Quantitative Trait Evolution in a Changing Environment in a Seed Beetle

Abstract: During the last decades the climate has been changing more rapidly than in the preceding periods. This is for instance characterized by an increase in temperature. Interestingly, such changes in the environment are not necessarily constant over time as they often show high levels of fluctuation. Organisms are exposed to these changes and respond to them and a recent theoretical model predicts that fluctuations in the environment are important for populations’ response to climate change. The aim of this thesis is to investigate how populations respond to a changing environment, including fluctuations. My thesis is based on the previously mentioned theoretical model and I used a suite of laboratory experiments on the seed beetle Callsosobruchus maculatus, to test the model predictions in a quantitative genetic framework. First, I assessed the genetic architecture of several life history and morphological traits in order to verify that there is sufficient additive genetic variation for the population to respond to changes in the environment. Second, I tested the detailed model predictions explicitly, by investigating whether different types of environmental fluctuations matter for a population’s response. Third, I investigated changes in quantitative genetic variation after i) a rapid shift in temperature and ii) long term selection under increasing temperature including fluctuations. Fourth, I concentrated on sex differences in response to temperature, and finally, I assessed the relative importance of genetic and nongenetic inheritance for traits that differ in their plastic response to a change in the environment. I found that environmental fluctuations are highly important for a population’s response to environmental change. I could detect changes in a set of quantitative genetic parameters, suggesting that a population’s potential to respond to selection, environmental sensitivity and the evolution of phenotypic plasticity are affected by the selective past. I also found that sexes differ in additive genetic variation and plasticity and that parental effects may play an important role in the evolutionary process. Therefore, future studies would benefit greatly from considering details of the selective past and especially environmental fluctuations during attempts to predict how populations respond to a changing environment, particularly with regards to climate change.