Arthonia cupressina (Golden Spruce Dots) is endemic to the Appalachian Mountains of eastern North America. It is known from a small number of scattered occurrences in remnant old-growth forests, with the majority of the population occurring in Great Smoky Mountains National Park in the eastern United States. Despite its small size, the species has been searched for extensively in suitable habitat throughout the southern Appalachian and central Appalachian Mountains. In addition to being restricted to old-growth forests, the species occurs on mature trees of specific conifer host species. The overall rarity and spatial dispersion of the population make the species particularly susceptible to stochastic events, such as wildfires and storms, which are increasing in much of the area where it occurs. Host trees are being impacted directly by invasive species, and indirectly through the loss of co-occurring dominant tree species. The southern Appalachian spruce-fir forests where much of the population occurs are considered endangered and likely to be greatly impacted by climate change in the near-term future. The species has an extent of occurrence (EOO) of 262,493 km2 and and Area of Occupancy (AOO) of 52 km2, the population is severely fragmented, there is a small number of extant locations (4), and there are inferred continuing declines in EOO, AOO, habitat quality, number of locations/subpopulations, and number of mature individuals. Therefore, it is listed as Endangered under criterion B2ab(i,ii,iii,iv,v).
Arthonia cupressina (Golden Spruce Dots) is endemic to the Appalachian Mountains of eastern North America where it occurs on mature conifers in remnant old-growth forest stands.
The population is distributed across four spatially restricted subpopulations separated by significant distances. The majority of extant individuals are concentrated in a single subpopulation located in Great Smoky Mountains National Park, in the eastern United States. The entire population is located on public lands, and the majority (>90%) are located in protected areas. A single historical occurrence from Massachusetts suggests that the species was more widespread and that there have been past declines in Extent of Occurrence and Area of Occupancy.
Population Trend: decreasing
Arthonia cupressina occurs on the bark of mature individuals of specific conifer species (Red Spruce, Picea rubens; Canadian Hemlock, Tsuga canadensis) in remnant old-growth forests.
This species was likely historically impacted by large-scale logging throughout eastern North America as it is now restricted to remnant old-growth conifer forests. Old-growth forest habitats have been greatly reduced from their historical extent throughout the Appalachian Mountains where the species occurs and the habitat is now highly fragmented. The Canadian, Pennsylvania and West Virginia subpopulations are located in small remnant stands of suitable habitat. The Pennsylvania subpopulation is currently being impacted by an invasive species that causes mass mortality of the host tree there (Hemlock Wooly Adelgid, Adelges tsugae and Canadian Hemlock, Tsuga canadensis; Ellison et al. 2018). The southern Appalachian subpopulations have likely been impacted by air pollution, including acid rain and fog in the past (Noss et al. 1995). Now the spruce-fir ecosystem where the species occurs in the southern Appalachians is imperilled by invasive species and climate change (Noss et al. 1995, Allen and Lendemer 2016, Lendemer et al. 2017).
The species is not currently included on lists of threatened taxa, but approximately 81-90% of the population occurs in the Great Smoky Mountains National Park. Monitoring of all extant sites is required to determine the degree, rate and time-frame of decline. Detailed surveys and increased protection for suitable habitat is also needed. A species-based management plan needs to be developed, and the species needs to be incorporated into existing management plans for suitable habitat and extant sites. Study of the potential reintroduction into formerly occupied areas should also be considered. Increased education about the species, its ecology, and how it could be conserved would also be highly beneficial.