Body size phenotypes are heritable and mediate fecundity but not fitness in the lepidopteran frugivore Cydia pomonella

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.