Phylogenetic review of Acaulospora genus and the homoplasic nature of its ornamentations
Biogeography; Diversity; 18S-ITS-28S; ITS; Morphology.
Acaulospora genus has undergone many updates, such as the transfer of some species to other genera and addition of newly discovered species. Still, there are some missing pieces in the taxonomic puzzle of phylogenetic relationships among Acaulospora species, such as (i) the evolutionary meaning of the different ornamentations found in this group, (ii) the best available molecular marker for phylogenetic inferences, and (iii) the resolution of some specific issues, concerning the polyphyletic nature of Acaulospora lacunosa and Acaulospora scrobiculata for some rDNA sequences and the inclusion of Kuklospora species as belonging to the genus Acaulospora. In this review we carried out (i) an update on the global geographical distribution of Acaulospora species, (ii) a review of its ornamentation patterns and (iii) a robust phylogenetic analysis, based on ITS and SSU-ITS-LSU (nrDNA). Moreover, we confirmed the hypothesis that A. sporocarpia does not belong to Acaulospora (Diversisporales) using already available and revisiting type material available data about this species. In both phylogenetic analyses, using BI and ML inferences, the monophyly of Acaulospora genus is strongly supported, including Kuklospora species, K. colombiana and K. kentinensis. The nrDNA phylogeny proved to have the best resolution and revealed the homoplasic nature of many ornamentations in Acaulospora species, a possible convergence associated to biochemical interactions between the AMF and its environmental conditions, pointing out their unfeasible phylogenetic signal, reinforcing the urgency of more molecular markers, in addition to the nrDNA sequences, for a definition of a multi locus phylogeny.