Assessment Notes

Justification

Rinodina chrysomelaena is a bright yellow crustose lichen occurring on non-calcareous rocks at scattered locations in the Appalachian Mountains of eastern North America and Mexican Highlands of Oaxaca, Mexico. The species can be recognised by its occurrence on non-calcareous rocks and bright yellow thallus with rounded dark purple-black disc-like fruiting bodes.This is an easily recognised lichen endemic to North America (including Mexico) that is considered to be extirpated from more than 95% of its historical range. Extensive efforts to relocate historical populations have failed and only two extant populations are known, both occurring in a highly limited geographic area.This species has been assessed as Critically Endangered, based on the pre-1990 vs. post-1990 reduction of extent of occurrence (EOO) to <100 km², this reduction has resulted in a population decline of 77% over the past three generations, and the total range of species has reduced by 95%.  Area of occupancy (AOO) (8 km² post-1990), and the extirpation of all known historical populations (balanced by discovery of two extant populations). In both cases the ranking is supported by 1) the extensive fragmentation of natural habitats and populations (both historical and modern), 2) severely fragmented, small number of extant populations (2), 3) decline in EOO, AOO, and total number of populations inferred from documented occurrences, and 4) historical and ongoing habitat degradation. The species also meets the criteria for Critically Endangered C2a(i,ii) based on the small number of mature individuals, the continuing decline in the number of locations, and the small number of mature individuals in the sole remaining subpopulation together with the fact that 100% of the remaining individuals exist within one subpopulation. 

The categorisation as Critically Endangered is based on the documented losses in number of populations as well as reductions of EOO and AOO. The causes of this reduction are unknown, but inferred to be the large scale degradation and loss of habitats throughout the range of the species. These losses have occurred in the past, are ongoing at present at smaller scales, and will likely continue in the future.

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Geographic range

Rinodina chrysomelaena is restricted to the Appalachian Mountains of eastern North America (Massachusetts south to Georgia) and Mexican Highlands of Oaxaca, Mexico. It was historically known from a small number of scattered locations where it grew on non-calcareous rocks. Online databases (CNALH) report a voucher from “mountains of western” North Carolina and from Colorado Springs, Colorado. The former voucher lacks precise locality data, was not included in modern treatments of the species (Lendemer and Sheard 2006, Sheard 2010) and is considered to be questionable. The record from Colorado is well outside the accepted geographic range of the species, includes an “?” indicating the identification was not certain, and was not annotated or cited by relevant taxonomic authorities. It is treated as an erroneous report and excluded from the estimates of extent of occurrence and area of occupancy used for this assessment.

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Population and Trends

The rarity of Rinodina chrysomelaena appears to be a modern phenomenon, as it was noted to be common at one locality where it occurred in 1932 but is no longer found (Degelius 1941, Sheard 2010). The species was collected by many 19th and early 20th century lichenologists, but is rarely collected now, illustrating that it was once widespread but has now been extirpated (Lendemer and Sheard 2006, Sheard 2010). None of the nine populations documented prior to 1990 have been relocated, and of the two populations discovered post-1990 (both in 2010) only one is located within a protected area (Great Smoky Mountains National Park). The majority of locations where the species was found historically are now developed (e.g., the metro-regions of Boston, Chattanooga and Philadelphia). The two known extant locations are small in size and isolated within a relatively small geographic area, each with fewer than 50 individuals. Extensive post-1990 fieldwork has been conducted within the range of the species by multiple experts (Massachusetts: E. Lay, E. Kneiper, P. May); Georgia: S.Q. Beeching and M. Hodges; Pennsylvania: J.C. Lendemer; southern Appalachians: J. Allen, J.C. Lendemer, T. Tønsberg, E. Tripp).

Population Trend: decreasing

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Habitat and Ecology

Habitat and ecological data from historical collections are limited, however, the extant populations occurs on non-calcareous rocks in shaded forests in high humidity microhabitats especially near waterfalls.

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Threats

The cause of the large scale extirpation of Rinodina chrysomelaena was not documented at the time it occurred, however, it is likely attributable to the large scale loss and degradation of suitable habitat throughout its range historically (Drummond and Loveland 2010, Napton et al. 2010). This species is threatened by transportation corridors increasing air pollution, and climatically suitable habitats shifting with climate change. Recreation may be an additional threat.The lack of protection of the species by state, federal, and international legislation is a further threat to the species.

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Conservation Actions

Monitoring of all extant populations is required to determine whether the species has stabilised or is still in decline. Increased acquisition of suitable habitat, and increased protections for suitable habitat already within management units is also needed. Study of the potential reintroduction into formally occupied areas should also be considered, but balanced by the extreme rarity of the species and the small size of extant populations to serve as source material. Increased education about the species, its ecology, and how it could be conserved would also be highly beneficial. Demographic studies of extant populations are needed to assess and monitor populations sizes. Species is presumed extirpated from much of its range, remaining extant populations small in size and number of individuals.

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Source and Citation

Lendemer, J., Allen, J., McMullin, T. & Tripp, E. 2018. Rinodina chrysomelaena. The IUCN Red List of Threatened Species 2018: e.T80703073A80703076. https://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T80703073A80703076.en .Accessed on 2 February 2024

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• Country occurrence