Individual animals of the same population often differ consistently in their (suites of) behaviours across time and context (so-called ‘personality’ and ‘behavioural syndromes’) and their degree of behavioural plasticity. These differences are intriguing because high behavioural flexibility should be favourable and yet it is far from being the norm. In my work, I am interested in understanding why this is the case, how is such variation maintained through time and how it affects the populations. In my recent work, I aim to integrate both an eco-evolutionary perspective to understand when and why selective pressures favour the evolution of stable individual differences with a proximate perspective to study the mechanisms responsible for the emergence and stability of personality variation.

My main research projects involving sticklebacks,flycatchers and great tits are listed below:

Stickleback project (2017-current)

Recently, I set-up two PhD projects on three spined sticklebacks (Gasterosteus aculeatus), a species very well suited for the study of personality and local adaptation processes. We are making use of a unique unintended experiment in the field (isolation of a migratory population) in combination with experiments in semi-natural ponds to study how personality variation emerges, evolves and feedback on eco-evolutionary processes. This research is performed in collaboration with Franjo Weissing and Ton Groothuis from the university of Groningen and with colleagues from van Hall Larenstein and the waterboard Hunze en Aa’s.

we use automated tracking in the wild and in semi-natural ponds to study how behavioural variation emerges and how it can affect adaptation to human-induced changes (credit:mavromatika)
  • The eco-evo-devo of migration syndromes (PhD project, Aparajitha Ramesh 2017-present):

In her PhD, Apu combines theoretical modelling and empirical studies to characterise personality differences between resident/migratory populations, determine the underpinning ontogenetic mechanisms of migration syndromes (‘eco-devo’ and ‘evo-devo’), and study the eco-evolutionary causes and consequences of individual variation in dispersal/migration (‘eco-evo’).

migratory (up) and land-locked (bottom) three-spined sticklebacks (photo credit: Ben Kawam)

  • The eco-evo-devo of social persoanlities (PhD project, Jakob Gismann 2019-present):
  • Jakob’s project aims to investigate the emergence and stability of social personalities (individual differences in social behaviour) in relation to the local environment. Using experiments in semi-natural ponds and theoretical modelling, Jakob scrutinizes how individual development depends on the environment (‘eco-devo’), whether and when the stability of social personalities is adaptive (‘evo-devo’), and how the mechanistic implementation of social personalities affects the distribution and evolvability of populations (‘eco-evo’).

    (photo credit: Ben Kawam)

    Flycatcher project (2015-present):

    Pied flycatchers (Ficedula hypoleuca) are small migratory birds that winter in Africa and readily breed in nest boxes in the Netherlands. They are often studied in the context of climate change because some populations were found to be unable to keep up with fast changing environmental conditions. Most work on has focused on whether flycatchers can adapt to changes via phenotypic plasticity and/or evolutionary adaptation. The role of adaptive dispersal has however been largely neglected.

    Therefore, my project investigates the role of dispersal in local adaptation process. Specifically, I aim to test if individual differences in dispersal tendency and associated competitive abilities (dispersal syndromes) are adaptive and may help populations to buffer environmental variation. This research performed in collaboration with Christiaan Both includes many subquestions such as:

    1. Are dispersers a non-random sample of the population? To answer this question, I apply different approaches. For example, I use quantitative genetic tools to quantify the amount of phenotypic and genetic variation in dispersal, life-history, morphological and behavioural traits and their underlying architecture (existence of phenotypic and genetic correlations among traits, i.e. ‘dispersal syndrome’). I also use natural colonization data to study if dispersers that settle successfully in new available habitats differ in their phenotype compared to philopatric individuals.
    2. Are dispersal syndromes stable and adaptive? For two years I performed a unique translocation experiment in the field where pairs of known personality were forced to breed in a new environment. By measuring individual aggression level before and after dispersal, and measuring the fitness of translocated pairs I can test whether high level of aggression is the cause or the consequence of dispersal and whether trait integration is beneficial to thrive in new habitats.
    3. What are the population consequences of dispersal syndromes? The existence of syndrome imposes that dispersal (and thus gene flow) is non-random. Using Individual Based Modelling (work in collaboration with Pim Edelaar) and field data, I quantify how population dynamics, structure, evolvability and persistence are affected by non-random gene flow.
    I used a ‘forced dispersal’ experiment using outdoor aviaries (left) and simulated territorial intrusion (right) to study the causes and consequences of dispersal syndromes

    Work that I co-supervise:

    Dispersing to northern breeding areas as adaptation to climate change (PhD project, Koosje Lamers 2017-present). Using translocation between the Netherlands and Sweden combined with a common garden experiment, Koosje’s project aims at quantifying the costs and benefits of long-distance dispersal and at establishing if the timing of the annual migratory cycle is determined by genes or ontogeny

    Evolution of annual timing (PhD project Xuelai Wang 2017-present). Using timing experiments in the wild, tracking data, and animal models Xuelai investigates the sources of variation in timing of arrival and lay date. She is particularly interested in how conditions experienced early in life can shape phenotypes.

    Great tit project (2010-2015):

    Fitness causes and consequences of individual differences

    To understand why individuals so greatly differ in behaviour and reproduction, we need to manipulate individual decisions and quantify the subsequent fitness consequences. In great tits, there exists a large variation in reproductive decisions and in levels of “risky” behaviours among individuals.

    To this end I have conducted large scale experiments that tested:

    1.  whether personality represents adaptive variation tuned to individual ‘state’
    2. if personality variation is linked to life-history strategies
    3.  whether individuals differ in levels of adaptive plasticity
    I used brood size manipulation to manipulate individual ‘state’ and study adaptive personality variation

    How are individual differences maintained?

    A central aspect of my research focuses on role of social effects in phenotypic evolution. Because most animals are social and experience fluctuations in their social environment, density- or frequency-dependent selection is likely to be a crucial mechanism in the maintenance of trait genetic variation in animal populations. Yet, behavioural traits are often correlated, and this underlying architecture may affect the trait-space that can evolve and affect whether/how populations may respond to selection.

    Using descriptive long-term and experimental data, I have shown that:

    1. population density variation (and presumably intraspecific competition level)  is as an important factor driving fluctuating selection onpersonality and maintaining genetic variation within popualtions5
    2. genetic correlations among behavioural traits can affect pace of microevolution