Are body size and volatile blends honest signals in orchid bees?

• Published in: Ecology and evolution 2017-05, Vol.7 (9), p.3037-3045
• Main Authors: Arriaga‐Osnaya, Brenda Jessica, Contreras‐Garduño, Jorge, Espinosa‐García, Francisco Javier, García‐Rodríguez, Yolanda Magdalena, Moreno‐García, Miguel, Lanz‐Mendoza, Humberto, Godínez‐Álvarez, Héctor, Cueva del Castillo, Raúl
• Format: Article
• Language: English
• Subjects: Animal behavior; Bees; Body size; Conveying; Courtship; Encapsulation; Euglossa imperialis; Females; Fungi; honest signals; Immune response; Immune system; Indicators; Insects; Males; Mating; Offspring; orchid bees; Original Research; Parasites; Pathogens; Perfumes; Phenolic compounds; Phenoloxidase; Phenols; Pheromones; Polymer blends; Resins; sexual selection; Volatile compounds; Volatiles
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.2903

Secondary sexual traits may convey reliable information about males’ ability to resist pathogens and that females may prefer those traits because their genes for resistance would be passed on to their offspring. In many insect species, large males have high mating success and can canalize more resources to the immune function than smaller males. In other species, males use pheromones to identify and attract conspecific mates, and thus, they might function as an honest indicator of a male's condition. The males of orchid bees do not produce pheromones. They collect and store flower volatiles, which are mixed with the volatile blends from other sources, like fungi, sap and resins. These blends are displayed as perfumes during the courtship. In this study, we explored the relationship between inter‐individual variation in body size and blend composition with the males’ phenoloxidase (PO) content in Euglossa imperialis. PO content is a common measure of insect immune response because melanine, its derived molecule, encapsulates parasites and pathogens. Body size and blend composition were related to bees’ phenolic PO content. The inter‐individual variation in body size and tibial contents could indicate differences among males in their skills to gain access to some compounds. The females may evaluate their potential mates through these compounds because some of them are reliable indicators of the males’ capacity to resist infections and parasites. Males of orchid bees collect and store flower volatiles, which are mixed with the volatile blends from other sources and displayed as perfumes during the courtship. We explored the relationship between inter‐individual variation in body size and blend composition with the males’ immune function [phenoloxidase activity (PO)] in Euglossa imperilis. Body size and blend composition were related to bees’ immune function. Thus, some compounds in the blends may represent for the females reliable indicators of the males’ capacity to resist infections and parasites.