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Department of Biology, Duke University, Durham, North Carolina 27708
Terry W. Henkel
Department of Biological Sciences, Humboldt State University, Arcata, California 95512
ABSTRACT |
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TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS TAXONOMY PHYLOGENETIC ANALYSES AND... LITERATURE CITED |
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Two new species of Clavulina are described from rainforests dominated by ectomycorrhizal Dicymbe spp. (Caesalpiniaceae) in the Pakaraima Mountains of Guyana. Clavulina nigricans, sp. nov. is unique for Clavulina in having 46 spores per basidium. Clavulina craterelloides, sp. nov. has an infundibuliform basidiome, previously unknown in the otherwise coralloid genus Clavulina. Macromorphological, micromorphological and habitat data are provided for each taxon, as well as justification for their placement in Clavulina based on morphological and molecular features.
Key words: basidiomycetes, coral fungi, Guyana, molecular phylogenetics, neotropics
INTRODUCTION |
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TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS TAXONOMY PHYLOGENETIC ANALYSES AND... LITERATURE CITED |
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Coralloid basidiomata and bisterigmate basidia, for the most part, have been good diagnostic features for Clavulina. There are records of Clavulina spp. with more than two sterigmata per basidium infrequently encountered in otherwise bisterigmate collections (Corner 1950, Petersen 1988). In contrast, Clavulina amazonensis Corner regularly possessed 24 spores per basidium and was assigned to Clavulina due to the presence of incurved sterigmata (Corner 1970, Petersen 1988b). C. amazonensis lacked many other features regularly seen in Clavulina, such as postpartal basidial septa, inflated hyphae and elongate basidia, and its placement in Clavulina has not been verified by molecular phylogenetics. These problems aside, all other species of Clavulina recorded to date have coralloid basidiomata and bisterigmate basidia.
Here we present evidence that coralloid basidiomata and bisterigmate basidia are not fully diagnostic for the genus Clavulina. Two morphologically distinct species, C. nigricans and C. craterelloides, are described as new. These fungi are part of an extensive assemblage of Clavulina spp. found in ectomycorrhizal Dicymbe (Caesalpiniaceae) forests of Guyana (Henkel et al 2002).
MATERIALS AND METHODS |
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TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS TAXONOMY PHYLOGENETIC ANALYSES AND... LITERATURE CITED |
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Micromorphological features from dried specimens were examined with an Olympus BX51 microscope with light and phase-contrast optics. For basidiospores, basidia, cystidia and other structures at least 20 individuals were measured. Rehydrated fungal tissue was mounted separately in H2O, 3% KOH, and Melzers solution. Number of sterigmata was assessed with scanning electron microscopy performed on a Phillips XL30 ESEM TMP microscope (FEI Co., Portland, Oregon) after sputter coating with a Hummer V (Anatech, Springfield, Virginia).
Specimens were deposited in these herbaria (Holmgren et al 1990): BRGUniversity of Guyana; and HSUHumboldt State University.
DNA sequencing. From two collections each of C. nigricans and C. craterelloides (including the holotypes), a small piece of fresh basidiome tissue was placed in 500 mL 2x CTAB buffer. DNA was extracted using a chloroform:isoamyl protocol (Zolan and Pukkila 1986). A portion of the nuclear gene coding for the large ribosomal subunit (nuc LSU rDNA) was amplified using the primer pair LROR and LR7 and sequenced with primers LROR, LR3R, LR5 and LR16 (http://www.biology.duke.edu/fungi/mycolab/primers.htm). PCR products were purified with Qiagen QIA-quick PCR Purification kit (Qiagen Inc., Chatsworth, California) and sequenced with BigDye Terminators using a 3700 ABI automated DNA sequencer (Applied Biosystems, Foster City, California). Sequences were assembled and edited with Sequencer version 4.1 (Gene Codes, Ann Arbor, Michigan).
Phylogenetic analyses. The two sequences for each species were found to be identical. The holotype sequence for C. craterelloides and C. nigricans was deposited in GenBank under accession AY391718 and AY391719, respectively. Sequences initially were assessed using BLAST (Altschul et al 1990) and found to have affinities with cantharelloid fungi. To further assess the phylogenetic affinities of the Guyana taxa, their sequences were aligned with nuc LSU rDNA sequences from these taxa in GenBank: Auricularia polytricha (Mont.) Sacc. AF261554, Cantharellus cibarius Fr. AY041156, Cantharellus cinnabarinus (Schwein.) Schwein. AY041168, Clavulina cinerea (Bull.) Schröt. AJ406433, Clavulina cristata (Holmsk.) Schröt. AF261553, Craterellus tubaeformis (Bull.) Quél. AF287851, Craterellus cornucopioides (L.) Pers. AJ279572, Gomphus novae-zelandiae Segedin AF261547, Hydnum rufescens Pers. AJ406427, Hydnum repandum L. AF347095, Sistotrema brinkmannii (Bres.) J. Erikss. AJ406430, Sistotrema niveocremeum (Höhn. & Litsch.) Donk AJ406429, Multiclavula corynoides (Pk.) Petersen U66440, Multiclavula mucida (Fr.) Petersen AF287875, Multiclavula vernalis (Schwein.) Petersen U66439, and Ramaria stricta (Pers.) Quél. AF287887. Auricularia polytricha, G. novae-zelandiae, and R. stricta were chosen as outgroups based on their phylogenetic placement and short branch lengths relative to the cantharelloid fungi (Hibbett et al 2000). An initial sequence alignment was produced with ClustalW (Thompson et al 1994) and manually optimized in Seaview (Galtier et al 1996). The final alignment was 1200 characters long. Three regions comprising 25, 101 and 133 base pairs were alignable only between C. cibarius and C. cinnabarinus and were excluded from the analysis. Three regions of 9, 10 and 21 base pairs alignable only between C. tubaeformis and C. cornucopioides were excluded from analysis. One region of 20 bases alignable only between Auricularia polytricha, G. novae-zelandiae and R. stricta was excluded from analysis. A total of 42 base pairs of ambiguously aligned regions were excluded from the analysis. A total of 361 unalignable characters were excluded from the analysis, and phylogenetic analysis was performed on the remaining 839 characters.
Phylogenetic analyses were performed using maximum-likelihood (ML) and Bayesian metropolis-coupled Markov Chain Monte Carlo (B-MC3) inference. The defaults of each program were used unless otherwise noted. ModelTest 3.06 (Posada and Crandall 1998) selected the TN93+G model with the likelihood ratio test; this model was used for the ML analyses. A corresponding six-parameter gamma model was used in B-MC3 analysis. A heuristic search for the most likely tree and a ML bootstrap analysis were performed in PAUP*4b10 (Swofford 1998). Support for internode placement was estimated using B-MC3 posterior probabilities with a six-parameter gamma model from MrBayes version 3.0 beta 4 (Huelsenbeck and Ronquist 2001), with the first 10 000 generations discarded as the burn-in phase. Trees generated by all three analyses were identical topologically. A Nexus file containing the aligned data and the executable commands for all analyses has been deposited in TreeBase (http://www.treebase.org/treebase/).
TAXONOMY |
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TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS TAXONOMY PHYLOGENETIC ANALYSES AND... LITERATURE CITED |
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Basidiomata in dense clusters of basally fused ramets (FIG. 1); entire clusters 120190 mm tall, 90135 mm wide; individual ramets 60130 mm x 1445 mm wide, dichotomously branching 46 times; base (below first branching point) 2245 mm x 38 mm, these bases frequently anastomosing to form a semicohesive basal unit; irregularly coronate clusters at apices of terminal branches 35 mm x 0.50.7 mm; tips acuminate; entire basidiome at first black at the base, light to medium gray above (18D118F1), paler toward the apical portion (17B117B2 KW), nearly white at the tips. Hymenium ripening light gray and then hispid, eventually entirely black. Context concolorous, hollow throughout, 0.31.5 mm thick. Odor fetid; taste mealy and slightly acrid. Macrochemical reactions: FeSO4 on basal context nil, KOH and NH4OH darkening context. Spore deposit not obtained.
Basidiospores 68 x 56 µm (mean Q = 1.23), subglobose, smooth, pale brown in H2O, brownishgray in KOH, with numerous opalescent guttules, inamyloid; wall 0.4 µm thick; apiculus 0.20.5 µm long (FIG. 3). Basidia 80110 µm long, width at apex 57 µm, at base 34 µm, cylindrical to subclavate, tapering evenly toward base, with numerous guttules and grayish granular contents; postpartal septa not observed (FIG. 2); sterigmata 56.5 µm long, 1.52.5 µm wide at base, cornute, 45(6) per basidium; basidioles numerous. Uninflated tramal hyphae 23 µm wide, smooth, some with internal, brownish-gray pigments, interwoven. Inflated tramal hyphae up to 15 µm wide, smooth, hyaline. Clamp connections abundant.
Etymology. Nigricans = "becoming black" in Latin.
Habit, habitat and distribution. Occurring singly or scattered on root mat and mineral earth in rainforests dominated by Dicymbe corymbosa Spruce ex Benth. and Dicymbe altsonii Sandwith; collected during the rainy season (MayJuly). Known from the type locality in the upper Potaro Basin, as well as the upper Ireng Basin, Guyana.
Specimens examined. GUYANA. REGION 8, POTARO-SIPARUNI: Pakaraima Mountains. Upper Potaro River Basin, 4 km southeast of base camp near confluence with White-water Creek, 750 m elevation, under D. corymbosa, 14 VI 2001, Henkel 8284 (HOLOTY PE: BRG; ISOTY PE: HSU); Upper Ireng River Basin, foothills leading to Mount Kukuinang, 1 km west of confluence of Ireng and Sukabi Rivers, 900 m elevation, under D. altsonii, 28 V 1998, Henkel 6754 (BRG, HSU); Upper Ireng River Basin, 1 km west of Kurutuik Falls on adjacent ridges, 750 m elevation, under D. corymbosa, 4 VI 1998, Henkel 6847 (BRG, HSU); Upper Potaro River Basin, 10 km east of Mount Ayanganna, east bank of Potaro River 1 km upstream from confluence with Whitewater Creek, 720 m elevation, under D. corymbosa, 6 VI 2000, Henkel 7440 (BRG, HSU); Pakaraima Mountains, Upper Potaro River Basin, 2 km east of base camp near mouth of Whitewater Creek, 780 m elevation. under D. corymbosa, 13 V 2001, Henkel 8125 (BRG, HSU).
Commentary. Clavulina nigricans is a distinctive coral fungus easily recognized in the field by its large, highly branched, gray to black basidiomata and fetid odor. In addition, C. nigricans appears restricted to groves of Dicymbe trees, which occur in a distinctive, patch-like mosaic in the upper Ireng and upper Potaro River watersheds. This fungus macroscopically does not resemble any currently described Clavulina species.
The hymenium of Clavulina nigricans is initially gray and later blackens during active spore production. The only other Clavulina species described as turning completely black at maturity is Clavulina geoglossoides Corner, which is unbranched to sparingly branched, bisterigmate, with an initially ivory-colored hymenium (Petersen 1988a). Other Clavulina species, such as Clavulina cristata, Clavulina cinerea and Clavulina rugosa, have been reported to turn a dark gray with age but not black. These species are usually cream-colored or light gray at maturity, unlike C. nigricans.
Clavulina nigricans is the only known species of Clavulina with four or more sterigmata per basidium. A maximum of six have been observed (FIG. 4). Other phenotypic features associated with Clavulina, such as inflated, clamped tramal hyphae and cornute sterigmata, were observed in C. nigricans.
Clavulina craterelloides Thacker et T.W. Henkel, sp. nov. FIGS. 57
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Basidiomata in caespitose clusters 90190 x 1880 mm (FIG. 5). Individual ramets 80190 x 822 mm (centrally); primordia present as filiform-acuminate bodies around base of caespitose clusters; young ramets acuminate and clavate, progressively rounding at apex, with apex rupturing with maturity to form a lobate margin; mature ramet deeply infundibuliform and centrally hollow, apex 1770 mm across, base 512 mm wide, non-fertile portion orangish-brown (6D86E8), margin lobate and splitting; flesh cartilaginous. Hymenium ripening and thickening somewhat in irregular to continuous patches over upper half, becoming grayish flesh (6B36B4). Interior basidiome surface sterile and concolorous with infertile exterior, hispid, hygrophanous; context concolorous. Basal mycelium sparse, cream-colored; subtended by brown ectomycorrhizae. Odor mild; taste mildly sour. Spore deposit white. Edible when cooked. Macrochemical reactions: FeSO4 on basal context nil.
Basidiospores (6.5) 7.58 x (5.5) 67 (7.5) µm (mean Q = 1.16), subglobose to broadly ellipsoid, smooth, hyaline, inamyloid, with several ill-defined guttules; spore wall 0.5 µm thick; apiculus 0.5 µm long (FIG. 7). Basidia (FIG. 8) (60) 6787 (90) µm long, (5) 7.48 µm wide at apex, 2.74.3 µm wide at base, cylindrical to subclavate, tapering evenly toward base, slightly curving, gloeoporous; postpartal septa not observed (FIG. 6). Sterigmata 55.5 µm long, 2 µm wide at base, subcornute to cornute, 2 (or rarely 3) per basidium. Uninflated tramal hyphae 23 µm wide, smooth, hyaline, interwoven, often gloeoporous; wall 0.5 µm wide. Inflated tramal hyphae up to 15 µm wide, smooth, hyaline. Clamp connections infrequently observed.
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Habit, habitat and distribution. Occurring as scattered caespitose clusters on mineral earth in forests dominated by D. corymbosa and D. altsonii; infrequently occurring in much higher densities locally; collected during the MayJuly rainy season. Known from the type locality in the upper Potaro Basin and adjacent upper Ireng Basin, Guyana.
Specimens examined. GUYANA. REGION 8, POTARO-SIPARUNI: Pakaraima Mountains. Upper Potaro River Basin, 3 km southwest of base camp on Potaro River, 1 km upstream from confluence with Whitewater Creek, 750 m elevation, under D. corymbosa, 2 VI 2001, Henkel 8234 (HOLOTY PE: BRG; ISOTY PE: HSU); upper Potaro River Basin, vicinity of base camp 1 km upstream from confluence with Whitewater Creek, 720 m elevation, under D. corymbosa, 2 VII 2002, Henkel 8520 (BRG, HSU).
Commentary. Clavulina craterelloides is recognized easily in the field by the large, rich orange-brown, infundibuli-form, caespitose basidiomata restricted to groves of Dicymbe trees. There are no records of other Clavulina species with an infundibuliform shape and smooth hymenophore, features otherwise indicative of Craterellus. While the type species for Craterellus, C. cornucopioides, is bisterigmate, most other species of Craterellus are not (Corner 1966). The two cornute sterigmata (or rarely three) per basidium and in-flated hyphae present in C. craterelloides are indicative of Clavulina. In addition, basidiome development in C. craterelloides is more suggestive of Clavulina than Craterellus. Whereas Craterellus basidomata are infundibuliform with incurved margins from early development (Corner 1966), C. craterelloides is coralloid with an unruptured, acuminate apex when young, expanding and rupturing in age to become infundibuliform.
PHYLOGENETIC ANALYSES AND DISCUSSION |
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TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS TAXONOMY PHYLOGENETIC ANALYSES AND... LITERATURE CITED |
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A clade with C. cinerea, C. craterelloides and C. cristata also received high support in both ML and B-MC3 bootstrapping analysis, showing C. nigricans to be clearly basal to these three taxa. A case could be made that C. nigricans should be placed in its own genus, sister to Clavulina. However, the basal position of C. nigricans likely could be an artifact of in-sufficient taxon sampling. The authors therefore have taken the more conservative view of placing C. nigricans in Clavulina.
With the discovery of C. nigricans and C. craterelloides, there are no inviolate phenotypic characters delimiting Clavulina. The presence of four-, five- and even six-spored basidia in C. nigricans rendered bisterigmate basidia as no longer diagnostic for Clavulina (Corner 1950). Postpartal basidial septa, already questioned by Petersen (1988) as diagnostic for Clavulina, were not observed in either C. nigricans or C. craterelloides. The cornute sterigmata present in most Clavulina species are also found in Craterellus (Corner 1966). The lack of consistent, definitive morphological features to describe Clavulina contrasts with the molecular studies that suggested that species of Clavulina, including these newly described species from Guyana, form a monophyletic clade within the Cantharellales (this study, Pine et al 1999, Hibbett et al 2000).
As the neotropical macromycota increasingly is explored, it is evident that many taxa depart from traditional morphology-based generic concepts (Henkel et al 2000, Miller et al 2001, Miller et al 2002). In such cases, molecular tools are useful for resolving the taxonomic affinities of these fungi.
ACKNOWLEDGMENTS |
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FOOTNOTES |
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1 Corresponding author. E-mail: jrt1{at}duke.edu
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