Distribution and peculiarities of biology of <i>Magadania olaënsis</i> (Apiaceae)

Magadania olaënsis (Gorovoi et N.S. Pavlova) Pimenov et Lavrova is a species of the oligotypic genus Magadania, endemic to North-Eastern Asian Russia, included in the Red Data Book of the Russian Federation. Information on its distribution in the Magadan Region, phytocenotic confinement and some features of biology is given. The herbarium specimens of M. olaënsis are kept in 4 herbaria: MAG – 38, VLA – 8, MHA – 5, MW – 1. The type specimen (holotypus) is deposited in VLA, the paratypes are probably lost. There are 39 specimens in digital Herbaria (MAG – 38, MW – 1). The main part of the range of M. olaënsis is located in the Magadan Region. An isolated locality on the Dzhugdzhur Ridge in the Khabarovsk Territory is also known, 730 km away from the nearest localities in the Magadan Region (Island Spafaryev). The identified area of the range of M. olaënsis in the Magadan Region is about 390 km2. The largest part of the range (about 380 km2) is located on the Okhotsk–Kolyma watershed on the Ola Plateau, where the area of habitats with the highest population density (2500–3000 per km2) is about 1.5 km2. Habitats on the coast of the Sea of Okhotsk take 4–5 km2, and on the islands – 0.1–0.5 km2. The total number of populations is approximately 4000–8500: 3500–7500 on the Okhotsk–Kolyma watershed, 600–900 on the coast, and about 50 plants on the islands. olaënsis is a perennial monocarpic plant. The formation of generative shoots occurs at the age of 5–10 years. The number of generative plants in the populations is approximately the same in different years. However, there was the season when generative plants were missing in the populations on the coast. In a plant at the generative stage, in addition to the central inflorescence, 2 lateral inflorescences are usually formed (somewhat less often none or one, rarely 3–5 lateral inflorescences), but the seeds on them, even if formed, rarely reach full maturity. Real seed productivity varies significantly from year to year from 0 to 694, and averages from 146 to 326 mature seeds per plant. Seeds do not germinate at temperature +18...+22°С. The total germination percentage after two periods of stratification was 84±3.7%. Seeds of M. olaënsis are in dormancy of different depths and probably only partially germinate in the next growing season, while the rest germinate over the next few years. olaënsis grows mainly in herb-shrub or shrub tundra, less often on open gravel screes at altitudes from over 700 to 1300 m a. s. l. (Okhotsk–Kolyma watershed, Zavyalov Island), or in communities with a large participation of forbs at 50–350 m a. s. l. (Atargan-Kharbiz coast, Spafaryev Island). The main limiting factors are a strict ecological confinement of the species to basic rocks (mostly basalts), as well as exclusively seed reproduction and irregular seed renewal in different years. Magadania olaënsis is a rare species (category 3), with III priority of conservation measures. According to the categories and criteria of the IUCN Red List the species is vulnerable (Vu). It is assigned to this category on the base of criterion B2a: a species with a limited range less than 2000 km2 with a highly fragmented habitat area. Existing local protected areas in the Magadan Region do not provide protection of the species. Current data on its presence at the territory of the Dzhugdzhur Nature Reserve are contradictory and need to be clarified.