Persistence of plant populations is influenced by the ability of individuals to successfully reproduce, including protecting reproductive structures from herbivores, and the recruitment of new individuals from seed. We studied herbivore defense and seed germination of Chapmannia floridana (Florida alicia), an herbaceous perennial. Individuals are often multi-stemmed; reproductive stems have glandular trichomes covering the upper part of the flowering stem, flower buds, and fruits, while non-reproductive stems lack glandular trichomes. We investigated whether glandular trichomes function as an indirect defense by trapping carrion, which can attract predators that deter herbivores, leading to reduced damage to reproductive structures. We measured the length of the trichome-covered portion of C. floridana flowering stems in four Florida scrub vegetation types, firelanes, and pastures. We counted the number of herbivores and predators on flowering stems, the number of damaged and undamaged flower buds, flowers, and fruits, and the number of carrion trapped on the stem. We conducted a field germination experiment to investigate differences in seed germination among habitats (scrubby flatwoods, firelanes, and pastures) and between microhabitats in scrubby flatwoods communities. We conducted laboratory germination experiments to investigate the effects of ash leachate and litter leachate from Florida rosemary, an allelopathic species, on seed germination.
Results/Conclusions
We found predators on 6% of stems and herbivores (grasshoppers, caterpillars, leafhoppers) on 37% of stems. The number of carrion trapped by flowering C. floridana stems was positively correlated with the length of the trichome-covered portion of the stem, and the number of trapped carrion did not vary among habitats. Fewer than 20% of reproductive structures had evidence of herbivore damage, and the probability of damage was negatively correlated with the number of carrion. This suggests that glandular trichomes on C. floridana may function as an indirect defense against herbivores. In the field germination experiment, ~50% of seeds germinated, and we found no association between habitat and germination. The ability of C. floridana seeds to germinate among grasses may partially explain why it's one of the few Florida scrub species that occurs in pastures. Within scrubby flatwoods, seeds under scrub oak were more likely to germinate than seeds in gaps, indicating that litter cover positively affects germination. In the lab, percent germination was similar between control and leachate treatments and was over 80% in some treatments. Overall, our studies suggest that C. floridana populations persist in part because of indirect defenses that protect reproductive structures and relatively high seed germination.