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SEPG 2096 - Date Awarded 2002
Variability of infection by the bacterium Wolbachia in its butterfly host Hypolimnas bolina throughout French Polynesia: a preliminary survey
Sylvain Charlat
Abstract
Wolbachia is an intracellular bacterium infecting many arthropod species. It can invade hosts population through various strategies, one of which being referred to as “male-killing”, where the bacterium kills infected females’ sons. Among the important consequences of this phenomenon, it has been suggested that the bacterium can make males so rare that sexual selection is deeply affected: competition between males for access to females is expected to be reduced, while females might often be awaiting copulation.
To test the view that Wolbachia can affect the evolution of sexually selected traits, one needs to identify a host species where infection frequency varies among populations, so that correlation between infection frequency and sexual traits can be investigated. One potential such system is the south pacific butterfly Hypolimnas bolina where male-killing has been recently described. In this project, I aimed to collect samples of H. bolina from French Polynesian islands, in order to assess variation of infection frequency.
I collected H. bolina in February and March 2003 and obtained samples from six islands distributed among four distant archipelagos: Moorea and Tahiti (Society Archipelago), Rurutu and Tubuai (Australes Archipelago), Tahuata and UaHuka (Marqueses Archipelago). H. bolina was not found on two other locations despite intense efforts: Rangiroa (Tuamotu Archipelago) and Mangareva (and other islands from the Gambiers Archipelago). Molecular analysis later performed on the samples collected revealed important between-island variation in infection frequency. This projected thus provided the preliminary data for a long term investigation, currently underway, focusing on the evolutionary impact of sex-ratio distorters on host reproductive biology.
Full report: SEPG2096
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