Absence of direct sexual selection for parasitoid encapsulation in Drosophila melanogaster

Abstract

Resistance against parasites may play a role in female mate choice, especially if males that have actually survived parasitism can be discriminated from males that have not been parasitised. Larvae of several Drosophilu species are subject to attack by hymenopteran parasitoids, but have the ability to kill the parasitoid egg through the process of encapsulation. Because an encapsulated egg remains visible in the abdomen of the adult fly throughout its life, its presence in a male signals to a female that the male has the genes to survive parasitism. The hypothesis that females preferentiahy mate with males bearing an encapsulated egg in their abdomen was tested using D. melunogasttcr. No indication was found for this female preference. The absence of preference for males with "good genes" could result from sensory constraints in the female or a negative correlation between encapsulation ability and some other fitness component. Alternatively, it is hypothesised that the black abdominal ends of the males of many species in the melunogaster-group evolved to mimic encapsulated eggs, leading to the breakdown of capsule recognition by the female.

The relative fitness of Drosophila melanogaster (Diptera, Drosophilidae) that have successfully defended themselves against the parasitoid Asobara tabida (Hymenoptera, Braconidae)

“…The most reasonable is that those with capsules have smaller testes and hence produce smaller numbers of spermatozoa in their ejaculate. Kraaijeveld et al . (1997 ) have shown that there is no difference in the likelihood of capsule‐bearing male D. melanogaster obtaining matings when compared to control males.…”

Lack of parasite-mediated sexual selection in a ladybird/sexually transmitted disease system

“…Parasites are known to affect host mate choice and mating patterns (see Kavaliers et al 2000 for a review; but also Kraaijeveld et al 1997;Rolff et al 2000). However, there has been limited investigation of the effects of .…”

The coevolution of host resistance and parasitoid virulence

“…Fewer studies have looked for genetic variation in For logistic reasons control encapsulation ability was assayed less frequently than that of the selected lines (from Kraaijeveld & Godfray, 1997).…”

“…In a test assay, wasps successfully survived in 43 % of control hosts but only 31 % of treatment hosts. Kraaijeveld & Godfray (1997) initiated a large outbred culture of D. melanogaster from wild Dutch flies. The aim was to study selection for increased resistance against parasitoids that themselves were prevented from evolving (and also to study tradeoffs, see next section).…”