An Experimental Study of Variation in the Agropyron spicatum-A. inerme Complex

Abstract

1. Studies in an experimental garden demonstrated that progenies from rhizomatous and caespitose individuals of Agropyron spicatum are genetically different with respect to this character. 2. Segregation of these biotypes in the field apears to be a result of habitat selection that allows rhizomatous individuals to prosper in less arid grassland, whereas only caespitose individuals survive in more arid grassland and semidesert. 3. In eastern Washington and northern Idaho early stages of primary succession favor the caespitose biotype, but, where aridity is not intense, the subsequent development of a dense vegetative cover results in a replacement of caespitose pioneers by rhizomatous plants, so that the two ecotypes have both a time and a space sequence. 4. Since inerme is distinguished from A. spicatum only by its awnless character, since awn lengths intergrade completely, and since the rhizomatous and caespitose differentiation cuts across both groups, it is proposed to group all plants under the ...