Coastal salt marshes in San Francisco Bay have seen aggressive expansion of invasive plants. Three recent invaders-Limonium ramosissimum, Limonium duriusculum, and a third, unidentified Limonium species-thrive in the mid to upper salt marsh and marsh-terrestrial ecotone where the both rare and common native Limonium persist. Marsh patches containing invasive Limonium have experienced a marked decline in native halophytes.
This study investigates the relative invasion potential of three Limonium species through vegetative growth and reproduction. Given the spatial proximity and relatedness, the congeners likely influence each other's growth and compete for resources. Using a randomized complete block design, we grew pairwise combinations of invasive seedlings in high and low salinity water to assess differences in vegetative growth. We also bagged flowers of each species and compared their seed set to those of uncovered plants in the field to understand the impact of pollinators in the system. Then, through controlled hand pollinations in the greenhouse, we crossed compatible species pairs to determine how interspecific pollen affects seed production and whether or not hybridization is possible. We counted any seeds produced in the crosses and germinated them to assess viability and morphological novelty.
Results/Conclusions
Our preliminary analysis indicates that L. ramosissimum has a competitive advantage at higher salinities and that all three species grow larger at lower salinities. These results suggest that directing resources towards controlling L. ramosissimum may be warranted.