Vocalization analyses
The PCA evidenced differences in vocalizations among subspecies. The
first three PCs explained 65% of song variation. PC1 correlated with
the fundamental frequency of the first and the last note, PC2 correlated
with the mean duration of the first and intermediate notes and PC3 did
not strongly correlate with any song variable (Table S4). Subspecies
statistically differed in PC1 (F = 11.32, p ˂ 0.01) and PC2 (F = 18.43,
p ˂ 0.01), whereas no significant differences were found for PC3 (F =
2.87, p = 0.09). In particular, pairwise comparisons showed thatT. r. jaczewskii significantly differed from T. r.
ruficapillus and T. r. cochabambae in PC1 and from T. r.
marcapatae in PC2 (Table S5). In turn, T. r. cochabambaediffered from all subspecies in PC2 (Table S5). These differences can be
observed in the space delimited by the first two PCs (Figure 4). No
differences were found in the rest of the pairwise comparisons between
subspecies for PC1, PC2 or PC3 (Table S5).
The results of the individual song variables provided more detail about
song variation and showed substantial differentiation among subspecies.
In fact, the ANOVA indicated significant differences for most song
variables (Tables S6 and S7). Moreover, the Bonferroni contrasts showed
significant differences in at least one variable for almost all
subspecific comparisons, with the only exceptions of T. r.
subfasciatus vs. T. r. ruficapillus and T. r.
subfasciatus vs. T. r. marcapatae (Table S8). Therefore, and
consistently with the PCA result, both T. r. jaczewskii andT. r. cochabambae significantly differed in their songs from all
other subspecies, being the subspecies with the most differentiated
vocalizations. In addition. T. r. jaczewskii was the subspecies
that differed in more song variables from the rest (and particularly so
from T. r. cochabambae and T. r. ruficapillus ) (Table S8).