アブラムシの好蟻性を決定する要因 : アリによる捕食と蜜源間のアリを巡る競争

抄録

Ant-aphid interactions have often been regarded as mutualism. However, the effects of ants on aphids depend on the situation, and many species of aphids are not myrmecophilous despite the fact that aphid excretion is a desirable food for ants. In this paper, I discuss the factors that influence the mutualism of these insects. First, I review the background of ant foraging strategy and the mechanism regulating their foraging behavior. Decision-making by ants to tend or attack aphids and selection of more appropriate food sources are considered to have important effects on the ecology and evolution of aphid myrmecophily. Second, I give an outline of the mechanism by which the foraging strategy of ants makes their relationships unstable and causes interference among sympatric sugar sources. Ant predation according to the supply-demand balance of honeydew can alter the effects of ants on the population growth of aphids from positive to negative, as the supply of sugary food increases. In addition, ant predation is directed to aphids that are less desirable as a honeydew source. In this way, the existence of a more desirable sugar source creates a negative effect of ants on aphids of lower value. Therefore, in order to be myrmecophilous, aphids must be more attractive to ants than other sugar sources. Otherwise, repelling of ants is considered to be an alternative strategy. This potential antagonism among sugar sources should restrict the mutualism between ants and aphids.