The Effect of Environmental Variability on the Heritabilities of Traits of a Field Cricket

Abstract

The presence of heritable variation in traits is a prerequisite for evolution. The great majority of heritability (h ) estimates are performed under laboratory conditions that are characterized by low levels of environmental variability. Very little is known about the effect of environmental variability on the estimation of components of quantitative variation, although theoretical extrapolations from lab studies have been attempted. Here we investigate the effects of environmental heterogeneity on variance component estimation using full-sib families of Gryllus pennsylvanicus split between a homogeneous laboratory environment and a more variable field environment. Although large standard errors prevent demonstration of statistically significant differences among h of traits measured in the two environments for all but one trait, the values of h are, on average, lower in the variable field environment, with a mean reduction of 19%. Developmental time is an exception, exhibiting high levels of additive variance in the field, leading to a higher value of h in the variable environment. Underlying the lower field h estimates are greater components of environmental variance as expected, as well as lower components of genetic variance. In this study, there is no evidence that the increase in the environmental component of variance in the field is any more important in the reduction of h than is the decrease in the additive genetic component. The implications of the relative changes in the two components of variance are discussed.

The quantitative genetics of two life history trade-offs in the yellow dung fly in abundant and limited food environments

“…As a result, our broad sense heritability of clutch size decreased in the food limited environment (consistent with Hypotheses 2 above), whereas it remained stable for egg volume (consistent with both Hypotheses 1 and 2, and consequently Hypothesis 3). The results for clutch size (but not necessarily egg volume) thus agree with the expectation that heritabilities in field situations, where environmental variation is typically high, should be lower than those estimated in the laboratory (Ebert, 1993;Ebert et al, 1993;Simons and Roff, 1994;Weigensberg and Roff, 1996). Our broad sense heritability estimates for egg and clutch size are roughly in line with averages reported for life history traits of other organisms (Mousseau and Roff, 1987).…”

“…Food limitation is one of the most common environmental stresses in natural populations. To date, a handful of studies have specifically studied effects of nutrition on genetic variation primarily of body size, and these have yielded variable results with regard to the hypotheses above de Moed et al, 1997;Grill et al, 1997;Lazarevic et al, 1998;summarized in Hoffmann and Merila¨, 1999;but also compare Hoffmann and Parsons, 1991;Simons and Roff, 1994;Roff, 1996;Weigensberg and Roff, 1996;Merila¨, 1997;Møller and Swaddle, 1997;Blanckenhorn, 2002). In this study, we investigate variation in phenotypic and genetic variances and covariances, i.e.…”

Quantitative Genetics of Growth and Development Time in the Burying Beetle Nicrophorus Pustulatus in the Presence and Absence of Post-Hatching Parental Care

“…Within a care treatment, we used restricted maximum likelihood to estimate all variance components using the function varcomp in S-Plus version 4.5 (MathSoft 1997) with the specification REML. Because the data were slightly unbalanced, we estimated the values and standard errors of heritabilities, maternal plus common environment effects, unshared environmental effects, and genetic correlations based on variance components using the jackknife method (Efron and Tibshirani 1993;Roff and Preziosi 1994;Simons and Roff 1994;Shao and Tu 1995). Unfortunately, the differences between REML and least-squares in this context is unclear (Fry 1992;Via and Conner 1995).…”

Sexual selection in the cricket Gryllus bimaculatus: no good genes?

“…Perhaps partly because there is no straightforward way of dealing with it from an analytical point of view, non-additive variance has historically been assumed to be negligible and unimportant for evolution (Falconer and Mackay 1996). There is growing interest in the importance of epistatic and dominance effects (Wade 2002), but still, many quantitative genetic studies, including studies of crickets, assume low non-additive variance and estimate heritability from the covariance between full siblings (Simons and Roff 1994;Grill et al 1997;Christe et al 2000;Bégin and Roff 2002;Réale and Roff 2002). Full-sib designs confound dominance and common environment effects with additive genetic effects, and may potentially lead to greatly inflated estimates of heritability.…”