We compare genomes within 3 genera: Oikopleura, Ciona, and Drosophila.
To ease plotting this function transforms the names of pairwise comparisons
in one of these three names, or NA for comparisons between genera.
compGenus(x)A vector of pair names such as Oki_Kum, Osa_Nor, etc
A factor of Oikopleura, Ciona, and Drosophila, or NA.
The levels are sorted so that Oikopleura is at the top in default ggplot
figures, followed by Ciona as both are tunicates.