Mitochondrial haplotypes
Finally, in agreement with a previous study by Duplouy et al. (2015), the majority of the H. horticola parasitoids carry the C-mitotype (N=145, 67%), while the remaining specimens carry the T-mitotype (Table 1, Figure 3). Noticeably, the C-mitotype is prevalent in all localities (57% in Saltvik, 71% in Sottunga, 84% in Finström, 95% in Föglö) except Seglinge-Kumlinge (28%) (Table 1, Figure 3). These general patterns hold across the different spatio-temporal groups (Table 2, Figure 3). The T-mitotype is significantly more prevalent in Seglinge-Kumlinge than in the rest of the Åland islands (Fisher exact-test P = 0.0001), and this holds if we only take into account the wasps carrying one of the five genotypes characterized from Seglinge-Kumlinge: three wasps carry the C-mitotype and 12 wasps carry the T-mitotype in Seglinge-Kumlinge, compared to 18 wasps carrying the C-mitotype and eight wasps carrying the T-mitotype in the rest of Åland (Fisher exact-test P =0.0036).
Wolbachia infection status
Wolbachia was detected in samples from all five localities. The mean infection rate across our samples is 50%, which is consistent with the work of Duplouy et al. (2015), who had previously investigated the prevalence of the w Hho strain across the entire Åland archipelago. Among the localities, Seglinge-Kumlinge shows the highest infection rate (95%), greatly contrasting with the lower infection rates of Finström (42%), Föglö (32%), Saltvik (59%), and Sottunga (23%) (Table 1, Figure 3). Wolbachia is significantly more prevalent in Seglinge-Kumlinge than in the rest of the Åland islands (Fisher exact-test P =0.0001), and this holds when we only consider the wasps carrying one of the five genotypes characterized from Seglinge-Kumlinge: one uninfected wasp and 13 Wolbachia -infected wasps characterized in Seglinge-Kumlinge, compared to 28 uninfected and 12 infected wasps in the rest of the Åland population (Fisher-exact testP =0.0001).
Among all Wolbachia -infected wasps sampled, 57% carry the T-mitotype, which is equal to or slightly lower than the infection rate characterized by Duplouy et al. (2015)go. However, the proportion of infected wasps carrying the T-mitotype differed among localities. In Saltvik, Finström and Föglö, 60%, 33% and 0% ofWolbachia -infected wasps carry the T-mitotype, respectively. In contrast, Sottunga and Seglinge-Kumlinge are more similar to each other than to any other population, with the great majority ofWolbachia- infected wasps carrying the T-mitotype (75% and 79%, respectively) rather than the C-mitotype. This is despite the two island populations showing contrasting proportions of specimens carrying the T-mitotype (see above).