Taxonomy and Distribution of Japanese Populations of Pyrus ussuriensis Maxim. (Rosaceae)

Abstract

Wild and naturalized populations of Pyrus ussuriensis Maxim. are taxonomically reinvestigated in Japan based on fresh materials and herbarium specimens. The species is newly circumscribed based exclusively on wild forms. It is characteristic in having leaves with the lamina less than 10 cm long, small fruits less than 3 cm long excluding the calyx and persistent calyx on the mature fruit. The species is divided into two varieties: var. ussuriensis and var. hondoensis (Nakai & Kikuchi) Rehder. Natural populations of P. ussuriensis are dispersedly distributed in Chubu and Northern Tohoku regions of Honshu. They grow in almost natural woodlands, but may hardly regenerate in wild. The present conditions may be endangered for P. ussuriensis var. ussuriensis and vulnerable for P. ussuriensis var. hondoensis in Japan. Conservation for the species should be necessary with its natural habitats.