Variation in a Host–Parasitoid Interaction across Independent Populations

Abstract

Antagonistic relationships between parasitoids and their insect hosts involve multiple traits and are shaped by their ecological and evolutionary context. The parasitoid wasp Cotesia melitaearum and its host butterfly Melitaea cinxia occur in several locations around the Baltic sea, with differences in landscape structure, population sizes and the histories of the populations. We compared the virulence of the parasitoid and the susceptibility of the host from five populations in a reciprocal transplant-style experiment using the progeny of five independent host and parasitoid individuals from each population. The host populations showed significant differences in the rate of encapsulation and parasitoid development rate. The parasitoid populations differed in brood size, development rate, pupal size and adult longevity. Some trait differences depended on specific host-parasitoid combinations, but neither species performed systematically better or worse in experiments involving local versus non-local populations of the other species. Furthermore, individuals from host populations with the most recent common ancestry did not perform alike, and there was no negative effect due to a history of inbreeding in the parasitoid. The complex pattern of variation in the traits related to the vulnerability of the host and the ability of the parasitoid to exploit the host may reflect multiple functions of the traits that would hinder simple local adaptation.

The more the merrier: Conspecific density improves performance of gregarious larvae and reduces susceptibility to a pupal parasitoid

“…Finally, consistent with previous work on the Glanville fritillary butterfly (development; Laine, ; and immunity; van Nouhuys, Niemikapee, & Hanski, ; Saastamoinen, Hirai, & van Nouhuys, ), we show that family rather than the common postdiapause environment explains a relatively high proportion of the total variance in most of the traits measured. The family effect assessed includes the genetic background as well as the common prediapausing and diapausing environment, and any parental effects.…”

“…This result is not surprising, given the ability of parasitoid wasps to adjust brood size and sex ratio (Frank, ; Slansky, ). In contrast, the proportion of wasps eclosed was primarily determined by butterfly family, highlighting the importance of host genetic background in the outcome of host–parasite interactions, as was shown for another parasitoid of M. cinxia (van Nouhuys et al., ).…”

Influence of Developmental Conditions on Immune Function and Dispersal-Related Traits in the Glanville Fritillary (Melitaea cinxia) Butterfly

“…It also plays a role in defence against viruses [ 32 ] and some bacteria [ 33 ]. In the Glanville fritillary butterfly, encapsulation is known to work at least against a specialist parasitoid [ 34 ] and there is also a significant correlation between encapsulation rate and survival to bacterial infection [ 35 ]. Encapsulation rate was measured by inserting a 2 ± 0.1 mm long piece of nylon monofilament (diameter 0.18 mm, rubbed with sandpaper) through a puncture in the pupal cuticle [ 20 ].…”

The Puzzle of Partial Resource Use by a Parasitoid Wasp

“…Insects can defend themselves against endoparasitoids by encapsulating or otherwise preventing development of parasitoid eggs or larvae (Lavine and Strand, 2002). For instance, M. cinxia caterpillars encapsulate up to half the larvae of the parasitoid Cotesia melitaearum (Hymenoptera: Braconidae) (van Nouhuys et al, 2012). If the majority of M. cinxia were resistant to parasitism by H. horticola, then the low rate of successful parasitism would be explained by host immunity.…”