Diatoms (Bacillariophyceae) from Sheeder Prairie, Guthrie County, lowa

Seventy-four diatom species, varieties, and forms representing 15 genera were found in collections from Sheeder Prairie. The most widely distributed taxa were Navicula mutica Kutz., Hantzschia amphioxys (Ehr.) Grun., and Pinnularia borealis Ehr. Three taxa which had not previously been reported from Iowa are Navicula charlatii f. simplex Hust., Navicula contenta var. parallela Petersen, and Navicula dismutica Hust. Marked differences in the floras from upland and lowland collections were observed. The greatest diversity of species was found at the two sites where standing water occurred occasionally. Fifty-six taxa were found in collections from one of these sites; 31 taxa were found in samples from the other. In contrast, 3-5 taxa were found in samples from upland sites considered to be relatively dry