Patterns of adaptation in three native grasses in northern California

Abstract

Provisional seed transfer zones were developed for 3 Poaceae grasses, Elymus glaucus Buckley ssp. glaucus, Bromus carinatus Hook. & Arn., and Bromus orcuttianus Vasey, from a 4-y study with 11 reciprocal-transplant gardens across the Plumas National Forest. To conserve existing adaptive patterns, 4 seed zones were proposed for B. carinatus and B. orcuttianus, and six for E. glaucus. Adaptive traits of source populations were correlated with their geographic, climatic, and ecologic origins. Findings based on seed source x environment interactions and the geographic-climatic patterns for local, distant, and proximal-paired populations suggest that natural selective pressures have produced weak to moderate broad-scale local adaptation. Three consistent “coarse-textured” adaptive patterns emerged: 1) sources from mesic west-side and east-side ecological zones formed two well-differentiated groups; 2) sources from the broad intermediate area (west-side central and transition) were less differentiated and often intergraded with the mesic west-side (southwestern) and east-side (northeastern) groups; and 3) mesic west-side was divided into 2 elevation bands. Local adaptation was found less often on a finely tuned local scale.