Population Studies in Predominantly Self-Pollinated Species. VI. Genetic Variability between and within Natural Populations of Wild Oats from Differing Habitats in California.

M U C H recent work points to the conclusion that remarkable stores of genetic variability exist in natural and in domestic species of plants and animals. Among the requirements for understanding the nature of this variability, and the forces by which it is maintained, are adequate data concerning the magnitude of genetic variability within populations. However, the evidence on variability in naturally occurring species of plants is largely observational and subjective and only a few studies have provided quantitative estimates of the genetic variability respecting measurement characters which exists within populations (e.g. BAKER 1957; BRADSHAW 1959; WEIL and ALLARD, in press). Precise quantitative estimates of genetic variability within naturally occurring populations of predominantly self-pollinating species is even more limited, apparently being restricted to that provided by KNOWLES' (1947) study of Bromus mollis. The present paper reports an investigation of genetic variability in another predominantly self-pollinated species, wild oats (Auena fatua L.) . The experiment was designed to permit quantification of three aspects of genetic variability within this species: that occurring between three geographically distinct regions, that due to spatial differentiation between sites within these regions, and that due to variability within individual sites. The experiment also provided information of a quantitative nature concerning the mating system of this species.