Didymodon daqingii

Ignatova, E. A., Fedosov, V. E., Kuznetsova, O. I., Fedorova, A. V. & Ignatov, M. S., 2024, On the genus Didymodon s. str. (Pottiaceae, Bryophyta) in Russia, Arctoa 33 (2), pp. 129-155 : 137

Didymodon daqingii and D. manchanensis

Didymodon daqingii was described from Inner Mongolia, China ( Kou et al., 2019). It is a peculiar plant with a combination of morphological characters which is infrequent in Didymodon : bistratose upper leaf margins; costa in transverse section with 2–3 layers of guide cells and no ventral stereids; costa excurrent into a long, fragile subula; leaf bases abruptly broadened, round; and laminal cells papillose. One GenBank accession of this species obtained from the type specimen was resolved in our tree within clade 4, in the grade at the base of the clade which includes D. icmadophilus , D. hengduanensis , D. tibeticus , and D. vulcanicola . Before it in the same grade, five accessions obtained from three specimens from Asian Russia (two from Yakutia and one from Tyva) formed a maximally supported clade. These specimens possessed almost the same combination of morphological characters as D. daqingii , except they had smooth laminal cells. Another species with similar character combination is D. manchanesis ; it was also described from Inner Mongolia, China ( Feng et al., 2022). It differs from D. daqingii in smooth laminal cells, ovate vs. round leaf bases, and red vs. yellow-green KOH reaction. ITS obtained from the type specimen of D. manchanensis is also represented in GenBank. In our tree, it is resolved in an “orphaned” position within clade 5, i.e., far from D. daqingii and a clade of similar specimens from Russia. Our specimens, despite having smooth laminal cells, in other respects (shape of leaf base, yellow-green KOH reaction) are closer to D. daqingii ; their ITS sequences differ from the sequence of Chinese D. daqingii in several substitutions, but the difference from D. manchanensis is greater. At the moment, we prefer to call our plants D. daqingii , but if other similar specimens will be found in Russia, it would be interesting to test their identity with molecular barcoding.