ARS | Publication request: Body size phenotypes are heritable and mediate fecundity but not fitness in the lepidopteran frugivore, Cydia pomonella

Submitted to: Naturwissenschaften
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 5, 2012
Publication Date: June 22, 2012
Citation: Davis, T.S., Landolt, P.J. 2012. Body size phenotypes are heritable and mediate fecundity but not fitness in the lepidopteran frugivore, Cydia pomonella. Naturwissenschaften. 99(6):483-491.

Interpretive Summary: Codling moth is a damaging insect pest of fruit orchards, and larval feeding causes substantial economic losses for growers by reducing commercial value of fruit crops. Although this insect is a serious management concern for orchardists, there is little information available regarding basic population dynamics of codling moth. Researchers at the USDA-ARS laboratory in Wapato, Washington are seeking to identify the role of body size in codling moth populations through a series of selective breeding experiments. They discovered that moth body size is an inherited trait, that large females lay more eggs, and that large males benefit female reproduction. Their studies provide new insight into the factors important for moth management, and suggest that assessments of body size may provide valuable information regarding moth population trajectories and assist growers in easily monitoring moth performance.

Technical Abstract: The inheritance and functional roles of quantitative traits are central concerns of evolutionary ecology. We report two sets of experiments that investigated the heritability and reproductive consequences of body size phenotypes in a globally distributed lepidopteran frugivore, Cydia pomonella (L.). In our first set of experiments, we tested the hypotheses that (1) body size is heritable; and (2) parental body size mediates egg production and offspring survival. Midparent-offspring regression analyses revealed that body mass is highly heritable for females and moderately heritable for males. The contribution of fathers to estimates of additive genetic variance was slightly greater than for mothers. Egg production increased with mean parental size, but offspring survival rates were equivalent. Based on this result, we tested two additional hypotheses in a second set of experiments: (3) male size moderates female egg production and egg fertility, and (4) egg production, egg fertility, and offspring survival rate are influenced by female mating opportunities. Females paired with large males produced more eggs and a higher proportion of fertile eggs than females paired with small males. Females with multiple mating opportunities produced more fertile eggs than females paired with a single male. However, egg production and offspring survival rates were unaffected by the number of mating opportunities. Our experiments demonstrate that body mass is heritable in C. pomonella, and that size phenotypes may mediate fecundity but not fitness. We conclude that male size can influence egg production and fertility, but female mate choice also plays a role in determining egg fertility.