Age-specific maternal effects interact with larval food supply to modulate life history in Coleomegilla maculata
Correspondence: J. P. Michaud, Department of Entomology, Agricultural Research Center-Hays, Kansas State University, 1232 240th Avenue, Hays, KS 67601, U.S.A. E-mail: firstname.lastname@example.org
- Maternal effects can modify progeny phenotypes to improve their survival under variable conditions, such as changes in food supply. In aphidophagous coccinellids, maternal effects can influence egg size, developmental rate, and final adult body size.
- Four cohorts of Coleomegilla maculata De Geer larvae were reared from four different points in their mothers' reproductive lives (1st, 12th, 24th, and 36th oviposition days) and divided into two diet treatments for rearing; 30-min daily access to eggs of Ephestia kuehniella Zeller or ad libitum.
- Progeny survival was lower on restricted food but increased over the first 12 oviposition days in both treatments, suggesting mothers did not conform to the theoretical norm of producing their ‘best’ progeny first.
- Larval development was delayed on the restricted diet, but there was no effect of oviposition day on total developmental time, although pupation was faster in the final cohort than in the first.
- The results suggest that mothers employ a mixed strategy and produce subsets of progeny that vary in response to food limitation. A small fraction adopt an ‘optimistic’ strategy and undergo an additional instar to take advantage of any possible improvement in the food supply, whereas a larger fraction adopt a ‘pessimistic’ strategy, forgoing an instar and the costs of a moult to pupate at a small size.
- The restricted diet increased the percentage of larvae that added or subtracted an instar, but larvae from later clutches were more likely to pupate after only three instars, independent of treatment, suggesting that a larger proportion of later-hatching progeny are maternally programmed for pessimism, as would be adaptive for larvae exploiting aphid populations in decline.