Orson K. Miller

Seasonal dynamics of ectomycorrhizal fungus assemblages on oak seedlings in the southeastern Appalachian Mountains

The potential for seasonal dynamics in ectomycorrhizal (EM) fungal assemblages has important implications for the ecology of both the host trees and the fungal associates. We compared EM fungus distributions on root systems of out-planted oak seedlings at two sites in mixed southeastern Appalachian Mountain forests at the Coweeta Hydrologic Laboratory in North Carolina, from samples taken in mid-July and early September. Species level EM fungus type specificity, and identification in some cases, was enabled by direct sequencing of the mycobionts from the seedling roots. Seventy-four EM fungal ITS types were documented, most of which occurred only in the midsummer or early-fall samples, respectively. Cenococcum geophilum (morphotyped) was ubiquitously present and accounted for the majority of root tips sampled. Abundance and relative frequency of types other than C. geophilum were significantly higher in the July samples, while C. geophilum was significantly more frequent and abundant in September. Several generalistic dominants were found fairly equally at both sites and on both sample dates. Other taxa with relatively high frequency were recovered from both sites and tree seedling species, but were reliable indicators occurring primarily in the July sample (e.g., Laccaria cf laccata). Notable shifts in mycobiont dominance were apparent in relation to sample date, including increases in Cortinarius spp. richness, decreases in Thelephoraceae richness, and the disappearance of Amanita spp. types in the early fall compared to midsummer samples. However, diversity and rarity were high and differences in overall community composition (other than C. geophilum) by season were not significant based on multi-response permutation procedures. Although these results based on a single growing season are preliminary, changes in abundance and frequency, detection of significant indicator species, and the apparent systematic affinities of shifting EM types support the potential for seasonal variability in EM associations in this system.

Biological species in the Collybia dryophila group in North America

Monosporous isolates were obtained from spore prints of 43 collections of the Collybia dryophila complex occuring in North America. Intercrosses among testers from different sources reveal four int...

The population biology of two litter decomposing agarics on a southern Appalachian mountain

Two litter decomposing agarics, Collybia subnuda and Marasmiellus praeacutus, were intensively sampled on permanent plots on a southern Appalachian mountain. Collybia subnuda is a dominant decomposer of deciduous tree detritus and M. praeacutus is a dominant decomposer of coniferous detritus. Tests of somatic incompatibility indicate that the observed population densities of C. subnuda and M. praeacutus are not less than 3.9-9.3 genets/100 m2 and 7.1-12.1 genets/100 m2, respectively. Self-crosses of single spore isolates obtained from both species indicate that C. subnuda has a bipolar mating system and M. praeacutus is tetrapolar. This is the first report of a bipolar mating system in the genus Collybia. Tests of somatic incompatibility between synthesized dikaryons and their parent progenitor indicate that somatic incompatibility tests can discriminate between closely related genets in some species but cannot in others.

Notes on Agaricales from Arctic Tundra in Alaska

Twelve species distributed among five families in the Agaricales are reported from Alaskan Tundra. Eight species are first reports from Alaska and one of these is previously unreported from North America. Four species, previously reported from limited material, are completely described. Additional information is provided on the habitats, ecology and distribution of all species.

Ectomycorrhizal sporophore distributions in a southeastern Appalachian mixed hardwood/conifer forest with thickets of Rhododendron maximum

Sporophore abundance of putatively ectomycorrhizal fungi was compared in a mature mixed hardwood/conifer forest inside of (+) versus outside of (−) Rhododendron maximum thickets (RmT). Experimental blocks (1/4 ha) were established inside of (3) and outside of (3) RmT at the Coweeta Hydrologic Laboratory in Macon County, North Carolina, USA. Litter and organic layer substrates were removed, composited and redistributed among 90 2 × 2m plots within the blocks. Plots received either +RmT or −RmT litter, and either +RmT or −RmT organic layers, or were unmanipulated for controls. Sporophores of 67 putatively ectomycorrhizal species were collected from the blocks. Species diversity and overall community structure were similar inside of and outside of RmTs, and no grouping was detected by substrate type. Differences within the ectomycorrhizal fungus community were associated only weakly with environmental parameters, as indicated by ordination. In light of these results, recent observations of ectomycorrhizal suppression and strong shifts in the proportions of morphotypes on tree seedlings inside of RmT do not appear to be related to differences in sporophore distributions. The changes in seedling mycobiont dominance in relation to RmT and the influence this has on seedling health should be examined directly from root tips.

Southern Appalachian Russulas. IV

Morphological and habitat descriptions, illustrations and taxonomic discussions of eight species of Russula occurring in the Southern Appalachian Mountains of North America are presented. Russula earlei, R. ballouii, R. mariae, R. flavida, R. claroflava and R. sanguinea are redescribed. A new subsection of Russula is proposed to accommodate an unusual new species, Russula ochricompacta. Russula aciculocystis, a previously unvalidated species proposed by C. H. KaufFman, is described. External basidiospore morphology of the species endemic to North America is examined by scanning electron microscopy.

Amanita marmorata subsp. myrtacearum?a new subspecies in Amanita section Phalloideae from Hawaii

A widely distributed Amanita was observed on six of the Hawaiian Islands fruiting in association with Eucalyptus and Casuarina species. Subsequent in? vestigation revealed it to be closely related to A. mar? morata subsp. marmorata. The holotype of A. marmorata was studied and found to be badly molded and mostly destroyed. Some anatomical details were visible and, though it is similar to our material, there are anatom? ical differences. The Hawaiian populations are also quite variable macroscopically and anatomically and, as a result, a new subspecies, A. marmorata subsp. myr? tacearum, is described for the Hawaiian Islands. A third taxon in this complex, A. reidii, recently described from South Africa, is discussed.

A Study of the Boreal, Alpine, and Arctic Species of Melanoleuca

SUMMARY Five new species of Melanoleuca (Tricholomataceae) from boreal, alpine and arctic habitats are described. In addition, five other species are treated including several previously unreported from North America. New ecological information and unreported distributions in tundra and boreal habitats are reported for all ten species. Microscopic and macroscopic features are described and discussed, accompanied by camera lucida drawings and black and white photographs. A key to the species is presented. There have been very few contemporary studies of the North American Melanoleucas. Smith (1944), Smith and Rea (1944), and Thiers (1958) have described several new species but have made no attempt to cover the entire flora. Most popular manuals of North American species usually include only M. melaleuca (Pers. ex Fr.) Murr. and M alboflavida (Pk.) Murr. The majority of the many species of Peck transferred into Melanoleuca by Murrill (1911a, 1911b, 1913, 1914, 1916, 1917) did not belong there in the first place. As a result much confusion exists concerning the status of many North American species of Melanoleuca. The use of Melzers solution to test for the

Higher Fungi in Tundra and Subalpine Tundra from the Yukon Territory and Alaska

Descriptions and illustrations are provided for six species of Inocybe and one Cortinarius collected in tundra and subalpine tundra mainly from the St. Elias Mountains, the Yukon Territory and Alaska. A new combination, Inocybe boltoni ssp. giacomi, is proposed.

A new genus, Leucopholiota, in the Tricholomataceae (Agaricales) to accommodate an unusual taxon

Armillaria subgenus Leucopholiota is elevated to the generic level to accommodate Tricholoma deco- rosum, originally placed in Agaricus tribus Tricholoma and best known as Armillaria decorosa. Included are a