| 1. |
- Hallsson, Lára R., 1983-
(author)
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Quantitative Trait Evolution in a Changing Environment in a Seed Beetle
- 2011
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Doctoral thesis (other academic/artistic)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.
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| 2. |
- Hallsson, Lára R., 1983-, et al.
(author)
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Selection in a fluctuating environment and the evolution of sexual dimorphism in the seed beetle Callosobruchus maculatus
- 2012
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In: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 25:8, s. 1564-1575
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Journal article (peer-reviewed)abstract
- Sexual dimorphism can be affected by environmental variables such as temperature. There are two hypotheses regarding sex differences in plasticity in a changing environment: the adaptivecanalization hypothesis, and the condition–dependence hypothesis. Here we use a quantitativegenetic framework to test these hypotheses and to investigate both immediate changes in, and theevolution of, sexual dimorphism in response to a changing environment (with and withoutfluctuations). We found a decreased sexual size dimorphism in higher temperature and femalesresponded more plastically than males, supporting the condition dependence hypothesis. However,selection in a fluctuating environment can alter sex-specific patterns of genetic and environmentalvariation, indicating support for the adaptive canalization hypothesis. Also, genetic correlationsbetween sexes (rMF) were affected by fluctuating selection, suggesting a facilitated independent evolution of the sexes. Thus, the selective past of a population is highly important for theunderstanding of the evolutionary dynamics of sexual dimorphism.
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| 3. |
- Hallsson, Lára R., 1983-, et al.
(author)
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Selection in a fluctuating environment leads to decreased genetic variation and facilitates the evolution of phenotypic plasticity
- 2012
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In: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 25:7, s. 1275-1290
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Journal article (peer-reviewed)abstract
- Changes in the environment are expected to induce changes in the quantitative genetic variation, which influences the ability of a population to adapt to environmental change. Furthermore, environmental changes are not constant in time, but fluctuate. Here, we investigate the effect of rapid, continuous and/or fluctuating temperature changes in the seed beetle Callosobruchus maculatus, using an evolution experiment followed by a split-brood experiment. In line with expectations, individuals responded in a plastic way and had an overall higher potential to respond to selection after a rapid change in the environment. After selection in an environment with increasing temperature, plasticity remained unchanged (or decreased) and environmental variation decreased, especially when fluctuations were added; these results were unexpected. As expected, the genetic variation decreased after fluctuating selection. Our results suggest that fluctuations in the environment have major impact on the response of a population to environmental change; in a highly variable environment with low predictability, a plastic response might not be beneficial and the response is genetically and environmentally canalized resulting in a low potential to respond to selection and low environmental sensitivity. Interestingly, we found greater variation for phenotypic plasticity after selection, suggesting that the potential for plasticity to evolve is facilitated after exposure to environmental fluctuations. Our study highlights that environmental fluctuations should be considered when investigating the response of a population to environmental change.
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| 4. |
- Hallsson, Lára R., 1983-, et al.
(author)
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Sex specific genetic variances in life history and morphological traits ofthe seed beetle C. maculatus
- 2012
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In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 2:1, s. 128-138
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Journal article (peer-reviewed)abstract
- Knowledge of heritability and genetic correlations are of central importance in the study ofadaptive trait evolution and genetic constraints. We use a paternal half-sib-full-sib breeding designto investigate the genetic architecture of three life history and morphological traits in the seed beetle, Callosobruchus maculatus. Heritability was significant for all traits under observation andgenetic correlations between traits (rA) were low. Interestingly we found substantial sex-specificgenetic effects and low genetic correlations between sexes (rMF) in traits that are only moderately(weight at emergence) to slightly (longevity) sexually dimorphic. Furthermore we found anincreased sire (s2sire) compared to dam (s2dam) variance component within trait and sex. Our resultshighlight that the genetic architecture even of the same trait should not be assumed to be the samefor males and females. Furthermore it raises the issue of the presence of unnoticed environmental effects that may inflate estimates of heritability. Overall, our study stresses the fact that estimatesof quantitative genetic parameters are not only population, time, environment but also sex specific.Thus, extrapolation between sexes and studies should be treated with caution.
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| 5. |
- Hallsson, Lára R., 1983-, et al.
(author)
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The colour of noise matters for the response of a population to environmental change
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Other publication (other academic/artistic)abstract
- Recent models predict that the pattern of stochastic fluctuations (noise) matters for theevolutionary response to environmental change. In this study we test predictions from a recenttheoretical model in a laboratory experiment using the seed beetle Callosobruchus maculatus as amodel organism. Populations were exposed to different regimes of temperature increase; withoutnoise and with noise with no temporal autocorrelation (white noise) and very high temporalautocorrelation (red noise) over 18 generations. Developmental time decreased in the treatmentwith white noise fluctuation, but not in the treatment without noise or with red noise fluctuation,compared to the control lines. The main conclusions is, that the pattern of environmentalstochasticity is important for the evolutionary response of a population to a changing environmentas predicted by model simulations.
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| 6. |
- Hallsson, Lára R., 1983-, et al.
(author)
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The relative importance of genetic and nongenetic inheritance in traits of varying degree of plasticity in Callosobruchus maculatus
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Other publication (other academic/artistic)abstract
- Both genetic and nongenetic mechanisms of inheritance are important in the study of a trait’sresponse to environmental change. Here we address the question of whether the relativeimportance of these mechanisms is related to the degree of trait plasticity. We investigate theinfluence of additive genetic effects and non genetic parental effects in traits that differ in theirdegree of plasticity. We predicted that more plastic traits will be more amenable to parentaleffects, and genetic variation/covariance will be more difficult to detect. Our findings are in linewith predictions. We suggest that environment dependent parental effects may influence theevolution of a highly plastic trait to a greater extent than traits with low degrees of plasticity.Hence, due to difficulties in detecting genetic variance and covariances and the potential influenceof environment dependent parental effects on heritability, our ability to predict evolutionarychange in highly plastic traits may be limited.
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