NEW TO THE FLORA OF YAKUTIA ELODEA CANADENSIS, HYDRILLA VERTICILLATA (HYDROCHARITACEAE) AND POTAMOGETON MAACKIANUS (POTAMOGETONACEAE)
New species of aquatic vascular plants (Elodea canadensis, Hydrilla verticillata, Potamogeton maackianus) to the flora of Yakutia are reported, all known earlier far outside Yakutia. Their habitat conditions in the republic were characterized and distribution patterns were analyzed. Elodea canadensis was found in oxbow branch and lakes of the Lena River valley (Lenskii and Khangalasskii distr.), everywhere being scanty. Its localities in Yakutia remote ca. 650 km to the northeast (Lenskii distr.) and 1370 km to the east-northeast (Khangalasskii distr.) from the nearest point in Irkutsk Region. It is an invasive species, spread out as a result of floods from the Upper Lena populations (Irkutsk Region) far downstream of the Lena River being a good invasive corridor. The populations of Elodea are rather depressed while, but the state and distribution of this potentially dangerous species needs monitoring. Hydrilla verticillata and Potamogeton maackianus were found in lakes in the lower Amga River (Tattinskii distr.). The plants are well-developed, form small stands, in places dominate. Both the species represent the thermophilic element of the Yakutian flora, their localities are situated ca. 1000 km to the north from their main geographical range in the Asian Russia. Their populations could originated rather recently (Holocene) as a result of long-distance dispersal of the germs by migrant waterfowls. H. verticillata and P. maackianus are recommended to include in a new edition of the republic Red Book, as rare and located far from their main geographical range. All the 3 species in Yakutia occur at their distribution limit: the records of E. canadensis are the northernmost in Asia (to 61.58° N) and the easternmost in Eurasia (to 129.23° E), those of H. verticillata and P. maackianus are the northernmost (to 62.18° N). In extreme environmental conditions of the region, the occurrence and surviving of these plants are probably promoted by less climatic contrasts in the valleys of large rivers and accordingly more favorable conditions in waterbodies of the valleys.