Taxonomic Notes: The species was transferred to the genus Santessoniella Henssen according to the characters of the thallus (it is semigelatinous, mostly homoiomerous) and the apothecia (biatorine, with hemiamyloidhymenium, I+ red-brown) (Jørgensen 2000, 2005). However, recent phylogenetic studies indicate thatthe genus is not monophyletic and the type species of it was included in Psoroma (Ekman et al. 2014). Santessoniella crossophylla was not treated in this study and its relationships to other species within Pannariaceae remain unclear.
This species merits ranking as Endangered B2a,b(i,ii,iii,iv,v) based its small area of occupancy (AOO = 96km2 historically, 52 km2 currently) coupled with a) severe fragmentation both of remaining natural habitats within the total geographic range of the species and the extant populations outside of a ca.1000 km2 area of Great Smoky Mountains National Park; and b) continuing decline: extirpation of the species from large areas of its geographic range, as is evidenced by the an absence of relocated historical populations; decline in habitat quality and loss of habitat that has occurred historically and continues to occur, throughout the range of the species; and documented loss of pre-1990 populations (although this is balanced by the discovery of a higher total number of extant populations that are interpreted as new detections of previously existing subpopulations).
Assessor/s: Randlane, T., Tripp, E. & Lendemer, J.; Reviewer/s: Scheidegger, C.; Contributor(s): Weerakoon, G.
Ekman, S., Wedin, M., Lindblom, L. & Jörgensen, P. M. (2014) Extended phylogeny and revised generic classification of the Pannariaceae (Peltigerales, Ascomycota). The Lichenologist46(5): 626–656.
IUCN (2019) The IUCN Red List of Threatened Species. Version 2019-3. Available at: www.iucnredlist.org. (Accessed: 10 December 2019).
Jørgensen, P. M. (2000) Survey of the Lichen Family Pannariaceae on the American Continent, North of Mexico. The Bryologist103(4): 670–704.
Jørgensen, P. M. (2005) Additions to the Pannariaceae of North America. The Bryologist108(2): 255–258.
Lendemer, J.C., Stone, H.B. & Tripp, E.A. (2017) Taxonomic delimitation of the rare eastern North American endemic lichen Santessoniella crossophyla (Pannariaceae). The Journal of the Torrey Botanical Society144(4): 459-468.
Lendemer, J.C. & F. Anderson (2008) Santessoniella crossophyllla is rare, but not extinct, in eastern North America. Evansia25(74-75).
Lendemer, J.C., R.C. Harris, & E.A. Tripp (2013) The Lichens and Allied Fungi of Great Smoky Mountains National Park. The New York Botanical Garden Press, Bronx, New York.
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