We monitored colonization, spread, and growth of an exotic Old World climbing fern on tree islands in the interior marsh of Arthur R. Marshall Loxahatchee National Wildlife Refuge, Florida to investigate linkages between its colonization and growth and environmental factors. Number of the patches continuously increased over a 2-yr monitoring period, but mean patch area and height did not increase. Lower water depth was associated with larger number of patches whereas higher water depth was associated with higher mean patch height. Patch occurrence probability at each 3 m (9.8 ft) grid within tree islands also increased and indicated that patches spread from outer areas to interiors of tree islands over time. Patch occurrence probability was lower in sawgrass-dominated locations, which typically occur at the margin of tree islands, compared to locations dominated by woody plants. Patch occurrence probability was higher on west sides of tree islands corresponding to the side of the islands most impacted by a recent major hurricane. This study revealed that colonization and growth of Old World climbing fern are characterized by several spatial and temporal factors. A detection protocol using ground surveys that focus on the edges of tree islands could be an efficient way to identify early infestations on tree islands in the Refuge. Such a protocol also might be useful to identify new infestations on tree islands in other areas of the Everglades.
Nomenclature: Old World climbing fern, small leaf climbing fern, Lygodium microphyllum (Cav.) R. Br.