Non-additive effects may affect the evolution of populations by lowering the heritability of the traits that they affect, thus causing inbreeding depression within populations and playing a role in the conversion of non-additive into additive variation during bottlenecks and in the evolution and maintenance of negative genetic correlations between traits (Crnokrak and Roff 1995, Wolf et al. 2000). Furthermore, dominance variance should be present to a greater degree in traits closer to fitness (Crnokrak and Roff 1995). This study uses diallel cross analyses of inbred lines of the sand cricket Gryllus firmus, to examine the sources of variation in weight at age, adult size, development time, fecundity and flight muscle weight and in particular the ratios of additive, dominance and maternal variance to total variance. We also examine the genetic relationships between the traits. / Our study also examines the presence of maternal effects in growth traits and adult size in the sand cricket Gryllus firmus using diallel cross analyses of inbred lines.

I investigated the genetic basis of the trade-off between early fecundity (measured as ovary weight) and flight capability (measured as flight muscle mass) in two different environments (ad libitum and reduced food treatments) in females of a wing dimorphic cricket, Gryllus firmus. I found that the food environment did not affect the fecundity ratio between the two wing morphs. Consequently, while long wing (LW) females partially histolyse their dorso-longitudinal wing muscles (DLM) it is not enough to compensate for the low food treatment. Genetic parameters were estimated using a half-sib analysis on the LW females. The genetic correlation between the two traits was not different from -1 in both environments. According to the mixed-model ANOVA, the genetic correlation across environments for both traits did not differ from +1. Therefore, the heritability estimates of the pooled ovary weight and the pooled DLM weight were calculated and were significant. These results indicate that fitness resulting from the trade-off between flight capability and fecundity is not affected by varying food conditions.

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