Niebla cornea

Morro Bay, CA, Hale 33688, July 1965, holotype	San Cruz Island, CA Bratt 4475	Bahía de San Quintín, BCN, Spjut 9329D, May 1986 (scanned from a black & white photocopy of specimen at US)
Los Angeles Co., Palo Verdes, CA Darrow 314 (COLO)	San Clemente Island, CA Murbarger 151 (COLO)	Santa Cruz Island, CA Schuster 15a (COLO)
+ Santa Barbara Island, CA Bratt 3712	San Luis Obispo Co., CA Riefner 86-25 (COLO, p.p., mixed with Vermilacinia laeviagata)

Niebla cornea is primarily a California species recognized by the presence of the lichen substance, sekikaic acid, and by the development of apical flattened branches with a thick glazed cortex.

Niebla cornea may be confused with Vermilacinia laevigata and N. homalea. Vermilacinia laevigata has terminal apothecia (with one exception noted by Spjut 1996), as opposed to apothecia in N. cornea positioned just below the apex near the branch margin. Also, V. laevigata, like all species in the genus, lacks medullary chondroid strands and does not have any of the terpenes or depsides found in Niebla. These species may be found growing together around Morro Bay and in Point Lobos Reserve, as evident from herbarium packets containing both species mixed together as noted in one of the examples above.

Niebla homalea is distinguished by the narrower branches with transverse cracks appearing more at regular intervals, and by the presence of divaricatic acid, instead of sekikaic acid. Although N. cornea has transverse cracks on the branches, and while it clearly differs by the presence of sekikaic acid, it is interesting to note that apothecia among specimens from disjunct locations show a remarkable similarity in position, number, arrangement, and shape on apical branches. This would appear to be an additional character feature of the species (N. cornea) that reinforces the importance of secondary metabolites for distinguishing species of Niebla, including those with similar depsides, sekikaic acid and divaricatic acid. Here, it might be noted that Rundel et al. (1972) had chosen types for N. josecuervoi and N. pulchribarbara that were different in their depsidones, salazinic acid (N. josecuervoi) and protocetraric acid (N. pulchribarbara). Niebla pulchribarbara (protocetraric acid) is a rare chemotype in the genus; however, it was later synonymized by Bowler and Marsh (2004) with N. josecuerovi (salazinic acid), because they apparently felt that the chemical differences in the genus should only be based on practical means such as chemical spot tests, while they also failed to account for the fact that. N. homaleoides (acid deficient) is more closely related to N. josecuervoi than to N. homalea (Spjut 1996).

Specimens collected by Charis Bratt (3712) from Santa Barbara Island and Riefner (86-25) from Morro Bay are another example of variants that are remarkably similar from disjunct localities. They appear related to N. lobulata by the lobulate margins, wavy cortical ridges, and irregular presence of fringed branchlets, but are also related to the California species, N. dissecta, by the thick cortex and sinuous cortical ridges. There is also strong similarity to the divaricatic-acid species, N. laminaria that is distinguished from N. homalea by branch marginal features . Whether a parallel distinction should be made for the sekikaic-acid species will probably have to await molecular studies. Niebla dissecta differs from N. cornea by the prismatic branchlets, as also N. testudinaria (divaricatic acid), and by the thallus spreading more at the base than in height, in contrast to N. disrupta, which is more like N. homalea (divaricatic acid), separated from that species primarily by chemistry.

Niebla cornea is also comparable to N. eburnea, especially in the type specimens, which are from disjunct locations—Cerro Solo (BCN) and Morro Bay (CA). Although best distinguished by their lichen substances, N. eburnea may be recognized by producing solitary apothecia on short side branchlets, that the apothecia are more lenticular at maturity instead of cupular, and that apothecia often abort development. The epithets for both species were chosen because of their similar cortical features.