1. ¹Instituto de Ecología y Evolución, Universidad Austral de Chile, Casilla, Chile
2. ²INRA, UMR BiO3P INRA/Agrocampus Rennes, Le Rheu cedex, France

Correspondence: Dr RF Nespolo, Instituto de Ecología y Evolucíon, Universidad Austral de Chile, Campus Isla Teja, Valdivia, Casilla 357, Chile. E-mail: robertonespolo@uach.cl

Received 28 August 2007; Revised 12 November 2007; Accepted 16 November 2007; Published online 23 January 2008.

Abstract

One of the most important factors that determine the evolutionary trajectory of a suite of traits in a population is the structure of the genetic variance–covariance matrix (G). We studied the cyclically parthenogenetic aphid Rhopalosiphum padi, whose populations exhibit two types of reproductive lineages respectively specialized in sexuality (that is, cyclically parthenogenetic lineages) and in asexuality (that is, obligate parthenogenetic lineages). We compared the quantitative genetics of life histories in these two lineage types. Our results suggest that both, the elements and the whole structure of the resulting G matrices differ in the very short term, between lineage types. This would involve the evolution toward different evolutionary optima in the same population, depending on whether sexual or asexual lineages predominate. Since sexual and asexual lineages vary seasonally in their abundance, a fluctuating selective regime has been proposed for this species, which would contribute to the maintenance of the reproductive polymorphism that these populations exhibit.