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RESOURCE INFLUENCED SEX ROLES OF ZAPROCHILINE TETTIGONIIDS (ORTHOPTERA: TETTIGONIIDAE).
L W Simmons1,2, W J Bailey1,2
1Department of Environmental and Evolutionary Biology, University of Liverpool, P.O. Box 147, Liverpool, L69 3BX, UK.
Summary
In tettigoniids, male nutrient gifts (spermatophylax) reverse sex roles. Resource availability dictates if females need these gifts, influencing mating behavior and sexual selection.
Area of Science:
- Behavioral Ecology
- Evolutionary Biology
- Entomology
Background:
- Male tettigoniids provide a spermatophylax, a nutrient-rich gift, to females during mating.
- This male parental investment can lead to a reversal of typical sex roles, with females becoming more competitive.
Purpose of the Study:
- To investigate how environmental food resource availability influences the reversal of sex roles in a zaphrochiline tettigoniid.
- To determine the relationship between resource availability, male spermatophylax production, and female fecundity and mating behavior.
Main Methods:
- Observational study of zaphrochiline tettigoniid behavior under varying food resource conditions.
- Measurement of male accessory gland weights (spermatophylax production) and female fecundity.
- Analysis of mating frequency and mate choice behaviors in males and females.
Main Results:
- Sex role reversal was directly linked to food availability. Females were less fecund and males produced smaller spermatophylaxes when resources were low.
- Under scarce resources, larger individuals had a reproductive advantage. Females mated more frequently to compensate for low resource availability.
- When resources were plentiful, males were less choosy, and females exhibited mate discrimination, with mating frequency decreasing.
Conclusions:
- Male parental investment (spermatophylax) is crucial for female reproduction primarily in resource-poor environments.
- Resource availability significantly impacts the operational sex ratio and the dynamics of sexual selection in tettigoniids.
- Females remate to offset low resource availability, highlighting the adaptive significance of male nutrient gifts.
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