Arising and development of the population of Matteuccia struthiopteris (L.) Tod. in the University Grove of Tomsk University

Matteuccia struthiopteris (L.) Tod. – Ostrich fern (Onocleaceae) is a circumboreal species widely distributed in the temperate zone of the northern hemisphere. We present the results of observations on the formation of M. struthiopteris population on a man-made lawn situated in the University Grove (Tomsk, Russia). The formation of the plant community on the new lawn occurred naturally, and sporophytes of the fern appeared naturally. During the observation period (2009–2025), we observed two wave of colonization of the lawn by M. struthiopteris, both waves coincided with covering of the lawn surface with a fresh soil. The first filling of the lawn occurred during its construction in 2007. The soil used for the lawn construction was taken from a native area located 6.65 km the southwest of the University Grove. The first M. struthiopteris sporophytes were found in 2009 in significant numbers: 263 individuals of early stages of ontogenesis. A new wave of colonization by spores occurred after a severe damage to the lawn and disruption of the established plant community in 2020 and subsequent refilling of the lawn with the new soil in 2023. By 2025, 315 new sporophytes of the initial stages of ontogenesis were added to sporophytes that survived the disruption. Thus, both waves of colonization of the lawn by M. struthiopteris were associated with its filling with the new soil, which means that the spores were presented in this soil. Both time, two years passed between the moments when the lawn was covered with the new soil and sporophytes became visible. This time was required for the germination of spores, development of gametophytes, fertilization and formation of sporophytes. No fertile (spore-bearing) sporophytes appeared during the whole observation period (17 years). For detection of the source of spores, from which the first wave of colonization occurred and M. struthiopteris population on the lawn formed, we conducted a molecular-genetic analysis of total DNA using ISSR method. The proven genetic identity of sporophytes from the lawn population to sporophytes growing at the site, where the soil was taken for the lawn construction, indicates that the spores were introduced to the lawn with this soil and that green spores of M. struthiopteris are capable of the formation of the spore bank, albeit a short-lived one.