Tomentella brunneoincrustata, the first described species of the Pisonieae-associated Neotropical Tomentella clade, and phylogenetic analysis of the genus in Mexico

Abstract

The /tomentella-thelephora lineage is one of the most highly dominant clades among ectomycorrhizal communities worldwide. Despite its importance as a root symbiont, its fruit bodies are inconspicuous and rarely found. Knowledge regarding the diversity of Tomentella in the Neotropics is scarce, and is based largely on environmental samples. Here, we describe a new species, Tomentella brunneoincrustata, including its basidiocarp morphology, mycorrhizal anatomy, and ecology. Because knowledge of Tomentella in Mexico is scarce, we provide the first phylogenetic analysis of this genus in the country. We sequenced the nrITS region of the fungal samples, and sequenced the rbcL and trnL regions to identify the host plant. The phylogenetic analyses were conducted by Bayesian inference. The Bayesian analysis showed that several paraphyletic clades within the lineage /tomentella-thelephora are associated with Pisonieae present across tropical regions of the world. However, the ectomycorrhizae sequences from Puerto Rico, Florida, Dominica, and Mexico constituted a well-supported monophyletic clade that we denote as the “Pisonieae-associated Neotropical Tomentella clade”. Within this clade, T. brunneoincrustata was characterized as follows: a thin crustose, strongly attached to the substrate basidiome; concolorous subiculum, undifferentiated and sterile margin; two types of subiculum hyphae; and small (<8 μm) globose to ellipsoid spores. This species develops in tropical dry forests, where it associates with hosts in the Pisonieae tribe within the Nyctaginaceae. The remaining Tomentella fruit body vouchers collected in temperate forests of Mexico belonged to clades related to T. atramentaria, T. pilosa, T. muricata, T. fuscocinerea, T. stuposa, T. punicea, T. atroarenicolor, T. bryophila, and T. lateritia. Five fruit body vouchers had unique sequences forming independent and unknown clades of Tomentella.