Comparing growth patterns among ecotypes of a habitat-forming species: A case study in a restored Spartina alterniflora marsh

Background/Question/Methods

Genetically diverse stands of habitat-forming species can have high productivity and be resilient to and recover from disturbances. Salt marsh restoration typically utilizes local grasses, which are usually clonal and therefore have relatively low genetic diversity. Creating a marsh with multiple ecotypes should increase genetic diversity, which may correlate with increased productivity. As a first step to understand the benefits of increased genetic diversity within a single plant species, we performed a common garden experiment in a constructed salt marsh in Galveston Bay, Texas to compare post-transplant growth patterns among Spartina alterniflora ecotypes. Plants from three coastal Texas locations (Port O’Connor, Bolivar, and Texas Point) at least 60 km away from the common garden were transplanted in July 2011. Transplanted sprig survival, vegetative growth, and inflorescence production were compared among ecotypes. Data were analyzed based on an initial growing period (July-October 2011) and a winter growth period (November 2011-January 2012).

Results/Conclusions

Three months after transplantation, survivorship was significantly different among ecotypes; 10% of Port O’Connor’s ecotype remained alive; other populations had less than 7% survival. Throughout the initial growing period, 56 Port O’Connor sprigs generated shoots; 60% more than Bolivar’s ecotype. By October, surviving Bolivar plants produced 2.2 inflorescences per transplant compared to 1.5 (Texas Point) and 1.0 (Port O’Connor). After winter growth, Port O’Connor produced an additional 210 shoots compared to 155 (Bolivar) and 99 (Texas Point). Overall, the Port O’Connor ecotype had the most surviving transplants and the most vegetative growth. However, this ecotype was out preformed reproductively by the Bolivar ecotype. Each ecotype displayed different strengths in terms of survivorship, growth patterns, and reproduction. In restoration, including different ecotypes with various strengths can contribute aspects that complement each other, possibly creating a more productive marsh than if a single ecotype had been used.