Various infrageneric classifications of the genus Geastrum have been proposed, all of them exclusively based on morphology. They are highly divergent due to the different relative value that each author gave to particular morphological features. There is no consensus about any of these classifications, and therefore most modern studies avoid classifying Geastrum species in supraspecific units. Here, a new subdivision of the genus Geastrum is presented, based on phylogenetic analyses of four molecular markers, viz., 5.8S nrDNA, nrLSU, rpb1, and atp6. This classification is also supported by chemical reactions with syringaldazine and guiaiac gum, and by some morphological characters. Most reliable morphological characters include both classically studied features (e.g., endoperidial surface, peristome structure, mycelial layer), and recently discovered ones (e.g., rhizomorph crystals). Previously published infrageneric classifications are reviewed, showing many discrepancies with the phylogenetic data. A new infrageneric subdivision is proposed: sect. Campestria sect. nov., sect. Corollina sect. nov. (including subsect. Lageniformia subsect. nov., subsect. Marginata, and subsect. Plicostomata), sect. Elegantia sect. nov., sect. Exareolata, sect. Fimbriata, sect. Fornicata, sect. Geastrum (including subsect. Arenaria subsect. nov., subsect. Geastrum, subsect. Quadrifida subsect. nov., and subsect. Sulcostomata), sect. Hariotia sect. nov., sect. Hieronymia sect. nov., sect. Myceliostroma (including subsect. Epigaea and subsect. Velutina subsect. nov.), sect. Papillata, sect. Pseudolimbata sect. nov., sect. Schmidelia sect. nov., and sect. Trichaster. The phylogenetic and morphological boundaries among three genera of Geastraceae, viz., Geastrum, Myriostoma, and Radiigera, are also evaluated. Myriostoma likely represents a different phylogenetic lineage within Geastraceae and is confirmed as distinct from Geastrum. However, Radiigera is nested in Geastrum, and therefore it is confirmed as a synonym of Geastrum.

A revision of the classification of Geastrum sect. Geastrum is presented on the basis of an integrative taxonomic approach, which involves the study of morphological, molecular, ecological, and chorological data. Four DNA regions are analysed: the ITS and LSU nrDNA, rpb1, and atp6. Phylogenetic reconstructions include 95 ingroup samples and show five main clades, which are considered as five subsections, one of them proposed as new (G. subsect. Hungarica), and a total of 27 lineages recognizable at species level. Discriminant function analyses, ANOVAs and Tukey’s HSD tests on more than 500 basidiomata reveal the utility of several quantitative morphological characters for species delimitation. As a result of the combination of the different sources of taxonomic information, a revised taxonomy is presented and seven new species, viz., G. austrominimum, G. benitoi, G. britannicum, G. kuharii, G. meridionale, G. papinuttii, and G. thanatophilum, are proposed.

Desert truffles belonging to Terfezia are well known mycorrhizal members of the mycota of the Mediterranean region and the Middle East. We aimed to test (i) whether the morphological criteria of Terfezia species regularly collected in Spain enable their separation and (ii) whether the previously hypothesized edaphic/biotic specificity of one group could be confirmed by study of a larger number of specimens. The species T. arenaria and T. claveryi can be identified unambiguously by morphological characters. We consider T. leptoderma as a distinct species while several lineages of similar spiny spored Terfezia truffles with cellular peridium were detected that have no obvious anatomical differences. Several species treated generally as synonyms of T. olbiensis have been described in this group, and because they cannot be unambiguously assigned to separate lineages we propose to consider the group as the T. olbiensis species complex. A high level of intrasporocarpic variation of the nrDNA ITS was detected in the T. olbiensis species complex, especially in one of its lineages. We detected no exclusive specificity to either plant associates or soil, except in T. leptoderma, which was associated with Quercus spp. and cistaceous plants on acidic soils. Nevertheless the clades showed a tendency either to associate with Quercus/Helianthemum/Cistus or Pinus hosts. Specimens having distinct anatomical features, reticulate spores and cellular peridium formed a separate group in the molecular phylogenetic analyses of nrDNA ITS and LSU regions; for these specimens we propose a new species, Terfezia alsheikhii sp. nov.

The taxonomic utility of two characters not previously used for identification of Geastrum species is evaluated. First, macrochemical spot tests with chemicals detecting phenoloxidase enzymatic activity (1-naphthol, guaiac gum, and syringaldazine), are performed. In addition, the usefulness of the crystalline deposits from the rhizomorphs, formed by calcium oxalate as monohydrate or whewellite, and dihydrate or weddellite, was evaluated. These features provide valuable data to distinguish some taxa difficult to separate using traditional morphology, such as G. lageniforme, G. saccatum, and G. triplex.

The data presented in this article are the results of field collections and the analysis of fungal specimens deposited in the URM Herbarium. The field trips were carried out in four Atlantic Forest remnants in the state of Pernambuco, between June 2008 and May 2009. The revision of specimens housed in the URM was restricted to the Brazilian exsiccatae. Geastrum specimens were examined macro- and microscopically following the traditional methodology used in the group. Geastrum javanicum and G. lloydianum are new records from the Northeastern Region of Brazil. Eight species are new records from the following states: Pará (G. fimbriatum), Ceará (G. lloydianum), Paraíba (G. fimbriatum, G. javanicum, G. schweinitzii and G. entomophilum), Pernambuco (G. lageniforme and G. triplex) and Rio de Janeiro (G. javanicum). In this article we present full descriptions for ten species of Geastrum with pictures and an identification key.