Parthenogenesis in weevils of the tribe Naupactini (Coleoptera, Curculionidae): aWolbachia-density dependent trait?

Abstract

AbstractThe intracellular bacteriaWolbachia pipientiscan manipulate host reproduction to enhance their vertical transmission. It has been reported an association between parthenogenesis andWolbachiainfection in weevils from the tribe Naupactini. A curing experiment suggested that a threshold density ofWolbachiais required for parthenogenesis to occur. The aim of this study was to analyzeWolbachiainfection status in the bisexual speciesNaupactus xanthographusandNaupactus dissimulator.Wolbachiainfection was detected in both species from some geographic locations, not being fixed. In all positive cases, faint PCR bands were observed. Quantification through real time PCR confirmed thatWolbachialoads in bisexual species were significantly lower than in parthenogenetic ones; this strengthens the hypothesis of a threshold level. Strain typing showed that both species carrywNau1, the most frequent in parthenogenetic Naupactini weevils. These infections seem to be recently acquired by horizontal transfer.Wolbachiawas located throughout the whole body, which reinforce the idea of recent transmission. Moreover, we demonstrated that this strain carries the WO phage.Finally, the analysis of eubacterial16S rRNAgene showed intense PCR bands for both bisexual species, suggesting –the presence of additional bacteria. Interspecific competition might explain why the parthenogenetic phenotype is not triggered.