Seed germination and seedling survival of five endemic Florida Scrub species in intact and degraded habitats

Background/Question/Methods

Knowledge of seed ecology is important for the restoration of ecosystems degraded by anthropogenic activities. Current efforts to preserve and reintroduce populations of plant species endemic to Florida are hindered by lack of information on demographic responses to human alteration. Comparisons of seed removal, germination and establishment in both intact and degraded habitats will aid in management decisions for species in need of protection. Our objectives were to assess the impact of post-dispersal seed predation on seed germination on plant populations in degraded and intact habitats, and to investigate the effects of habitat and microsite on seed germination and establishment. For five endemic Florida scrub species with different seed sizes (Liatris ohlingerae, Eryngium cuneifolium, Polygonella basiramia, Hypericum cumulicola, Paronychia chartacea subsp. chartacea), we conducted a seed removal experiment by filtering access of insects and vertebrates to exposed seeds, planted seeds in replicated degraded and intact scrub sites (trial I: bare sand, trial II: in bare sand, litter only, and under shrubs with litter), and determined background germination rates in a growth chamber.

Results/Conclusions

The contrasting pattern in seed removal among treatments suggests that habitat and seed size affect the likelihood of removal in Florida scrub. Species with large seeds such as L. ohlingerae were removed in higher frequency in degraded scrub, mostly by vertebrates. Species with small seeds such as H. cumulicola and P. chartacea were removed by invertebrates and in higher frequency in intact scrub. E. cuneifolium had significantly more seedlings in degraded scrub, and P. chartacea had significantly more germination in the intact scrub in the first trial. E. cuneifolium and H. cumulicola had trends of higher germination in bare sand, and P. chartacea germinated significantly better in bare sand microsites than in litter only or under shrubs. For restoration success, it will be important to provide the conditions for germination and establishment preferred by each of these endemic species.