The hand fern, Cheiroglossa palmata (L.) C. Presl, is state-listed as endangered in Florida. It is found primarily in wet hammocks growing in the accumulated detritus under the persistent leaf bases of Sabal palmetto. Little is known about the biology and ecology of hand fern, which makes it difficult to conserve this species and identify possible threats to its persistence. We sought to answer the following questions: 1) is the morphology of hand fern leaves influenced by age of the leaf, palm tree in which is growing, or field site; and 2) is leaf mortality, leaf production, growth, and onset of fertility influenced by rainfall and temperature? We selected two field sites, one relatively dry and the other wet, at the Tosohatchee State Reserve (Orange County, Florida) and monitored production, survival, and fertility of all fern leaves within our reach for 27 months. We measured seven morphological characteristics of leaves and also calculated the increase in growth every two months. Daily rainfall, high temperature, and low temperature were ascertained from the closest weather station. We used multiple regression to test for correlations between the phenology of hand fern and weather from 0-90, 91-180, and 181-270 days before a field survey.
Results/Conclusions
Morphology of hand fern leaves was most closely associated with its age. However, five of the seven morphological characteristics varied among palm trees, and four of the morphological characteristics varied between the two field sites. Morphological variation of hand fern among trees may indicate that microhabitat, genetics, or a microhabitat x genetic interaction influences fern morphology. Leaves were wider and produced longer sporangial spikes in the wet site, but were more lobed and produced more spikes in the dry site. Weather influenced leaf production, growth, and onset of fertility, but was not correlated with mortality. More leaves were produced when rainfall and temperatures were higher within the prior 90 days. Leaves grew more when rainfall was higher within 90 days and 91-180 days and the minimum temperature was higher 91-180 days prior to a field survey. The onset of fertility was positively correlated with the number of days of rainfall within the prior 90 days. Leaf production, growth, and fertility were negatively correlated with some measures of temperature and rainfall 91-180 and 181-270 days before a field survey, especially higher rainfall 181-270 days beforehand. Future research should elucidate how changing climate may impact populations of hand fern.