Seed type and origin-dependent germination patterns in Danthonia
californica, a cleistogamous species commonly used in grassland
restoration
Abstract
Danthonia californica is a native perennial bunchgrass commonly used in
the restoration of prairie ecosystems in the western United States.
Plants of this species simultaneously produce both chasmogamous
(potentially outcrossed) and cleistogamous (obligately self-fertilized)
seeds. Restoration practitioners almost exclusively use chasmogamous
seeds for outplanting, which are predicted to perform better in novel
environments due to their greater genetic diversity. Meanwhile,
cleistogamous seeds may exhibit greater local adaptation to the
conditions in which the maternal plant exists. We performed a common
garden experiment at two sites in the Willamette Valley, Oregon to
assess the influence of seed type and source population (eight
populations) on germination and found no evidence of local adaptation
for either seed type. Cleistogamous seeds outperformed chasmogamous
seeds regardless of whether seeds were sourced directly from the common
gardens (local seeds), or other populations (nonlocal seeds).
Furthermore, average seed weight had a strong positive effect on
germination success, despite the fact that chasmogamous seeds had
significantly greater mass than cleistogamous seeds. At one common
garden we observed that seeds of both types sourced from north of our
planting site performed significantly better than local or
southern-sourced seeds. We also found a significant seed type and
distance-dependent interaction, with cleistogamous germination peaking
approximately 125km from the garden, which may be explained by
differences in the pathogen content of cleistogamous and chasmogamous
seeds. These results suggest that cleistogamous seeds should be
considered for greater use in D. californica restoration.