Final Report Summary - SUPAFLY (Multivariate selection and human-induced environmental stress: Adaptive genetic and plastic responses in the yellow dung fly) One of the main tasks of evolutionary ecology is to characterise and explain the causes of phenotypic variation. Quantifying the relative contribution of genetic and ecological processes and their interaction is also important to predict future response of populations to human-induced environmental changes. The overall goal of this project is to determine whether and to what extent two simultaneously induced new selection pressures are likely to slow or accelerate evolution relative to the case where only one selection pressure is present. Using the yellow dung fly (Scathophaga stercoraria) as a model system the project aimed at collecting data on the nature of multivariate selection in the wild, assessing genetic architecture, phenotypic plasticity and evolutionary potential under laboratory conditions and develop and parameterise a predictive model for dung fly performance under future climate scenarios. The project has investigated how different forms of stress influence survival, development and growth, reproduction and morphology and how environmental factors influence genetic architecture of life-history traits. Firstly, to investigate the extent to which morphological characters affected by stress are important for reproductive fitness, we have compared the form and intensity of pre- and postmating sexual selection on male morphology in the field. Some of the sample processing remains before data analysis can commence, but we expect to be able to present the results at conferences and in scientific papers from summer 2013. Secondly, quantitative genetic laboratory experiments have shown that there is substantial genetic variation for a number of life-history traits such as larval development time, adult morphology and survival. Thirdly, we have studied the ability of male and female flies in different genetic lineages to cope with three kinds of stressful environment; low food availability, high temperature and the antiparasite veterinary medication Ivermectin. Fourthly, we have tested if genetic variation for resistance to environmental stress is associated with suboptimal performance in other aspects of life-history. Fifthly, we have investigated synergistic effects of multiple stresses on life-history traits we subjected larval yellow dung flies to Ivermecin in combination with another stress factor; restricted food or high temperature. Sixthly, to assess the influence of multiple environmental stress on the genetic architecture of adaptive traits we raised half-sib families under single and multiple stressful environments. For this work we have developed procedures for assessing morphology of adult flies, including dissecting flies, mounting body parts on measurement sheets, photographing and digitally measuring morphology. The initial goal of this task was to develop, parameterise and test a model of eco-evolutionary dynamics under different predicted climate scenarios. Finally, while a relative good amount of data exists on larval growth, development and mortality under different environmental conditions and we have data on the effects of stressfully high temperatures on female fecundity and male success in siring offspring, less is known about adult longevity and mortality. The planed model will thus have to be based on certain assumptions about average and variation in lifespan and is under development. The yellow dung fly, Scathophaga stercoraria is not particularly resistant to high temperature stress; survival, growth, development and reproductive performance in both sexes are reduced under high temperature conditions. All of these traits could potentially influence population dynamics and the persistence of populations, but the extent to which they do is still unclear. This is partly because extrapolating from single stress experiments to the complexity of natural environments is challenging. Therefore, this project has taken this field of research a step further by in simultaneously assessing how antiparasitic pharmaceuticals excreted in cow dung (an important human-induced stressor relevant to wild flies) complicate phenotypic and evolutionary responses to temperature and other kinds of stress. The results will be the basis for further research on the translation of individual-level effects of stress to population-level effects. For instance, by manipulating the constancy of the pharmaceutical stress my future aim is to clarify how coincident selection can help or hinder thermal adaptation to new temperature regimes, using: 1. selection experiments in which we artificially select for increased temperature tolerance in the presence or absence of pharmaceuticals and 2. natural evolution experiments in which replicate lab populations are allowed to adapt to temperature regimes without intervention. Finally, I plan to use the results of the experiments from the SUPAFLY project to investigate food web responses to multiple stress with both experimental and theoretical approaches, such as dynamical models of food webs exposed to different combinations of abiotic environmental stress (e.g. high temperature, pharmaceuticals) and food resource levels to predict the stability of food webs under climate change.
