Risk of predation increases susceptibility to parasitism via trait-mediated indirect effects

The presence of natural enemies can cause organisms to change habitat use, foraging behaviour and/or resource allocation in response to a perceived risk; responses that may come at the cost of other fitness-related traits. Since most species encounter multiple natural enemies, defensive behaviours against one attacker may make the focal organism more vulnerable to attack by a different natural enemy. Anti-predator behaviours can lead to trait-mediated indirect effects such as an increased risk of attack by parasites, and vice versa. Few empirical studies have examined the response of a single focal species to the risk of attack by multiple species. Our experiments provided Drosophila nigrospiracula with opportunities to prioritise either anti-predator or anti-parasite behaviour at the cost of increased infection or predation, respectively. When exposed to parasites in the presence of predator cues, D. nigrospiracula experienced increased infection compared to flies without predator cues..., Flies, mites, and spiders: Drosophila nigrospiracula flies were cultured on Drosophila media (Formula 4–24 Instant Drosophila Medium; Carolina Biological Supply Company, Burlington, NC), instant mashed potato, and autoclaved necrotic tissue of Saguaro cacti (Carnegiea gigantea). Macrocheles subbadius mites were maintained in a mix of 2:1 mix of wheat bran to wood chips and co-cultured with free-living nematodes as a food source, hereafter referred to as ‘mite media’. Drosophila nigrospiracula and M. subbadius were both collected from the Sonoran Desert, Arizona, USA, in 2019 and maintained separately in continuous culture at the University of Alberta in climate controlled incubators (Percival Scientific, Perry, IA, USA) at 25 °C, 70 % relative humidity (RH) and a 12 h:12 h light:dark regime. Salticus scenicus spiders were collected by hand on the campus of the University of Alberta, Canada. Spiders were maintained in 100 mL specimen jars and provided with water and one D. nigrospiracula..., , Title - Risk of predation increases susceptibility to parasitism via trait-mediated indirect effects

Summary: The presence of natural enemies can cause organisms to change habitat use, foraging behaviour and/or resource allocation in response to a perceived risk; responses that may come at the cost of other fitness-related traits. Since most species encounter multiple natural enemies, defensive behaviours against one attacker may make the focal organism more vulnerable to attack by a different natural enemy. Anti-predator behaviours can lead to trait-mediated indirect effects such as an increased risk of attack by parasites, and vice-versa. Few empirical studies have examined the response of a single focal species to the risk of attack by multiple species. Our experiments provided Drosophila nigrospiracula with opportunities to prioritise either anti-predator or anti-parasite behaviour at the cost of increased infection or predation, respectively. When exposed to parasites in the prese...,