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.

    Niebla sorediata is a species of lichen known from Isla Guadalupe and the Channel Islands.  It is characterized by producing soredia, often with isidia, in which the isidia also become sorediate, and by containing the lichen substance divaricatic acid (with triterpenes). Several other isidiate species, namely N. isidiaescens and N. usneoides, develop isidia that detach easily, leaving a sorediate appearance to the remaining segment. Pycnidia in N. sorediata were noted to be sparse, one or two on a branchlet, in contrast to frequent pycnidia in N. isidiaescens, and sparse pycnidia in N. usneoides.  The latter species also differs also in having sekikaic acid.  Another isidiate species, N. isidiosa,  endemic to Isla Guadalupe, has a flattened thallus with cortical features similar to N. caespitosa.

      Niebla sorediata is most similar to Niebla suffnessii as seen on the Vizcaíno Peninsula of Baja California.  Indeed, a few thalli of Niebla suffnessii were found to have isidia at the base of the thallus, in contrast to isidia normally developing on the upper branches. This species also differs in having sekikaic acid (with triterpenes).