How much does the host matter to the parasitoid? Distribution of Eurytoma (Hymenoptera, Chalcidoidea) species amongst two locally co-occurring gall-inducing hosts in the genus Diplolepis (Hymenoptera, Cynipidae)

Jamie M Macewen,Robert G Lalonde,Nathan G Earley

doi:10.4039/tce.2020.55

Jamie M Macewen, Robert G Lalonde + Show 1 more

Open Access

https://doi.org/10.4039/tce.2020.55

Copy DOI

Abstract

AbstractGall wasps in the cynipid genus Diplolepis Geoffroy (Hymenoptera: Cynipidae) attack various species of native and introduced roses in Canada. Although gall forms are diverse, gall wasps are parasitised by highly concordant complexes of parasitoids and inquilines. Many species of gall wasps attack the same host plants and develop over the same periods in the season, suggesting that opportunistic parasitoids may be exploiting a range of hosts rather than specialising. We sampled larvae of Eurytoma Illiger (Hymenoptera: Cynipidae) from galls of D. variabilis (Bassett) and D. rosaefolii (Cockerell), gall inducers that develop fairly synchronously late in the growing season on leaves of Rosa woodsii Lindl. (Rosaceae) in the Okanagan Valley of central British Columbia, Canada. Galls were sampled at five different sites along a gradient from the north end of the valley to the Canada–United States border, a distance of 100 km. We extracted DNA, then amplified and sequenced the cytochrome b segment for each Eurytoma larva. We identified two well-supported clades that were differentiated by neither sampling location nor host. Instead, at least two species of Eurytoma, E. imminuta Bugbee and E. longavena Bugbee, exist at these localities, and both exploit at least two of the Diplolepis hosts found at these sites.

Highlights

One of the biggest challenges to characterising parasitoid communities is the existence of cryptic species
Co-occurring galls of D. variabilis and D. rosaefolii from a number of sites in the Okanagan Valley, British Columbia and, using molecular tools to identify individuals to species, asked whether or not the assemblage of Eurytoma species present in the samples was affected by host species or by geographic location
Our calibrated cytochrome b tree shows that the valley supports two well-supported clades of Eurytoma that parasitise the inhabitants of galls of both Diplolepis variabilis and D. rosaefolii (Fig. 3), with no evident preference by either parasitoid for a particular host (X2 = 1.65, 1 df, P > 0.05) or for a particular location

Summary

Introduction

One of the biggest challenges to characterising parasitoid communities is the existence of cryptic species. A recent study that combines classical morphology and molecular characterisation has demonstrated that at least four closely related species, E. calcarea Bugbee, E. iniquus Bugbee, E. longavena Bugbee, and E. imminuta Bugbee (= E. spongiosa 1; Zhang et al 2017), inhabit D. variabilis galls in the Okanagan Valley.

Results

Conclusion