Evol Ecol Res 5: 893-902 (2003)     Full PDF if your library subscribes.

Consequences of reduced genetic variance on developmental instability estimators

Cino Pertoldi,1,2* Ditte Holm Andersen,2,3 Torsten Nygaard Kristensen2,4 and Volker Loeschcke2,5

1Department of Landscape Ecology, National Environmental Research Institute, Rønde, Denmark,  2Department of Ecology and Genetics, University of Aarhus, Aarhus, Denmark,  3Dipartimento di Biologia Evoluzionistica Sperimentale, Bologna, Italy,  4Department of Animal Breeding and Genetics, Danish Institute of Agricultural Sciences, Tjele, Denmark and  5Institute for Advanced Study, La Trobe University, Bundoora, Victoria, Australia

Address all correspondence to Cino Pertoldi, Department of Applied Biology, Estación Biológica Doñana, CSIC, Pabellón del Perú, Avda. Maria Luisa, s/n 41013 Seville, Spain.
e-mail: cino@ebd.csic.es

ABSTRACT

Several studies have failed to find the negative relationship between genetic variability and developmental instability hypothesized by Lerner in 1954. Developmental instability is often assessed using its common estimator, fluctuating asymmetry. In this study, we use a computer simulation procedure that enables us to quantify the effect of a loss of genetic variability on average fluctuating asymmetry. We simulated a systematic loss of genetic variability, which in populations can be generated by a process of stabilizing selection or by a reduction in population size. Average fluctuating asymmetry decreased during the simulated process of a systematic loss of genetic variability, even though developmental instability was held constant and equal for all the individuals comprising the simulated populations. The error associated with the use of fluctuating asymmetry to estimate developmental instability of the simulated population is assessed and discussed. This study is the first to apply a theoretical rationale to the relationship between genetic variability and developmental instability as estimated by fluctuating asymmetry. The results presented here should be taken into account in future studies of fluctuating asymmetry, as they may help to explain some of the contradictory results reported in the literature regarding the correlation between genetic variability and fluctuating asymmetry. Furthermore, the results of this study also show how difficult it can be when comparing fluctuating asymmetry among populations with different population size and/or different genetic variability. In fact, the observed positive relationship between genetic variability and fluctuating asymmetry can counteract the hypothesized negative relationship between genetic variability and developmental instability hypothesized by Lerner. The results of the present study will have an impact on research into the application of fluctuating asymmetry as an indicator of genetic and environmental stress.

Keywords: fluctuating asymmetry, genetic drift, genetic variance, phenotypic variance.

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