Taxonomic revision transferring species inKuklosporatoAcaulospora(Glomeromycota) and a description ofAcaulospora colliculosasp. nov. from field collected spores

Abstract

In a phylogenetic study of arbuscular mycorrhizal fungal species in Acaulospora (Acaulosporaceae, Glomeromycota) we discovered that species classified in genus Kuklospora, a supposed sister clade of Acaulospora, did not partition as a monophyletic clade. Species in these two genera can be distinguished only by the position of the spore relative to a precursor structure, the sporiferous saccule, as either within (entrophosporoid) or laterally (acaulosporoid) on the saccule subtending hypha. Subsequent spore differentiation follows identical patterns and organization. Molecular phylogeny reconstructed from nrLSU gene sequences, together with developmental data, support the hypothesis that the entrophosporoid mode of spore formation evolved many times and thus represents a convergent trait of little phylogenetic significance. Therefore genus Kuklospora is rejected as a valid monophyletic group and it is integrated taxonomically into genus Acaulospora. Thus Acaulospora colombiana and Acaulospora kentinensis are erected as new combinations (formerly Kuklospora colombiana and Kuklospora kentinensis). Mode of spore formation is demoted from a genus-specific character to one that is included with other traits to define Acaulospora species. In addition we describe a new AM fungal species, Acaulospora colliculosa (Acaulosporaceae), that originated from a tallgrass prairie in North America. Field-collected spores of A. colliculosa are small (,100 mm diam), hyaline or subhyaline to pale yellow and form via entrophosporoid development based on structure and organization of cicatrices and attached hyphae. Each spore consists of a bilayered spore wall and two bilayered inner walls. A germination orb likely forms after the completion of spore development to initiate germination, but this structure was not observed. A character distinguishing A. colliculosa from other Acaulospora species is hyaline to subhyaline hemispherical protuberances on the surface of the outer spore wall layer. A phylogeny reconstructed from partial nrLSU gene sequences unambiguously placed A. colliculosa in the Acaulospora clade.

Phylogenetically Structured Differences in rRNA Gene Sequence Variation among Species of Arbuscular Mycorrhizal Fungi and Their Implications for Sequence Clustering

“…Six species were represented by two to three different geographic isolates, and nine species or geographic isolates had replicate DNA extractions, including both single and multiple spore extractions for some isolates (see Data Set S1 in the supplemental material for culture accession numbers and sampling information). Spore preparation and DNA extraction procedures were performed as described previously (24). Briefly, spores were cleaned by sonication, and either single or multiple spores were crushed in Tris-EDTA (TE) buffer, heated to 100°C, and then frozen until use as a template for PCRs using primer LR1 (36) and barcoded primer FLR2 (37).…”

“…While recent genome sequencing of isolates of the genus Rhizoglomus (20) has expanded our understanding of genetic variation in AM fungi beyond the rRNA genes (21)(22)(23), it remains largely unknown how either genome-wide or rRNA gene sequence variation may itself differ across evolutionary lineages. Previous studies that sampled a limited amount of rRNA gene sequence variation found that sequences from morphologically defined species generally formed clades on the gene tree (24)(25)(26), which is an essential prerequisite for clustering sequences into species-level OTUs. However, it is unclear whether this correspondence will remain robust to the sampling of additional sequence variation in AM fungi, as other work has called it into question for species of the genus Claroideoglomus (27,28).…”

<I>Glomus candidum</I>, a new species of arbuscular mycorrhizal fungi from North American grassland

“…The LSU nrRNA gene sequence (GU980757) was obtained from a single spore of the new fungus and was similarly subjected to various analyses (BLAST search, similarity index) as previously described (Kaonongbua et al 2010). Additional LSU nrRNA sequences broadly representing the phylum Glomeromycota and outgroups (Mortierella polycephala -AF113464 and Basidiobolus ranarum -AF113452) were acquired from the NCBI's GenBank and then aligned using Clustal X (v. 2.0) (Larkin et al 2007).…”

Preliminary study on biodiversity of arbuscular mycorrhizal fungi (AMF) in oil palm (Elaeis guineensisJacq.) plantations in Thailand

“…AMF spores obtaining from each air-dry soil sample (50 g each) were extracted by wet sieving, decanting and a 60% sucrose gradient centrifugation [3,5]. The supernatant was rinsed with tap water for 2 min in a 38-m sieve and transferred to 9 cm petri dishes for observation.…”