|HARWOOD, JAMES - University Of California|
|CHEN, KEHUI - University Of Pittsburgh|
|MULLER, HANS-GEORGE - University Of California|
|WANG, JANE-LING - University Of California|
|CAREY, JAMES - University Of California|
Submitted to: Physiological Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2012
Publication Date: 6/1/2013
Citation: Harwood, J.F., Chen, K., Muller, H., Wang, J., Vargas, R.I., Carey, J.R. 2013. Effects of diet and host access on fecundity and lifespan in two fruit fly species with different life history patterns. Physiological Entomology. 38(1):81-88.
Interpretive Summary: Reproduction and longevity are mutually dependent in sexually reproducing organisms, with an increase in the energy expended for reproduction resulting in a subsequent decrease in longevity. The nutritional conditions in an environment influence the trade-off between current reproductive effort and lifespan. Poor dietary conditions in which all of the dietary requirements of an organism cannot be met, lead to reduced or arrested reproductive effort, thereby increasing the allocation of resources to somatic upkeep and survival until conditions improve and reproduction can resume. The primary objective of this life history trade-offs study was to evaluate specific responses to delay mechanisms in Mediterranean fruit fly Ceratitis capitata and Melon fly, Bactrocera cucurbitae. This study conducted at the Agricultural Research Service, ARS, USDA, PBARC, Hilo, Hawaii, indicated that the life expectancy of the female melon fly is reduced by host access, but delaying host access does not alleviate the loss of life expectancy. Conversely, the lifespan of the medfly is not influenced by oviposition. Medfly females are able to lay a few eggs on the day that full diet and the hosts were introduced. Conversely, egg laying in the melon fly does not begin until several days after the introduction of the full diet. The medfly has a broader host range than the melon fly so in nature, the medfly is not likely to experience a long period of host scarcity since it can easily switch to other available hosts. The melon fly, in contrast, has a narrower host range that may lead to periods that hosts may be unavailable. Therefore, the extended lifespan and reproductive period of the melon fly along with its ability to avoid the cost of egg production when hosts are unavailable, suggests it is better adapted to periods of host deprivation than the medfly. Overall, these results demonstrate that delaying reproduction may lower the fitness of female by constraining the gross reproductive output for the remainder of the life span without substantially improving the life expectancy.
Technical Abstract: The reproductive ability of female tephritids can be limited and prevented through denying host access and restricting the dietary precursors of vitellogenesis. Each of these mechanisms of delayed egg production is initiated by different physiological processes that are anticipated to have dissimilar effects on lifespan and reproductive ability later in life. The egg laying ability of laboratory reared Mediterranean fruit fly (Ceratitis capitata) and melon fly (Bactrocera cucurbitae) females from Hawaii are delayed or suppressed by limiting access to host fruits and dietary protein. Both of these mechanisms of delaying egg production are expected to prevent the loss of lifespan associated with reproduction until protein or hosts are introduced. Two trends are observed in each species: 1) protein access at eclosion leads to a greater probability of survival and higher reproductive ability than when it is delayed; 2) delayed host access reduces lifetime reproductive ability without improving life expectancy. Following delayed host access and protein availability, the rate of reproductive senescence is reduced in the medfly while the rate of reproductive senescence is generally increased in the melon fly. Overall, delaying reproduction lowers the fitness of females by constraining their fecundity for the remainder of the lifespan without extending the lifespan.