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.