Understanding the ecology of rare epiphytes, including phorophyte (host tree) preference, is important for making predictions about population trajectories and for management of endangered species. We studied the phorophyte preference of Dendrophylax lindenii (ghost orchid), a state-listed, leafless epiphytic orchid found in Florida, Cuba, and the Bahamas. This species is of particular concern due to the risk of poaching. To support conservation efforts, researchers have made advances in rearing D. lindenii under greenhouse conditions; however, the ecology of this species in its natural habitat remains understudied. We predicted that D. lindenii would colonize preferentially on stems of Fraxinus caroliniana (pop ash) and on relatively small stems.
We studied a population of D. lindenii in Fakahatchee Strand Preserve State Park in Collier County, Southwest Florida. We recorded the location and height (> 3m or < 3m) of all individuals within a 30m by 90m transect, along with the phorophyte species and dbh. We also recorded location, species, and dbh (> 4cm) of trees and lianas within the transect that were not hosts for D. lindenii. We conducted tests of independence to assess preference in host plant and host plant dbh.
Results/Conclusions
Dendrophylax lindenii showed a significant host preference for F. caroliniana (G = 36.5; p < 0.0010). Of 695 tree stems recorded at the study site, 33.5% were F. caroliniana; however, 80% of D. lindenii individuals were found on F. caroliniana stems. The remaining D. lindenii were found on Hippocratea volubilis (medicine vine; 16%) and Annona glabra (pond apple; 4%). The greatest frequency for host tree dbh occurred in the 14.1-17.2 size class, but this pattern was not significant (chi-square = 8.02, p = 0.09). The spatial distribution of the orchids across the 0.27 ha plot showed clumped patterns, though the principal host plant was randomly distributed.
Our results support those of Mujica et al. (2018), though we show a stronger host preference for F. caroliniana and also report an additional host species (H. volubilis). Continued research on the ecology of these endangered orchids will be critical in habitats that are subjected to human development and human-driven climate change.