Laura S. Domínguez

Epiparasitic plants specialized on arbuscular mycorrhizal fungi

Over 400 non-photosynthetic species from 10 families of vascular plants obtain their carbon from fungi and are thus defined as myco-heterotrophs. Many of these plants are epiparasitic on green plants from which they obtain carbon by ‘cheating’ shared mycorrhizal fungi. Epiparasitic plants examined to date depend on ectomycorrhizal fungi for carbon transfer and exhibit exceptional specificity for these fungi, but for most myco-heterotrophs neither the identity of the fungi nor the sources of their carbon are known. Because many myco-heterotrophs grow in forests dominated by plants associated with arbuscular mycorrhizal fungi (AMF; phylum Glomeromycota), we proposed that epiparasitism would occur also between plants linked by AMF. On a global scale AMF form the most widespread mycorrhizae, thus the ability of plants to cheat this symbiosis would be highly significant. We analysed mycorrhizae from three populations of Arachnitis uniflora (Corsiaceae, Monocotyledonae), five Voyria species and one Voyriella species (Gentianaceae, Dicotyledonae), and neighbouring green plants. Here we show that non-photosynthetic plants associate with AMF and can display the characteristic specificity of epiparasites. This suggests that AMF mediate significant inter-plant carbon transfer in nature.

Historical biogeography and diversification of truffles in the Tuberaceae and their newly identified southern hemisphere sister lineage.

Truffles have evolved from epigeous (aboveground) ancestors in nearly every major lineage of fleshy fungi. Because accelerated rates of morphological evolution accompany the transition to the truffle form, closely related epigeous ancestors remain unknown for most truffle lineages. This is the case for the quintessential truffle genus Tuber, which includes species with socio-economic importance and esteemed culinary attributes. Ecologically, Tuber spp. form obligate mycorrhizal symbioses with diverse species of plant hosts including pines, oaks, poplars, orchids, and commercially important trees such as hazelnut and pecan. Unfortunately, limited geographic sampling and inconclusive phylogenetic relationships have obscured our understanding of their origin, biogeography, and diversification. To address this problem, we present a global sampling of Tuberaceae based on DNA sequence data from four loci for phylogenetic inference and molecular dating. Our well-resolved Tuberaceae phylogeny shows high levels of regional and continental endemism. We also identify a previously unknown epigeous member of the Tuberaceae – the South American cup-fungus Nothojafnea thaxteri (E.K. Cash) Gamundí. Phylogenetic resolution was further improved through the inclusion of a previously unrecognized Southern hemisphere sister group of the Tuberaceae. This morphologically diverse assemblage of species includes truffle (e.g. Gymnohydnotrya spp.) and non-truffle forms that are endemic to Australia and South America. Southern hemisphere taxa appear to have diverged more recently than the Northern hemisphere lineages. Our analysis of the Tuberaceae suggests that Tuber evolved from an epigeous ancestor. Molecular dating estimates Tuberaceae divergence in the late Jurassic (∼156 million years ago), with subsequent radiations in the Cretaceous and Paleogene. Intra-continental diversification, limited long-distance dispersal, and ecological adaptations help to explain patterns of truffle evolution and biodiversity.

The southernmost myco-heterotrophic plant, Arachnitis uniflora: root morphology and anatomy

Root morphology and anatomy of the myco-heterotrophic Arachnitis uniflora (Corsiaceae) were studied in relation to their association with a Glomus species (Glomeromycota). The mycorrhizal features were studied in three distinctive stages of development: (i) shoot and flower restricted to a small, underground bud; (ii) shoot and flower bud up to 1.5 cm; and (iii) shoot and flower already withered. The hyphae penetrate through and between the epidermal and exodermal cells; the exodermis and outer cortical cells become colonized in an inter- and intracellular manner, with some coils being formed in these layers. The fungi colonize the middle cortex, where intracellular vesicles in bundles are abundant. Arbuscules are formed profusely at very early stages of development, while in older stages they almost disappear and abundant vesicles are formed. Except for some details, the pattern of root colonization corresponds to a Paris-type. Presence of storage substances (starch and oil) also was recorded. Starch is produced and stored within root cells, mainly in the outer and inner root cortex. In senescent stages, plant and fungal tissues collapse.

Ocurrence of ectomycorrhizal, hypogeous fungi in plantations of exotic tree species in central Argentina

Eleven hypogeous, ectomycorrhizal species of Basidiomycota, including two new species, and one of the Zygomycota were collected in exotic tree plantations in Córdoba Province, Argentina. Descomyces fusisporus sp. nov., D. varians sp. nov., Hydnangium archeri (Berk.) Rodway, H. carneum Wallr., Hysterangium gardneri E. Fisch. and Setchelliogaster tenuipes (Setch.) Pouzar were associated with Eucalyptus spp. Endogone lactiflua Berk., Hymenogaster lycoperdineus Vittad., H. griseus Vittad., H. rehsteineri Bucholtz, Rhizopogon couchii A.H. Sm. and R. roseolus (Corda) Th. Fr., were associated with various northern hemisphere tree species. Descriptions are provided to aid identification of the hypogeous fungi in exotic plantations of Argentina.

Tulostoma domingueziae sp. nov. from Polylepis australis woodlands in Córdoba Mountains, central Argentina

The new species, Tulostoma domingueziae, is described and illustrated. It was found in Polylepis australis woodlands in central Argentinean highlands. Tulostoma domingueziae is characterized by the combination of a warty exoperidium, contorted stipe covered by thin scales that break off, mouth slightly projected and the socket with up to six dentate hanging membranes. DNA sequence data demonstrated that T. domingueziae is distinct from Tulostoma species for which sequence data are available.

Morphology, molecular analysis and ecological aspects of the South American hypogeous fungus, Alpova austroalnicola sp. nov.

Field studies in Argentina’s Yunga District revealed Alpova austroalnicola sp. nov., a hypogeous fungus associated with Alnus acuminata ssp. acuminata. Morphological and molecular studies based on amplification and sequencing of the nuclear LSU rDNA gene showed its unique identity within Alpova. Related genera included in the analyses were Boletus edulis, Rhizopogon spp., Suillus luteus and Truncocolumella citrina. Additional observations of animal diggings around the sites and microscopic examination of fecal pellets of the nine-banded armadillo (Dasypus novemcinctus novemcinctus) indicate A. austroalnicola is consumed and its spores dispersed by animals.

Molecular and morphological data validate the new combination of Lysurus sphaerocephalum from Argentina, with some additional records on Phallales (Agaricomycetes)

ABSTRACT On the basis of morphological and molecular analysis of several specimens of Lysurus periphragmoides collected in Argentina, the examination of materials collected in the type locality of Simblum sphaerocephalum (nowadays known as L. periphragmoides), also collected in Argentina (Córdoba), and the examination of specimens of L. periphragmoides from the old world, we conclude that Argentinean and South American material identified and synonymized to L. periphragmoides by Dring in 1980 should be emended as L. sphaerocephalum. As this species lacks type material designated on its protologue, and there is no type material either, we propose a lectotype and an epitype for L. sphaerocephalum. On the basis of species descriptions found in literature, we constructed a table with relevant differences between these two species: L. periphragmoides and L. sphaerocephalum. We fully describe L. sphaerocephalum, including lecto- and epitypes, and its position within the Lysuraceae clade. This work also includes descriptions and images of Blumenavia rhacodes, Itajahya galericulata, L. cruciatus, and Phallus indusiatus from Argentina, with the aim of expanding our knowledge of their distribution ranges in the studied regions.

Broomeia congregata Berk., 1844 (Agaricales: Broomeiaceae): New distribution record for San Luis, Argentina

Broomeia congregata Berk. is a gasteroid fungus with a predominant African distribution. However, it has been documented twice, in 1912 and 1973, as occurring in Catamarca Province (Argentina, South America). Nearly forty years later, a new finding is reported for San Luis Province, Argentina. The report includes new morphological information based on scanning electron microscopy (SEM). In addition, some phenological, biogeographical and ecological implications concerning B. congregata are discussed.