Effects of aphid parasitism on host plant fitness in an aphid-host relationship

Abstract

Aphids are serious agricultural insect pests which exploit the phloem sap of host plants and thus transmit pathogens to their hosts. However, the degree to which aphid parsitism affects the fitness of the host plants is not well understood. The aphid, Macrosiphoniella yomogicola, parasitizes the mugwort Artemisia montana in Japan. During summer most mugworts carry aphids, but most aphid colonies die out after the budding of A. montana inflorescences in late summer. A few aphid colonies survive to late autumn, at which point sexuparae appear to later lay overwintering eggs after copulation. The death of the aphid colonies seems to be caused by biochemical changes in the phloem sap in the host plant coincident with the budding of inflorescences. The surviving aphid colonies may suppress the budding of inflorescences to allow persistence of their genetic line into the following year. Our investigations demonstrate that aphid parasitism did not affect host plant growth, but that it did significantly decrease the number of inflorescences and the average weight of floral buds. Our results indicate that aphid parasitism has a strong negative effect on the fitness of host plants. The manner in which the aphids suppress floral budding in their hosts is worth examining from the perspective of the evolution of aphid-plant interactions.

Genetic Differentiation between Color Morphs of a Color-Polymorphic Aphid Macrosiphoniella yomogicola

“…From late June to early August, most of the mugwort shoots are inhabited by the mixed morph aphid colonies. After inflorescences of the host shoot have emerged, aphid colonies rapidly decrease [10]. When an aphid colony survives until mid-October when sexuparae of M. yomogicola emerge, inhabited shoots rarely produce inflorescences.…”

“…Additionally, the attending ants prefer the green morph under both experimental and field conditions [10], likely owing to the highquality honeydew excreted by the green morph. If this observation is correct, although the ants can discriminate between the morphs since they manipulate the green morph only, why is the red morph maintained in aphid colonies by the ants?…”

“…Maintenance of genetic polymorphisms is important for understanding the emergence and maintenance of biodiversity in nature [1,2]. Four main hypotheses may explain this phenomenon: 1) different adaptations of each allele in a gene pool to heterogenous patches in a habit forming a gene pool [3,4]; 2) frequencydependent selection among multiple alleles [5][6][7][8]; 3) heterosis; and 4) in a symbiotic system, manipulations by one species that neutralize reproductive competition among genetic morphs of the other species [9,10]. In particular, there have been few studies investigating hypothesis 4, although a symbiotic system requires and simultaneously maintains biodiversity.…”

“…In Hokkaido, the morphs can be classified into two types, green and red [12]. When the aphids are not attended by ants, there is a higher increasing rate of the red morph compared to that of the green morph [9,10]. However, when ants attend the aphids, the frequencies of the red and green morphs are similar, indicating manipulation by the ants to neutralize the reproductive competition between the two aphid morphs [9,10].…”

A new trophic interaction between invasive weed, its biological control agent, and local insects: A case study of Chromolaena odorata

“…In this research, we did not investigate the effect of aphids on the growth of C. odorata but presumably has a similar effect with C. connexa. Research by Watanabe et al (2018) found that the parasitism of aphid, Macrosiphoniella yomogicola, in the mugwort (Artemisia montana) did not affect the host plant growth, but significantly decreased the number of inflorescences.…”