Nephromopsis endocrocea is an attractive macrolichen which is easily identified also in the field if one is familiar with the main diagnostic trait of the taxon, bright orange colour of the medulla.
The species is supposed to belong to the core group of cetrarioid lichens in fam. Parmeliaceae (Thell et al. 2009; Randlane et al. 2013).

Synonyms: 
Cetraria clarkii Tuck., Ann. Rep. Sapporo Agr. Coll. 3: 16. 1879 (nom. nud.).

Cetraria endocrocea (Asahina) M. Satô in Nakai & Honda, Nov. Fl. Jap. 5: 37. 1939.

Nephromopsis endoxantha Hue, Nouv. Arch. Mus. Hist. Nat., Sér. 4, 1: 220. 1899 [pro parte Nephromopsis endocrocea Asahina, pro parte Nephromopsis ornata (Müll. Arg.) Hue].

Nephromopsis endocrocea is a rare corticolous species with very restricted distribution in East Asia (Japan and Russian Far East). The majority of records of the species are from the period before 1970. The decline in records and therefore probably in the populations are mainly caused by the destruction of suitable habitats (montane forests), possible due to either human activities or natural causes – forestry (tree cutting) and forest fires (Russia’s Boreal Forests 2007).

Assessment.
A criterion: population reduction has been estimated ca 40% as altogether 30 localities are accounted, 19 of them from the period 1913–1960s, and only 11 localities are documented since 1970. It is difficult to assess continuance of several historic locations due to the lack of exact locality data, but some locations in Japan are certainly considered extinct (see under Populations and current Trends). The species qualifies VU according to A2ac and A3c.
B criterium: not applicable as the species has no evidence of severe fragmentation, and too many locations are known for listing under threat categories.
C and D criteria: not applicable as relevant numbers of individuals are not available; E criterium: not applicable as no quantitative analyses have been carried out.
Conclusion: Nephromopsis endocrocea is assessed VU according to the criteria A2ac and A3c.

The species occurs in East Asia: Japan – several collections from islands Hokkaido and Honshu; Russia – Far East, Habarovsk (Sakhalin and Kuril Islands) and Primorje Regions (Skirina 1995; Randlane & Saag 1998). Altogether 30 locations are recorded, most of them belong to the the period 1913–1960s. After 1970 only 11 locations have been documented – Japan, isl-s Honshu (prov. Shinano; prov. Kai; Nagano-ken; Saitama-ken) and Hokkaido; Russia, Primorje (2 localities in Sikhote-Alin, Terneiskii district and one in Dalnegorskii district); Kuril islands, Kunashir; isl. Sakhalin.
The species has also been reported from China, prov. Jilin, Mt. Changbai (Chen et al. 1981; Wei 1991) but the specimens (Chen 2015, 2337) have been re-determined as Nephromopsis ornata (Lai et al. 2007). Thus, N. endocrocea has no verified records in China.

It is difficult to assess continuance of several historic locations in Japan due to the lack of exact locality data, but the species is considered extinct e.g. from the island Kyushu, Oita Prefecture (latest record from Mt. Kurodake, 1950). There are quite some, also recent records from the island Honshu, but in few localities (e.g. Mt. Nikko in Tochigi Prefecture) the species was reported several times during 1930s, and none later.
Literature data (Skirina 1995) indicate that the species is very rare in the Russian locations, and it is redlisted in Primorje Region of Russia (Red data book of Primorje Region).

Nephromopsis endocrocea is corticolous on coniferous (Abies, Larix, Tsuga) or deciduous (Betula) trees in montane coniferous and mixed forests at lower and medium altitudes (up to 2500 m).

Main threat includes decline and destruction of typical habitat (montane forests), possible due to either human activities or natural causes – forestry (tree cutting) and forest fires. It has also been indicated that the species is sensitive to air pollution (Skirina 2008).

Two localities in Russia, Primorje region are in a protected area, Sikhote-Alin Nature Reserve.

More records are needed to monitor the current state of populations both in Russia and Japan. As the species is very attractive and easily recognizable (dark yellow to orange medulla!), the information about its occurrence could be obtained not only from the specialists but also from botanists, forestry workers etc. Ecological analyses to more fully understand the factors influencing the populations of this species should follow.

Chen, X. L., Zhao, C. F. & Luo, G. Y. 1981. A list of lichens in NE China. J. North-eastern Forestry Inst. 3: 127–135; 4: 150–160.

Lai, M.-J., Chen, X.-L., Qian, Z.-G., Xu, L. & Ahti, T. 2009. Cetrarioid lichen genera and species in NE China. Annales Botanici Fennici, 46(5): 365–380.

Randlane, T. & Saag, A. 1998. Synopsis of the genus Nephromopsis (fam. Parmeliaceae, lichenized Ascomycota). Cryptogamie, Bryol. Lichenol. vol. 19, no. 2–3: 175–191.

Randlane, T., Saag, A., Thell, A. & Ahti, T. 2013. Third world list of cetrarioid lichens – in a new databased form, with amended phylogenetic and type information. Cryptogamie, Mycologie 34(1): 79–94.

Skirina, I. F. 1995. Lichens of of Sikhote-Aline biospheric region. Vladivostok, Dalnauka.

Skirina, I. F. 2008. Nephromopsis endocrocea. In: Red data book of Primorje Region. http://redbookpk.ru/index_plants.html

Thell, A., Högnabba, F., Elix, J. A., Feuerer, T., Kärnefelt, I., Myllys, L., Randlane, T., Saag, A., Stenroos, S., Ahti, T. & Seaward, M. R. D. 2009. Phylogeny of the cetrarioid core (Parmeliaceae) based on five genetic markers. Lichenologist 41: 489– 511.

Wei, J. C. 1991. An enumeration of lichens in China. International Academic Publishers, Beijing.