Taxonomy and phylogeny of the manna lichens and allied species (Megasporaceae)

terricolous and saxicolous species of the genera Aspicilia A. Massal. and Circinaria Link (Megasporaceae, Pertusariales, lichenized Ascomycota), particularly those traditionally referred to as ‘manna lichens’. The group has previously been defined on the basis of relatively few morphological characters (mainly growth form), and the phylogeny of the group has not been previously studied. The phylogeny of the family Megasporaceae is inferred from the combined dataset of nuLSU and mtSSU sequences. Five genera i.e., Aspicilia, Circinaria, Lobothallia (Clauzade & Cl. Roux) Hafellner, Megaspora (Clauzade & Cl. Roux) Hafellner & V. Wirth, and Sagedia Ach. are recognized. Lobothallia is sister of the four other genera, while Aspicilia and Sagedia form the next clade. All these genera have small asci with eight spores. Circinaria is a sister genus of Megaspora, and these two have in common asci with (1–4) 6–8 large spores. In the resulting trees, Circinaria forms a monophyletic group and sphaerothallioid species form a monophyletic group within Circinaria. The presence of certain morphological characters such as pseudocyphellae, thickness of cortex and medulla layers, as well as ecological differences in sphaerothallioid species distinguish it from some other crustose species, especially those containing aspicilin and characterised by thin cortex and medulla layers, conidium length c. 6–12 μm and absence of pseudocyphellae. If sphaerothallioid species are accepted as a distinct genus, the rest of the Circinaria species would remain as a paraphyletic assemblage. The combined dataset of nrLSU and mtSSU did not fully resolve infrageneric relationships in Megasporaceae. Currently, the genus Circinaria includes all the sphaerothallioid species and its generic position is confirmed and accepted. Thus, it is proposed as a correct generic name also for the peculiar ‘manna lichens’ described originally in other genera. Phylogeny at the species level has been studied using nrITS sequence data. Traditionally, certain morphological characters (e.g., growth form, anatomy of apothecium, pycnidia and cortex layer) have been used for the recognition of species in Aspicilia s.lat. In order to find more reliable characters they were re-evaluated in the light of molecular data. Since characters such as vagrant, erratic and crustose growth forms proved to be misleading for the recognition of some species, a combination of several characters (including molecular data) is recommended for species recognition. Vagrant growth form seems to have evolved several times among the distantly related lineages and even within a single population, resulting in either crustose or erratic and vagrant growth forms. This pattern of crustose, erratic and vagrant growth forms distribution in the genus Circinaria may help us to interpret the morphological convergence and ecological adaptation through the evolutionary history. Despite these insights, the reasons behind the high plasticity in the external morphology of vagrant, erratic and crustose species in the sphaerothallioid Circinaria still remain unknown. Of the 15 species placed in the ‘manna lichens’ (except Circinaria tominii nom. provis.), 14 are included in the molecular study along with some additional species from closely related groups. Four new species of ‘manna lichens’ are recognized: Circinaria rogeri nom. provis. , (syn. Aspicilia rogeri) from the U.S.A. ; C. digitata nom. provis. (syn. Aspicilia digitata) from Kyrgyzstan; C. gyrosa nom. provis. from Armenia, Azerbaijan, Iran, Turkey, Turkmenistan and Spain, and C. rostamii nom. provis. from Azerbaijan, Iran and Turkey. Circinaria arida, described from the USA, contains aspicilin and lacks pseudocyphellae. Aspicilia tibetica, a terricolous species with small spore size (8–14 × 5–9 μm) and a 8-spored ascus, is described from China. Based on an analysis of nrITS dataset, three new erratic, vagrant and crustose species were also recognized, but these require additional study. The results also reveal that C. elmorei and C. hispida are not monophyletic as currently understood. In addition, 13 new combinations in the genus Circinaria are proposed.