An analysis of secondary spread by putative clones of Sitobion avenae within a Hampshire wheat field using the multilocus (GATA)₄ probe

Abstract

Grain aphids (Sitobion avenae (F.)) were collected from forty-four wheat ears in a Hampshire field at three times during the growing season. On each occasion, individual aphids were profiled using the multilocus (GATA)4 probe. During the full head emergence and full anthesis growth stages of wheat, each ear generally supported a genetically distinguishable aphid colony which consisted of genetically indistinguishable individuals (putative clones). This information strongly suggests that individual ears were colonized by single immigration events. By the late milky ripe stage, most ears supported two or more such clones. The total number of clones declined and the spatial separation of identical clones increased markedly over the duration of the study, which strongly suggests that secondary spread rather than increased immigration was responsible for the increased clonal diversity of ears. In addition, the profiles of individual S. avenae became more alike as the season progressed and samples became dominated by particular clones indicating either differential survival or reproduction among clones.

Grain aphid population structure: no effect of fungal infections in a 2‐year field study in Denmark

“…Winged aphids are important for S. avenae population dynamics during a large part of the season ( Fievet et al , 2007 ) due to their high migration capacity over large distance, but also due to local movements. In addition, apterous S. avenae showed a high disposition to move between plants within fields ( Dean, 1973;Holmes, 1988;DeBarro et al , 1994 ); thus, migration may explain the time-dependent differentiation.…”

“…Aphid populations in cereal fields are regulated by a range of natural enemies, such as predators, parasitoids and fungal pathogens, which all exert a potential selection pressure on the aphids ( Heie, 1980;DeBarro et al , 1994 ). In temperate regions, entomophthoralean fungi, most commonly Conidiobolus obscurus (Hall et Dunn) Remaudière et Keller, Entomophthora planchoniana Cornu and Pandora neoaphidis (Remaudière et Hennebert) Humber, are often observed infecting grain aphids with prevalences possibly exceeding 75% ( Steenberg & Eilenberg, 1995;Plantegenest et al , 2001 ).…”

Evidence for gene flow and local clonal selection in field populations of the grain aphid (Sitobion avenae) in Britain revealed using microsatellites

“…As for competition, the population density of S. avenae in wheat crops during the sampling season was low; hence, direct clonal competition for feeding sites was unlikely, although evidence for such competition has been found in other studies of this aphid (eg De Barro et al, 1994).…”

“…In terms of selection, proliferation of specific clones, spatially and temporally, may well be dictated by differences in local microclimate (eg temperature, humidity), wheat cultivar, crop density and possibly insecticide regime (Carter et al, 1980;Lowe, 1980Lowe, , 1981 Genetic structure in grain aphids at the field scale KS Llewellyn et al Honek, 1987; see also De Barro et al, 1994Fenton et al, 2003). Although insecticide resistance has not, to date, been reported in S. avenae, it has evolved in several other aphid species, including most recently in the greenbug, Schizaphis graminum (Rondani) (Homoptera: Aphididae) (Ono et al, 1999).…”

Slaves of the environment: the movement of herbivorous insects in relation to their ecology and genotype

“…This apparent adaptation breaks down later in the season, probably as the frequency of local movements increases, both within a ¢eld and between ¢elds leading to a lowering of the distinction between the host-adapted clones. However, within a ¢eld, certain genotypes (clones) can colonize greater areas, possibly because of increased adaptive performance, and hence clonal variation declines (De Barro et al 1995a). Shufran et al (1991) also using a method of DNA ¢ngerprinting, showed that populations of the cereal aphid, the greenbug, Schizaphis graminum, in the USA had numerous genotypes but none was unique at any spatial scale from ¢eld to county level.…”