Life‐History Consequences of Egg Size inDrosophila Melanogaster

Abstract

We used a novel approach to study the effects of egg size on offspring fitness components in Drosophila melanogaster. Populations that differed genetically in egg size were crossed, and the female offspring from these reciprocal crosses were examined for life-history traits. These flies expressed effects of egg size, because they developed from eggs of different sizes as a result of maternal genetic effects, but displayed an equivalent range of nuclear genetic variation. The crosses used four independent pairs of outbred populations that differed in the pattern of covariation between egg size and life-history traits, so that the maternal genetic effects of egg size on offspring characters could be contrasted to the associations present among the parental populations. Egg size showed positive maternal genetic effects on embryonic viability and development rate, hatchling weight and feeding rate, and egg-larva and egg-adult development rate but no consistent effects on larval competitive ability, adult weight, or egg size in the offspring. Our method revealed a pattern of causality that could not be deduced from interpopulation comparisons and therefore provides a good way of disentangling the causes and consequences of variation in egg size while controlling for zygotic genetic effects.

Life history evolution and cellular mechanisms associated with increased size in high‐altitude Drosophila

“…However, selection may also be acting directly upon egg size to maximize hatching success and embryonic viability (Azevedo et al. 1997). Additional work examining the relationship between adult size, development time, and egg size is needed to tease these explanations apart.…”

“…1994a; James and Partridge 1995; Azevedo et al. 1997; Conlon and Raff 1999). Moreover, understanding developmental and cellular level processes underlying phenotypic variation can provide insight into the genetic underpinnings of trait evolution.…”

“…Larger egg size within this species has been associated with larger hatching larvae and faster developmental rate, but not with adult body size (Azevedo et al. 1996, 1997), and it has been found to result from laboratory evolution at low temperature (Azevedo et al. 1997).…”

“…1996, 1997), and it has been found to result from laboratory evolution at low temperature (Azevedo et al. 1997). …”

Realized correlated responses to artificial selection on pre-adult life-history traits in a butterfly

“…Stearns, 1992;Fox and Czesak, 2000;Roff, 2002). Egg size in insects, for instance, can considerably affect the fitness of the progeny resulting from these eggs; larger offspring were frequently found to mature earlier, to have improved ability to avoid or withstand predation or competition, or to survive better in stressful environments compared with the small offspring (Azevedo et al, 1997;Fox and Czesak, 2000;Roff, 2002;Czesak and Fox, 2003;Fischer et al, 2003Fischer et al, , 2006. The considerable and wide-ranging ecological importance of a large body size is clearly demonstrated by its positive effect on various fitnessrelated traits (e.g.…”