We thus continued our analysis to explore how well this structure corresponded to our morphological assignment of individuals to species and to detect putative hybrids, using prior information (USEPOPINFO = 1).
Without reference to the morphological assignment, two distinct algorithms, STRUCTURE 2.2 and BAPS 4, were used to test the number of distinct populations (K) sampled.
The cluster patterns for the two data sets were also very similar; moreover, the two genetically distinct clusters corresponded well to our morphological assignment of populations to Q. liaotungensis and Q. mongolica (Fig. 5 and Fig. 6).
As most of the individuals in these two populations tend to have admixed genetic characteristics despite the clear morphological assignment to one species, we inferred that hybridization and continuous introgression might be occurring in these two populations.
The individuals from Florencia fell into the H. melpomene and H. cydno clades as predicted from their morphological assignment.
It is difficult to assess how our results would compare with morphological assignment accuracy by a non-specialist.
The phenotype of this tree is typical for Q. robur (see Figure 1) ruling out any possibility of wrong morphological assignment.
In our dating analysis, we followed the recent recommended best practice guidelines for fossil calibration [ 83] and placed fossil calibrations at stem nodes of the most inclusive extant groups using apomorphy-based morphological assignment.
All the individuals that had a prior morphological assignment clustered within the expected mitochondrial lineage, with the exception of the individual BEV7337, which morphologically resembles a "Galera type" individual (P.A. Crochet, pers. comm).
Detailed radiological review, which was blind to morphologic assignment, identified a triad of features, hemorrhage, midline location, and the presence of cysts or necrosis, that distinguished the two morphological groups with a sensitivity of 91% and specificity of 100%.
