Do ecological niches differ between sexual and asexual lineages of an aphid species?
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According to environmental-based theories on the maintenance of sexual reproduction, sexual and asexual populations may coexist if they occupy different ecological niches. The aphid Rhopalosiphum padi offers a good opportunity to test this hypothesis since sexual and asexual lineages show local coexistence during a large part of their respective life-cycles. Because these two reproductive variants are morphologically identical but genetically distinct, we first characterized them using genetic markers in populations of R. padi in areas where sexual and asexual lineages may occur in sympatry. We then inferred the natal host plant of sexual and asexual genotypes by analysing stable isotopic ratios and showed that sexual ones mostly originated from C3 Poaceae while asexual ones originated from C3 and C4 plants, although the majority came from C4 Poaceae. These findings indicate that ecological niches of sexual and asexual lineages of R. padi differ, offering a plausible explanation for the local coexistence of the two reproductive modes in this species through habitat specialisation.
KeywordsRhopalosiphum padi Isotopic analyses Reproductive mode Habitat differentiation Maintenance of sex
We thank J-F. Le Gallic, P. Lhomme and L. Mieuzet for their help with sampling and genotyping, and T. Forde and J. Foucaud for comments on the manuscript. Isotopic analyses were performed at the Mylnefield Research Services (Scotland, UK). This research was supported by Bayer CropScience France and a CIFRE grant from the Association Nationale de la Recherche Technique.
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