Authors: Johanna m. de Kort* , Conor V. Dolan*,** and Dorret I. boomsma** In the classical twin study, genetic and environmental influences on a phenotype are usually estimated under the assumption that genotype-environment covariance (Ge covariance) is absent. We explore possibilities to accommodate Ge covariance in longitudinal data using the genetic simplex model. First, the genetic simplex ...

Studies of the genetic covariance between habitat preference and performance have reported conflicting outcomes ranging from no covariance to strong covariance. The causes of this variability remain unclear. Here we show that variation in the magnitude of genetic covariance can result from variability in migration regimes. Using data from walking stick insects and a mathematical model, we find ...

The genetic covariance structure for life-history characters in two populations of cyclically parthenogenetic Daphnia pulex indicates considerable positive correlation among important fitness components, apparently at odds with the expectation if antagonistic pleiotropy is the dominant cause of the maintanence of genetic variation. Although there is no genetic correlation between offspring size...

I examined patterns of covariation of three morphometric blossom characters [gland area (GA), gland-stigma distance (GSD), and bract length (BL)] within genets, among genets, and among populations of the tropical vine, Dalechampia scandens (Euphorbiaceae). Covariance between BL and GA was evenly distributed among the three levels. This observation, coupled with developmental information, indica...

In this contribution we describe an approach to evolve composite covariance functions for Gaussian processes using genetic programming. A critical aspect of Gaussian processes and similar kernel-based models such as SVM is, that the covariance function should be adapted to the modeled data. Frequently, the squared exponential covariance function is used as a default. However, this can lead to a...

Question: Is the pattern of phenotypic divergence among populations influenced by constraint in the form of the genetic covariances among characters? Background: Quantitative genetic theory predicts that when evolutionary lineages diverge simultaneously by genetic drift, the pattern of among-population divergence will parallel the pattern of within-population genetic variation and covariation. ...

Fitting only the leading principal components allows genetic covariance matrices to be modelled parsimoniously, yielding reduced rank estimates. If principal components with non-zero variances are omitted from the model, genetic variation is moved into the covariance matrices for residuals or other random effects. The resulting bias in estimates of genetic eigen-values and -vectors is examined.

A general observation emerging from estimates of additive genetic variance in sets of functionally or developmentally related traits is that much of the genetic variance is restricted to few trait combinations as a consequence of genetic covariance among traits. While this biased distribution of genetic variance among functionally related traits is now well documented, how it translates to the ...