Determinants of the size of aphid–parasitoid assemblages

Abstract

Abstract: Aphid parasitoids have to cope with a range of different life‐history features of their hosts in terms of size at maturity, abundance, ant‐attendance, host specificity, host alternation and many more. Their hosts often show large fluctuations in numbers during a season or in different habitats and the plants they live on strongly shape their performance. Plant characteristics (i.e. life form, ecological strategy, light exposure, nutrient provision, habitat type) also affects the environment of aphids and their associated parasitoids. Using data restricted to Central European aphids and their primary parasitoids, effort is directed to identifying significant ecological variables, which might influence the diversity of parasitoid assemblages in aphids. Most parasitoid species were reported from the Aphidini and Macrosiphini. Aphids, which are very abundant, host‐alternating, polyphagous and live on grasses appear to support larger parasitoid assemblages than those which are less abundant, non‐host‐alternating, mono‐ or oligophagous and feed on trees or herbs. Obligate myrmecophiles support fewer parasitoids than facultative myrmecophiles. Different degrees of mobility, the production of wax wool and alate adults did not have significant effects on parasitoid numbers. Discriminant function analysis using different degrees of ant attendance as dependant variable indicated that aphid specific characters and the number of primary parasitoids contributed most to the separation of the groups. Plant specific characters seem to contribute little to the development of different degrees of myrmecophily and parasitization patterns.