A study of the Phylloscopus warblers in the Sino-Himalayan region published in Vertebrate Zoology in 2008 by Martens, Sun and Päckert (pdf available) is examining the relationships between P. fuscatus, P. fuligiventer, P. affinis, P. armandii and P. subafinis and is proposing 2 new taxon names. The authors have shown that P. fuscatus and P. fuligiventer were sister taxa and are proposing that P. fuscatus weigoldi (from Qinghai) should in fact be considered a subspecies of P. fuligiventer. They also found that the Himalayan (incl. SE Tibet) populations and the Chinese populations (Yunnan, Sichuan, Qinghai, Gansu) of P. affinis are differentiated on the species level. The there recommend splitting the Chinese populations from P. affinis and provided the new name Phylloscopus occisinensis nov. sp. They also found the Himalayan group (P. affinis sensu stricto) itself divided into 2 subspecies: Phylloscopus affinis perflavus nov. ssp. in the west and the nominate form P. affinis affinis in the east.
Martens, J.; Sun, Y-H. & Päckert, M. 2008. “Intraspecific differentiation of Sino-Himalayan bush-dwelling Phylloscopus leaf warblers, with description of two new taxa (P. fuscatus, P. fuligiventer, P. affinis, P. armandii, P. subaffinis)”. Vertebrate Zoology 58 (3): 233-265.