CYTOGEOGRAPHIC RACES OF ARCTAGROSTIS-LATIFOLIA (POACEAE) IN ALASKA

Chromosome counts were obtained on 117 plants of the circumpolar grass Arctagrostis latifolia (R. Br.) Griseb. collected across mainland Ala ska. Three chromosome races were found in the state. A widespread dist ribution was indicated for the tetraploids (2n = 28) and octoploids (2 n = 56) and a limited distribution for the hexaploids (2n = 42), heret ofore unreported for North America. Both tetraploids and octoploids ap peared to be well represented through the boreal interior and arctic, unglaciated refugia of Alaska. Only tetraploids were found on the heav ily glaciated terrain of southcentral Alaska. Six hexaploid counts wer e obtained on plants collected from two locales at the ecotone of glac iated and unglaciated areas. Cytotype distribution was interpreted as indicating a greater mobility for the tetraploid race, better enabling it to occupy deglaciated terrain and other disturbances, and the poss ibility of survival of the tetraploid in local refugia within the exte nsively glaciated southcentral region. The data provided support for t he inclusion of different chromosome races within a single taxon.