Morphological diversification of Teucrium montanum sensu lato on the Balkan Peninsula

In this work, the overall morpho-anatomical variability of Teucrium montanum sensu lato on the Balkan Peninsula was described. A total of 60 populations were collected all over the Balkans. For each analysed individual, the morphological characters of the stem, leaves, and flowers, as well as the anatomical characters of leaves were measured. The habitats of each population were characterized by altitude zone, type of geological substrate, vegetation, and climate type. Basic descriptive statistics were calculated for each character state, and multivariate analyses were used to compare all assessed characters and groups. The results showed that the analysed populations exhibit high morphological variability and broad ecological preferences. Five of the seven morphologically defined groups fit the already described taxa (T. montanum subsp. montanum, T. montanum subsp. helianthemoides, T. pannonicum, T. skorpili, T. montanum var. parnassicum), whereas two groups are morphologically specific but did not fit the existing taxonomic concepts. The patterns of observed morphological variability only partially match the patterns of ecological differentiation of the habitats of the analysed populations. The occurrence of different morphological groups inhabiting similar habitats in the same biogeographic region suggests that the morpho-anatomical differentiation of T. montanum s.l. may be due to genetic or evolutionary factors.