A phylogeny (modified from Kiontke et al., 2011) showing the convergent evolution of selfing in the Elegans group species of Caenorhabditis. Derived aspects of tra-2 regulation in C. elegans are depicted in cartoon form. The GLD-1-tra-2 mRNA regulation was strengthened in XX hermaphrodites by 1) multimerization of GLD-1 binding elements in the tra-2 mRNA’s 3’-untranslated region, or UTR (Beadell et al., 2011), and 2) recruiting the novel cofactor FOG-2 (Nayak et al., 2005). The convergently evolved hermaphrodite C. briggsae lacks these two features, and uses GLD-1 to opposite effect in germline sex determination (Beadell et al., 2011; Nayak et al., 2005).