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Pluteus aurantipes sp. nov. from Wisconsin, United States

     Department of Plant Biology, Southern Illinois University, Carbondale, Illinois 62901-6509

S.F. Nelsen

     Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706-1396

	ABSTRACT

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Pluteus aurantipes sp. nov. was discovered in Wisconsin, United States. This agaric species is characterized by its yellowish brown pileus, reddish orange stipe, pileipellis consisting of a trichoderm and lack of pleurocystidia.

Key words: Agaricales, Belmont Mound Woods, Hispidoderma, Pluteaceae

	INTRODUCTION

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The fleshy mycota of the central United States has not been fully documented. Studies by Smith (1971) and Banerjee and Sundberg (1993a, 1995), a survey of herbarium collections, and communications with other mycologists indicate that Midwestern Pluteus Fr. diversity is greater than previously reported.

In Jun 2005 a distinctive species of Pluteus, a genus in the family Pluteaceae Kotl. & Pouzar characterized by pink basidiospores, free lamellae, a convergent lamellar trama and the lack of a well developed volva, was collected in a mixed deciduous forest near Belmont, Wisconsin. A comprehensive literature search including treatments by Murrill (1917), Singer (1956, 1958, 1959, 1961), Smith and Stuntz (1958), Horak (1964, 1977, 1983), Homola (1972), Orton (1986), Vellinga (1990) and Banerjee and Sundberg (1993a, 1993b, 1995) confirmed the unique nature of this fungus. Thus a circumscription of this previously undescribed Pluteus species is offered.

	MATERIALS AND METHODS

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Color terms are from Kornerup and Wanscher (1978). Standard techniques were used to prepare material for anatomical study (Smith 1949, Largent et al 1977). Dried material was wetted with 95% ethanol for 1 min, soaked in water 1 min, blotted to remove excess water and sectioned by hand. Material was viewed in 3% KOH or Melzer’s reagent. Basidiospore dimensions are based on observation of 30 basidiospores. Length to width ratios are reported as Q. Mean values for length, width and Q are designated as L^m, W^m and Q^m respectively.

	TAXONOMY

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Pluteus aurantipes Minnis, Sundberg, & Nelsen, sp. nov. FIGS. 1–6

View larger version (110K): [in this window] [in a new window]   FIGS. 1–6. Pluteus aurantipes (AMM 5-06-19-1, HOLOTYPE) 1. Basidiomes. 2. Basidiospores. 3. Basidium. 4. Cheilocystidia. 5. Terminal cuticular segments. 6. Caulocystidia. Bars: 2 = 10 µm, 3–6 = 20 µm. Illustrated anatomical features are from representative structures.

Pileus up to 23 mm diam, initially narrowly to broadly convex then becoming plano-convex, slightly umbonate; surface yellowish brown (5E6), villose with upright scales abundant on disc, scales becoming smaller and more separated toward the margin; margin entire, initially incurved then becoming decurved, faintly striate with light yellow ground color apparent beneath and between the cuticular elements. Lamellae free, close, broad, light yellow (2A5) with faces and edges concolorous. Stipe 10–20 x 0.5–1.5 mm, tapered above and becoming enlarged toward the base, reddish orange (near 7A7), remaining so when dried then slowly fading to yellow after a few months.

Basidiospores brownish pink in mass, typically ellipsoid in face and profile views, some subglobose to oblong, circular in end-view, 5.7–7.5 x 3.5–5.3 µm, Q = 1.08–1.88 (L^m = 6.4 µm, W^m = 4.6 µm, Q^m = 1.41), apiculate, smooth, walls slightly thickened, subhyaline to pale yellow in KOH, usually with a single large oil drop inside. Basidia clavate, tetrasterigmate, 18–29 x 6–9 µm without sterigmata, walls thin and hyaline in KOH, usually with granular contents. Pleurocystidia not observed. Cheilocystidia abundant, vesiculose to clavate to utriform to fusoid-ventricose, 24–50 x 7–17 µm, walls thin and hyaline in KOH. Lamellar trama convergent. Subhymenium cellular. Pileipellis a trichoderm of 1–4-celled, erect to appressed, thin-walled elements often containing brown intracellular pigment, terminal segments cylindrical to clavate to fusoid-ventricose, 39–72 x 9–21 µm. Stipitipellis a cutis of cylindrical hyphae, 4–9 µm wide, thin-walled, hyaline in KOH, without apparent pigment. Caulocystidia vesiculose to cylindrical to clavate to fusoid-ventricose, 18–53 x 9–14 µm, walls thin and hyaline in KOH, contents appearing yellowish in Melzer’s reagent. Clamp connections absent. All anatomical features inamyloid in Melzer’s reagent.

Habit, habitat, and distribution. – Scattered on rotten, decorticated deciduous log. June. Wisconsin.

Specimens examined. – USA. Wisconsin: Lafayette County, near Belmont, Belmont Mound Woods State Natural Area. Scattered on rotten deciduous log, 19 Jun 2005, AMM 5-06-19-1, coll. by Adrienne and Stephen Nelsen (HOLOTYPE F).

Etymology. – auranti (Latin) orange; pes (Latin) foot; refers to the reddish orange stipe.

	DISCUSSION

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The reddish orange coloration of the stipe is rare for Pluteus. Pluteus aurantiopustulatus E. Horak, P. aurantiorugosus (Trog) Sacc., P. flammipes E. Horak, P. glabrescens Murrill, P. laetifrons (Berk. & M.A. Curtis) Sacc., P. laetus Singer, P. roseipes Höhn. and P. rubrotomentosus Singer are reported to have at least occasionally some hint of pink to orange pigment in the stipe (Singer 1956, 1958, 1961; Horak 1964, 1977, 1983; Orton 1986). Pluteus aurantiorugosus, P. flammipes, P. laetifrons and P. laetus differ from P. aurantipes in part by having cellular pileipelli. Pluteus glabrescens, P. roseipes and P. rubrotomentosus are distinguished by the possession of pleurocystidia and/or pileus coloration. Last, Pluteus aurantio-pustulatus differs by its orange colored pileus. No Pluteus species other than P. aurantipes possess the combination of characters described above.

Following the infrageneric classification used by Singer (1986), Pluteus aurantipes is in Pluteus section Hispidoderma Fayod. This section is characterized by a pileipellis consisting of elongate hyphal elements and thin-walled cystidia. Pluteus aurantipes also is included in stirps Leoninus. This stirps is an admittedly artificial assemblage of taxa that possess red or yellow hues in the pileus and/or stipe (Singer 1986). Although it is difficult to recognize a related taxon based on morphology alone, Pluteus aurantio-pustulatus might be relatively close to P. aurantipes. These two taxa are diminutive, share a similar pileipellis, a lack of pleurocystidia and an orange stipe.

Although Pluteus aurantipes is known from only one collection, we think that it is acceptable to describe it at this time because it is rare. We have collected numerous times in the general area where P. aurantipes was found and have not seen it again. In our experience some species may be found only once at a site or only once per decade or more. Smith (1971) described similar observations of Pluteus fruiting.

	ACKNOWLEDGMENTS

 
We thank Ellen Thiers for assistance with the Latin diagnosis. We also thank Andrew Methven for his review of the manuscript before submission. Finally, we extend our gratitude to the Field Museum of Natural History (F) for access to Singer’s notes and use of the herbarium.

	FOOTNOTES

 
Accepted for publication June 2, 2006.

¹ Corresponding author. E-mail: drew3{at}siu.edu

	LITERATURE CITED

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Banerjee P, Sundberg WJ. 1993a. Three new species and a new variety of Pluteus from the United States. Mycotaxon 47:389–394.

———. 1993b. Reexamination of Pluteus type specimens: types housed at the New York Botanical Garden. Mycotaxon 49:413–435.

———. 1995. The genus Pluteus section Pluteus (Pluteaceae, Agaricales) in the midwestern United States. Mycotaxon 53:189–246.

Homola RL. 1972. Section Celluloderma of the genus Pluteus in North America. Mycologia 64:1211–1247.[CrossRef]

Horak E. 1964. Fungi Austroamericani II. Pluteus Fr. Nova Hedwigia 8:163–199, 20 pl.

———. 1977. Neue zairische Arten der Gattung Pluteus. Bull Jard Bot Nat Belg 47:88–89.

———. 1983. Mycogeography in the South Pacific region: Agaricales, Boletales. Austral J Bot, Suppl Ser 10:1–41.

Kornerup A, Wanscher JH. 1978. Methuen handbook of colour. 3rd ed. London: Eyre Methuen. 252 p.

Largent D, Johnson D, Watling R. 1977. How to identify mushrooms to genus III: microscopic features. Eureka, California: Mad River Press. 148 p.

Murrill WA. 1917. (Agaricales), Agaricaceae (pars), Agariceae (pars). N Amer Fl 10:77–144.

Orton PD. 1986. Pluteaceae: Pluteus and Volvariella. In: Henderson DM, Orton PD, Watling R, eds. British Fungus Flora: Agarics and Boleti. Vol. 4. Edinburgh, Scotland: Royal Botanic Garden. 99 p.

Singer R. 1956. Contributions towards a monograph of the genus Pluteus. Trans Brit Mycol Soc 39:145–232.

———. 1958. Monographs of South American Basidiomycetes, especially those of the east slope of the Andes and Brazil. Lloydia 21:195–299.

———. 1959. Contributions towards a Monograph of the genus Pluteus. II. Trans Brit Mycol Soc 42:223–226.

———. 1961. Monographs of South American Basidiomycetes, especially those of the east slope of the Andes and Brazil. 4. Inocybe in the Amazone region, with a Supplement to part 1 (Pluteus in South America). Sydowia 15:112–132. 7 pl.

———. 1986. The Agaricales in modern taxonomy. 4th ed. Koenigstein, Germany: Koeltz Scientific Books. 981 p.

Smith AH. 1949. Mushrooms in their natural habitats. Portland, Oregon: Sawyer’s Inc. 626 p.

———. 1971. The origin and evolution of the Agaricales. In: Petersen RH, ed. Evolution in the higher basidiomycetes. Knoxville, Tennessee: University of Tennessee Press. 562 p. 13 pl.

———, Stuntz DE. 1958. Studies on the genus Pluteus I. Redescriptions of American species based on a study of type specimens. Lloydia 21:115–136.[Medline]

Vellinga EC. 1990. Genus Pluteus. In: Bas C, Kuyper THW, Noordeloos ME, Vellinga EC, eds. Flora Agaracina Neerlandica. Vol. 2. Rotterdam, Netherlands: A.A. Balkema. 137 p.

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