Chromatin structure changes in Daphnia populations upon exposure to environmental cues - or - The discovery of Wolterecks "Matrix (original) (raw)
Related papers
Journal of Limnology, 2004
It is commonly accepted that within-population phenotypic variation is caused by genotypic and environmental heterogeneity. Non-genotypic variation is thought to result from diversity of environmental conditions alone. This however contradicts experimental data showing that even when both genetic and environmental sources of phenotypic variation are neglected, residual variation still exists. This residual phenotypic variation is caused by deviations of developmental trajectories from the target trajectory determined for particular genotype and environment, i.e. by developmental instability. This variation is well-known for morphological traits where it is measured most often by fluctuating asymmetry, i.e. random deviations from perfect symmetry, which can be easily separated from the other type of phenotypic variation. In morphological characters which do not possess symmetry or in non-morphological characters this variation cannot usually be separated from other type of non-genotypic variation, caused by environmental heterogeneity. Most researchers still believe that all non-genotypic variation, even under standardised experimental conditions, is caused by insufficient standardization of environment, rather than by other sources of phenotypic variation. When special efforts are undertaken to analyse variation caused by developmental instability, this variation contributes substantially to non-genotypic variation. To exemplify how variation caused by developmental instability can be separated from phenotypic plasticity we analysed phenotypic variation of resting egg formation in Daphnia pulicaria. The proportion of females carrying resting eggs has been shown to depend on the photoperiod of their mothers, revealing transgeneration effects . Developmental instability manifests itself in differences between clonemates within an experimental vessel in a standardized environment. Some females produce resting eggs whereas others do not. Our estimations based on results obtained in experimental conditions and extrapolation to conditions in the wild showed that phenotypic plasticity, i.e. phenotypic response to changes of day duration in maternal environment (phenotypic plasticity) explains only 1-2% of phenotypic variation whereas developmental instability explains approximately 98-99% of phenotypic variance of this trait (i.e. producing or not producing resting eggs), if other factors causing phenotypic plasticity are absent. This example demonstrates a major role of developmental instability in variation of the trait under study. The contribution of developmental instability to phenotypic variation should be considered in studying evolutionary patterns of phenotypic traits.
Environmental stress and local adaptation in Daphnia magna
Limnology and Oceanography, 1999
The effects of fish kairomones, crowding chemicals, and day length on the life-history traits of a set of 16 Daphnia magna clones, derived from four populations that differ in fish-predation pressure, were studied. Significant among-population differences were observed, the differences being in concordance with the hypothesis of local adaptation. The among-population genetic differences were not mediated through a change in response to fish kairomones, but through an overall smaller body size, smaller eggs, and a higher number of eggs in clones derived from habitats in which fish are present. Using a model, we show that the observed changes in life-history characteristics may lead to differences in fitness under different predation regimes, such that populations from habitats with fish have highest fitness under fish-predation regimes and populations without a fish background have higher fitness values under invertebrate predation regimes. 1.5012.96N. P.S. was supported by a fellowship from the Max Planck Society. Huppel and Depup are thanked for the production of fish water. The authors acknowledge Winfried Lampert, Larry Weider, Herwig Stibor, Hinnerk Boriss, Martina Teschner, Sue Mitchell, Alan Tessier, and two anonymous reviewers for fruitful discussions and comments on earlier versions of the manuscript.
Phenotypic plasticity in development and evolution: facts and concepts
Philosophical Transactions of the Royal Society B: Biological Sciences, 2010
This theme issue pursues an exploration of the potential of taking into account the environmental sensitivity of development to explaining the evolution of metazoan life cycles, with special focus on complex life cycles and the role of developmental plasticity. The evolution of switches between alternative phenotypes as a response to different environmental cues and the evolution of the control of the temporal expression of alternative phenotypes within an organism's life cycle are here treated together as different dimensions of the complex relationships between genotype and phenotype, fostering the emergence of a more general and comprehensive picture of phenotypic evolution through a quite diverse sample of case studies. This introductory article reviews fundamental facts and concepts about phenotypic plasticity, adopting the most authoritative terminology in use in the current literature. The main topics are types and components of phenotypic variation, the evolution of orga...
Phenotypic plasticity and ecology
Phenotypic plasticity is the capability of an individual to produce several phenotypes rn response to environmental changes In the algae, plasticity studies predate those in other groups with numerous examples at the morphological and physiological levels.
2008
Mainstream evolutionary biology lacks a mature theory of phenotype. Following from the Modern Synthesis, researchers tend to assume an unrealistically simple mapping of genotype to phenotype, or else trust that the complexities of developmental architecture can be adequately captured by measuring trait variances and covariances. In contrast, the growing field of evolutionary developmental biology (evodevo) explicitly examines the relationship between developmental architecture and evolutionary change, but lacks a rigorous quantitative and predictive framework. In my dissertation, I strive to integrate quantitative genetics and evo-devo, using both theoretical and empirical studies of plasticity. My first paper explores the effect of realistic development on the evolution of phenotypic plasticity when there is migration between two discrete environments. The model I use reveals that nonadditive developmental interactions can constrain the evolution of phenotypic plasticity in the presence of stabilizing selection. In my second paper, I examine the manner in which the genetically controlled responsiveness of traits to each other is shaped by selection and can in turn shape the phenotypic response to selection. Here, results indicate that developmental entanglement through plasticity can facilitate rapid multivariate adaptation in response to a novel selective pressure. In my final paper, I examine patterns of gene expression underlying ancestral plasticity and adaptive loss of melanin in Daphnia melanica. My results indicate that the developmental mechanism underlying ancestral plasticity has been co-opted to facilitate rapid adaptation to an introduced predator.
Environmental pollution (Barking, Essex : 1987), 2015
Generally, ecotoxicologists rely on short-term tests that assume populations to be static. Conversely, natural populations may be exposed to the same stressors for many generations, which can alter tolerance to the same (or other) stressors. The objective of this study was to improve our understanding of how multigenerational stressors alter life history traits and stressor tolerance. After continuously exposing Daphnia magna to cadmium for 120 days, we assessed life history traits and conducted a challenge at higher temperature and cadmium concentrations. Predictably, individuals exposed to cadmium showed an overall decrease in reproductive output compared to controls. Interestingly, control D. magna were the most cadmium tolerant to novel cadmium, followed by those exposed to high cadmium. Our data suggest that long-term exposure to cadmium alter tolerance traits in a non-monotonic way. Because we observed effects after one-generation removal from cadmium, transgenerational effect...
The contribution of individual and maternal experience in shaping Daphnia life history
Hydrobiologia, 2016
Maternal effects are among the key mechanisms generating phenotypic diversity in natural populations, but no general explanation has been found for why maternal effects are involved in shaping some, but not all, phenotypic traits. We investigated experimentally the relative importance of maternal and own risk perception in multi-trait response of a small planktonic crustacean Daphnia magna to the presence of fish. It appears that maternal effect is involved in shaping some key traits relating to adaptive changes in life history, such as duration time of egg holding in the brood chambers, age and size of mothers at first reproduction, and the number of firstclutch neonates. Other life history parameters, such as duration time of the release of the first clutch of neonates from the brood chamber and the size of neonates, were determined upon direct exposure to environmental risk. The relative contribution of maternal and own perception of risk in shaping individual phenotype depends on the time needed to express particular life history trait. Long onset time increases the importance of maternal risk perception in the shaping of offspring phenotype.