VARIATION AND INTEGRATION IN THE RARE GRASS ACHNATHERUM (ORYZOPSIS) HENDERSONII - PHENOTYPIC COMPARISON WITH PARAPATRIC COMMON CONGENERS

Phenotypic properties indicating levels of variation and integration w ere compared among three populations of a rare bunch grass, Achnatheru m (Oryzopsis) hendersonii (tribe Stipeae), and one parapatric populati on of each of its common relatives Achnatherum (Stipa) lemmonii and Ac hnatherum (Stipa) thurberiana, sampled from the Colockum Pass area of central Washington, U.S.A. Twenty-five randomly selected plants from e ach population were measured for both vegetative and spikelet features . The vegetative features were represented by morphometric measurement s taken from one leaf on a tiller and the flag leaf on a flowering cul m. The spikelet features were based on two to eight spikelets per plan t. The three data sets were analyzed separately to compare population level variation both among individuals and among variables (variable c ovariation). Phenotypic variation among individuals is lowest for A. h endersonii in estimators of both size and shape; within-individual phe notypic variation, as evaluated through among-variable correlation coe fficients, is highest for A. hendersonii and lowest for A. thurberiana . The lower level of among-individual variation for A. hendersonii is consistent with biological beliefs about rare species; its higher amon g-variable variation may indicate less precise control of integration.