Coincident evolution and functional adaptation of the taxonomically-restricted genes ivph-3 and gon-14 in Caenorhabditis nematodes.

Poorly-conserved or taxonomically-restricted genes represent a sizable portion of most genomes. Many of these genes participate in essential processes and can contribute to evolutionary innovation in species. Here we evaluate two of the Caenorhabditis-restricted class of LIN-15B-domain-encoding genes, ivph-3 and gon-14, and compare their in vivo functions in two species, C. elegans and C. briggsae. We show that within the Elegans supergroup, ivph-3 and gon-14 exhibit sequence constraints distinct from other family members, including maintenance of a one-to-one orthology and a higher degree of sequence conservation. Coincidentally, mutants for either of the genes exhibit strong phenotypic defects that are similar within-species (C. elegans or C. briggsae), but with notable differences when comparing between species. These findings highlight the genetic and genomic features associated with the evolution of a taxonomically-restricted gene family.