ecology, where recent research focuses on understanding the conditions favoring phenotypic plasticity in response to the phenotype of conspecifics (‘social responsiveness’). Social responsiveness is assumed to have evolved because it allows for the adaptive modification of costly signals in dynamic social environments, thereby increasing its relative fitness benefits. Interestingly, directional selection is normally expected to deplete standing variation in social responsiveness unless mechanisms constraining its evolution act simultaneously or instead. This could occur, for instance, when less responsive individuals adopt alternative mating tactics with negative frequency-dependent fitness pay-offs. Alternatively, or additionally, fitness pay-offs associated with social responsiveness may vary as a function of (a)biotic factors. Social responsiveness should thus be studied in an ecological context in the wild to further our understanding of its evolution in natural populations. In my project fully integrate concepts developed in behavioral ecology and quantitative genetics by studying selection on social responsiveness directly in the wild by using field cricket, Gryllus campestris, as a model. My main questions are i) whether social responsiveness is under selection, ii) the exact pathways by which selection acts on social responsiveness and ii) whether individual differences in social responsiveness represent alternative reproductive tactics.top

The role of social environments in behaviour-related settlement decisions in a wild passerine bird

Funded by the DFG, Postdoc Benedikt Holtmann, Advisor: N.J. Dingemanse

Repeatable individual differences in behaviour (often referred to as ‘animal personality’) are ubiquitous among animal species. In recent years, evidence has accumulated that individuals do not disperse randomly, but aggregate in habitats that best match their own personalities. Such non-random assortment of behavioural phenotypes may have implications for an individual’s fitness, as well as the social dynamics of the whole population. While theoretical concepts of the interplay between animal personality, the distribution of behavioural phenotypes, and the social environment have been developed, their relationship remains poorly understood in natural populations. In this project, I will, therefore, investigate how social structures within wild populations drive the assortment of behavioural phenotypes (and vice versa) and what fitness consequences result from such interactions. I will use the great tit (Parus major) – a key species in animal personality research – as a study system. In this project, I will first examine how the composition of the local social environment affects the settlement and fitness of different behavioural phenotypes. Second, by experimentally altering the social structure, I will test if individuals actively settle in social neighbourhoods, which match their own personalities, or whether the settlement is a random process. Overall, the proposed project will advance our understanding of how selection acts on behavioural traits and provide novel insights into the ecological and evolutionary dynamics of the spatial structuring of communities in natural populations.