Mapping of Geographic Distribution of C3 and C4 Species of the Family Chenopodiaceae in Iran

The patterns of geographic distribution of c3 and c4 species of the family chenopodiaceae have been analyzed in iran, using a database of 11151 georeferenced records. the members of chenopodiaceae family with 45 genera and 204 species are widely distributed in iran. there they show a ratio of about 2:1 between c4 and c3species. all available data were organized in ms access database, and analyzed in point-to-grid analysis tool of diva-gis software, using 10 × 10 km grid cells and the circular neighborhood option. the highest species numbers, with a peak at 83 per grid unit, occur in tehran, semnan, and east azerbaijan provinces but the density of records is extremely uneven. consequently, the same areas also are the hot spots of both c4 and c3 species. the comparison between the distribution patterns of carbon isotope composition (?13c) values of species and the annual precipitation gradient map represents that c4 chenopods are well adapted to regions with high degree of aridity and low precipitation.