Polymorphism is common in the natural world. In many damselfly species (Odonata) multiple female morphs are encountered in natural populations. Typically, two distinct morphs occur. While one female morph (called the andromorph) resembles the conspecific male in body colouration and sometimes behaviour, the other morph (called the gynomorph) is distinct. Recent studies suggest female polymorphism to be genetically determined and female morphs to face differential selective pressures. As such, it is widely believed that the polymorphism results from sexual conflict in which females have evolved traits to avoid excessive male harassment. The overall goal of my doctoral research is to come closer to understanding the maintenance and evolution of female-limited polymorphism.
My main focus will be on evaluating the following questions:
¿Although a crucial assumption, evidence remains circumstantial on whether male harassment affects female fitness negatively, and does so differential with respect to female morph. This question will be studied experimentally by exposing female morphs to variable numbers of copulations and levels of male harassment while determining female morph longevity and fecundity. In addition levels of male harassment will be quantified in natural populations that differ in male densities and female morph frequencies. Also, I will evaluate whether female morph behaviour is variable under such different densities and frequencies.
¿Quantifying the spatial and temporal variation in female morph frequencies and male densities. This will be achieved through standardised sampling in natural populations using fixed transects or a uniform sample technique with an insect net.
¿Differences in body colouration and/or behaviour may have relevance for a species' thermal ecology, especially for ectothermic insects such as damselflies. Generally darker individuals heat up faster then paler ones which allows them to achieve a higher activity level (e.g. predator avoidance, egg maturation) under unfavourable weather condition, ultimately resulting in fitness advantages. Thus, I will study thermal characteristics of males and female colour morphs under laboratory conditions and in the field.
¿Several hypotheses suggest female morphs to vary in costs and benefits under different environmental conditions and assume female morph fitness to be variable. I will study variation in female morph condition (by determining several long-term and short-term signals) under varying environmental conditions (throughout an entire flight season). Different signals may indicate individual condition during different periods within an individual's lifetime. Body size and developmental stability (fluctuating asymmetry) reflects past (larval) history, whereas short-term signals depend on current nutritional status and are highly sensitive to changes in the environment.