Wildfire, invasive weeds, and climate change are threatening sagebrush ecosystems including the flora and fauna that are dependent upon them. Both Forest Service and BLM policies dictate that successful restoration requires putting the right seed in the right place. However, for many desert species little or no information is available to address these policies, including big sagebrush.
Plants are adapted to their local/regional environments. Recognizing this adaptive variation and the environmental causes are key to determine how seed or seedling can be moved on the landscape. However, before these seed movement strategies can be implemented, it is also important to identify closely related taxa, since they also reflect adaptive divergence.
Big sagebrush is a good example. Big sagebrush is composed of three subspecies that occupy different environments. These subspecies can co-occur in some areas, while in other areas they do not, depending on the heterogeneity of the environment. Moreover, visually differentiating subspecies in the field can sometimes be difficult. These properties of big sagebrush make assessments of the subspecies composition of commercial seed collections challenging for both seed collectors and certifiers.
Our research evaluates seed weight variation to show that: 1) environment has very little influence on seed weight, 2) Wyoming and basin big sagebrush subspecies have significantly different seed weights, and 3) seed weight can be used as a diagnostic to assess the proportion of the two subspecies in a seed collection. This provides land managers with information to put the seed in the right place.
Among plants in different environments, genetics explained the vast majority (91 percent) of variation in the weight of big sagebrush seeds.
Seed from Wyoming big sagebrush weighed approximately 40 percent heavier than co-occurring basin big sagebrush.
Much (83 percent) of the seed certified as Wyoming big sagebrush in 2013 and 2014 had lower weights reflecting a high proportion of basin big sagebrush.