Sexual selection in mantis (Parastagmatoptera tessellata): in the search of decision-making mechanisms underlying male mate choice

LORENA POMPILIO; ESTEBAN AVIGLIANO; ROMINA SCARDAMAGLIA; FABIAN GABELLI

Oxford

Conferencia; THE ASSOCIATION FOR THE STUDY OF ANIMAL BEHAVIOUR (ASAB); 2009

Mantises are popular because females are capable of cannibalizing males either before, during or after mating. Approximately 30% of sexual encounters begin or end in cannibalism (Lawrence, 1992), being the probability of cannibalism dependent on females’ nutritional state: the better the females’ nutritional state, the least the chance of cannibalism (Liske & Davis, 1987). From the point of view of the female, males have value both as a meal and as a couple, since they can obtain sperm and a meal from the same male. Thus, sexual cannibalism would be favored even in virgin females. On the other hand, cannibalism can only benefit males if: 1) the chances of finding a new mate opportunity are low and 2) their own consume increase their fitness. Statement 2) basically depends on: i) the difference in size between females and males: the smaller the male, the lower the benefit from their consumption; ii) the energetic state of females: the higher the energetic condition of the female the lower the fitness gain provided by the consumption of the male and more costly the act of cannibalism for the male. State-dependent choices have been previously shown in insects (Pompilio et al., 2006) in the context of food search. Male mantises are a good candidate to test state-dependent preferences in the context of sexual selection. Specifically, we investigated whether male mantises are sensitive to: 1) Environmental keys that provide relevant information on females’ nutritional state. 2) Keys that provide information on females’ level of aggressiveness. Male mantis prefer females that were eating a prey. Approaching a female once she has started feeding on prey may be a male strategy to reduce the risk of cannibalism (Prenter et al. 1994a; Gemeno and Claramunt 2006). In the present study, however, choices were made after females consumed the whole prey thus suggesting that males are not using the prey as a direct way to avoid being cannibalized by keeping the female busy but as an indicator of the energetic state of females. Visual or olfactive keys would trigger this behavior. The elucidation of mechanisms of mate choice sensitive to female energetic state and tending to favour the choice of females in the best nutritional state, supports the hypothesis of “conflict”between males and females, at least in the mantis species studied. Regarding the effects of females’ aggression levels on male choice, male preferences changed according to the number of strikes exhibited by females. A possible explanation is that aggressive females were chosen when they exhibited many strikes due to a phenomenon of enhancement (when females strike, they move markedly and this could have driven males’ attention to them). Thus, just a few strikes would be an effective stimulus, avoiding any enhancement of females. Additional experiments are needed to understand the mechanisms underlying the reversion of preferences found in the present study.