Data from: Genome divergence and reproductive incompatibility among populations of Ganaspis near brasiliensis

A colony of Ganaspis near brasiliensis from Yunnan was started from field collections in Kunming, Yunnan, China in 2016. Wild berries of Rubus foliosus Weihe, Rubus niveus Thunberg, Fragaria moupinensis Cardot (Rosaceae), and Sambucus adnate Wallich (Adoxaceae) were collected in the suburbs of Kuming. The berries were often infested by D. suzukii and the closely related Drosophila pulchrella. Initially, about 600 adult parasitoids emerged from imported puparia at the quarantine facility of University of California Berkeley (UCB). These specimens were assigned to two lineages, G1 and G3, based on COI sequences. A colony of the G3 lineage from Yunnan was started at USDA-ARS Beneficial Insects Introduction Research Unit (BIIRU), Newark, Delaware, USA, from about 100 females and 50 males received from UCB in 2018. A colony of parasitoids from Tokyo (referred to as Ganaspis cf. brasiliensis in Girod et al. (2018a); Seehausen et al. (2020) was started from collections in 2016 from D. suzukii on wild cherry Prunus serrulata in Naganuma Park,Hachioji, Tokyo (Girod et al. 2018a). This population was assigned to the G1 lineage based on its COI sequence (Nomano et al. 2017; Seehausen et al. 2020). The colony is maintained in the quarantine laboratory at CABI in Delémont, Switzerland (Girod et al. 2018a). An Italian colony of the parasitoids from Tokyo was started in 2020 from 150 wasps from the CABI colony, and the BIIRU colony was established from about 500 wasps from Italy in 2021. A colony of D. suzukii was started with field collections of infested cherries during 2010 in Davis, California. Some of the material from British Columbia was identified as G3 in the present study. In the rest of this paper, we will refer to the material from these six populations as G1-BC, G1-Tokyo, G1-Yunnan, G3-BC, G3-Nagano, and G3-Yunnan.

The parasitoids were reared and crosses made in plant growth chambers (23 ± 1°C, 146: 10D, 40–60% RH) at the containment facility at BIIRU. Colonies of D. suzukii and the two COI lineages were maintained using the methods decribed by Rossi-Stacconi et al. (2022). Briefly, D. suzukii was maintained on artificial diet in 250 ml flasks. The parasitoid populations were maintained on blueberries infested by D. suzukii. Fruits were exposed to D. suzukii for 1-2 days for oviposition in screen cage (30 x 30 x 30 cm). The parasitoids were reared in clear plastic containers (9.2 x 11.7 x 7.6 cm) by exposing 5–10 female wasps to 10–20 infested blueberries for 4–5 days, with droplets of honey streaked on the container’s screen as food source. Following the exposure, infested fruits were removed from the cage and kept in new plastic containers with filter paper at the bottom to absorb leaking fruit juice. Newly emerged wasps were collected in plastic vials (95 × 25 mm) and honey provided.

We did crosses to test reproductive compatibility between G3-Yunnan and G1-Tokyo. For these crosses, parasitized D. suzukii puparia from the parasitoid colonies were isolated in plastic vials (95 × 25 mm). A piece of moisturized tissue paper was placed in each vial to provide humidity. When individuals emerged, they were supplied with a streak of honey on the bottom of the vial plug and paired within 48-72h with an individual of either the same or different population with the same emergence date. We made four crosses, two within populations and two between populations: G1♀ × G1♂, G3♀ × G3♂, G1♀ × G3♂, and G3♀ × G1♂. To control for thelytoky, that is females developing from unfertilized eggs (e.g., from Wolbachia infection), virgin females were also tested for each parasitoid population. For all crosses and controls, each female was provided with two infested blueberries containing approximately 10 first and second instar D. suzukii larvae, based on counts of initial host eggs laid in berries. After three days, females were removed and placed in 95% ethanol. Exposed host larvae were kept for 6 weeks during which adult flies should emerge (about two weeks) or parasitoids should emerge (about 30 days). All emerged insects were counted, sexed, and stored. The remaining (assumed dead) host puparia were reconstituted in water for 1 day and then dissected under a microscope to determine the presence or absence of parasitoids. The number of parasitoid offspring produced and the percent parasitism were estimated from the flies and wasps that emerged as adults, as well as the dissected hosts with versus without parasitoids, and the sex ratio was estimated from the sexes of adult wasps. We did 20 replicates for each cross, except 10 for G3 ♀ × G3 ♂, and five replicates for the unmated female controls.