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.

Blue and great tit research - We monitor 12 nestbox plots situated in the Forstenrieder Park, south of Munich. Here we collect unique longitudinal data of blue and great tit breeders with respect to various key life-history, morphological and behavioural traits. Much of our research focuses on behaviours mediating the trade-off between current and future reproduction, such as aggressiveness and exploratory tendency. Our main approach consists of performing largescale multiyear environmental manipulations (e.g. of predation risk, resource availability, competitive regimes) aimed at revealing the causal pathways shaping selection and evolution of behaviour and life-history. An important current line of research focuses on how selection acts on the integration of life-history and other phenotypic traits into “pace-of-life syndromes”, where we consider the key role of intra- and interspecific competition in shaping selection on life-histories and pace-of life syndromes. We study these question using social selection, indirect genetic effects, and social evolution paradigms.

House sparrow research – Much of our research focuses on the causes and consequences of effects that individuals have on each other’s phenotypes and fitness. We study individual and genetic variation in social responsiveness to phenotypes of conspecifics as well as the social impact that individuals have on others. As a study model to investigate such indirect genetic effects we focus on social foraging behaviour in house sparrows, which we study with international collaborators.

Multi-level statistical tools - Our group is at the forefront of the development of statistical tools to quantify multi-level and multi-variate variation. 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.

Social competition within- and among-species: drivers of pace-of-life in wild passerine birds?

Grant of the German Science Foundation to Niels Dingemanse; PhD-student Merit Prokriefke and postdoc Barbara Class

Contemporary behavioural ecology increasingly focuses on the question of why individual animals differ in suites of correlated behavioural and morphological traits, whether those differences are associated with life-history variation, and whether life-history trade-offs can explain the evolutionary maintenance of this variation in “pace-of-life”. There is considerable debate on this issue because life-history trade-offs cannot by themselves maintain variation. My overarching aim is to test the predictions of a novel eco-evolutionary explanation that has great potential to resolve this debate. The framework has wide applicability, and can explain variation among species, populations, genotypes, and individuals alike. We propose that variation in pace-of-life results from a trade-off between intrinsic rate of density-independent reproduction and competitive ability.

This incorporates ecological variation required to maintain variation as faster (vs. slower) paces-of-life are favoured when competition for resources is relaxed (vs. intensified). We will test this new idea by combining behavioural ecology and quantitative genetics, and by applying experimental and population comparative approaches. Key objectives are: (WP1) To manipulate intra- and interspecific competitive regimes as drivers of selection on pace-of-life syndromes within and among species; we will use sympatric nest box populations of blue and great tits as a perfect model. (WP2) To use DNA metabarcoding of faecal samples to acquire quantitative estimates of relative abundances of arthropods (and the plants those ate) in the tits’ diet to study whether habitat selection and dietary specialisation mediate pace-of-life-related adaptations to intra- and interspecific competitive regimes. (WP3) To study whether competition-related selection on pace-of-life can explain variation in behaviour, morphology, and life history among populations, among-genotypes within populations, and among-individuals within genotypes, thus, among all major levels of the biological hierarchy.

This latter aim will be achieved using long-term pedigreed datasets of >40 European blue and great tit populations monitored by European researchers collaborating through SPI-Birds. The proposed work will provide crucial new insights in the adaptive integration of behaviour, morphology, and life history, and the role of intra- and inter-specific competition as drivers of the maintenance of variation among species, populations, genotypes, and individuals in natural populations.

Ecology and evolution of social impact and responsiveness in a wild sparrow population

Grant of the German Science Foundation to Niels Dingemanse; PhD-students Corné de Groot & Rori Wijnhorst

Social interactions characterize all wild populations and affect evolution whenever heritable traits are plastic in response to heritable traits of conspecifics. The evolution of “social responsiveness” to and “social impact” on other’s phenotypes has attracted theoretical attention, but progress requires addressing key outstanding questions: Do wild populations contain individual variation in degrees of social impact and responsiveness? Does selection act on this variation, and which processes maintain it?

These key challenges will be addressed in a research programme to understand social evolution. My overarching aim is to combine the strengths of cutting-edge behavioural ecology and quantitative genetics theory to uniquely study the interplay between social interactions and social selection in the wild. I will focus on social foraging strategies in house sparrows on Norwegian islands that use either private information and actively find food (“producers”) or social information to exploit food patches found by others (“scroungers”). Game theory predicts and empirical studies on this and other species have shown socially responsive shifts towards scrounging when others produce, and vice versa. Using innovative high-throughput behavioural screening of entire populations, I will assay >600 birds for their producer-scrounger social impact and responsiveness in >4,000 assays and determine genomic relatedness, survival, and reproductive fitness for all individuals.

Key objectives are: (WP1) To establish whether individuals are repeatable in (i) average level of producing-scrounging (“personality”), (ii) level of adjustment in producing-scrounging to phenotypes expressed by partners (“social responsiveness”) and (iii) producing-scrounging elicited in partners (“social impact”). I will quantify covariances between these ‘traits’, describe (social) environmental sources of variation within and among individuals, and test for covariances with various key behavioural (aggression, exploratory tendency) and morphology traits (body size and shape) predicted by adaptive theory. (WP2) To quantify how natural selection acts on producing-scrounging reaction norms and study whether selection pressures covary with key socioecological conditions; and thus determine the pathways (components of fitness) by which selection acts on this variation in the social phenotype in this well-studied system. This will make it possible to start exploring the potential evolutionary consequences of selection on social impact and responsiveness in the wild, thereby providing crucial new insights into the evolution of social behaviour and the role of social interactions in ecological and evolutionary processes.

Human persecution as an evolutionary driver of individual variation in risk perception of an apex predator

Grant of the German Science Foundation to Anne Hertel (Eigene Stelle)

Behavior plays a pivotal role in shaping predator-prey interactions with prey showing remarkable adaptive behavioral plasticity in response to predation risk. In the wild, predation risk is variable in space and time which creates a landscape of fear through which prey species move. Experimental behavioral ecologists have studied individual variation in prey responsiveness to risk for the past two decades, however individual variation has not been formally integrated into landscapes of risk in the wild.

I will use the brown bear (Ursus arctos) as a model species to test predictions from behavioral ecology theory in the wild. As apex members of the trophic community, the brown bear’s landscape of fear consists of a single predator – humans. For no other predator do we have such excellent records of the intensity of past and current predation pressure (i.e. hunting), as well as spatiotemporal predator presence, as we do for humans. I will evaluate the extent, heritability, life history consequences, and evolutionary drivers of individual variation in human avoidance behavior of brown bears. I have access to a unique dataset of long-term monitoring data (> 25 years) of brown bears in Sweden, including movement data for more than 170 individuals, documentation of complete life histories (e.g. annual reproduction, survival), annual diet and stress metabolite determination, and a pedigree spanning 7 generations and virtually the entire study population. This dataset will enable me to answer questions related to the extent and heritability of individual variation in spatiotemporal human avoidance behavior and the life-history consequences (e.g. through lost feeding opportunities) arising from human-avoidance behavior. If behavioral variability is heritable, human hunting may selectively target and remove certain behavioral types from the population leading to less behavioral variability in remnant populations.

I will test this hypothesis in a natural experiment by compiling movement behavior data from 10 extant brown bear populations world-wide which have been exposed to different historic persecution pressures. I will test whether the long and selective persecution history in Europe has eroded behavioral variability as compared to the comparably short and unselective persecution in North America. My proposed project will answer research questions at the forefront of behavioral and evolutionary ecology.

Social interactions: constraints or driving forces of evolution?

Scholarship of the von Humboldt Foundation to Tom Ratz

Understanding how organisms respond to changes in their environment is a major goal of current research in ecology and evolution. Yet the responses to environmental change are obscured by social interactions taking place among conspecifics. Social interactions can facilitate or constrain the response to selection and make the evolutionary trajectories difficult to predict. The goal of my project is to investigate how social interactions alter the potential for evolution using the Mediterranean field cricket Gryllus bimaculatus as a study system. The first aim of the project will be to examine the evolutionary impact of interactions taking place during mating and aggression.

The second aim will be to test whether variation in population density, which greatly influences the occurrence of social interactions and their outcome, shapes the evolutionary potential of a population. To do so, I will first combine a breeding design with behavioural assays and statistical methods to determine whether social interactions increase or reduce the total heritable component of a phenotype and the intensity of selection acting on it. I will next manipulate population density in two experimental group to test whether density determine to which extent social interactions affect the heritability and evolutionary potential.

Overall, I expect that antagonistic interactions such as same-sex aggression represent a constraint to evolution, whereas positive interactions such as mating behaviour represent a driver of evolution. This project will contribute to refining the theory in evolutionary biology by incorporating social interactions as a novel component often overlooked in models forecasting evolution in changing environments.