A new record of Betula litwinowii (Betulaceae) and a review of the geographical distribution of the genus Betula L. in Iran.

INTRODUCTION This paper is the outcome of a longer-term revision of the Betulaceae family for the project Flora of Iran (Assadi 1989). At present, there are about 60 species of Betula distributed in most parts of the northern hemisphere, among which Betula pendula Roth. has a wide distribution in Europe and Asia Minor (Krussmann 1984). The distribution range of Betula pendula covers Europe, eastern Turkey, northern Iraq, northern Iran, western Siberia and Caucasia. Browicz (1972), in the Flora Iranica, family Betulaceae, reported Betula pendula, B. tadzhikistanica V. N. Vassil., B. kunarensis Browicz and B. chitralica Browicz. According to the present revision, of these, Betula pendula is the only species distributed in Iran with known occurrences in the Oshtorak valley, Toochal and Shahrestanak. The latter three species, with Asian origin, are not distributed in Iran. Sabeti (1976) reported Betula pendula from many habitats viz. Taleghan, Shahrestanak, at high elevations in Talar and western Azerbaijan. It seems that Browicz (1972) did not refer to any subalpine stand of Betula of the Hyrcanian region. Later, Browicz (1982, p. 27) stated that Betula pendula in Iran is “very rare, and its few localities are located in the central part of the Elburz, in the province of Mazandaran (above 2000 m a. s. l.).” Therefore, we found it necessary to carry out a detailed investigation on stands of Betula in the Hyrcanian region. Our investigation confirms the presence of