Abstract
Phylogenetic analyses of sequences of the nuc rDNA small subunit (18S), internal transcribed spacer (ITS1-5.8S-ITS2 = ITS), and large subunit (28S) region (= 18S-ITS-28S), as well as sequences of this region concatenated with sequences of the largest subunit of RNA polymerase II (RPB1) gene, proved that the species originally described as Acaulospora polonica (phylum Glomeromycota) represents a new genus and a new family of the ancient order Archaeosporales, here introduced into the Glomeromycota under the names Polonospora and Polonosporaceae, respectively. The phylogenetic analyses and BLASTn queries also indicated that the Polonosporaceae with P. polonica comb. nov. still contains several morphologically undescribed taxa at the ranks of genus and species, which have a worldwide distribution.
Highlights
Among 58 species so far described in the genus Acaulospora, family Acaulosporaceae, is A. polonica, accommodated in this genus because forming spores laterally directly on the neck of a sporiferous saccule (Gerdemann and Trappe 1974; Błaszkowski 1988; 2012), as described for A. laevis, the type species of Acaulospora
The 18S-ITS-28S and 28S sequences represented 17, and those of RPB1 eight species of the Archaeosporales ingroup, including the species originally described as A. polonica, and the Paraglomerales outgroup
The results of molecular phylogenetic analyses and comparisons of sequences discussed above confirmed our hypothesis that the species originally described as A. polonica (Błaszkowski 1988) does not belong to Acaulospora but represents a new genus in a new family of the Archaeosporales, here introduced into the Glomeromycota under the names Polonospora and Polonosporaceae, respectively
Summary
Among 58 species so far described in the genus Acaulospora (see Online Resource 1 for species authors), family Acaulosporaceae, is A. polonica, accommodated in this genus because forming spores laterally directly on the neck of a sporiferous saccule (Gerdemann and Trappe 1974; Błaszkowski 1988; 2012), as described for A. laevis, the type species of Acaulospora. Several morphological characters of A. polonica spores did not fit those of most Acaulospora species. Spore wall 1 consists of two to three layers, and its laminate layer in many species is ornamented. Spore wall 2 usually contains two tightly adherent thin (< 1 μm thick), smooth, flexible to semi-flexible layers, and occasionally is one-layered. Spore wall 3 consists of two layers, of which layer 1 is thin and ornamented with fine granules, rarely smooth. Layer 2 in most species is thin when mounted in water but becomes plastic, strongly thickening in lactic acid-based mountants, e.g., in polyvinyl alcohol/lactic acid/glycerol (PVLG, Omar et al 1979), and stains dark in Melzer’s reagent. This layer remains thin in PVLG and stains faintly or does not stain in Melzer’s
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