Wildlife in southern Everglades wetlands invaded by melaleuca (Melaleuca quinquenervia)
Authors: O'Hare Nancy K. , Dalrymple George H. 
Published: February 2024

In the Everglades region of southeastern Florida invasion of graminoid/herhaceous wetlands by the invasive, non-native tree melateuca (Melaleuca quinquenervia) results in a closed-canopy forested wetland, with a sparse understory. Intermediate stages in this transformation include a savannah with scattered mature melaleuca trees, and mature dense melaleuca heads surrounded by areas with moderate to low levels of melaleuca. Intermediate levels of melaleuca invasion have not received any attention and were the rationale for our study. Wildlife was surveyed monthly for two years to determine species richness and abundance in wetlands with different melaleuca coverages. Wildlife included all vertebrate classes, as well as selected macro-invertebrates such as crayfish (Procambarus alleni) and grass shrimp (Paleomonetus paludosus). Species richness was highest in areas with moderate melaleuca coverage. Higher species richness is typical of sites with greater vegetative structural diversity, i.e., as in the savannah stage of invasion, as well as areas in an early stage of disturbance. The higher species richness was primarily the result of an increased number of migratory, upland birds. Many of these transient and winter-resident birds occurred at much lower abundances than in native forested habitats such as cypress swamps (Taxodium distichum), tropical hardwood hammocks, and pine (Pinus elliottii var. densa) rocklands. In contrast to the birds, number of species and the abundance of herpetofauna varied little across the melaleuca gradient. There was no shift in species composition from wetland to upland species as the melaleuca coverage increased. The number of fish species was similar across the melaleuca gradient. Unlike the herptiles, fishes were less abundant in the closed-canopy melaleuca forests indicating poorer habitat quality. Complex patterns of hydrology and gapping in the forest canopy due to wind storms and fires permitted light penetration and the persistence of productive pockets of aquatic life even within dense stands of melaleuca. The mosaic of areas with low to moderate infestations of melaleuca surrounding mature dense melaleuca stands allowed higher numbers of individuals and species to persist in or seasonally use mature dense melaleuca stands. This interspersion of habitats resulted in stands of melaleuca with ecotonal edges that provided marginal habitat for species characteristic of natural communities. Higher degree of interspersion (more edge) may also mean that the natural areas experience higher exposure to melaleuca seed source, which may result in a faster rate of spread of melaleuca. The results demonstrated that animal populations persisted in areas with disturbed vegetation, as long as critical abiotic factors (in this case hydrology) remained in operation. Areas with moderate levels of melaleuca retained species composition and productivity typical of the natural wetland community. The dominant characteristic of the faunal shifts along the gradient of increasing melaleuca coverage was increased numbers of upland, arboreal, and/or forest species, not the loss of wetland species. Regional permitting and natural resource agencies should recognize that lands with moderate levels of melaleuca may retain significant habitat quality. Restoration of such lands will demonstrate higher levels of success if the method used for melaleuca removal allows for retention of the in situ wildlife community.