Based on ML and BI phylogenetic trees of two thrush complexes, we found
that different combinations of priors (evolutionary scenarios:
population size and divergence time) yielded different results by
Bayesian species definition on each node, but the results of the
analysis using algorithms 0 and 1 were similar (Table 5). This result
indicated a convergence of MCMC chains. Combined with the guidance tree
(Fig. 3), the results showed that nodes 3 and 4 had high speciation
probabilities =1.000 when using combinations of priors that represent
different evolutionary scenarios. At the same time, these two nodes of
the guide tree were supported by high posterior probabilities
(PPs> 95%). For nodes 1 and 2, the choice of different
evolutionary scenarios resulted in different speciation probabilities
that were low in most cases. Therefore, the prior probability
distribution had a greater influence on the speciation probabilities
between Naumann’s thrush and the dusky thrush and between the
red-throated thrush and the black-throated thrush.
We used five morphological features to further analyze the
classification status of the species in the two thrush complexes. The
PCA showed that the five quantifiable traits were difficult to
distinguish between Naumann’s and the dusky thrush or the red-throated
thrush and the black-throated thrush. These traits were not sufficient
to constitute the boundary of the species (Fig. 4a and b). We classified
the Naumann’s and dusky thrush complexes as one group and the
red-throated and black-throated thrush complexes as another group and
conducted PCA of both groups (Fig. 4c). Although there was a small
amount of intersection between the two groups, there was separation
between them. All the results from the above molecular and morphological
analyses indicated that the two thrush complexes should be two
independent species (Naumann’s thrush, T. naumanni , and the
red-throated thrush, T. ruficollis ), while the dusky thrush
(T. naumanni eunomus ) should be a northern subspecies of T.
naumanni , and the black-throated thrush (T. ruficollis
atrogularis ) should be a black-throated subspecies of T.
ruficollis .