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Species Interactions in Arthropod Communities: Density Dependence and Ant Interactions on Aphid Per Capita Population Growth

Authors: Lopez, M.; Mooney, K.ORCID
Year: 2010
Publisher: UNKNOWN
Keywords: ANT, APHID, INTERACTIONS

Abstract

Ant and aphid interactions are often assumed to be mutualistic, with both participating parties receiving a benefit that outweighs the cost. Yet this interaction can range between mutualistic and antagonistic due to factors that alter this ratio of cost and benefit. Some factors that can affect the cost-benefit ratio are the abundance of predators, aphid population density, availability of alternative nutrients for the ants, and host plant quality. This study investigated the effects of ants, plant sex, and aphid density on aphid per capita population growth of Aphis valerianae feeding on the host plant Valeriana edulis and tended by several ant species (Formica podzolica, Tapinoma sessile, and Lasius neoniger). In addition to monitoring aphid population size, predator density and aphid emigration were observed to determine what mechanisms were responsible for the effects observed. It was found that per capita population growth was effected by population density due to a combination of intra-specific competition and predator recruitment. Contrary to other studies, we found that ants negatively affected per capita population growth and did not differ with a change in density. As well the effect of ants negatively effected aphid colony survival, but there was no effect of initial density. Ant tending did differ between plant sexes, in that there was less tending on male plants. This resulted in no effect of ants on aphid per capital population growth on male plants, regardless of density, which is unlike studies that have been done previously.

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