Florida Perforate Cladonia
Florida Perforate Cladonia
|Listed||April 27, 1993|
|Family||Cladoniaceae (Reindeer lichen)|
|Description||Lichen with dense groupings with spore-producing branches.|
|Habitat||Scrub, high pine, dry upland communities in central Florida and in the coastal scrub of the northwestern part of the state.|
|Threats||Habitat conversion to citrus groves, pasture, and urban developments.|
The Cladoniaceae is represented in Florida by the two large, widespread, and closely related genera, Cladonia and Cladina. This conspicuous and diverse group is one of the most important in the Florida lichen flora, represented by a total of 33 species, three of which are endemic to the state. Cladonia perforata var. C. perforata is a member of the family Cladoniaceae, commonly called the reindeer lichens. Unlike the more common and widely-distributed species of the Cladoniaceae it occurs with,
C. perforata is restricted to the high, well-drained sands of rosemary scrub in Florida. C. perforata was listed as endangered because of the significant loss of scrub habitat in Florida. This species is known to occur on 27 sites in Florida; all but four sites are in the South Florida ecosystem. Twelve of the 27 sites are protected, and others are proposed for acquisition in the future.
Florida perforate cladonia, C. perforata, is easily recognized in the field by the conspicuous holes or perforations below each dichotomous branch point and its wide, smooth, yellowish gray-green branches. Unlike other fruticose lichens whose branches develop from the primary or vegetative body, the branches of members of Cladonia and Cladina are developmentally derived from spore-producing structures called apothecia, present as colored, expanded tips of fertile branches. These specialized, hollow branches are called podetia and are structurally characteristic of this group. C. perforata differs in color, shape, and texture, in addition to having specific habitat requirements. C. perforata has rather wide, pale yellowish gray-green podetia, punctuated in the axils by 0.04-0.06 in (1-1.5 mm) perforations. The branching pattern is complex and consists of roughly subequal dichotomies near the tips and, more commonly, sympodia (un-equal branchings with the smaller branch deflected to one side) below, resulting in a more-or-less compressed tuft. Its outer surface is mostly uniformly smooth. Individual podetia are typically 1.6-2.4 in (4-6 cm) long, although specimens of up to 3.1 in (8 cm) across and several inches high have been observed. No primary thallus is known. The oldest parts of the podetia degenerate, leaving no means of determining ages. No studies of growth rates inC. perforata have been completed. In boreal areas, growth studies of Cladonia species suggest that one branching occurs each year; however, in more tropical areas, more than one branching per year may be possible.
Reproduction in the Cladoniaceae is typically by means of sexually-produced spores or dispersal of vegetative fragments, either by soredia (microscopic clumps of algal cells surrounded by fungal threads that emerge from the lichen surface as a powder) or simple fragmentation. However, neither spore-producing structures nor soredia are known from C. perforata. Presumably, the main form of reproduction is by vegetative fragmentation.
C. uncialis is a closely related and similar looking species; its podetia are wide and perforate, though not at every dichotomy, and are glossy with greenish areolae. The other fruticose, terrestrial species of Cladonia and Cladina that commonly co-occur withC. perforata can easily be distinguished from it. Although C. leporina may sometimes have small perforations in the podetia and is occasionally confused with C. perforata, C. leporina is a darker yellow green color, has narrower podetia with rough surfaces and can often be found with conspicuous red apothecia. Cladina pachycladodes is similar in color to C. perforata but is more of a light bluish gray color and has finer branches, drooping at the tips. Cladina subsetacea, Cladina evansii, and Cladina subtenuis all have much narrower, filiform podetia, usually less than 0.04 in (1 mm) wide, compared to 0.2 in (4 mm) forC. perforata.
Several of the fruticose, terrestrial Cladonia and Cladina species form a conspicuous and characteristic part of Florida's white sand scrub communities. Typical habitat for C. perforata is found on the high sand dune ridges of Florida's peninsula, including the Atlantic coastal and the Lake Wales ridges. In these areas Florida perforate cladonia is restricted to the highest, xeric white sands in sand pine scrub, typically in the rosemary phase. Such rosemary scrubs, frequently referred to as "rose-mary balds," are particularly well-drained and structurally open. Specific aspects of Florida perfo-rate cladonia microhabitat require further investigation and, presently, can only be roughly generalized with the following associated plant species: scrub oaks, which are clumped and scattered throughout; sand pine, which dominates the tree layer, although the canopy may be sparse or absent; and Florida rosemary, which dominates the shrub layer. Florida perforate cladonia typically occurs in open patches of sand between shrubs in areas with sparse or no herbaceous cover.
In Highlands and Polk counties on the Lake Wales ridge, Florida perforate cladonia occurs at relatively higher elevations than surrounding areas, on excessively well-drained, nutrient-poor, white sands. A small site in xeric scrubby flatwoods on Lake Wales ridge (formerly Lake Arbuckle) was discovered in 1997. Other Lake Wales ridge sites are on open rosemary scrubs or under dense sand pine in rosemary scrub. In the coastal scrubs of Jonathan Dickinson State Park in Martin County, Florida perforate cladonia is reported from open areas in oak-dominated sand pine scrub and scrubby flatwoods. The Okaloosa County sites are on undifferentiated coastal beach sands in white-sand scrub.
Florida perforate cladonia occurs most commonly with Florida rosemary and sand pine, typically in patches of bare sand with other Cladonia and Cladina species, sometimes forming mixed-species tangled clumps. It can, however, occasionally occur in dense, long-unburned sand pine scrub on a mat of pine needles. However, Florida perforate cladonia decreases in dominance in sites that have gone unburned for more than 20 years. This decrease in dominance on unburned sites may be a result of a combination of factors that influence microhabitat, such as decreased insulation or increased litter accumulation.
In northern biomes such as boreal forests and the tundra, members of Cladonia and Cladina form continuous mats which cover the ground and provide important forage for caribou and reindeer. In temperate and subtropical regions, open rock outcrops or patches of bare ground or sand provide habitat for reindeer lichens. Florida scrub, which is characterized in part by long-lived, open patches of sand, supports a relatively rich assemblage of these terrestrial lichens. Up to eight species of reindeer lichens commonly occur in Florida scrub. Florida perforate cladonia is the most unique member of the scrub lichen community, by virtue of its restricted and unusual disjunct distribution and overall global rarity.
In 1991, the Florida Natural Areas Inventory surveyed 111 sites throughout central and coastal Florida to determine the status of Florida perforate cladonia. A total of only 12 sites were located, six of which were at Archbold Biological Station. Two additional sites were later located at Archbold Biological Station. With one Eglin Air Force Base site in Okaloosa County, and several other more recently discovered south-central and coastal Florida locations, a total of 25 sites for Florida perforate cladonia are currently known from four disjunct geographic regions. The farthest and most disjunct region, supporting the only remaining north Florida site, is defined by Santa Rosa Island in Okaloosa County. This region is about 400 mi (644 km) north of the next closest region. Central Florida's Lake Wales ridge supports the bulk of the known sites. South-coastal Martin and Palm Beach Counties support three sites, and southwest Florida's Manatee County has one disjunct site for this lichen. The east side of Santa Rosa Island in Escambia County also supports a population.
The current patchy distribution of Florida perfo-rate cladonia may reflect all or only part of its historic range, represented by the fragmented scrubs on high white-sand ridges of central Florida.
The loss of scrub habitat is the primary threat to Florida perforate cladonia. Less than 15% of the historic distribution of scrub habitat remained as of 1992, and land conversion to citrus and residential development continues to diminish scrub habitat almost daily. As with all species restricted to the developable upland landscape, including species of the scrubs of the Lake Wales ridge, nearby parallel central ridges, and the Atlantic Coastal ridge, habitat loss is the most critical concern.
In addition to habitat loss, Florida perforate cladonia is also threatened by trampling, off-road vehicles, hurricane washover, and improper land management. Twelve of the 27 known sites for Florida perforate cladonia occur on dedicated conservation lands and are protected. In Highlands County, eight sites are protected on Archbold Biological Station and one site is protected at the Lake Apthorpe Preserve. In Polk County, two sites occur on the Lake Wales Ridge SF. In Martin County, one site occurs at Jonathan Dickinson SP Other protected areas include two sites at the Jupiter Inlet tract, owned and managed by the Bureau of Land Management in Martin County, the one north Florida site in Okaloosa County on Eglin Air Force Base. The Okaloosa County site occurs on a beach with restricted vehicular access, but completely open to foot traffic. In addition to the already-protected sites for Florida perforate cladonia, the Trout Lake site in Polk County is proposed for inclusion in the state's Preservation 2000 program. Other potential sites for protection include several privately held properties in Highlands County.
A low proportion of all known sites supports large areas of Florida perforate cladonia. At only two of the Archbold Biological Station sites is this lichen very abundant, making up the dominant ground cover in most of the site with densely crowded and overlapping thalli. Abundant stands are also reported from the site at Jonathan Dickinson State Park and from the east end of Santa Rosa Island.
Despite the conservation status of these sites, populations of this lichen may be extremely limited in areal extent and, therefore, subject to significant losses from local events. For example, two Okaloosa County sites supported only small fragments of Florida perforate cladonia prior to Hurricane Opal, which severely impacted Santa Rosa Island in October of 1995. One estimate suggested that more than half of the potential habitat of Florida perfo-rate cladonia at that site was negatively affected by the storm, with large areas swept clean of all ground lichens or inundated with salt water. Only a few fragments of the lichen were relocated after the storm. At Archbold Biological Station, Florida perforate cladonia occurs on eight of more than 100 discrete, available habitat patches (rosemary balds). Five of these eight sites were partially burned in a prescribed fire in 1993, but in each, the lichen persisted in unburned patches, although almost certainly in lower numbers.
Throughout its distribution, Florida perforate cladonia is considered as rare. It has a limited areal extent and its management is further complicated by its limited reproduction and dispersal capability.
Conservation and Recovery
Florida scrub has historically experienced variable fire frequencies and patchy high-intensity fires. Scrub plant communities are therefore fire adapted, and recover relatively quickly. In sand pine and rosemary scrub, however, recovery of dominant species is slower than in oak-dominated scrubs, and open spaces between shrubs persist longer. In fire-maintained systems, low-fuel, bare sand patches may serve as refugia from fire for Florida perforate cladonia and other lichen species that cannot survive fire. These refugia provide a local source for recolonization and population recovery. Land managers should avoid complete burns in large areas supporting Florida perforate cladonia. Such fires likely reduce the possibility of recolonization from unburned patches within sites or from nearby sites. Additionally, complete lack of fire is also detrimental to the species. Fire suppression creates closed canopies and causes microsite characteristics to change. Management recommendations for Florida perforate cladonia should provide for fire return intervals long enough to restore vigorous lichen growth and to allow regeneration of mature shrub layers, since reburning rosemary scrub too frequently can deplete its soil seed banks. More frequent burns in adjacent habitats may serve to occasionally burn small areas of rosemary and reduce fuels enough to prevent large, complete fires. Spatially patchy fires leave unburned areas within a burned matrix from which species of Cladonia may recolonize, and without which Florida perforate cladonia may be threatened with local extinctions. Patchy burns in rosemary scrub at Archbold Biological Station and the Lake Apthorpe Preserve may be successful in promoting the persistence of this species, creating or re-opening new bare sand patches adjacent to occupied, unburned areas.
Management of Florida perforate cladonia should include protection of all sites from vehicle or heavy foot traffic and promoting fire management planning at sites where fire is an important part of that site's ecology. Unpredictable events, like hurricanes and wildfires, are best mediated by having a large number of protected sites, which provide local sources for natural recolonization and population recovery. It may be possible to reintroduce Florida perforate cladonia into severely damaged sites, if impacts have been so severe that the nearby natural population has not been able to re-colonize the site.
U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
Ecological Services Field Office
6620 Southpoint Drive, Suite 310
South Jacksonville, Florida 32216-0912
Phone: (904) 232-2580
Fax: (904) 232-2404
U.S. Fish and Wildlife Service. 27 April 1993. "Endangered and Threatened Wildlife and Plants; Endangered or Threatened Status for Seven Central Florida Plants." Federal Register 58 (79): 25746-25755.