Parthenogenesis in weevils of the tribe Naupactini (Coleoptera, Curculionidae)

Abstract

The intracellular bacteria <i>Wolbachia pipientis</i> can manipulate host reproduction to enhance their vertical transmission. It has been reported an association between parthenogenesis and <i>Wolbachia</i> infection in weevils from the tribe Naupactini. A curing experiment suggested that a threshold density of <i>Wolbachia</i> is required for parthenogenesis to occur. The aim of this study was to analyze <i>Wolbachia</i> infection status in the bisexual species <i>Naupactus xanthographus</i> and <i>Naupactus dissimulator</i>. <i>Wolbachia</i> infection 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 that <i>Wolbachia</i> loads in bisexual species were significantly lower than in parthenogenetic ones; this strengthens the hypothesis of a threshold level. Strain typing showed that both species carry <i>w</i>Nau1, the most frequent in parthenogenetic Naupactini weevils. These infections seem to be recently acquired by horizontal transfer. <i>Wolbachia</i> was 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 eubacterial 16S <i>rRNA</i> gene 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.