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Sporodophoron americanum (Lendemer, E.A. Tripp & R.C. Harris) Ertz & Frisch

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Scientific name
Sporodophoron americanum
Author
(Lendemer, E.A. Tripp & R.C. Harris) Ertz & Frisch
Common names
 
IUCN Specialist Group
Lichens
Kingdom
Fungi
Phylum
Ascomycota
Class
Arthoniomycetes
Order
Arthoniales
Family
Arthoniaceae
Assessment status
Published
Assessment date
2021-02-01
IUCN Red List Category
EN
IUCN Red List Criteria
B2ab(i,ii,iii,iv,v); C2a(i)
Assessors
Lendemer, J.
Reviewers
Allen, J.

Assessment Notes

The content on this page is fetched from The IUCN Red List of Threatened Species: https://www.iucnredlist.org/species/175710398/175710722

Justification

This species has an area of occupancy in the range of 164-400 km2, a severely fragmented population estimated to comprise fewer than 500 mature individuals (196-410 mature individuals; maximum subpopulation size comprised of 50 mature individuals), and there are continuing declines in EOO, AOO, number of locations, number of mature individuals and habitat quality inferred or observed across its range. Past and ongoing declines are due largely to logging, development, air pollution, and climate change. These factors likely disproportionately impacted historical occurrences in the Appalachian foothills and adjacent Piedmont, where the species is known from few occurrences. Tentatively, the higher estimate for the area of occupancy is used here, as this incorporates additional potential sites that have so far been unsampled. Thus, it is listed as Endangered under criterion B2ab(i,ii,iii,iv,v) and C2a(i).


Geographic range

Sporodophoron americanum is endemic to eastern North America. The majority of known occurrences are located in the southern Appalachian Mountains, especially eastern Tennessee (Blount, Monroe, Sevier Counties; Great Smoky Mountains and Unicoi Mountains). Scattered sites are also known from the Ozarks and Piedmont in the south-eastern United States. Several disjunct sites have been located in Minnesota, and one has been found in Ontario, Canada.

Population and Trends

This species was described in 2013 from scattered sites in the south-eastern United States as Tylophoron americanum (Lendemer et al. 2013). Since that time, additional subpopulations have been located in the region, and several northern disjunctions have been found. No occurrences outside of eastern North America have been found and the species has been treated in detail as part of a taxonomic revision (Frisch et al. 2015) wherein it was transferred to the genus Sporodophoron. The species is easily recognized by its blue-grey crustose thallus, Trentepohlia photobiont, and white sporodochia. As an old-growth associated species, primarily restricted to mature host trees, nearly all sites host only 1-10 functional individuals (the only exception is a location in Sevier Co., Tennessee which hosts 30-50 individuals). All of the known disjunct sites in Minnesota and Ontario occur in protected rock overhangs and consist of 1-5 functional individuals that are highly clustered spatially. We suspect that the population declined historically (during the last 3 generations; 90 years, based on a 30 year generation time) due to extensive logging, habitat loss, and land use change throughout its range (Yarnell 1998, Martinuzzi et al. 2015). These activities have led the extant population to become highly fragmented, as the species is almost entirely restricted to mature forest stands in suitable habitat and these areas have become very limited in extent and are no longer contiguous (e.g. Ervin 2016). We suspect that the already fragmented and reduced population is currently decreasing due to numerous ongoing and projected trends in anthropogenic and climate change impacts that would directly affect this species (Keyser et al. 2014, Klepzig et al. 2014, Cartwright and Wolfe 2016).

Population Trend: decreasing


Habitat and Ecology

This species occurs primarily on the bark of hardwood trees, especially chestnut oak (Quercus montana), in the grooves formed on the boles of mature individuals. It also rarely occurs on sheltered non-calcareous rock overhangs in high humidity habitats, usually directly associated with talus slopes or bodies of water. All of the northern disjunct occurrences are from rock overhangs associated with bodies of water. It is found primarily in temperate hardwood forests, especially riparian area, and infrequently occurs in boreal forests and rocky areas.

Threats

The primary threats to this species are habitat fragmentation and loss (historical and ongoing) and impacts from air pollution, climate change and natural disasters (historical, ongoing and projected). The species occurs primarily in existing protected areas, some of which are large in overall area. However it occurs in isolated locations where suitable habitat exists within large areas that are not suitable (i.e. mature forest stands or massive rock outcrops with high humidity are spatially restricted within a matrix of younger forests, forests without appropriate tree hosts, drier habitats as well as more generally within a highly fragmented matrix anthropogenic land uses). These naturally dispersed locations were degraded and fragmented historically (last 90 years) due to extensive logging, building of roads, alteration of riparian corridors by dams, air pollution, agriculture and urbanization. All of the above are still impacts to the species across its range in the south-eastern United States, although threats vary depending on the individual location. Within the last 30-40 years, fragmentation has continued as the region has undergone rapid population growth (Anderson et al. 2013, Klepzig et al. 2014). Available data indicate that the species is highly localized where it occurs, the habitat it has occurred in has become fragmented in the past and is increasingly fragmented in present. Further the region is currently experiencing climate change impacts (increased fire frequency and severity, intense storms that damage forest stands, droughts, temperature changes) and extensive alteration of forest communities due to invasive species. Although the small number of sites in Minnesota are less threatened by the above forces, all occur along rivers and could be extirpated by a major flooding event.

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 impacted by resource extraction 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 comprehensive location level demographic data and population estimates are needed. Targeted efforts to locate additional occurrences in suitable habitats are also needed, and a monitoring and recovery plan needs to be developed.


Source and Citation

Lendemer, J. 2021. Sporodophoron americanum. The IUCN Red List of Threatened Species 2021: e.T175710398A175710722. https://dx.doi.org/10.2305/IUCN.UK.2021-2.RLTS.T175710398A175710722.en .Downloaded on 1 October 2021

Country occurrence