Evol Ecol Res 8: 1487-1498 (2006)     Full PDF if your library subscribes.

Lerner’s theory on the genetic relationship between heterozygosity, genomic co-adaptation, and developmental instability revisited

Cino Pertoldi,1,2* Jesper G. Sørensen,1 Jean R. David3 and Volker Loeschcke1

1Department of Ecology and Genetics, University of Aarhus, DK-8000 Aarhus, Denmark,  2Department of Wildlife Ecology and Biodiversity, National Environmental Research Institute, DK-8410 Rønde, Denmark and  3Laboratoire Populations, Génétique et Evolution, CNRS, 91198 Gif-sur-Yvette cedex, France

Address all correspondence to Cino Pertoldi, Department of Ecology and Genetics, University of Aarhus, Building 540, Ny Munkegade, DK-8000 Aarhus, Denmark.
e-mail: biocp@nf.au.dk


Question: What is the genetic relationship between heterozygosity and developmental instability?

Methods: Using a new method for the quantification of developmental instability, we compare homozygous strains of Drosophila mercatorum (either parthenogenetic or highly inbred) and of their F1 progeny for the analysis of a symmetrical meristic trait (sternopleural bristle number). The method also implies the choice of samples in which the left–right correlation is close to zero.

Conclusions: In the parthenogenetic strain, developmental instability was seven times greater than in the F1 progeny. In the highly inbred strain, developmental instability was only 2.6 times greater than in the F1 progeny. The greater developmental instability in the parthenogenetic strain may be accounted for by the immediate fixation of a large number of deleterious alleles. In the inbred strain, on the other hand, progressive inbreeding is likely to have purged the genome of some of its genetic load and its most deleterious variants. The greater developmental instability in the parthenogenetic and inbred strains implies a non-linear relationship between heritability (h2) and additive genetic variance (σ2a) (which are both related to evolutionary potential), which is discussed in an evolutionary context. A linear relationship between the σ2a of a trait and its h2 is expected if developmental instability is constant and independent of the σ2a of that trait. If the relationship between the σ2a of a trait and its developmental instability is negative, an increased σ2a, which is in the numerator of the h2 equation, will imply a reduced phenotypic variability (σ2p), which is in the denominator of the heritability equation. Consequently, the concomitant increase in σ2a and reduction in σ2p both contribute to an increase in h2 and therefore an increase in evolutionary potential.

Keywords: admixture analysis, developmental instability, environmental variability, homeostasis, Lerner’s conjecture.

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