title: Population-level consequences of complementary sex determination in a solitary parasitoid.
abstract: BACKGROUND
  Sex determination mechanisms are known to be evolutionarily labile but the factors driving transitions in sex determination mechanisms are poorly understood. All insects of the Hymenoptera are haplodiploid, with males normally developing from unfertilized haploid eggs. Under complementary sex determination (CSD), diploid males can be produced from fertilized eggs that are homozygous at the sex locus. Diploid males have near-zero fitness and thus represent a genetic load, which is especially severe under inbreeding. Here, we study mating structure and sex determination in the parasitoid Cotesia vestalis to investigate what may have driven the evolution of two complementary sex determination loci in this species.
  
  
  RESULTS
  We genotyped Cotesia vestalis females collected from eight fields in four townships in Western Taiwan. 98 SNP markers were developed by aligning Illumina sequence reads of pooled DNA of eight different females against a de novo assembled genome of C. vestalis. This proved to be an efficient method for this non-model species and provides a resource for future use in related species. We found significant genetic differentiation within the sampled population but variation could not be attributed to sampling locations by AMOVA. Non-random mating was detected, with 8.1% of matings between siblings. Diploid males, detected by flow cytometry, were produced at a rate of 1.4% among diploids.
  
  
  CONCLUSIONS
  We think that the low rate of diploid male production is best explained by a CSD system with two independent sex loci, supporting laboratory findings on the same species. Fitness costs of diploid males in C. vestalis are high because diploid males can mate with females and produce infertile triploid offspring. This severe fitness cost of diploid males combined with non-random mating may have resulted in evolution from single locus CSD to CSD with two independent loci.
authors.affiliation: Evolutionary Genetics, Centre for Ecological and Evolutionary Studies, University of Groningen, P.O. Box 11103, 9700 CC, Groningen, The Netherlands. jetske.deboer@wur.nl.|Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands. jetske.deboer@wur.nl.
authors.forename: Jetske G
authors.initials: JG
authors.lastname: de Boer
authors.affiliation: Animal Breeding and Genomics Centre, Wageningen University, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands. martien.groenen@wur.nl.
authors.forename: Martien A M
authors.initials: MA
authors.lastname: Groenen
authors.affiliation: Laboratory of Genetics, Wageningen University, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands. bart.pannebakker@wur.nl.
authors.forename: Bart A
authors.initials: BA
authors.lastname: Pannebakker
authors.affiliation: Evolutionary Genetics, Centre for Ecological and Evolutionary Studies, University of Groningen, P.O. Box 11103, 9700 CC, Groningen, The Netherlands. l.w.beukeboom@rug.nl.
authors.forename: Leo W
authors.initials: LW
authors.lastname: Beukeboom
authors.affiliation: Department of Biology, University of Konstanz, 78457, Konstanz, Germany. robert.kraus@uni-konstanz.de.|Max Planck Institute for Ornithology, Department of Migration and Immuno-Ecology, Am Obstberg 1, 78315, Radolfzell, Germany. robert.kraus@uni-konstanz.de.
authors.forename: Robert H S
authors.initials: RH
authors.lastname: Kraus
mesh_terms: D000818:Animals; D005075:Biological Evolution; D004171:Diploidy; D005260:Female; D005838:Genotype; D006238:Haploidy; D006927:Hymenoptera / Q000145:classification / Q000235:genetics* / Q000502:physiology; D008297:Male; D020641:Polymorphism, Single Nucleotide; D012098:Reproduction; D019849:Sex Determination Processes; D013624:Taiwan