Does provenance matter? Assessing ecotypal variation to promote restoration success

Background/Question/Methods

Restoration of native ground cover is a top conservation priority in the longleaf pine ecosystem of the southeastern United States, but a major obstacle is the lack of commercially available seed from southeastern U.S. sources.  Many species associated with longleaf pine grow throughout the Southeast and Midwest, and ecotypes may vary considerably across the range of a species, depending on the degree of adaptation to local environmental conditions. Even within the Southeast, the distance an ecotype can be moved and still be ecologically appropriate for reintroduction is unknown and likely varies by species. Therefore, information is needed to help delineate seed transfer zones that are most likely to lead to successful restoration outcomes across the Southeast. We collected seed of six species that are desirable restoration candidates in the longleaf pine ecosystem from three natural populations within each of five geographic subregions, and have planted all populations in four common gardens located throughout the Southeast. Additionally, a sample of seeds from each population was sown in a shadehouse environment to monitor germination phenology.  Differences in phenology within and among subregions were determined using ANOVA with days until 50 percent of seed germination had occurred as a response variable.

Results/Conclusions

Patterns of germination phenology within and among geographic subregions vary by species. The two forb species each had significantly different germination phenologies within some subregions, while showing no significant differences among subregions. Two of four grass species exhibited significantly different patterns in germination phenology both within and among subregions, while the other two species did not differ across the range of the species. Therefore, the environmental cues that trigger germination differ at relatively small spatial scales for some species, which could have important implications for the timing of seed sowing in a restoration setting across geographical subregions. In the next phase of the project, we will examine differences in growth and reproductive characteristics among plants of different seed sources at each of the common gardens. Average performance of each geographic subregion will be compared to determine the amount of ecotypal variation within each species. Preliminary results suggest that leaf morphology differs among subregions for both species of forbs in the study, with no interaction between seed source and garden site. Our data suggests that ecotypal variation is species specific and the development of biologically meaningful seed transfer zones will require comparisons among a large suite of species.