Pluteus Fr . ( Pluteaceae , Agaricales ) in Paraguay : morphological studies and new records

Four species of Pluteus Fr. are documented based on recently collected specimens from Alto Paraguay and Central Department, which correspond to the Pantanal and Humid Chaco ecoregions, respectively. Pluteus fibulatus Singer, P. longistriatus (Peck) Peck, P. petasatus (Fr.) Gillet, and P. triplocystis Singer are newly recorded species of the mycobiota of Paraguay; P. triplocystis is also a newly recorded for South America. Descriptions and photographs of both macroand microscopic features of each species are included along with a brief discussion on their taxonomy, ecology, and distribution.


Introduction
Based on traditional morphological concepts (Pegler 1983, Singer 1986), Pluteaceae Kotl.& Pouzar include 3 genera with free and pinkish lamellae: Chamaeota (W.G.Sm.) Earle, characterized by basidiomata with annulus but without volva, Volvariella Speg., with volva but lacking of an annulus, and Pluteus Fr., characterized by the absence of both annulus and volva.Based on phylogenetic analyses with molecular sequence data, the recognition of Chamaeota was questioned by Minnis et al. (2006), who transferred 2 species with annulus from this genus to Pluteus.The definition of Volvariella has also been modified based on molecular sequence data since Justo et al. (2011a) proposed a new genus, Volvopluteus Vizzini, Contu & Justo, which was segregated from Volvariella on account of differences in the basidiospore size and pileipellis structure.
Pluteus is a monophyletic genus (Moncalvo et al. 2002, Justo et al. 2011a) with approximately 300 wide spread species (Kirk et al. 2008).They are mostly saprotrophic and found on wood with a high degree of decomposition but also in humus, sand, and the tissues of living plants (Pegler 1983).The genus has a global distribution and is very common in boreal to tropical regions (Pegler 1983, Justo et al. 2014, Menolli et al. 2014).The type species of the genus is Pluteus cervinus (Schaeff.)P. Kumm., which is common in temperate forests in Eurasia and eastern North America.It is characterized by pluteoid basidiomata which are variable in size and pileus color, ranging from white to brown, gray-brown or orangebrown.Pluteus cervinus mostly grows in angiosperm wood of temperate forests and is rarely found growing in conifers.It is characterized by metuloidal pleurocystidia of entire hooks, and without clamp-connections on pileipellis hyphae (Justo et al. 2014).Singer (1959Singer ( , 1986) considered 3 sections in the infrageneric classification of Pluteus, based on the arrangement of the pileipellis and the pleurocystidia type.Justo et al. (2011b) later complemented this classification with molecular sequence data.Pluteus sect.Pluteus is characterized by metuloidal pleurocystidia and a pileipellis formed by a cutis.Pluteus sect.Hispidoderma Fayod has thin-walled pleurocystidia and a pileipellis composed of elements forming a trichoderm or a hymenoderm.Pluteus sect.Celluloderma Fayod. is characterized by non-metuloid pleurocystidia or with the pleurocystidia absent and, in most cases, with a pileipellis composed of short clavate or spheropedunculate cells, mixed or not with elongated cystidioid elements, but also including taxa characterized by the presence of the annulus and/or pileipellis as a cutis.
Paraguay comprises 2 distinct geographical regions, the eastern and the western, which are separated by the Paraguay river.The western region is also known as the Chaco.The Chaco region includes 3 ecoregions: Humid Chaco, Dry Chaco, and Pantanal.The ecoregions of eastern Paraguay include in the Humid Chaco, Atlantic Forest, and Cerrado (Dinerstein et al. 1995).The Pantanal in the Chaco region comprises wetlands and floodplains where the vegetation is composed of a low stratum of herbaceous and Copernicia alba Morong forests adapted to periodic and prolonged flooding (Hamilton 1999).
Here, we present the new records and morphological descriptions of 5 species of Pluteus collected in the Pantanal and Humid Chaco ecoregions of Paraguay.Four species are newly reported from Paraguay and 1 for the first time from South America.

Pluteus fibulatus
Habit and habitat.Gregarious, on a decaying trunk, in a forest remnant in the UNA Campus; found during the summer season.
Pluteus fibulatus is similar to P. spinulosus because of similar macroscopic features, similar size of pileus and stipe, and both have a typical bulbous base of the stipe.They both have clamp connections in the trama, pileipellis and context as well as Magnus-type pleurocystidia (Singer 1956, Pegler 1983).However, P. fibulatus has globose basidiospores (Menolli et al. 2015a) in contrast with the subglobose basidiospores described for P. spinulosus (Singer 1956).In addition, Magnustype pleurocystidia with lateral spinulose outgrowths towards the apex are described for P. spinulosus (Singer 1956, Pegler 1983), while P. fibulatus has Magnus-type and metuloid pleurocystidia (Menolli et al. 2015a) with bifurcations that bear apical spinules as observed in the Paraguayan material (Fig. 2f).Finally, P. fibulatus does not have cheilocystidia with distorted apical outgrowths and lateral spinulose outgrowths like P. spinulosus.Singer (1959) had not described them.The Paraguayan collection presented caulocystidia, although they were smaller than those found by Menolli and Capelari (2010)   Campi 293 (FACEN 004082).
Habit and habitat.Solitary on rotting trunk, in urban area, collected during the winter.
According to Rodríguez and Guzmán-Dávalos (2007), P. triplocystis has more inflated metuloidal pleurocystidia with shorter horns and clamp connections are present in all micromorphological structures.Rodríguez (2013) pointed out that P. martinicensis only bears clamp connections in the pileipellis and stipitipellis hyphae and that it represents the main difference between both species.
Another well-known feature to distinguish these species is the presence of cheilocystidia with brown content in Maine, Massachusetts, Michigan, Mississippi, Missouri, New York, Tennessee, andWisconsin (Banerjee andSundberg 1995, Justo et al. 2014), and in Mexico in the states of Jalisco, Sinaloa, Sonora, and Queretaro (Esqueda-Valle et al. 1995, Rodríguez 1998, Rodríguez and Guzmán-Dávalos 2001, Rodríguez 2013).Finally, in South America, there are records from Argentina and Brazil as P. viscidulus Singer (Singer andDigilio 1952, Singer 1959), which was later considered as synonym of P. petasatus (Justo et al. 2011b(Justo et al. , 2014)).Finally, Pluteus triplocystis had been described from Mexico by Singer (1973) and is only known from the type locality.These 4 species are the first records of the family Pluteaceae from Paraguay, and for Pluteus triplocystis, the first record from South America.Our study is the first attempt in Paraguay to find and document records of the practically unexplored family Pluteaceae, which has been fairly well studied elsewhere in South America.This is only the second documentation of fungi from the Paraguayan Pantanal, one of the less explored areas in the Paraguayan Chaco.

Figure 2
Figure 2 Material examined.Paraguay: Central Department, San Lorenzo city, Universidad Nacional de Asunción Campus
≡ Agaricus longistriatus Peck, Annual Report on the New York State Museum of Natural History 30: 40 (1878)Material examined.