Does the definition of a novel environment affect the ability to detect cryptic genetic variation?

Anthropogenic change exposes populations to environments that have been rare or entirely absent from their evolutionary past. Such novel environments are hypothesized to release cryptic genetic variation, a hidden store of variance that can fuel evolution. However, support for this hypothesis is mixed.

Pollution induces epigenetic effects that are stably transmitted across multiple generations.

It has been hypothesized that the effects of pollutants on phenotypes can be passed to subsequent generations through epigenetic inheritance, affecting populations long after the removal of a pollutant. But there is still little evidence that pollutants can induce persistent epigenetic effects in animals. Here, we show that low doses of commonly used pollutants induce genome-wide differences in cytosine methylation in the freshwater crustacean .

Measuring life history in the wild: The efficacy of individual field cages.

Life-history studies are often conducted in a laboratory environment where it is easy to assay individual animals. However, factors such as temperature, photoperiod, and nutrition vary greatly between laboratory and field environments, making it difficult to compare results. Consequently, there is a need to study individual life histories in the field, but this is currently difficult in systems such as where it is not possible to mark and track individual animals.

Embryogenesis plasticity and the transmission of maternal effects in Daphnia pulex.

Understanding how genetic, nongenetic, and environmental cues are integrated during development may be critical in understanding if, and how, organisms will respond to rapid environmental change. Normally, only post-embryonic studies are possible. But in this study, we developed a real-time, high-throughput confocal microscope assay that allowed us to link Daphnia embryogenesis to offspring life history variation at the individual level.

Temperature and clone-dependent effects of microplastics on immunity and life history in Daphnia magna.

Microplastic (MP) pollution is potentially a major threat to many aquatic organisms. Yet we currently know very little about the mechanisms responsible for the effects of small MPs on phenotypes, and the extent to which effects of MPs are modified by genetic and environmental factors. Using a multivariate approach, we studied the effects of 500 nm polystyrene microspheres on the life history and immunity of eight clones of the freshwater cladoceran Daphnia magna reared at two temperatures (18 °C/24 °C).

Offspring Provisioning Explains Clone-Specific Maternal Age Effects on Life History and Life Span in the Water Flea, Daphnia pulex.

Genetic inheritance underpins evolutionary theories of aging, but the role that nongenetic inheritance plays is unclear. Parental age reduces the life span of offspring in a diverse array of taxa but has not been explained from an evolutionary perspective. We quantified the effect that maternal age had on the growth and maturation decisions, life history, rates of senescence, and life span of offspring from three Daphnia pulex clones collected from different populations.

How to measure maturation: a comparison of probabilistic methods used to test for genotypic variation and plasticity in the decision to mature.

Maturation is a developmental trait that plays a key role in shaping organisms' life-history. However, progress in understanding how maturation phenotypes evolve has been held back by confusion over how best to model maturation decisions and a lack of studies comparing genotypic variation in maturation. Here, we fitted probabilistic maturation reaction norms (PMRNs) to data collected from five clones of Daphnia magna and five of Daphnia pulex collected from within and between different populations.

How to put all your eggs in one basket: empirical patterns of offspring provisioning throughout a mother's lifetime.

Maternal effects arise when a mother's phenotype or the environment she experiences influences the phenotype of her progeny. Most studies of adaptive maternal effects are a "snapshot" of a mother's lifetime offspring provisioning and do not generally consider the effects of earlier siblings on those produced later. Here we show that in soil mites, offspring provisioning strategies are dynamic, changing from an emphasis on egg number in young females to egg size in older females.

Complex population dynamics and complex causation: devils, details and demography.

Population dynamics result from the interplay of density-independent and density-dependent processes. Understanding this interplay is important, especially for being able to predict near-term population trajectories for management. In recent years, the study of model systems-experimental, observational and theoretical-has shed considerable light on the way that the both density-dependent and -independent aspects of the environment affect population dynamics via impacting on the organism's life history and therefore demography.

Context-dependent intergenerational effects: the interaction between past and present environments and its effect on population dynamics.

Intergenerational effects arise when parents' actions influence the reproduction and survival of their offspring and possibly later descendants. Models suggest that intergenerational effects have important implications for both population dynamical patterns and the evolution of life-history traits. However, these will depend on the nature and duration of intergenerational effects.

Age and size at maturity: sex, environmental variability and developmental thresholds.

In most organisms, transitions between different life-history stages occur later and at smaller sizes as growth conditions deteriorate. Day and Rowe recently proposed that this pattern could be explained by the existence of developmental thresholds (minimum sizes or levels of condition below which transitions are unable to proceed). The developmental-threshold model predicts that the reaction norm of age and size at maturity will rotate in an anticlockwise manner from positive to a shallow negative slope if: (i) initial body size or condition is reduced; and/or (ii) some individuals encounter poor growth conditions at increasingly early developmental stages.