Defence variation within a guild of aphid‐tending ants explains aphid population growth

Abstract

Mutualism studies often focus on the service provided by single species, while variation in benefits provided by multiple partners is less understood. Ant‐aphid food‐for‐protection mutualisms are suitable to study the implications of intra‐guild service variation because they often involve several ant species with varying levels of aggressiveness. We studied an aphid species and its associated ant guild to address whether intra‐guild defence variation against aphid natural enemies explains aphid performance on plants (thistles). We surveyed plants with natural abundances of aphids associated with different ant species and estimated aphid population growth. We conducted confrontation experiments between ant species and aphid natural enemies (ladybugs and hoverfly larvae). In plants patrolled by the most aggressive ant species, we determined the ant's probability of expelling aphid natural enemies and tested whether ant exclusion affects the abundance of aphids and their natural enemies. The ant Dorymyrmex tener was the most abundant and frequent species on plants and the most aggressive against aphid natural enemies. Aphid populations grew faster on plants patrolled by D. tener compared to plants patrolled by Camponotus distinguendus or D. richteri. Field experiments confirmed that D. tener effectively expels aphid natural enemies from plants. When D. tener was excluded, the density of aphids decreased, while the abundance of aphid natural enemies increased. The disruption of aphid predation by aggressive and numerically dominant ant species is a determinant of aphid population dynamics. This study illustrates the importance of considering intra‐guild service variation to better understand multi‐partner mutualisms.

Act locally, think globally: Ant studies in Argentina in the context of ecological theory

“…For example, in northwestern Patagonia, refuse dumps of the leaf-cutting ant Ac. lobicornis increase plant fitness Ghermandi 2004, 2008), enhance aphid infestation on plants and increase aphid-tending ant activity (Lescano et al 2012), which may further impact on aphid predators (Devegili et al 2020). In sum, ants belonging to different functional groups (hemipteran-tending, nectarivores, and leaf-cutting ants) modulate and trigger top-down and bottom-up trophic cascades with an important impact on community composition and ecosystem function.…”

“…Indirect facilitation occurs when one species benefits a second one by suppressing its antagonists, such as predators or competitors (White et al 2006). For example, in northwestern Patagonia, the aggressive aphidtending ant Dorymyrmex tener deters ladybugs and syrphid larvae which in turn increases aphid fitness (Devegili et al 2020). Indirect facilitation also occurs when one species relaxes competition between two other species (Sotomayor and Lortie 2015; Figure 3b).…”

“…The biotic resistance of native seed-harvesting ants may thus depend on species identities and habitat type. In the Patagonian steppe, a native aphidtending ant, Dorymyrmex tener, decreases exotic thistle fitness by protecting aphids against their predators and increasing aphid infestation and damage (Chalcoff et al 2019;Devegili et al 2020Devegili et al , 2021. Therefore, through positive effects on aphid populations, native aphid-tending ants may trigger indirect biotic resistance toward exotic plants.…”

Ant (Hymenoptera: Formicidae) ‐ aphid (Hemiptera: Aphididae) interactions in different habitats from Turkey with new mutualistic associations

“…Also, ant presence has positive effects on important biological features of aphids such as population growth (Rice & Eubanks, 2013). Conversely, the removal of ants from the environment reduces the intensity of the aphid population and the damages they cause (Nagy et al ., 2013; Devegili et al ., 2020). From an ecological perspective, the honeydew and cuticular hydrocarbons secreted by aphid species play an important role in the aphid partner selectivity of ants, as it helps ants recognize and not kill aphids (Endo & Itino, 2013; Hayashi et al ., 2015).…”

Influência da identidade e padrões comportamentais das formigas e da qualidade do recurso mediador (>i<honeydew>/i<) nos resultados da interação formiga-planta-hemíptero

“…Dessa forma, as formigas acabam promovendo a sobrevivência desses hemípteros e também moldando a composição das assembleias de formigas nas plantas em que eles ocorrem . Todavia, embora exista um certo consenso sobre as formigas protegerem esses hemípteros (MOREIRA; DEL-CLARO, 2005), o efeito positivo sobre a abundância e sobrevivência desses insetos tende a depender da espécie VILELA et al, 2018;DEVEGILI et al, 2020) e potencialmente da estratégia de dominância da formiga associada. Entretanto, a extensão pela qual essas estratégias de dominância podem influenciar nos resultados das interações formigashemípteros é desconhecida.…”