Effects of brood parasitism on host reproductive success: evidence from larval interactions among dung beetles

Abstract

This paper investigates the effect of brood parasitism in a dung beetle assemblage in an arid region of Spain. The study was conducted during the spring season (March-May 1994-1998) using mesh cylinders buried into the ground, filled with sand and with sheep dung on top. We quantified the proportion of nests containing larvae of parasitic beetles and their effect on host larvae survival. Experiments on the effect of parasitic larvae on host-larvae survival were conducted by placing scarab brood masses (raised from captive scarabs in the laboratory) in containers with and without aphodiid larvae. During the spring, dung desiccation is rapid, preventing aphodiids nesting in the dung, and forcing these species to adopt brood parasitism as a nesting strategy. Parasitic aphodiids were found in 12-47% of scarab nests of three species. The incidence of brood parasitization was positively related with the number of brood masses contained in the nests, being also higher in the most abundant species. Field data and experiments showed that brood parasites significantly reduced host larvae survival from 74.8% in non-parasitized nests to 8.8% in parasitized nests. Because different rates of nest parasitization and mortality were caused by parasites, brood parasitism had a differential effect on different host species. Thus, brood parasitism constitutes an important mortality factor reducing the reproductive success of the host species and potentially affecting the beetle abundance in the area.

Reproductive competition promotes the evolution of female weaponry

“…There is evidence that reproductive competition is a feature of female life histories in the genus Onthophagus; females have been found to exhibit intraspecific brood parasitism, raiding other females' brood balls, stealing dung or replacing existing eggs with their own, thereby exploiting a competitor's investment (Moczek & Cochrane 2006). Onthophagine females can also be victims of interspecific parasitism (González Megías & Sánchez-Piñ ero 2003). A female's probability of success in such encounters, whether it be defence of her own brood or attack of another female's, is likely to be strongly determined by her competitive ability.…”

Trophic interactions in an arid ecosystem: From decomposers to top-predators

“…Among the dominant Aphodiidae species, Euorodalus tersus and Mecynodes leucopterus are brood parasites in our study area, because rapid dung desiccation (46.5% water loss in 24 h) prevents endocoprid nesting (i.e., nesting within the dung). Thus, these species are able to actively locate and reach Scarabaeus and Onthophagus nests (González-Megías and Sánchez-Piñero, 2004). Field and laboratory experiments showed that brood parasitism by Aphodiidae affected 12% (Scarabaeus puncticollis nests) to 47% (Onthophagus merdarius) nests, causing high mortality (66%) of host larvae (González-Megías and Sánchez-Piñero, 2003).…”

“…Thus, these species are able to actively locate and reach Scarabaeus and Onthophagus nests (González-Megías and Sánchez-Piñero, 2004). Field and laboratory experiments showed that brood parasitism by Aphodiidae affected 12% (Scarabaeus puncticollis nests) to 47% (Onthophagus merdarius) nests, causing high mortality (66%) of host larvae (González-Megías and Sánchez-Piñero, 2003). Experimental manipulation of Onthophagus brood masses in the laboratory demonstrated that aphodiid larvae actively killed host larvae within the brood mass, although the dung-feeding aphodiid larvae did not consume the host larvae, but only killed them apparently to eliminate competing larvae of the host (González-Megías and Sánchez-PiñGonz ero, 2003).…”

Distribución y patrones de diversidad de los Afódidos en la Comunidad de Madrid (Coleoptera, Scarabaeoidea, Aphodiidae, Aphodiinae y Psammodiinae)

“…Además del comportamiento típicamente endocóprido, algunas especies son capaces de construir primitivos nidos en el suelo (p.e. en el subgénero Colobopterus: Aphodius erraticus, Rojewski, 1983), otras presentan estados larvarios radicícolas, y otras incluso presentan comportamiento cleptoparasitos (es decir, aprovechan el momento de la construcción del nido para introducirse o depositar su huevo en las bolas creadas por otras especies; Cambefort & Hanski, 1991;Martín-Piera & Lobo, 1993;González-Megías & Sánchez-Piñero, 2003). Aunque Cambefort & Hanski (1991) consideran este último comportamiento poco significativo, estudios recientes demuestran que puede ser común cuando existen altas densidades de rodadores (Martín-Piera & Lobo, 1993), e incluso ser un factor importante en la estructuración de las comunidades coprófagas de ambientes mediterráneos semiáridos (González-Megías & Sánchez-Piñero, 2003), como los presentes en buena parte de la Península Ibérica.…”