A female-emitted pheromone component is associated with reduced male courtship in the parasitoid wasp Spalangia endius

During courtship interactions, the courted individual may not always be prepared to mate. For example, mating or courtship may be detrimental to its fitness and resistance is expected under these circumstances. As such, various resistance strategies have evolved, from physically fending off courting individuals to producing behavioural signals of unreceptivity. In the parasitoid wasp Spalangia endius, females rarely re-mate and mated females are avoided by males in favour of virgin females. Further, mated females appear to advertise their mating status by the release of a pheromone component (methyl 6-methylsalicylate), but direct evidence of the nature of this release is lacking. Here we used real-time chemical analysis to track the emission of the pheromone component during courtship interactions between virgin males and either virgin or mated females. We found that females actively release methyl 6-methylsalicylate when courted and that significantly greater concentrations are released by previously mated females. Further, high concentrations of this component are associated with both the prevention and termination of courtship

Brood Reduction in Neotropical Birds: Mechanisms, Patterns, and Insights from Studies in the Imperial Shag (Phalacrocorax atriceps)

Brood reduction is a within-brood partial mortality due to sibling rivalry and has been observed in a large number of bird species from diverse taxa. Here, I summarize several hypotheses accounting for the adaptive value of brood reduction and discuss different factors that modulate it. A description of different brood reduction systems is made with focus on Neotropical birds. Finally, an integrative approach analyzing brood reduction in Imperial Shags (Phalacrocorax atriceps) is presented to illustrate causes, consequences, and benefits of this breeding strategy.Fil: Svagelj, Walter Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentin