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Abstract
Twelve California populations of Avena barbata (slender wild oat) were evaluated by three criteria to determine if they belong to xeric and mesic ecotypes. The criteria are: physical estimates of moisture in the populations' environments, quantitative-character phenotypes determined by uniform-garden study, and marker genotypes.
Seven populations are well described as belonging to a xeric ecotype. Six of these are nearly identical for marker genotype and most quantitative-character phenotypes, but are differentiated into an early flowering biotype (three southern California populations) and a late-flowering biotype (three northern California populations). The seventh population has a different marker genotype, but from its quantitative-character phenotypes and the environmental estimates for its site, it is well described as belonging to the xeric ecotype.
Five populations having a total of three marker genotypes are appropriately classified as belonging to a mesic ecotype. These five populations are differentiated into three biotypes by the marker genotypes and quantitative-character phenotypes. Marked and consistent differences among these three biotypes indicate that they might be separated into different ecotypes on the basis of some environmental variable other than moisture.
Results from the sample of populations surveyed suggest that further uniform-garden study of other populations would likely reveal additional biotypes of the mesic ecotype and possibly also others of the xeric ecotype. This study indicates that ecotypic differentiation has been important in the evolution of California populations of A. barbata, as it acts to bring about finer and finer adaptation of genotypes to local environments.
