Evolutionary Biology

Phenotypic plasticity describes the ability of individual genotypes to develop alternative phenotypes in different environmental settings. Such plasticity is therefore a central concept for our understanding of adaptive evolution as it offers organisms a flexible way to optimally adjust to current conditions. This is especially important for organisms living in a variable and to some extent unpredictable environment and that are constrained in their ability to move to more favourable sites.

Phenotypic plasticity concerns essentially all types of biological traits, including physiological, morphological, life-history and behavioural traits. Illustrative and well-studied examples include environment dependent sex determination in many reptiles, predator-induced morphological defence in many animals (such as tadpoles and Daphnia), and nutrition-dependent phenotypic plasticity of horn development in beetles. Analysing individuals’ norm of reaction to environmental cues can thus offer an exciting and powerful tool to study ecological adaptations.

However, organisms also differ widely in the degree of plasticity. Some species are more plastic than others, and even within species, there is often genetic variability in plasticity, commonly observed as genotype × environment interactions. Hence, plasticity itself is an evolvable trait, which offers the opportunity to explore under which circumstances it is beneficial to be more or less plastic.

Current Focus of Research

We study the evolution of phenotypic plasticity for a variety of traits in different species, but with a strong focus on traits associated with life-history and sexual selection. Current projects include:

• The effect of seasonality and food limitation on growth, body size, metabolic rate, and reproductive behaviour in scorpionflies
• Phenotypic plasticity of sperm traits in insects, birds, and hermaphroditic flatworms
• Effects of larval food and density on adult courtship behaviour and behavioural plasticity in moths
• Plasticity of behaviour associated with food acquisition - such as foraging, intra- and interspecific aggressiveness around food items, and risk-intensive kleptoparasitism - in scorpionflies

Although plasticity is an effective way to adjust to variable environment, many animal behaviours are surprisingly consistent – both over different environments and over time. This constrains how plastic an individual’s behaviour can be. In this respect, we study how and when consistent behaviour – and, consequently, reduced plasticity of behaviour – develops throughout the ontogeny of a model species, the lesser wax moth. We also use theoretical approaches to address adaptive phenotypic plasticity.