Location: Stored Product Insect Research Unit
Title: Influence of Maternal Age on the Fitness of Progeny in the Rice Weevil, Sitophilus Oryzae (Coleoptera: Curculionidae) Authors
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 10, 2006
Publication Date: January 31, 2007
Citation: Opit, G.P., Throne, J.E. 2007. Influence of maternal age on the fitness of progeny in the rice weevil, Sitophilus oryzae (Coleoptera: curculionidae). Environmental Entomology 36: 83-89. Interpretive Summary: The rice weevil is one of the most serious pests of stored grain in the U.S. and throughout the world. Population models have been developed to optimize management of rice weevils, but recent studies have shown that the models need to be refined to account for differences in fitness of progeny produced by females of varying age. We showed that progeny of younger females produce more offspring, live longer, and produce offspring that are heavier than those of older females. This information will be used to modify rice weevil population models in order to improve their predictive ability to aid in insect pest management.
Technical Abstract: We investigated the effects of maternal age on fitness of progeny in the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae). Five-, 20-, and 50-day-old female rice weevils were used to investigate the effects of maternal age on the life-time fecundity and longevity of their daughters. In addition, we looked at the effects of maternal age on the weight and survivorship of daughters’ progeny. Daughters of 5- and 20-day-old weevils lived longer and the numbers and weights of the progeny of these daughters were higher than for daughters of 50-day-old weevils. Survivorship of immature grand-offspring of 5-day-old weevils was higher than for immature grand-offspring of 50-day-old weevils. None of the fitness characteristics of the daughters and grand-offspring of 5- and 20-day-old weevils that were measured differed significantly. We believe maternal age effects on rice weevil progeny fitness may be acting through maternal age effect on egg size. Individuals that developed from larger eggs produced by 5- and 20-day-old weevils had a greater fitness than those produced by 50-day-old females. The greater fitness of rice weevils developing from larger eggs compared to that of those developing from smaller eggs may mean that egg size variation in rice weevils is adaptive. In addition, the greater fitness of offspring of younger weevils compared to that of older weevils may have influence on the evolution of aging. Our paper also discusses the possible adaptive significance of age-related egg size plasticity in rice weevils and its implications for population modeling.