Rinodina chrysomelaena is a bright yellow crustose lichen occurring on non-calcareous rocks atscattered 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 bodies. This is an easily recognised lichenendemic 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 ofoccurrence (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 km²post-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 populationsas 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.
Assessor/s: Lendemer, J., Allen, J., McMullin, T. & Tripp, E.; Reviewer/s: Scheidegger, C.
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