Assessment Notes

Justification

Sticta deyana is a rare macrolichen endemic to south-eastern North America with a suspected future population reduction that will occur in the future as the entire North Carolina subpopulation, containing >80% of the individuals, is projected to be inundated by sea-level rise by 2100 which is less than three generations (based on a 30 year generation time), while invasive species also provide a threat. Therefore, it is listed as Critically Endangered under criterion A3ce.

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Geographic range

Sticta deyana is endemic to south-eastern North America where it is restricted to two extant 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). An historical occurrence (1965) was reported by McDonald et al. (2003) from central Florida as S. fragilinata. Despite extensive study of S. deyana in the south-eastern United States, and field surveys in much of this region, no additional occurrences of the species have been found.

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Population and Trends

The species is known from three subpopulations total, two extant and on presumed extirpated, 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 on a single peninsula, all projected to be inundated by sea-level rise by 2100. The subpopulation in Alabama is restricted to three sites 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.

Population Trend: decreasing

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Habitat and Ecology

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.

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Threats

There are numerous threats to this species. The largest extant subpopulation is projected to be entirely inundated by sea-level rise by 2100 (Lendemer and Allen 2014, Allen and Lendemer 2016) 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 subpopulations are also within a short distance of major proposed road construction projects. The smaller subpopulation in Alabama is restricted to remnant mature forest stands that will likely undergo major shifts in climate and humidity regimes as the keystone forest species (American Hemlock; Tsuga canadensis) is lost at these sites due to an invasive species (Ellison et al. 2018).

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Conservation Actions

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. As such, additional protection of sites on both public and private lands is needed. Invasive species management is also needed to prevent the spread of the Hemlock Adelgid to disjunct inland sites where the species occurs, and to prevent the loss of that tree species if the adelgid does spread there. The species is not presently listed as threatened or endangered in any formal conservation framework, hence inclusion in existing policy and management frameworks is needed at both the national and regional levels. Also, increased education about the species and its threatened status is needed, as well as research and conservation planning.

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Source and Citation

Lendemer, J. 2020. Sticta deyana. The IUCN Red List of Threatened Species 2020: e.T175710321A175710717. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T175710321A175710717.en .Accessed on 2 February 2024

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• Country occurrence