Terry W. Henkel

Ectomycorrhizal fungi and their leguminous hosts in the Pakaraima Mountains of Guyana

Ecologically important ectomycorrhizal (EM) associations are poorly known from equatorial rain forests of South America. Recent field studies in the Pakaraima Mountains of western Guyana revealed previously undocumented forests dominated by EM leguminous trees, with a rich assemblage of EM mycobionts. Along transects, basidiomes from 75 species or morphospecies of putatively EM fungi were spatially associated with leguminous host trees. These fungi belonged to the basidiomycete families Boletaceae, Amanitaceae, Russulaceae, Cortinariaceae, Cantharellaceae, Clavulinaceae, and Entolomataceae, all of which are poorly documented from the lowland neotropics. Ectomycorrhizas were confirmed on D. corymbosa, D. altsonii, and D. jenmanii (Caesalpiniaceae, tribe Amherstieae), and a fourth species, Aldina insignis (Papilionaceae). The tribe Amherstieae contains most of the EM leguminous species forming monodominant forests in Guineo-Congolian Africa. Dicymbe species constituted the first record of EM Amherstieae in the New World. A variety of other co-occurring caesalpiniaceous trees failed to exhibit ectomycorrhizas. Transect surveys indicated that D. corymbosa and D. altsonii were: (1) highly clumped and dominant at specific sites; (2) occurred on soils with widely varying chemical and textural characteristics; and (3) the most important hosts for EM fungi in the local landscape. Dicymbe species have life history attributes, including the ectomycorrhizal habit, which enhance their competitive abilities irrespective of soil conditions. The spatial restriction of EM fungal basidiomes indicated that discrete groves of EM trees harbour an important component of regional macromycete diversity.

Monodominance in the ectomycorrhizal Dicymbe corymbosa (Caesalpiniaceae) from Guyana

Dominance of primary rain forests by the ectomycorrhizal, leguminous canopy tree Dicymbe corymbosa (Caesalpiniaceae) was investigated in the Pakaraima Mountains of western Guyana. In five 1-ha forest inventory plots in the Upper Ireng and Upper Potaro River drainages basal areas of D. corymbosa ranged from 38.4-52.8 m 2 ha −1 (63- 85% of total) among all trees 10 cm diameter at breast height (dbh), values in the upper range for tropical moist forests worldwide. The high basal areas for D. corymbosa were due to the prevalence of large (>150 cm dbh), multi- stemmed individuals. Stem densities in Dicymbe plots ranged from 276-433 ha −1 , with D. corymbosa contributing 24.6- 59.8%. In three 1-ha mixed forest plots adjacent to the Dicymbe plots, D. corymbosa was absent. In the mixed forests, stem densities were higher (480-585 ha −1 ), basal areas were lower (36.7-39.8 m 2 ha −1 ), species diversity was higher, and canopy tree species were more equitably distributed than in the Dicymbe plots. Tree community composition was not qualitatively different between Dicymbe and mixed forests. In the Dicymbe plots, mean sapling and seedling densities of D. corymbosa were significantly higher than most other canopy species, indicating persistent monodominance. Edaphic variation did not account for variation in forest composition. Life history traits are discussed which may contribute to clumping in D. corymbosa, including coppicing and mast-fruiting, and the potential role of litter-trapping physiognomy and ectomycorrhiza-mediated nutrient dynamics in promoting monodominance is noted.

Systematics of pleurotoid Russulaceae from Guyana and Japan, with notes on their ectomycorrhizal status

Three species of pleurotoid, putatively lig- nicolous basidiomycetes previously described in the genus Lactarius sect Panuoidei were redescribed from fresh material collected in Guyana andJapan. In Guy- ana, Lactarius panuoides and Lactarius campinensis were restricted to forests dominated by ectomycor- rhizal Dicymbe species (Caesalpiniaceae) and basi- diomata of both pleurotoid species were subtended by ectomycorrhizal rootlets. This suggested an ecto- mycorrhizal nutritional mode for these fungi. Analy- sis of DNA sequences in the nuclear large subunit region taken from basidiomata and co-occurring ec- tomycorrhizae of L. panuoides and L. campinensis confirmed that these fungi are ectomycorrhizal and that their fruiting habit on organic deposits and well rotted wood at elevated positions is not due to sap- rotrophy, as previously assumed. Lactarius uyedae was collected in Japan from mature temperate forests dominated by Fagaceae, yet ectomycorrhizal rootlets were not found in association with the basidiomata. Morphological features and analysis of DNA sequenc- es suggested that L. panuoides and L. uyedae have affinities with established sections of the genus Lac- tarius, regardless of the pleurotoid morphology of their basidiomata, and that L. campinensis should be transferred to the genus Russula. Discussion is pro- vided for the genus Pleurogala, which was erected to accomodate putatively lignicolous, pleurotoid species

Pseudotulostoma , a remarkable new volvate genus in the Elaphomycetaceae from Guyana

Pseudotulostoma volvata gen. sp. nov. is described from the south-central Pakaraima Mountains of Guyana. Pseudotulostoma volvata is associated with ectomycorrhizal Dicymbe corymbosa trees (Caesalpiniaceae) and placed in the Ascomycota, Eurotiales, Elaphomycetaceae. Included are a description of the genus and species, illustrations of the macroscopic and microscopic features, and a discussion of the distinctive features and phylogenetic placement of this fungus.

New species of Elaphomyces (Elaphomycetaceae, Eurotiales, Ascomycota) from tropical rainforests of Cameroon and Guyana.

The sequestrate false truffles Elaphomyces favosus, E. iuppitercellus, and E. labyrinthinus spp. nov. are described as new to science from the Dja Biosphere Reserve, Cameroon. Elaphomyces adamizans sp. nov. is described as new from the Pakaraima Mountains of Guyana. The Cameroonian species are the first Elaphomyces taxa to be formally described from Africa, occurring in lowland Guineo-Congolian tropical rainforests dominated by the ectomycorrhizal (ECM) canopy tree Gilbertiodendron dewevrei (Fabaceae subfam. Caesalpinioideae). The Guyanese species is the third to be discovered in lowland tropical South America, occurring in forests dominated by the ECM trees Pakaraimaea dipterocarpacea (Dipterocarpaceae) and Dicymbe jenmanii (Fabaceae subfam. Caesalpinioideae). Macromorphological, micromorphological, habitat, and DNA sequence data are provided for each new species. Molecular and morphological data place these fungi in Elaphomycetaceae (Eurotiales, Ascomycota). Unique morphological features are congruent with molecular delimitation of each of the new species based on a phylogenetic analysis of the rDNA ITS and 28S loci across the Elaphomycetaceae. The phylogenetic analysis also suggests that a common ancestor is shared between some Elaphomyces species from Africa and South America, and that species of the stalked, volvate genus Pseudotulostoma may be nested in Elaphomyces.

Kombocles bakaiana gen. sp. nov. (Boletaceae), a new sequestrate fungus from Cameroon

Kombocles bakaiana gen. sp. nov. is described as new to science. This sequestrate, partially hypogeous fungus was collected around and within the stilt root system of an ectomycorrhizal (ECM) tree of the genus Uapaca (Phyllanthaceae) in a Guineo-Congolian mixed tropical rainforest in Cameroon. Molecular data place this fungus in Boletaceae (Boletales, Agaricomycetes, Basidiomycota) with no clear relationship to previously described taxa within the family. Macro- and micromorphological characters, habitat, and DNA sequence data are provided. Unique morphological features and a molecular phylogenetic analysis of 304 sequences across the Boletales justify the recognition of the new taxa. Kombocles bakaiana is the fourth sequestrate Boletaceae described from the greater African tropics, and the first to be described from Cameroon.

New species of Auritella (Inocybaceae) from Cameroon, with a worldwide key to the known species

Two new species in the genus Auritella (Inocybaceae) are described as new from tropical rainforest in Cameroon. Descriptions, photographs, line drawings, and a worldwide taxonomic key to the described species of Auritella are presented. Phylogenetic analysis of 28S rDNA and rpb2 nucleotide sequence data suggests at least five phylogenetic species that can be ascribed to Auritella occur in the region comprising Cameroon and Gabon and constitute a strongly supported monophyletic subgroup within the genus. Phylogenetic analysis of ITS data supports the conspecificity of numerous collections attributed to the two new species as well as the monophyly of Australian species of Auritella. This work raises the known number of described species of Auritella to thirteen worldwide, four of which occur in tropical Africa, one in tropical India, and eight in temperate and tropical regions of Australia. This is the first study to confirm an ectomycorrhizal status of Auritella using molecular data.