Submitted to: Journal of Orthoptera Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/7/2005
Publication Date: 12/1/2005
Citation: Branson, D.H. 2004. Relative importance of nymphal and adult resource availability on reproductive allocation in melanoplus sanguinipes (orthoptera: acrididae). Journal of Orthoptera Research. 13(2):239–245. Interpretive Summary: The effect of resource availability on reproductive allocation and survival of grasshoppers, under often food limited field conditions, has received little attention. A better understanding of how nymphal resource availability affects life history variation of adults would aid in our ability to predict grasshopper population dynamics. I examined the relative importance of nymphal and adult resource availabilities on Melanoplus sanguinipes (Fabricius) adult survival and reproductive allocation. Nymphal resource availability did not affect reproductive allocation or adult survival of females. The primary effect of adult resource availability was on reproduction, but not on survival of adult females. These results indicate that there were no residual effects of limited resource availability for developing nymphs that would subsequently affect reproduction and survival of surviving adults. The results provide more knowledge on the impact of both nymphal and adult resource availability on the ecological interactions affecting population dynamics, and will aid in the development of biologically based grasshopper management tools.
Technical Abstract: The effects of food availability for both nymphal and adult grasshoppers on reproductive allocation in the field have not been examined. I conducted a field experiment to examine the relative importance of nymphal and adult resource availabilities on Melanoplus sanguinipes (Fabricius) reproductive allocation in field cages. Female nymphs were reared on either high or low nymphal resource availability in an outdoor laboratory until they molted to adults. To achieve a range of adult resource availabilities, field cages received either 250 ml of water every two days or no additions. M. sanguinipes were stocked below their average carrying capacity at the site to allow an examination of the variation in reproductive allocation in response to adult and nymphal resource availabilities. Females reared with ad libitum resource availability as nymphs had increased body mass. However, nymphal resource availability did not affect reproductive allocation or adult survival of females. The primary effect of adult resource availability was on reproduction, but not on survival of adult females. Female M. sanguinipes responded to increased adult resource availability by increasing reproductive allocation, even when resources were not strongly limiting. Egg production and future reproduction were higher in the watered adult resource treatment. M. sanguinipes females did not reduce vitellogenesis in response to decreased adult resource availability, but completed development of a lower percentage of ovarioles that initiated development. Nymphal and adult resource availability did not interact in their effects on reproductive allocation, indicating that there were no significant residual effects of limited resource availability for developing nymphs on adult reproduction and survival.