Stereocaulon tomentosoides, a new combination for a western North American endemic species with cyanobiont and chemotype polymorphisms

Abstract

Based on resampling the type locality and surrounding regions, along with phylogenetic analysis of molecular data, we elevate Stereocaulon sasakii var. tomentosoides to the species level, while we treat S. sasakii var. simplex as an environmental modification of S. tomentosoides. We found no phylogenetic evidence that any variety of S. sasakii occurs in North America, so we suggest that the species be removed from the North American list and its North American varieties transferred to S. tomentosoides. Stereocaulon tomentosoides is so far confirmed only from the Pacific Northwest of North America. Furthermore, it is largely allopatric with S. tomentosum, apart from a small region of overlap in northern Idaho and western Montana. While S. tomentosum always contains stictic acid and never lobaric acid as secondary metabolites, S. tomentosoides differs in having a predominant chemotype of lobaric acid as the major substance, with an infrequent chemotype containing both lobaric and stictic acids. While S. tomentosoides usually contains Nostoc in the cephalodia, occasional individuals, especially from old mossy lava flows, contain Stigonema; one specimen was found with both kinds of cephalodia on a single thallus. Phylogenetic analysis of these species and other close relatives revealed an additional species described here, S. cyaneum, so far known only from the Great Lakes region of the United States and Canada and separated from S. tomentosum by its bluish coloration, wet or dry