UNASSIGNED: Sex determination mechanisms play a central role in life-history characteristics, affecting mating systems, sex ratios, inbreeding tolerance, etc. Downstream components of sex determination pathways are highly conserved, but upstream components evolve rapidly. Evolutionary dynamics of sex determination remain poorly understood, particularly because mechanisms appear so diverse. Here we investigate the origins and evolution of @entity204 ( @entity204 ) in ants and @entity5157 . The @entity5157 has a well-characterized @entity204 locus, containing tandemly arranged homologs of the transformer gene [complementary sex determiner (csd) and feminizer (fem)]. Such tandem paralogs appear frequently in aculeate hymenopteran genomes. However, only comparative genomic, but not functional, data support a broader role for csd/fem in sex determination, and whether species other than the @entity5157 use this pathway remains controversial. Here we used a backcross to test whether csd/fem acts as a @entity204 locus in an ant (Vollenhovia emeryi). After sequencing and assembling the genome, we computed a linkage map, and conducted a quantitative trait locus (QTL) analysis of diploid male production using 68 diploid males and 171 workers. We found two QTLs on separate linkage groups (CsdQTL1 and CsdQTL2) that jointly explained 98.0% of the phenotypic variance. CsdQTL1 included two tandem transformer homologs. These data support the prediction that the same @entity204 mechanism has indeed been conserved for over 100 million years. CsdQTL2 had no similarity to CsdQTL1 and included a 236-kb region with no obvious @entity204 gene candidates, making it impossible to conclusively characterize it using our data. The sequence of this locus was conserved in at least one other ant genome that diverged >75 million years ago. By applying QTL analysis to ants for the first time, we support the hypothesis that elements of hymenopteran @entity204 are ancient, but also show that more remains to be learned about the diversity of @entity204 mechanisms.

QTL Mapping of Sex Determination Loci Supports an Ancient Pathway in Ants and XXXX .

@entity204 :: ('MESH:D003643', 'Disease') :: ['complementary sex determination', 'CSD'] @entity5157 :: ('7460', 'Species') :: ['honey bee', 'bees']
@entity5157 :: (7460,Species) :: ['Honey Bees']
