A Floristic Study of Vascular Plants in Ushishir, the Middle Kuril Islands

Abstract

A preliminary list of vascular plants is provided for the southern Yankicha and northern Ryponkicha islets of Ushishir, the middle Kuril Islands, based on herbarium specimens. The list represents 45 families, 114 genera, and 158 species for the whole of Ushishir. Only two species of non-native plants have been recorded from Ushishir-Yankicha. The main dominant families in Ushishir are Asteraceae, Poaceae, Cyperaceae, and Caryophyllaceae. Although the entire flora of Ushishir does not show distinguishing features different from those of adjacent Ketoi and Rasshua, a clear contrast of floristic composition was confirmed between Yankicha and Ryponkicha in Ushishir. Notably, a higher number of species and collections of Cyperaceae in Ryponkicha than in Yankicha was confirmed. A Ryponkicha bias is evident in several taxa, for example Rubus chamaemorus, Vaccinium uliginosum var. alpinum, Carex rariflora, and C. stylosa. The floristic contrast mainly reflects the common occurrence of herbaceous meadows on Yankicha and the presence of a shrubby heath community on the terrace of Ryponkicha. A clear difference of flora and vegetation between Yankicha and Ryponkicha may be due to the different topographical and geological features of the two islets.