Revision of the Aspicilia reptans group, a major lichen component of soil biocrusts in western North America

<p><i>Aspicilia </i>in the broad sense is one of the most common and speciose genera of saxicolous lichens in the World. It is also a common genus in the biological soil crusts of arid and semi-arid parts of North America, as well as on other continents. Analysis of DNA sequences and morphology from <i>Aspicilia</i> in soil crusts revealed previously unrecognized species that are ecologically, geographically, morphologically, and genetically distinct. We describe six previously unrecognized species (<i>Aspicilia albonota, A. diploschistiformis, A. papilliformis, A. spicata, A. subcontinua, </i>and<i> A. wyomingensis</i>), supported by phylogenetic reconstruction from ITS and nuLSU sequence data. The combined ITS+LSU tree with 368 specimens (339 ITS, 145 LSU, including 177 new sequences) places these species in various genera that have been segregated from <i>Aspicilia</i>, but because of problems in generic delimitation, we adopted a broad genus concept and assigned all of the new species to <i>Aspicilia</i> for simplicity and practicality. Previous segregates from <i>Aspicilia</i> (<i>Agrestia, Aspiciliella, Aspilidea, Chlorangium, Circinaria, Lobothallia, Oxneriaria, Sagedia, Sphaerothallia, </i>and<i> Teuvoa</i>) were in some cases nested within each other, lacking statistical support, or polyphyletic. Recognition of these genera would require erection of at least three new small genera to accommodate the sequenced species of <i>Aspicilia</i> s.l. that fall outside of those clades. The new species are mostly infertile, primarily terricolous, and are separable in most cases by a key to subtle differences in morphology, anatomy, and secondary chemistry. Nevertheless, the plastic, substrate-coating morphology and common sterility present serious challenges to purely microscopic identification. In addition to recognizing these new species, we describe a new variety, <i>A. californica</i> var. <i>gigantea</i> from Oregon, allopatric with the typical variety, and having thalli about twice the size of typical <i>A. californica</i>. We hypothesize that the new variety has a polyploid origin. We synonymize <i>A. mansourii</i> described from Iran under <i>A. reptans</i> s. str., based on morphology, chemistry, and ITS sequences. <i>Aspicilia reptans</i> s. str. is thus new to Eurasia. The other new taxa are so far known only from western North America, with the exception of <i>A. wyomingensis</i>, which occurs in Spain, based on phylogenetic placement of a specimen with an ITS sequence. The Eurasian species <i>A.</i> <i>aspera</i> is tentatively confirmed for North America. Two additional new species are described, <i>A. maritima</i> and <i>A. supralittorea</i>, both from the Pacific coast of Oregon.</p>