| predators and mutualists influence the exclusion of aphid species from natural communities. | we investigated why two species of aphids (aphis jacobaeae and brachycaudus cardui) were very rare in a study site despite their abundance in the surrounding area. the study site contained many common species of aphid and we tested the hypothesis that the community of aphid predators in the field excluded the missing species. colonies of the two aphid species were artificially initiated in the experimental site and allocated to one of four treatments: control; ground predator exclusion; total pr ... | 1999 | 28308151 |
| tritrophic interactions between aphids (aphis jacobaeae schrank), ant species, tyria jacobaeae l., and senecio jacobaea l. lead to maintenance of genetic variation in pyrrolizidine alkaloid concentration. | we hypothesize that the tritrophic interaction between ants, the aphid aphis jacobaeae, the moth tyria jacobaeae, and the plant senecio jacobaea can explain the genetic variation observed in pyrrolizidine alkaloid concentration in natural populations of s. jacobaea. the ant lasius niger effectively defends s. jacobaea plants infested with a. jacobaeae against larvae of t. jacobaeae. s. jacobaea plants with a. jacobaeae which are defended by ants escape regular defoliation by t. jacobaeae. plants ... | 1991 | 28313199 |
| relative importance of fertiliser addition to plants and exclusion of predators for aphid growth in the field. | herbivore dynamics and community structure are influenced both by plant quality and the actions of natural enemies. a factorial experiment manipulating both higher and lower trophic levels was designed to explore the determinants of colony growth of the aphid aphis jacobaeae, a specialist herbivore on ragwort senecio jacobaea. potential plant quality was manipulated by regular addition of npk-fertiliser and predator pressure was reduced by interception traps; the experiment was carried out at tw ... | 2005 | 15756583 |