| Popis: |
Precopulatory mate guarding is a complex behavior and a challenging example of intersexual conflict. A conflict is initiated when the sexes are in disagreement on the mate guarding duration: males decide to start guarding, because their cost (i.e., time investment) is lower than their benefit (mating event), but females are resisting because their cost (in term of energy) is higher than their benefit (mating event). I used clam shrimp (branchiopod crustaceans) as my study organisms, which allow for the unique opportunity among animals to compare the same behaviors among species characterized by different mating systems: dioecy (co-presence of male and females) and androdioecy (co-presence of males and hermaphrodites).I analyzed mate guarding starting from the proximate mechanisms of this behavior. Males are not attracted to the opposite sex (while hermaphrodites are) but swim fast searching for hermaphrodites close-to-receptivity. Males do not react to molting hormone as a soluble cue in the water or as a direct contact cue on the hermaphrodites’ carapace. I analyzed costs and benefits for each sex (guarding is more costly to hermaphrodites than to males), I created a size “power” asymmetry between males and hermaphrodites (and confirmed that the stronger sex can better control the guarding duration), and I measured the optimal guarding time of each sex in order to compare it with the compromised guarding time. The results perfectly matched a theoretical model (Jormalainen, 1998): hermaphrodites “prefer” to be guarded less than the compromised guarding time, while males are willing to guard longer. I compared four species (two dioecious and two androdioecious) in order to assess the influence of the mating system on mate guarding strategies. The benefit of outcrossing is higher for females than hermaphrodites (who can self-fertilize if guarding is too costly) while males experience different social environments in the two mating systems (due to different sex ratios). As a result, dioecious species guarded longer than androdioecious species. Finally, I observed a dioecious species in the field to verify my laboratory results, performing in this way a comprehensive analysis of mate guarding behavior as a case of intersexual conflict in these interesting crustaceans. |
