Sexual selection and paternal care in Rhynocoris tristis (Hemiptera: Reduviidae)
Date
2006
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Publisher
University of Delaware
Abstract
Exclusive paternal care is the rarest form of care in the animal kingdom. Since Triver’s (1972) landmark paper, several hypotheses have been proposed to explain why male care occurs at all. Rhynocoris tristis (Stål 1855) is a small, African reduviid exhibiting exclusive male-care of multiple adjoining clutches of eggs. Its small size, relatively short life cycle, and close phylogenetic relationship to the maternally caring R. carmelita make R. tristis an excellent candidate for studying the existence of exclusive male care. ☐ A laboratory colony of R. tristis, derived from stock collected at Namulonge Agricultural and Animal Production Research Institute near Kampala, Uganda and housed at the University of Delaware, was manipulated to examine behavioral characteristics leading to male care. Females showed no egg-laying preference for sites near food sources. Nor did females show any preference for larger or smaller males. ☐ Females did show a significant preference for laying eggs adjacent to other females egg masses. Additional female choice experiments were abandoned when the colony died prior to their completion. With the death of the colony, I was unable to definitively determine if male guarding is driven by natural or sexual selection or by some combination. ☐ This thesis also provides the first record of amphisexual care in an insect. Female R. tristis were observed to take up a guarding stance over their clutch of eggs if the guarding male died or abandoned the clutch. Both males and females were tested for guarding tenacity with a simulated predator. Males and females showed no significant difference between the number of attacks by the predator that they tolerated while guarding an egg mass. Non-guarding males and females quickly departed when attacked. This suggests that both sexes can provide care for the eggs, but the female will only do so if there is no male present. The existence of amphisexual care in R. tristis suggests that male egg-guarding behavior in this species could be dependant on a particular set of circumstances, and not a fixed behavior.