Diversity and function of fungi associated with the fungivorous millipede,Brachycybe lecontii

Fungivorous millipedes (subterclass Colobognatha) likely represent some of the earliest known mycophagous terrestrial arthropods, yet their fungal associates remain elusive. Here we describe relationships between fungi and the fungivorous millipede, Brachycybe lecontii. Their fungal community is surprisingly diverse, including 176 genera, 39 orders, four phyla, and several undescribed species. Of particular interest are twelve genera conserved across wood substrates and millipede clades that comprise the core fungal community of B. lecontii. Wood decay fungi, long speculated to serve as the primary food source for Brachycybe species, were absent from this core assemblage and proved lethal to millipedes in pathogenicity assays while entomopathogenic Hypocreales were more common in the core but had little effect on millipede health. This study represents the first survey of fungal communities associated with any colobognath millipede, and these results offer a glimpse into the complexity of millipede fungal communities.     

Abundance of Collembola (Insecta) inhabiting the hyphal mat of an ectomycorrhizal fungus,Sarcodon scabrosus,in a Pinus densiflora forest

The total number of collembolans collected from the hyphal mat of the ectomycorrhizal fungus Sarcodon scabrosus was less than half of that collected from the adjacent non-mat soil. The same was true of all families of collembolans except one, although not all differences were significant. The exception was the Hypogastruridae, with more individuals in the hyphal mat on the sampling day in the fruiting season; these were also the most abundant collembolans on the fruiting bodies. These results indicate that most collembolans avoid the hyphal mat of S. scabrosus in a Japanese red pine forest.     

The production of nematode-immobilizing secretory cells by Climacodon septentrionalis

The ability of Climacodon septentrionalis to immobilize and kill a mycophagous nematode (Aphelenchoides sp.) in vitro is described for the first time. Two isolates produced droplets (20–45 μm in diameter) that formed at the apices of tall, stalked, and branching secretory cells (700–1,500 μm tall). On 2% modified malt extract agar, nematodes became enveloped in the droplets, which restricted their ability to move and resulted in complete immobilization and death within several hours of contact. The rate of decomposition of the nematodes varied considerably, with most individuals persisting for weeks whereas others were degraded within several days and appeared to be colonized by dense hyphal growth. This study provides the first documentation of a non-agaricoid fungus producing secretory cells that are able to immobilize nematodes.     

Evidence for a new lineage of primary ambrosia fungi in Geosmithia Pitt (Ascomycota: Hypocreales)

Geosmithia is a genus of mitosporic filamentous fungi typically associated with phloeophagous bark beetles world-wide. During this study, the fungal associates of ambrosia beetles Cnesinus lecontei, Eupagiocerus dentipes, and Microcorthylus sp. from Costa Rica, were studied using morphology and DNA sequences. Fungal associates belonged to four undescribed Geosmithia species. Geosmithia eupagioceri sp. nov. and G. microcorthyli sp. nov. are evidently primary ambrosia fungi of their respective vectors E. dentipes and Microcorthylus species. They both have convergently evolved distinct morphological adaptations including the production of large, solitary and globose conidia, and yeast-like cells. Tunnels of C. lecontei contained an undescribed Geosmithia species, but its nutritional importance for its vector is unclear. An auxiliary ambrosia fungus, Geosmithia rufescens sp. nov., was found associated with both G. eupagioceri and the Geosmithia species associated with C. lecontei. G. microcorthyli is genetically quite similar to the phloem-associated Geosmithia sp. 8 from Europe. Large differences in morphology between these two species suggest the rapid co-evolution resulting from the close symbiosis of the former with its beetle host. The ITS rDNA sequences of G. microcorthyli and Geosmithia sp. 8 were not diagnostic, suggesting that alternative markers such as EF-1α, IGS rDNA or β-tubulin should be used, together with morphological and ecological data, for species delimitation in this genus. The primary ambrosia fungi described here are derived from phloem-associated ancestors, and represent two independent lineages of ambrosia fungi in the Hypocreales and a new ecological strategy within Geosmithia.     

小型哺乳类食果动物可能对蛇菰科葛菌种子散布的初次报道

初次报道了哺乳类食果动物可能对蛇菰科葛菌(Balanophora harlandii)的种子散布,葛菌具有酷似蘑菇且醒目显著的肉质佛焰状果序,食菌的啮齿类动物很可能由于对其进行取食而起到种子散布的作用,本文对此现象进行了初步探讨.     

Prescribed burning in a Eucalyptus woodland suppresses fruiting of hypogeous fungi, an important food source for mammals

Fruit bodies of hypogeous fungi are an important food source for many small mammals and are consumed by larger mammals as well. A controversial hypothesis that prescribed burning increases fruiting of certain hypogeous fungi based on observations in Tasmania was tested in the Australian Capital Territory to determine if it applied in a quite different habitat. Ten pairs of plots, burnt and nonburnt, were established at each of two sites prescribe-burnt in May 1999. When sampled in early July, after autumn rains had initiated the fungal fruiting season, species richness and numbers of fruit bodies on the burnt plots were extremely low: most plots produced none at all. Both species richness and fruit body numbers were simultaneously high on nonburnt plots. One of the sites was resampled a year after the initial sampling. At that time species richness and fruit body abundance were still significantly less on burnt plots than on nonburnt, but a strong trend towards fungal recovery on the burnt plots was evident. This was particularly so when numbers of fruit bodies of one species, the hypogeous agaric Dermocybe globuliformis, were removed from the analysis. This species strongly dominated the nonburnt plots but was absent from burnt plots in both years. The trend towards recovery of fruit body abundance in the burnt plots one year after the burn was much more pronounced with exclusion of the Dermocybe data. The Tasmanian-based hypothesis was based mostly on the fruiting of two fire-adapted species in the Mesophelliaceae. Neither species occurred on our plots. Accordingly, the results and conclusions of the Tasmanian study cannot be extrapolated to other habitats without extensive additional study. Implications for management of habitat for fungi and the animals that rely on the fungi as a food source are discussed.     

Digestive responses of two omnivorous rodents (<Emphasis Type="Italic">Peromyscus maniculatus</Emphasis> and <Emphasis Type="Italic">P. alstoni</Emphasis>) feeding on epigeous fungus (<Emphasis Type="Italic">Russula occidentalis</Emphasis>)

The sporocarps of hypogeous and epigeous fungi are important dietary items for forest dwelling rodents in temperate and tropical forests throughout the world. However, results of some pioneering works have demonstrated that fungi cannot be considered as nutritionally high-quality food items for some mycophagous small rodents. According to these studies, when mycophagous rodents feed on fungus, they showed a minimal digestibility, but whether this applies to most rodent species that include fungi in their diets is unknown. In this study, we experimentally evaluated body mass changes and feed preferences in captive deer (Peromyscus maniculatus) and volcano (P. alstoni) mice when fed on epigeous fungus (Russula occidentalis). In experiment 1, the animals were fed with fungus as the only feedstuff in comparison to regular rodent chow and oat. In experiment 2, the animals were fed with fungus in a free-choice arrangement together with equal amounts of rodent chow and oat. Both species lost ∼15% of their body mass within 4 days when fed on fungus alone, but gained 5–10% body mass during the same time period when ingesting oat and rodent chow, respectively, as the only feedstuff. However, in contrast, in the free-choice arrangement with all three feedstuffs, both species gained 20–30% body mass, and showed the highest feed preference for fungus followed by oat and rodent chow. In addition, apparent digestibility of energy and nitrogen were analyzed in both rodent species, which were 50–60% for fungus, whereas approximately 90–94% for rodent chow and oat. According to our results, animals need to supplement their diets with alternative high-quality food items in order to maintain and increase their body mass, suggesting that epigeous fungi are only of moderate nutritional value for small rodents. Futures studies should focus on exploring the importance of a mixture of fungal species in the diet of small mycophagous rodents.     

Seasonal consumption of mycorrhizal fungi by a marsupial-dominated mammal community

The temperate forests of Australia support a high diversity of hypogeous fungi and a wide variety of mycophagous mammals, yet many mammal-fungal relationships are still poorly understood. We studied the seasonal fungal diets of eight sympatric mammals (seven marsupials and one rodent) in a remnant montane eucalypt forest. Fifty-five different fungal taxa were identified from 305 scat samples. Swamp wallabies (Wallabia bicolor), yellow-footed antechinus (Antechinus flavipes) and brown antechinus (A. stuartii) were the primary mycophagists in this community, but all mammals consumed fungi, including three species not previously recorded as mycophagous (eastern grey kangaroo, Macropus giganteus;common wallaroo, Osphranter robustus; and common dunnart, Sminthopsis murina). Winter was the peak season for fungal consumption and dietary diversity of fungi, however, the diversity of taxa ingested varied between species and season. Our work supports the idea that a diverse mycophagous mammal community is important for maintaining natural variation in fungal community composition.     

Seasonal fungal diets of small mammals in an Australian temperate forest ecosystem

Australian temperate forests support a high diversity of truffle-like fungi, and a rich assortment of mammals that feed upon them. We sampled seasonal diets of four sympatric mammals (two rodents, two marsupials) in an eastern Australian wet sclerophyll forest and identified all dietary fungi. Fifty-two different spore types were found in diets, most of which were from truffle-like fungi. All mammals consumed fungi, but occurrence of fungi and the variety of taxa in the diets peaked in winter and spring. Bush rats (Rattus fuscipes) were significantly more mycophagous than other mammals sampled in terms of proportion of scats containing fungi, number of taxa per sample, and overall diversity of dietary fungi. Most fungal taxa were eaten only occasionally, but a few truffle-like taxa dominated diets and appear to be staple food for the small mammal community. Our work supports the view that mycophagous mammals are important for maintenance of ecosystem health through their spore dispersal abilities.     

Mycophagy by small mammals in the coniferous forests of North America: nutritional value of sporocarps of Rhizopogon vinicolor, a common hypogeous fungus

We evaluated the nutritional value of sporocarps of Rhizopogon vinicolor, a common hypogeous fungus in the coniferous forests of North America, for two small mammal species: the Californian red-backed vole (Clethrionomys californicus) and the northern flying squirrel (Glaucomys sabrinus). Although the nitrogen concentration of sporocarps was high, much of it was in non-protein form or associated with cell walls, suggesting that it may be of low nutritional value or protected from mammalian digestive enzymes. Sporocarps also had high concentrations of cell wall constituents, indicating low availability of digestible energy. When fed a diet of this fungus alone in a controlled feeding experiment both mammal species lost a small amount of body mass. Digestibilities of dry matter, nitrogen, cell wall constituents and energy from sporocarps by both species were lower than the digestibilities of other food types by other similarly sized small mammals. Red-backed voles digested the various components of sporocarps at least as well as the flying squirrels, even though they were almost six-fold smaller in body mass. This observation supports the notion that red-backed voles, like other microtine rodents, have morphological and physiological adaptations of the digestive system that are postulated to permit greater digestion of fibrous diets than predicted on the basis of body size. Despite this, our results re-affirm previous conclusions that hypogeous fungi are only of moderate nutritional value for most small, hindgut-fermenting mammals. Future studies should focus on the importance of mixed-species of fungi in the diet of small mammalian mycophagists. Accepted: 4 December 1998