This species was described in 2015 (Lendemer & Goffinet 2015) based on a small number of collections from two areas of southeastern North America. It was previously confused with Sticta fragilinata, but can easily be recognized by its smaller size and allopatric distribution. The distinction is supported by morphological and molecular data. Since its description, extensive taxonomic work on Sticta in North America and the Neotropics has not led to the discovery of additional sites.
Sticta deyana is endemic to southeastern North America where it is restricted to two subpopulations that are both highly limited in spatial extent. One is located in the Dare Regional Biodiversity Hotspot of eastern North Carolina (Lendemer et al. 2016) and the other is located in a small area of the Southern Appalachian Biodiversity Hotspot in northern Alabama (Tripp et al. 2019). A historical occurrence (1965) was reported by McDonald et al. (2003) from central Florida as Sticta fragilinata. Despite extensive study of Sticta in the southeastern United States, and field surveys in many areas of its range, no additional occurrences of the species have been found.
The total historical EOO for this species is, 4751591 km2 and AOO is 32 km2.
The current presumed extant EOO is 25033 km2 and AOO is 28 km2.
The suspected loss of the Florida subpopulation since 1965 resulted in a reduction of EOO by >99% and a reduction of AOO by 13%.
The species is known from three subpopulations total, all separated by substantial geographic distances. The subpopulation in Florida, represented by one site, is suspected to have been extirpated as it was known from a single record made in 1965 and has not been relocated there since despite extensive lichen study in the area subsequently. The subpopulation in North Carolina is restricted to five sites at three locations on a single peninsula, all projected to be inundated by sea-level rise by 2100. The subpopulation in Alabama is restricted to three sites at two locations in highly restricted slot canyons. At all extant sites the species occurs as small numbers of individuals that are spatially restricted. The population is estimated to comprise 95 functional individuals (15 Alabama; 80 North Carolina) based on visual assessment of in the field.
ASSESSMENT: Critically Endangered A3c.
This species meets the criteria for critically endangered under A3c based on suspected population reductions that will occur in the future as the entire North Carolina subpopulation, containing >80% of the individuals, will be inundated by sea-level rise by 2100 which is less than three generations (based on a 30 year generation time). The loss of this subpopulation will result in substantial declines in EOO and AOO.
Population Trend: Decreasing
Sticta deyana is restricted to mature forests in high humidity habitats, where it occurs on the bark of mature trees (North Carolina) and large shaded rock outcrops (Alabama). In North Carolina it is associated with mature swamp forests while in Alabama it is associated with remnant old-growth in slot canyons associated with streams and rivers.
There are numerous threats to this species. The largest extant subpopulation is projected to be entirely inundated by sea-level rise by 2100 (Allen & Lendemer 2016, Lendemer & Allen 2014) and is restricted to the largest remaining unfragmented swamp forests in the Mid-Atlantic Coast and these are already being impacted by salt-water intrusion and erosion (see Lendemer et al. 2016 for detailed discussion and citation of literature). Several sites of the North Carolina subpopulation is also within a short distance of major proposed road construction projects. The smaller subpopulation in Alabama restricted to remnant mature forest stands that that will likely undergo major shifts in climate and humidity regimes as the keystone forest species (American hemlock; Tsuga canadensis) is lost at these locations due to an invasive species (Ellison et al. 2018).
The majority of areas where the species is known are within existing public lands, however locations outside of federally designated wilderness could be subjected to resource extraction, habitat alteration or further fragmentation in the future. Increased education about the species and its threatened status is needed. Inclusion in local and national conservation policy is needed.
The distribution and ecology of the species are well known, however location level demographic data and population estimates are needed. A monitoring and recovery plan needs to be developed.