Niebla and Vermilacinia (Ramalinaceae) from California and Baja California.  
Spjut, R.W., 1996. ISSN 0833-1475, 208 pp.  
Sida, Botanical Miscellany: 14. Botanical Research Institute of Texas, Inc.

Evolutionary history of coastal species of fog lichen genera
Niebla, Ramalina and Vermilacinia
Emmanuel Sérusiaux & Richard  Spjut
Baja California, Jan-Feb 2016

Punta Cono, Spjut & Marin 11534, Apr 1990

El Marrón, ridge S of Punta
Negra, Spjut 9958, May 1986

Niebla aff. N. homaleoides, N. spatulata.

Niebla sp. aff. N. homaleoides

Spjut & Marin 13842
8'O-methyl-salazinic acid

Pacific Coast: Chaparral-Desert Transition. Low rocky peninsula, to 5 m elev., just south of northwest corner of Bahía Falsa, west of San Quintín; 30°29'743, 116°00.044', 4 m. Diverse coastal scrub of Ambrosia chenopodiifolia, Atriplex julacea, Lycium  californicum, Simmondsia, Dudleya spp, Agave shawii, Cneoridium dumosum, Echinocereus maritimus, Rosa minutifolia, Aesculus parryi.  Thallus branching most similar to N. josecuervoi, but the paucity of pycnidia—occasionally evident along branch margins in tiny clusters—is associated with the species N. palmeri, distinguished primarily by having sekikaic acid.

Lichen Substances Det. Cassandra Diaz-Allen and Liva Rakotondraibe: Usnic acid and unknown aldehyde (scabrosin?). Triterpenes absent. A compound new to Niebla reported 8'O-methyl-salazinic acid (see Diez-Allen et al. 2021, referenced below.

      Niebla homaleoides is a rare species of lichen known only from three locations in Baja California; two are from ridges south of Punta Negra, and a third is from a rocky peninsula near sea level at Punta Cono.   The type locality is a large rock pile on a ridge where collected in close association with N. josecuervoi and N. infundibula.  An attempt was made in the field to sort these (May 1986); however, it was not until later that it was concluded that they could only be distinguished by their lichen substances as a result of using thin-layer chromatography (TLC). 

     Their close resemblance to each other is clearly evident in the image above that includes the TLC graphic.  They are similar in overall size and branching, have the same sublinear branch shape, have the same glossy and color cortical features, have prominent large and abundant pycnidia on upper branches, all lack reticulate ridging, and all show similar development in branchlets including shape and size—somewhat elliptical and flattened—rarely seen in other species with cylindrical branches.  This seems more than coincidental considering the wide range of morphological variation in Niebla observed elsewhere on the ridge and generally in Baja California (e.g., see associated species with reference to collection numbers under N. caespitosa). 

     For example, Niebla josecuervoi, which has secondary metabolites of salazinic acid, occasionally with a scabrosin derivative and consalazinic acid, usually has a reticulately ridged cortex, evident in all 12 other specimens shown on the WBA page. Did a spermatium from N. homaleoides contribute to a spore progeny thallus of N. josecuervoi originating from an apothecium of N. josecuervoi?  Niebla infundibula, another relatively rare lichen known from this location, shows similar hybrid characteristics. Did a spermatium from N. homaleoides contribute to a spore progeny thallus of N. infundibula originating from an apothecium of N. infundibula?   Other specimens of N. homaleoides from the same ridge and from Punta Cono have more flattened blades, which may be characteristic of its true form.  In the higher plant world such blending of character traits among three species would be viewed as evidence of introgression.  Perhaps, secondary chemical substances in Niebla are allelopathic towards  related species (Molnára & Farkas 2010) in which case N. homaleoides lacking in secondary metabolites is less competitive and more freely hybridizes?

      Nonetheless, Niebla homaleoides is identified by its lack of key lichen substances.  Its chemical relationship is clearly allied to the salazinic-acid species subgroup by the presence of an unidentified pigment thought to be a scabrosin derivative, and further linked to the Depsidone Species Group of Niebla by the absence of triterpenes (Spjut 1996).  This pigment has been found in N. effusa, N. flabellata, N. marinii, and N. josecuervoi.    

       Bowler and Marsh (2004) failed to account for the chemical relationships when they erroneously placed Niebla homaleoides in synonymy with N. homalea (divaricatic acid); i.e. in following their taxonomic scheme they should have lumped it with N. josecuervoi.  Just because N. homaleoides does not react to p-phenylenediamine (PD-) does not mean that it is related to other species that are PD-.   The resemblance to N. homalea is seen in the blade morphology in the one specimen from Punta Cono.  The relationship of N. homaleoides to the depsidone group is also evident by the pycnidia that develop at the tips of the spine-like branchlets, some of which are shortly bifurcate.

      Chemically deficient thalli in the genus Niebla occur at one other location, Arroyo Sauces for which a specimen is shown above.  It  differs from N. homaleoides in having more flattened lacerated branches as in N. spatulata. This lacerated branch form was also collected at Punta Cono.  Their similar morphology at two disjunct locations would seem to represent another acid-deficient species, referred to as Niebla sp. undescribed, shown above for the one from Arroyo Sauces. 

     The phylogeny of Niebla  homaleoides might be assessed from two acid-deficient specimens collected by Spjut and Sérusiaux from the Vizcaíno Peninsula; however, only ITS was employed, and only one of the two specimens showed a difference of a single mutation in the N. spatulata complex.  Acid deficient thalli had not been reported by Spjut (1996) from the Vizcaíno Peninsula, although he identified four specimens in the field as N. homaleoides based on stretched marks on the cortex, two of which  confirmed by TLC.   

Additional Reference Cited:

Diaz-Allen, C., R. W. Spjut, A. Douglas Kinghorn, and H. L. Rakotondraibe. 2021. Prioritizing natural product compounds using 1D-TOCSY. Trends in Organic Chemistry 22: 99-114.

Molnára, K.  and E. Farkas. 2010. Current results on biological activities of lichen secondary metabolites: A review. Z. Naturforsch. 65 c, 157 – 173.

Further References: See Niebla.