Asexual reproduction of a few genotypes favored the invasion of the cereal aphidRhopalosiphum padiin Chile

Abstract

BackgroundAphids (Hemiptera: Aphididae) are insects with one of the highest potentials for invasion. Several aphid species are present globally due to introduction events; they represent important pests of agroecosystems. The bird cherry-oat aphidRhopalosiphum padi(Linnaeus) is a major pest of cereals and pasture grasses worldwide. Here, we report the genetic features of populations ofR. padithat colonize different cereal crops in central Chile.MethodsRhopalosiphum padiindividuals were collected in central Chile and genotyped at six microsatellite loci. The most frequent multilocus genotype (MLG) was then studied further to assess its reproductive performance across cereal hosts under laboratory conditions.ResultsPopulations ofR. padiin Chile are characterized by a low clonal diversity (G/N= 62/377 = 0.16) and the overrepresentation of a few widely distributed MLGs. One of the MLGs constituted roughly half of the sample and was observed in all sampled populations at high frequencies. Furthermore, this putative aphid “superclone” exhibited variations in its reproductive performance on cereals most commonly cultivated in Chile. The sampled populations also exhibited weak signs of genetic differentiation among hosts and localities. Our findings suggest that (1) obligate parthenogenesis is the primary reproductive mode ofR. padiin Chile in the sampled range and (2) its introduction involved the arrival of a few genotypes that multiplied asexually.