Longitudinal clines in the frequency distribution of 'super-clones' in an aphid crop pest.
Parthenogenesis is the main mode of reproduction of aphids. Their populations are therefore composed of clones whose frequency distribution varies in space and time. Previous population genetic studies on aphids have highlighted the existence of highly abundant clones ('super-clones'), distributed over large geographic areas and persisting over time. Whether the abundance of 'super-clones' results from their ecological success or from stochastic forces, such as drift and migration, is an open question. Here, we looked for the existence of clines in clonal frequency along a climatic gradient in the cereal aphid Rhopalosiphum padi (Linnaeus, 1758) and examined the possible influence of geographical distance and environmental variables in the buildup and maintenance of such clonal clines. We investigated the spatial distribution of the commonest genotypes of R. padi by sampling populations along an east-west transect in maize fields in the northern half of France in both spring and late summer. Individual aphids were genotyped at several polymorphic loci, allowing the assessment of frequency distributions of multilocus genotypes (MLGs) across the cropping season. We found several MLGs showing longitudinal clines in their frequency distribution in both spring and summer. In particular, two dominant asexual genotypes of R. padi showed inverted geographical clines, which could suggest divergent adaptations to environmental conditions. We concluded that while the distribution of some 'super-clones' of R. padi seems most likely driven by the action of migration and genetic drift, selection could be also involved in the establishment of longitudinal clines of others.
INRA UMR 1349 IGEPP,Domaine de la Motte,F-35653 Le Rheu,France.
A
A
Gilabert
INRA UMR 1349 IGEPP,Domaine de la Motte,F-35653 Le Rheu,France.
C-A
CA
Dedryver
INRA UMR 1349 IGEPP,Domaine de la Motte,F-35653 Le Rheu,France.
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S
Stoeckel
Agrocampus-ouest UMR 1349 IGEPP,65 rue de Saint-Brieuc,F-35042 Rennes,France.
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M
Plantegenest
INRA UMR 1349 IGEPP,Domaine de la Motte,F-35653 Le Rheu,France.
J-C
JC
Simon
D063147:Animal Distribution; D000818:Animals; D001042:Aphids / Q000235:genetics / Q000502:physiology*; D001499:Bayes Theorem; D014644:Genetic Variation; D005838:Genotype; D018895:Microsatellite Repeats; D010312:Parthenogenesis; D058974:Phylogeography; D011156:Population Density; D011157:Population Dynamics; D012098:Reproduction / Q000235:genetics
aphids; cyclical parthenogenesis; drift; genotypic diversity; selection