Fig. 1.

Localities and phylogenetic relationships of the 6 tit species. (A) Sampling locations. The high-altitude species (Lophophanes dichrous, Periparus rubidiventris, and Aegithalos iouschistos) were sampled from altitudes of 2730–3900 m above sea level on the Qinghai-Tibet Plateau. The low-altitude species (Poecile palustris, Pardaliparus venustulus, and A. concinnus) were sampled from areas below 500 m above sea level in eastern China. (B) Maximum likelihood phylogeny of the 6 tit species with the zebra finch (Taeniopygia guttata) as an out-group based on 4-fold-degenerate sites of one-to-one orthologous coding sequences. Maximum likelihood bootstrap support values for all high- and low-altitude pairs were 100%. The scale bar indicates the number of substitutions per site. Red branches indicate the high-altitude species; blue branches indicate the low-altitude species. Bird illustrations reprinted with permission from ref. 15.