Hymenopteran species in which sex is determined through a haplo-diploid mechanism known as complementary sex determination (CSD) are vulnerable to a unique form of inbreeding depression. Diploids heterozygous at one or more CSD loci develop into females but diploids homozygous at all loci develop into diploid males, which are generally sterile or inviable. Species with multiple polymorphic CSD loci (ml-CSD) may have lower rates of diploid male production than species with a single CSD locus (sl-CSD), but it is not clear if polymorphism is consistently maintained at all loci. Here we assess the rate of diploid male production in a population of Cotesia rubecula, a two-locus CSD parasitoid wasp species, approximately 20 years after the population was introduced for biological control. We show that diploid male production dropped from 8–13% in 2005 and 2006 to 3–4% by 2015. We also show from experimental crosses that the population maintained polymorphism at both CSD loci in 2015. We use theory and simulations to show that balancing selection on all CSD alleles promotes polymorphism at several loci in ml-CSD populations. Our study supports the hypothesis that ml-CSD populations have lower diploid male production and are more likely to persist than comparable sl-CSD populations.
Cotesia rubecula Data
Data from mother-son crosses, outcrosses, and field-gathered Cotesia rubecula cocoons is available in Microsoft Excel format, “Weis et al. Evolution Cotesia.xlsx”, and is accompanied with a metadata description on the first worksheet. The first data worksheet contains summary information on mother-son and outcrosses of Cotesia rubecula conducted at the University of Minnesota in 2015. The second data worksheet contains detailed information on the offspring of mother-son and outcrosses. The third data worksheet contains detailed information on Cotesia rubecula cocoons gathered near the University of Minnesota campus in the 2015 and 2016 growing seasons.
Weis et al. Evolution Cotesia.xlsx
Figures 2 and 3 Simulation Data
Simulated data presented in Figures 2, and 3 is available here in Microsoft Excel format, “Weis et al. Evolution Fig2 Fig3.xlsx”, and is accompanied with a metadata description on the first worksheet.
Weis et al. Evolution Fig2 Fig3.xlsx
Supporting Information F1 Data
Expanded data presented in Supporting Information F is available here in text file format: “SIF1.Data.txt” (Supporting Information F1).
SIF1.Data.txt
Supporting Information F2 Data
Expanded data presented in Supporting Information F is available here in text file format: “SIF2.Data.txt” (Supporting Information F2).
SIF2.Data.txt
Flow Cytometry Data
Files containing all raw flow cytometry data for individual adult C. rubecula are in .fcs format. For individual fcs files the middle value of each file name references an individual reported in “Weis et al. Evolution Cotesia.xlsx” above. For instance, “samples_C25_001.fcs” contains the data for individual C25 on the field pupae worksheet, “samples_N4a3_020.fcs” contains data for individual N4.a.3 on the cross pupae worksheet.
Figure 2 Simulation Code
Note that this code is set for the expanded parameter space explored in Supplementary Information F. Also note dependencies in the R code available through the R CRAN; doParallel, foreach, and doRNG.
Weis.Figure2.Code.R
Figure 3 Simulation Code
Note that this code is set for the expanded parameter space explored in Supplementary Information F. Also note dependencies in the R code available through the R CRAN; doParallel, foreach, and doRNG.
Weis.Figure3.Code.R