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Observation 417953: Agaricus floridanus Peck

When: 2020-07-17

Collection location: Wharton State Forest, Burlington Co., New Jersey, USA [Click for map]

(coordinates hidden from public) 14m

Who: I. G. Safonov (IGSafonov)

Specimen available

Notes:
A cluster of 5 fruiting bodies growing in grass on the edge of woods / road shoulder. They were in not great shape (mushy and buggy) due to being exposed to a lot of afternoon sun, and all were mature judging by the color of the gills. Three fbs were collected, of which the largest one was absolutely riddled with fly larvae and was discarded.
The nearby trees were pitch pines, white oaks and sweet gum saplings (the latter tree is very unusual for this habitat). I’ve been visiting this spot for many years, but have never seen these mushrooms there before. Agaricus is pretty rare in this ecological niche, and A. vinosobrunneofumidus is by far the most commonly encountered species there, and it’s obviously not that.
The attached images showing the details of morphology. The cottony ornamentation on the lower stipe, including yellow concentric rings near the base (universal veil?), lack of a basal bulb, and a small, fragile ring are the salient features of this species. The thin-fleshed caps were creamy with splashes of yellow and pinkish pigments (?) and some light fluffy scales of brighter yellow (the blackish areas are actually a spore drop from overlapping caps). The largest cap had a footprint of 6-6.5 cm. The odor was strong, pleasant, sweetish, with a chocolate note and perhaps some fragrant tobacco note, not all that dissimilar from vinosobrunneofumidus.
Upon returning home I immediately saved a fresh tissue sample in CTAB buffer, and it will be sequenced.
Here is Dr. Kerrigan’s comment on this critter:
“From the color and general aspect I would guess it is either a member of section Arvenses or else a closely related section. It reminds me most of what Murrill called A. floridanus (at least as I interpret it) and what M. A. Curtis called A. amygdalinus (an illegitimate name). We know it comes as far up the East Coast as Long Island”.
I found what looks like the original description of A. floridanus by Peck in Murril’s “Dark-Spored Agarics: III. Agaricus”, Mycologia 14(4): p. 207 (1922)1:
“Pileus hemispheric or campanulate, becoming nearly plane, solitary or subcespitose, 9-I5 cm. broad; surface rimosely areolate or slightly strigose, becoming glabrous, whitish with a yellow or yellowish center; lamellae at first white, then pink, and finally dark brown or blackish; spores globose or broadly ellipsoid, 5-6 × 4-5 μ; stipe easily separable from the pileus, equal or slightly thickened at the base, solid, becoming fibrous when old, whitish, 5-10 cm. long, 1.5-3 cm. thick; annulus small.
TYPE LOCALITY: DeFuniak Springs, Florida.
HABITAT: In sandy soil among grass in fields.
DISTRIBUTION: Known only from the type locality. A number of specimens, preserved at Albany as the types, were collected by Dr. G. Clyde Fisher on March 29, 1910.
Reference:
1https://www.mykoweb.com/...

DNA Results and Discussion (posted on 11-Feb-2021):
> A super-clean and sharp nrDNA sequence of 727 bps was derived from a single forward read by Dr. Kudzma from this collection and posted here. It consists of the last 20 bps of nrSSU, followed by the full-length ITS sequence of 669 bps and then by the first 38 base pairs of nrLSU. There are no ambiguities, it’s a single haplotype.
> A BLASTn of the full-length ITS sequence returned several accessions labeled mostly as ‘Agaricus floridanus’ or ‘cf. floridanus’ as top hits, with 99.4-100% similarity:
https://www.ncbi.nlm.nih.gov/nucleotide/MN945966
https://www.ncbi.nlm.nih.gov/nucleotide/AJ884624
https://www.ncbi.nlm.nih.gov/nucleotide/KM349610 (by R.W. Kerrigan)
https://www.ncbi.nlm.nih.gov/nucleotide/MG050106
https://www.ncbi.nlm.nih.gov/nucleotide/KM349609 (by R.W. Kerrigan)
https://www.ncbi.nlm.nih.gov/nucleotide/MK393920

Proposed Names

92% (2)
Used references: Dr. R. W. Kerrigan
Based on chemical features: The derived nrITS sequence matches GenBank accessions of A. floridanus — see the above discussion.

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= Observer’s choice
= Current consensus

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