Assortative pairing with respect to parasite load in the beetle Timarcha maritima (Chrysomelidae)

Frédéric Thomas (1, 2) , E. Oget (1, 2) , Pascal Gente (1, 2) , Didier Desmots (1, 2) , François Renaud (2, 1)

1 CEPM - Centre d'Etude sur le Polymorphisme des Micro-Organismes
2 UMR ISEM - Institut des Sciences de l'Evolution de Montpellier

Because of their effects on host reproductive behaviour, parasites are theoretically expected to create sometimes assortative mating among hosts, with heavily parasitized individuals pairing together and lightly parasitized ones pairing among themselves. We investigated the influence of protozoan gut parasites on the pairing pattern of the chrysomelid beetle Timarcha maritima. In the field, fecundity was negatively correlated with the parasite load of females, unpaired males were significantly more heavily infected than paired ones and, among pairs, males and females were matched for parasite load. Mate choice experiments in the laboratory showed that males have some ability to avoid heavily infected partners when given the choice between two females. Male competitiveness, measured as their mobility, was also negatively correlated with parasite load. These results indicate that parasite-related assortative pairing in this beetle could result from parasitized females being less fecund and parasitized males less competitive.

Mots clés: Assortative mating; Chrysomelidae; Gregarina munieri; Parasitism; Sexual selection; Timarcha maritima

Domaines: Parasitologie; Zoologie des invertébrés; Interactions entre organismes

Frédéric Thomas, E. Oget, Pascal Gente, Didier Desmots, François Renaud. Assortative pairing with respect to parasite load in the beetle Timarcha maritima (Chrysomelidae). Journal of Evolutionary Biology, 1999, 12 (2), pp.385-390. ⟨10.1046/j.1420-9101.1999.00042.x⟩. ⟨hal-02530818⟩