Biology subjects

Corazon-Guivin, M. A.

Publications and source records attributed to Corazon-Guivin, M. A..

3 recordsLinked to original sources

bioRxiv2026

Revision of Paraglomeromycetes unveils a new order (Pervertustales), a new family (Innosporaceae), and a new genus (Opikia) in Glomeromycota

Currently, the fungal class Paraglomeromycetes (phylum Glomeromycota) consists of one order, Paraglomerales, with two families: Paraglomeraceae, comprising the genera Paraglomus with ten species and Innospora with one species, and the monogeneric and monospecific Pervetustaceae represented by Pervetustus with Pe. simplex. However, our morphological analyses of these species and an undescribed specimen morphologically resembling other Paraglomeromycetes species, as well as analyses of sequences of these fungi and environmental sequences, indicated that the current taxonomic composition of this class should be updated. We did so here by creating in Paraglomeromycetes Pervetustales ord. nov. with Pervetustus and Opikia catenata gen. nov. and sp. nov., as well as transferring Innospora with In. majewskii to Innosporaceae fam. nov. These novelties were introduced primarily based on strong genetic divergences of the analyzed taxa, as many morphological and histochemical features of their spores and mycorrhizal structures overlap. Only Op. catenata possesses the unique trait of occasionally producing spores in chains. This mode of sporulation has also not been recognized in any other Glomeromycota species. Unlike species of Pervetustales and Innosporaceae, which produce single-walled spores, the subcellular spore structure of Paraglomus species contains one or two walls.

microbiology↗

bioRxiv2026

Revision of Archaeosporomycetes with two old and two new fungal orders: Archaeosporales, Geosiphonales, Polonosporales, and Ambisporales

Currently, the fungal class Archaeosporomycetes consists of one order, Archaeosporales with four families: Archaeosporaceae, Ambisporaceae, Geosiphonaceae, and Polonosporaceae. In the present study, the objective was to re-analyze the phylogeny and morphology of the Archaeosporomycetes from order to genus level. The different ecological strategies and, consequently, distinct evolutionary patterns of these taxa, as well as their morphological characters and other data updated here, suggest the need to divide Archaeosporales into four orders: (i) the type order Archaeosporales, (ii) Ambisporales ord. nov., both with four genera, (iii) Geosiphonales and (iv) Polonosporales ord. nov., both with single families and genera. Remarkably, the order Geosiphonales was described in the past, but was not considered in the Archaeosporomycetes until now. Phylogenetically, the four main clades (orders here proposed) of Archaeosporomycetes are well supported, with bootstrap values higher than 95% in all analyses, except Ambisporales/Ambisporaceae for RAxML-NG FBP analysis in the SSU tree (75%). Ecologically, this class includes three orders of arbuscular mycorrhizal fungi (AMF) forming symbiotic associations with plants, while Geosiphonales form an endocytobiosis with the cyanobacterium Nostoc. Morphologically, there are at least two AMF orders with spore bimorphism, which has not (yet) been described for Polonosporales. The only known species of Polonosporales, Polonospora polonica, forms spores directly on the neck of sporiferous saccules and the spores can morphologically be differentiated from all other taxa in Archaeosporomycetes by the formation of three permanent, rather thick spore walls, of which two form de novo during spore formation. The outer spore wall of Archaeosporales and Ambisporales are semi-permanent, evanescent or even short-lived, or show multiple fissures during aging, when it is more resistant. Ambisporales can easily be differentiated from Archaeosporales for instance by larger spores of the acaulosporoid morph and thicker spore walls. Our phylogenetic analyses suggested that Archaeosporales can be divided into two families: Antiquisporaceae that was described to form intraradical hyphae, vesicles and spores, staining darkly in Trypan blue, and Archaeosporaceae whose hyphae generally do not or only faintly stain in this reagent, and vesicles and intraradical spores have been rarely, if ever reported.

microbiology↗

bioRxiv2026

Revision of Ambisporaceae, with three new genera and one new species and a morphological identification key for all the species currently attributed to this family

The objective of this study was to re-analyse the molecular phylogeny and/or the morphology of all species, which have been attributed to the so-far mono-generic fungal family Ambisporaceae. The genus Ambispora has been well-known for its spore bi-morphy described even from single spore clusters. Triple-walled spores are differentiated on sporiferous saccules, while mono-walled spores are formed on simple subtending hyphae. New phylogenetic analyses reveal dissimilarities of [≥]10% in partial nrDNA gene of three different stable phylogenetic clades and thus suggest the division of Ambispora into three genera, which simultaneously request for advanced morphological separations. These advances are primarily based on the more diverse spore wall composition of the ambisporoid-acaulosporoid morph rather than on the rather simple-glomoid morph. While all known species of the triple-walled morph have an evanescent to semi-permanent outer spore wall, i) Am. fennica, Am. brasiliensis, Am. gerdemannii and Am. nicolsonii have a smooth, permanent central spore wall (Am. fennica clade, A), ii) the central wall of Am. appendicula, Am. callosa, Am. leptoticha and Am. jimgerdemannii is alveolate (Am. appendicula clade, B), and iii) the central wall of Am. granatensis is smooth, but easily degraded, thus rather short-lived and not permanent but evanescent (Am. granatensis clade, C). In conclusion, species of the Am. fennica clade represent the genus Ambispora, while species of the Am. appendicula clade represent the new genus Appendiculaspora, and the mono-specific Am. granatensis clade represents the new genus Ephemerapareta. Species of an additional morph, with triple-walled spores, but apparently formed on subtending hyphae, and having a diagnostic reticulate, football-like middle wall, are here separated from the revised genus Ambispora based solely on morphological analyses, since molecular identification analyses so far failed and remained merely unknown. This later morph and genus is based on the type species Pelotaspora reticulata comb. nov, and on P. austrolatina sp. nov. Concomitant molecular phylogenetic and morphological analyses are needed to attribute not only Pelotaspora spp., but also those species, for which hitherto only the ambisporoid-glomoid morph has been observed correctly within the family Ambisporaceae. Without molecular analyses, such species with glomoid but unknown ambisporoid-acaulosporoid morph have to be retained within Ambispora.

microbiology↗