Goryushko, I.M., D.I. Podoprigorina, S.V. Surovov, A.O. Emelyanova, A.Y. Litovets, A.E. Smirnov, G.M. Zaitsev, U.N. Spirina, M.S. Ignatov. 2024. On the expansion of Atrichum flavisetum in Moscow Province: how does it divide habitats with A. undilatum

Arctoa (2024) 33: 226–238

doi: 10.15298/arctoa.33.22

Atrichum flavisetum was a rare species in 19th and 20th centuries in Moscow Province, where it grew on soil on eroded slopes of exceptionally deep ravines. However, since the first decade of 21st century it started to spread in old-growth forests, inhabiting soil banks under upturned roots of fallen trees. Observations in two recent decades in the reserved forest area at the Zvenigorod biological station of Moscow University, near Moscow documented its invasion and tendency of partial substitution of the most common indigenous species Atrichum undulatum, which occurred in such habitats in 19th and 20th centuries. However, it is likely that in a relatively flat places A. flavisetum is unable to compete with A. undulatum. A comparison of morphology of these two species revealed the differences in one of the largely neglected structures, the rhizoidal ropes, that has been sometimes interpreted as underground rhizome, which is actually absent in Atrichum. In both species the rhizoidal ropes are highly hygroscopic and capable for vigorous movements, making effort possible for moving a weight three times exceeding the weight of whole plant itself. The ‘rhizoidal rope force’ is studied and shown to be stronger in A. undulatum than in A. flavisetum. The comparison of the rhizoidal rope structure in these two species suggests stronger structural differentiation of rhizoids in A. undulatum. Such differiation probably makes the hygroscopic movements stronger and favors survival of A. undulatum on the more dense soil where A. flavisetum doesn’t grow, and it results in a division of preferable habitats between these two Atrichum species.