Assessment Notes

Justification

Sticta fragilinata is a macrolichen that is endemic to south-eastern North America. Its population is severely fragmented, and continuing declines in quality of habitat have been observed and at sites across its range. Therefore, it is listed as Endangered under criterion B2ab(iii) based on the Area of Occupancy (348-448 km²).

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Geographic range

Sticta fragilinata is endemic to the southern Appalachian Mountains of eastern North America (Georgia, North Carolina, South Carolina, Tennessee) (see McDonald et al. 2003, Lendemer and Goffinet 2015).

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Population and Trends

The population of this species was likely naturally fragmented historically, occurring at sites in mature forest stands located in spatially restricted habitat types. At a site, the species is typically locally abundant, occurring as 1-5 clustered functional individuals. The current population size is estimated at 550-1,110 individuals based on a conservative estimate of 5-10 functional individuals per site, and its known occurrence at 111 sites. Although there may be a small number of undiscovered additional sites, at this time the it is suspected that the overall population size would not significantly differ from this figure. We suspect that the population declined historically (during the last 3 generations; 90 years, based on a 30 year generation time) due to the extensive history of logging throughout its range (1900-1970; Mastran and Lowerre 1983, Yarnell 1998), as well as substantial impacts from air pollution and acid rain/fog. These activities have led the present extant population to become highly fragmented, as the species is restricted to mature forest stands in suitable habitat and these areas are very limited in extent and are no longer contiguous (Ervin 2016). We suspect that the already fragmented and reduced population is currently decreasing due to numerous ongoing and projected trends in anthropogenic impacts that would directly affect this species (Keyser et al. 2013).

Population Trend: decreasing

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Habitat and Ecology

Sticta fragilinatas is restricted to mature forest stands in high quality habitats with high humidity, especially riparian corridors and Northern Hardwood Forests. It occurs primarily on the bark of hardwoods, especially mature sugar maple (Acer saccharum), buckeye (Aesculus flava) and oaks (Quercus montana, Q. rubra).

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Threats

There are two primary pressures on this species, habitat fragmentation and loss (historical and ongoing) and impacts from air pollution and climate change (historical, ongoing and projected). The species occurs primarily on existing public land, some of which is large in overall area and some of which is available for multiple uses including resource extraction (Anderson et al. 2013). However, the species naturally occurs in isolated sites where suitable habitat exists within large areas that are not suitable (i.e. mature forest stands with high humidity are spatially restricted within a matrix of younger forests, forests without appropriate tree hosts, and drier habitats). These naturally dispersed locations were degraded and fragmented historically due to extensive logging, building of roads, alteration of riparian corridors by dams, and air pollution. Logging is ongoing at small scales within the range of the species. Fragmentation has continued as the region has undergone rapid population growth, suburbanisation and development of non-primary residences/infrastructure for vacation and recreation. Hence, available data indicates that the species is highly localised where it occurs, the habitat it has occurred in has become fragmented in the past and is now increasingly fragmented (Anderson et al. 2013). Further the region is currently experiencing climate change impacts (increased fire frequency and severity, droughts, increased temperatures, decreased precipitation) and extensive alteration of forest communities due to invasive species (Keyser et al. 2014), all of which are likely to impact the species.

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Conservation Actions

Many areas where the species is known are within existing public lands, however locations outside of National Parks and federally designated wilderness could be subjected to resource extraction or further fragmentation in the future. Increased education about the species and its threatened status is needed, as is inclusion in local and national conservation policy. Further research and conservation planning would also be beneficial.

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Source and Citation

Lendemer, J. 2020. Sticta fragilinata. The IUCN Red List of Threatened Species 2020: e.T175710297A175710712. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T175710297A175710712.en .Accessed on 31 January 2022

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