Differences in host specificity and gene sequences between closely related species of aphid parasitoids

Aphelinus comprises 90 described species in several complexes.  Perhaps because of their recent origin, species within these complexes have diverged little in morphology and are difficult to distinguish so the taxonomy within the complexes is confused. Aphelinus atriplicis Kurdjumov and Aphelinus certus Yasnosh are closely related species that are partially reproductively compatible in laboratory crosses. In nature, they are separated by over 5000 km of deserts and mountains, including some of the highest mountain ranges in the world, thus partial compatibility is a plesiomorphy resulting from lack of selection against hybridization.  These species are phylogenetically distinct and differ in morphometry of wing, antenna, and mesosoma, courtship behavior, and host specificity.  We sequenced and assembled their genomes and transcriptomes, analyzed for putative genes, determined sequence divergence between species, and annotated the functions of the divergent genes.  We found 29 genes with female-limited expression and ratios of non-synonymous to synonymous substitutions greater than three. We discuss the potential role of the genes in differences in host specificity.