New species of Boletellus from Guyana Tara D. Fulgenzi Department of Biology, Humboldt State University, Arcata, California 95521 Jordan R. Mayor Department of Botany, University of Florida, Gainesville, Florida 32611 Terry W. Henkel 1 Department of Biology, Humboldt State University, Arcata, California 95521 Roy E. Halling Institute of Systematic Botany, New York Botanical Garden, Bronx, New York 10458 Abstract: Boletellus exiguus sp. nov. and Boletellus dicymbophilus sp. nov. (Boletaceae, Boletales, Basidio- mycota) are described as new to science. These boletes were collected from tropical forests dominated by ectomycorrhizal Dicymbe corymbosa (Caesalpiniaceae) in the Pakaraima Mountains of western Guyana. Key words: Boletaceae, Dicymbe, ectomycorrhizal fungi, Guiana Shield, neotropics INTRODUCTION The genus Boletellus Murrill (Boletaceae, Boletales, Basidiomycota) encompasses , 44 described species worldwide, the majority with tropical distributions (Heinemann and Goossens-Fontana 1954, Snell and Dick 1970, Smith and Thiers 1971, Corner 1972, Horak 1977, Singer 1986, Singer et al 1992, Watling 2001, Halling and Mueller 2005, Ortiz-Santana et al 2007). Boletellus has been variably defined, yet all definitions have in common these features: basidio- spores that are olivaceous brown in deposit, a yellow hymenophore becoming olivaceous with time, and boletoid (i.e. strongly divergent) tube trama. Despite these commonalities individual author concepts vary. Singer (1986) adhered to a broad definition of Boletellus by including species with longitudinally winged or ridged spores (sections Boletellus, Chrysen- teroidei, Ixocephali and Dictyopodes), smooth spores (section Mirabilis), spores with imbedded short spines or pits (section Allospori) and reticulate spores (section Retispori). Heinemann (1951) and Snell and Dick (1970) included species that have spores with imbedded short spines or pits (e.g. Boletellus purpur- ascens Heinem.), smooth spores (e.g. Boletellus mirabilis (Murrill) Singer) as well as those with longitudinally striate spores. Smith and Thiers (1971) argued against Singer’s broad concept of the genus and included only species with spores that are longitudinally winged, ridged or striate; by doing so Boletellus can be determined easily microscopically and is consistent with the type species’ morphology (Smith and Thiers 1971). Corner (1972) and Pegler (1983) also adhered to a narrower definition of Boletellus characterized by spores that are longitudi- nally winged, ribbed, costate or striate. Here we describe Boletellus exiguus sp. nov. and Boletellus dicymbophilus sp. nov. discovered in ectomy- corrhizal (EM) Dicymbe (Caesalpiniaceae) forests in Guyana. These two new species are placed in Boletellus based on their olivaceous brown, longitudinally ridged basidiospores, dry pilei, tubulose, blue-staining hyme- nophores and lack of clamp connections. MATERIALS AND METHODS Annual collecting expeditions were conducted during the rainy seasons (May–Jul) 1998–1999 in the Upper Ireng River Basin along Guyana’s western border with Brazil in the west- central Pakaraima Mountains, and 2000–2005 in the Upper Potaro River Basin , 30 km north of the Ireng site. At each site fungi were collected within a 5 km radius of a previously established base camp in forests dominated by Dicymbe corymbosa Spruce ex Benth. (Henkel 2003). Basidiomata were examined in the field for their fresh characteristics. Color was subjectively described and record- ed according to Kornerup and Wanscher (1978) with color plates noted in parentheses (e.g. 3C4). Macrochemical spot tests were performed following Singer (1986). Basidiomata were field-dried with silica gel beads. Microscopic anatomical details were determined on fresh specimens at base camp with an EPOI microscope and in the laboratory with an Olympus BX51 microscope with bright field and phase contrast optics. Fungal tissue of dried specimens was rehydrated and mounted in either H 2 O, 3% KOH, or Melzer’s reagent. For each taxon a minimum of 20 basidiospores, basidia, cystidia and other structures were measured. Line drawings were made with a drawing tube, inked and scanned. Scanning electron micrographs of basidiospores were obtained with either a Jeol JSM-6400 or Topcon ABT32 scanning electron microscope using 200 kV. Specimens are deposited in these herbaria as indicated: BRG, HSU and NY (Holmgren et al 1990). TAXONOMY Boletellus exiguus T.W. Henkel and Fulgenzi sp. nov. FIGS. 1–2, 5a, b Accepted for publication 19 March 2008. 1 Corresponding author. E-mail: twh5@humboldt.edu Mycologia, 100(3), 2008, pp. 490–495. # 2008 by The Mycological Society of America, Lawrence, KS 66044-8897 490