Sex without sex chromosomes: genetic architecture of multiple loci independently segregating to determine sex ratios in the copepod Tigriopus californicus

• DOI: 10.1111/jeb.12743
• Publication Date: 2015-09-02T16:54:36Z
• Authors: H. J. Alexander; J. M. L. Richardson; S. Edmands; B. R. Anholt
• Keywords: Genetic architecture; Trait; Polygene; Sex linkage

Sex-determining systems are remarkably diverse and may evolve rapidly. Polygenic sex-determination predicted to be transient evolutionarily unstable, yet examples have been reported across a range of taxa. Here, we provide the first direct evidence polygenic sex determination in Tigriopus californicus, harpacticoid copepod with no heteromorphic chromosomes. Using genetically distinct inbred lines selected for male- female-biased clutches, generated genetic map 39 SNPs 12 Quantitative trait locus mapping ratio phenotype (the proportion male offspring produced by an F2 female) four families revealed six independently segregating quantitative loci on five separate chromosomes, explaining 19% variation ratios. The varied among chromosomes both direction magnitude, strongest phenotypic effects chromosome 10 moderated some degree other For given locus, magnitude individuals derived from different dam lines. These data, together environmental factors known contribute determination, characterize underlying complexity potential lability confirm architecture T. californicus.