Nivicolous Trichiales from the austral Andes: unexpected diversity including two new species

Abstract

Nivicolous myxomycetes are a group of amoebozoan protists dependent on long-lasting snow cover worldwide. Recent fine-scale analysis of species diversity from the austral Andes revealed high intraspecific variability of most taxa, suggesting independent evolutionary processes and significant differences in species compositions between the Northern (NH) and Southern (SH) Hemispheres. The present study is the second part of this analysis based on representatives of Trichiales. A total of 173 South American collections were studied based on morphological and molecular data, and 15 taxa have been identified. Two of them, Hemitrichia crassifila and Perichaena patagonica, are proposed as new species confirmed by a phylogeny of Trichiales. However, their affinity to the genera in which they are proposed are not confirmed due to polyphyletic character of all genera of Trichiales. Four species, Dianema subretisporum, Trichia contorta var. karstenii, T. nivicola, and T. sordida, are reported for the first time from the Southern Hemisphere. One species, T. alpina, is new for Argentina. Additionally, we provide the first record of Perichaena megaspora from Chile. Specimen frequency and species diversity of Trichiales found at nivicolous localities in the austral Andes are unexpectedly high, exceeding those of Stemonitidales, the most numerous group in the Northern Hemisphere, where Trichiales play a marginal role. By contrast, Trichiales appear the main component of nivicolous assemblages in the Andes. Results of the present work, together with the earlier analysis of Stemonitidales, indicate that the Andes constitute an exceptionally important evolutionary hot spot for nivicolous myxomycetes characterized by an outstanding species diversity.

Phylogeny and evolution of morphological structures in a highly diverse lineage of fruiting-body-forming amoebae, order Trichiales (Myxomycetes, Amoebozoa)

“…Subclade H2. Subclade H2 encompassed the three Perichaena species studied that form plasmodiocarps, as previously reported by Ronikier et al (2020). However, a broader representation of P. vermicularis revealed that this taxon encompasses cryptic diversity, comprising distinct non-sister species, as detected with Calomyxa metallica (clade D).…”

“…Within the three orphan taxa, Trichia varia presents pilate spores and capillitium ornamented with smooth spirals (García-Cunchillos et al, 2021b), similar to subclade H3 species. Hemitrichia crassifila (baculate spores, capillitium with spirals bearing cylindrical projections) highly resembles Hemitrichia intorta, while we did not recover such phylogenetic affinities, as pointed out in Ronikier et al (2020). Remarkably, the species Cornuvia serpula shows distinctive, large discs embracing the capillitium filaments (sometimes named rings) and unique cristate reticulate-like spores (Estrada-Torres et al 2015).…”

“…Previous studies recovered close affinities among the genera Calomyxa, Dianema, and Prototrichia (Fiore-Donno et al 2013;Ronikier et al 2020); however, a broader Dianema taxa sampling demonstrated no such circumscriptions as different genera (Fig. 3).…”

“…When S2 or S3 amplifications failed, we completed these positions as Ns (any base) in the alignment, treated as missing data in subsequent analyses. For the amplification of the first fragment (S1), we employed primers SF01, SF02*, and SR01 (Ronikier et al 2020), in which F and R refer to forward and reverse, respectively, and an asterisk (*) designates its use as inner forward primer in semi-nested PCRs. Following the same nomenclature, we designed new primers (sequences in 5 ′ → 3 ′ direction) to amplify fragments S2 (SF03: ACGGGTACA-GAGGATCAG; SF04*: AGCCTGAGAGATCGCTAC, and SR02: CCTTGTGTGCTCTTCCGT) and S3 (SF05: TAGGGGTGAAATCCGTTGA, SF06*: ACGAAAGTCTGGGGAT, and SR3: TACAAAGAGCAGGGACA).…”

“…The EF1A was amplified and sequenced as a single amplicon, including the intron present in every Myxomycetes species (Fiore-Donno et al 2005), and sequences ranged from 876 to 1453 bp. Forward primers for EF1A amplification were EF03 and EF04* (Ronikier et al 2020), and the reverse primer was KEF_R3 (García-Martín et al 2018). The mtSSU sequences comprised 334-667 bp, amplified as a single amplicon with the primers pair Kmit_F and Kmit_R ).…”