Data analyses
Hymenoptera males are haploid, and females are diploid. We analysed the
genetic structure of female wasps only (N=195), to avoid overestimating
the impact of the haploid males, from the five localities and across the
22 years of collection using three analyses implemented in the BAPS
software (Corander, Marttinen, Sirén, & Tang, 2008; Corander, Waldmann,
& Sillanpää, 2003). First, we ran a Bayesian clustering of individuals
analysis, using the whole Åland as a unique population
(Npop=1), to identify the maximum number of genetic
clusters across all our samples. Then, we ran two independent spatial
Bayesian clustering analyses with the ‘clustering of groups of
individuals’ (Npop=5 or Npop=12), and
with respective admixture analyses settings (Figure 3) to evaluate the
degree of admixture at each locality, and in each locality through time.
Multiple ‘k’ parameters were provided for each run and the parameter was
not set as a strict limit; and the Bayesian model in BAPS estimated the
posterior probabilities for the optimal number of clusters (Appendix
1-3) (Corander et al., 2003).
We used the software GenoDive 3.04 (Meirmans & van Tienderen, 2004) to
calculate population genetics measures using only the samples that were
successfully genotyped for at least seven microsatellite markers using
either only diploid females (N=195), or combined diploid females and
haploid males dataset (N=313). We tested Hardy-Weinbergequilibrium at each locus in each locality, and for each of the 12
spatio-temporal groups, using the Least-Square Amova Method with 999
permutations (estimator Fis given in Appendix 1C and 3C). We
calculated the F ST values between the five
localities and between the 12 spatio-temporal groups. Finally, we
calculated the observed (HO ) and expected
heterozygosity (HE ) at each locus, as well as the
inbreeding coefficient (Gis ) between each locality (N=5), and
each spatio-temporal group (N=12) (Appendix 1B and 3B).
To test whether samples from the Seglinge-Kumlinge islands were more
often Wolbachia -infected, or carry the T-mitotype over the
C-mitotype more than the rest of the Åland population, we used Fisher
exact tests for count data (two-sided) in R 3.6.3 (R Core Team, 2020).