Provenance, experience and plant utilisation by the polyphagous aphid, Aphis fabae

Abstract

AbstractTwenty‐nine clones of Aphis fabae Scopoli (Aphididae: Homoptera) were isolated into laboratory culture from the primary host plants Euonymus europaeus and Viburnum opulus and the secondary host plants Arctium lappus, Impatiens glandulifera, Tropaeolum majus and Vicia faba. All clones performed well on either T. majus or V. faba, with mean intrinsic rates of increase (rm) in the range 0.35–0.41 aphids aphid−1 day−1, but none performed well on both plant species. Each clone could, therefore, be described as affiliated to either V. faba or T. majus. All of the 13 T. majus‐affiliated clones and 15 of the 16 V. faba‐affiliated clones could not be maintained beyond two parthenogenetic generations on the contrary plant. These results confirm that the performance of A. fabae on T. majus and V. faba is negatively correlated. Exceptionally, one V. faba‐affiliated clone (clone AED95/119) persisted indefinitely on T. majus, exhibiting a progressive improvement in performance across four parthenogenetic generations: larval mortality dropped from 80% to <20%, mean adult weight almost doubled from 0.28 to 0.53 mg, and mean number of embryos per adult aphid increased threefold from 8.6 to 24.4 embryos. The mean rm of clone AED95/119 that had been reared on T. majus for more than 4 generations was 0.17 aphids aphid−1 day−1, significantly lower than the value of 0.34 aphids aphid−1 day−1 on V. faba. It was also shown that the rm on V. faba did not differ significantly between aphids of clone AED95/119 that had been derived from long‐term cultures on V. faba and T. majus. It is concluded that the negative correlation between performance on V. faba and T. majus is not genetically fixed, but may diminish with exposure to T. majus. The implication is that this clone may have a capacity to utilise T. majus that is independent of its capacity to utilise V. faba, and is expressed only on sustained exposure to T. majus. It is suggested that, although the ‘latent’ capacity to utilise T. majus is probably not exhibited widely under natural conditions, aphids possessing it may be at a selective advantage when more suitable host plants are temporarily unavailable.