It is good to see a study of genetic diversity of Melanaphis sacchari/sorghi on a worldwide scale, but were voucher specimens of the samples analysed sent to a Museum?
And why is it concluded that there is no evidence of host association? It is quite clear from Table S1 that all the samples from cult. sorghum (=Sorghum bicolor) were either multilocus genotype "A" (from Africa) or "E" (the two from China), and in the factorial analysis (Fig 3) these two MLGs were grouped distinctly apart from the others by their Factor 1 scores . My interpretation is that MLGs "B", "C" and "D" are Melanaphis sacchari, and that "A" and "E" are Melanaphis sorghi (see Blackman et al. 1990; the reference is in the article).
