Agaricus sect. Kerrigania, L.A. Parra, Angelini, B. Ortiz, Linda J. Chen & Callac, 2018

Parra, Luis A., Angelini, Claudio, Ortiz-Santana, Beatriz, Mata, Gerardo, Billette, Christophe, Rojo, Carlos, Chen, Jie & Callac, Philippe, 2018, The genus Agaricus in the Caribbean. Nine new taxa mostly based on collections from the Dominican Republic, Phytotaxa 345 (3), pp. 219-271 : 246-247

Agaricus sect. Kerrigania, L.A. Parra, Angelini, B. Ortiz, Linda J. Chen & Callac , sect. nov.

MycoBank: MB823278.

Type: Agaricus porphyropos L.A. Parra, Angelini & B. Ortiz

Etymology: This specific epithet honours our good friend and mycologist Richard Kerrigan for his contribution to the knowledge of the genus Agaricus .

Original description, Morphological description: Schäffer’s and KOH reactions not performed on fresh collections. Schäffer’s reaction positive dark reddish purple or reddish brown and KOH reaction yellow when observable on the pileus surface of dried collections. Odor of anise or of almonds when rubbed or cut (see note below). Annulus superous, thick at the margin, two layered (double), fibrillose-squamose sometimes with the scales radially arranged as a cogwheel near the margin in its lower surface. Cheilocystidia generally simple or with one or two septa at the base, usually clavate, pyriform, more or less globose or fusiform, sometimes rostrate or absent in some collections. Spores lacking a rudimentary apical pore.

Note: For some collections belonging to this section other odors have been recorded but none of them was collected by one of the authors of this paper. These odors such as iodate in the collection F1779, light in LAPAM66 or like A. campestris L.: Fr. in CJL090302.05 are pointed out in field notes by the collectors.

Stem age and phylogenetic support: in the MCC tree of Chen et al. (2017) the well-supported (PP ≥ 0.99) clade corresponding to A. sect. Kerrigania is sister to A. sect. Minoriopsis (also proposed in this paper as new section), and consequently has the same stem age of 22.83 Ma. In our ITS tree ( Fig. 1 ), it is also well supported (ML bootstrap support 94 %; PP = 1) and includes ten named or putative species.

Section-specific ITS markers: Ten differences between the sequences of A. sect. Kerrigania and A. sect. Minoriopsis are indicated above under the description of A. sect. Minoriopsis. Only the difference at position 118 of the alignment merits to be described in detail. Based on the sequence of A. porphyropos , the DNA segment including this marker is [ggttgTYggaaa@112–113]. It is relatively well conserved except at the 3’ end of the flanking sequence where ‘aaa’ is highly variable (‘tat’ in most species of A. sect. Minores ). In this segment TY is, in fact, an insertion of two nucleotides (TC or TT), which, in both subgenera ( Minores and Minoriopsi s), is found exclusively in all the sequences of A. sect. Kerrigania. It can be noted that an insertion of a single nucleotide (T or C) is found only in two species, A. argenteopurpureus within A. sect. Minoriopsis, and A. candidolutescens within A. sect. Pantropicales.

Figures

FIGURE 1. Maximum likelihood phylogram of Agaricus subg. Minores, A. subg. Minoriopsis, and A. subg. Flavoagaricus resulting from analysis of ITS sequence data. The best scoring RAxML ITS tree is rooted with A. campestris. The bootstrap support values greater than 50% are indicated, and branches with Bayesian posterior probabilities greater than 0.8 are in bold. Species sampled from the Dominican Republic are in red; new taxa are in bold. T = Type specimen.