Saddling the Truffles

The black elfin saddle Helvella lacunosa, photographed by Fred Stevens.

The subject of today's post is the fungus family Helvellaceae. In the past, the Helvellaceae have been treated as the family including the morels and false morels. False morels and morels are ascomycetes* that produce convoluted fruiting bodies generally supported above ground by a stalk. However, molecular analyses have unanimously indicated the non-monophyly of the morels and false morels relative to the truffles (Percudani et al. 1999), which produce their fruiting bodies underground (while above-ground fungi have their spores generally dispersed by the wind, truffles have spores dispersed by passing through an animal's digestive system after it eats the truffle). The intermingled relationship between truffles and morels had already been indicated by morphologists based on microscopic features of the spores and asci, and so past members of the Helvellaceae have been dispersed among multiple families. At the same time, genera of truffles have been shown to have a relationship with the Helvellaceae, so of the five genera listed in Helvellaceae in the most recent "Outline of Ascomycota" (Lumbsch & Huhndorf 2007) only two (Helvella and Cidaris) are above-ground fruiters, while the other three (Balsamia, Barssia and Picoa) are truffles. This is ignoring the point that the single known species of Cidaris has not seemingly been identified since its original description (Underwood 1896) and its relationship to Helvella would probably require investigation.

*One of the major groups of fungi, ascomycetes produce spores in an ascus, an elongate structure with spores contained in a row within it.

A stem-less Helvella, H. astieri, photographed by Thomas Læssøe.

Members of the genus Helvella are commonly known as 'saddle fungi' or 'elfin saddles' due to the appearance of the fruiting bodies in some species. Other species possess a variety of different fruiting morphologies, some cup-like, some irregularly folded and lumpy. Not all Helvella species produce fruiting bodies supported by a stalk: in some, the fruiting body sits on the ground or remains partially submerged (Kimbrough et al. 1996), and it has been suggested that such forms may provide some indication how the truffles evolved from above-ground forms. All Helvella species fruit on soil (i.e. never on rotting wood or other such substrates) and it seems likely that all members of the Helvellaceae form ectomycorrhizal associations with plant roots (Hansen 2006).

How to spot desert truffles... (from here)

The truffle members of the Helvellaceae have a solid gleba (the spore-bearing inner mass) interspersed with veins or pockets of hymenia (the spore-producing tissues) separated by sterile tissue (Kimbrough et al. 1996). Picoa species grow in association with Helianthemum (rockrose) species and are among the 'desert truffles' collected in arid parts of the Mediterranean. They are eaten, but are not considered commercially significant due to their small size. Among Helvella species, the white saddle Helvella crispa and black saddle Helvella lacunosa have been described as edible, so long as they are cooked properly.

What the picture above may lead you to... Picoa juniperi, from here.

REFERENCES

Hansen, K. 2006. Systematics of the Pezizomycetes—the operculate discomycetes. Mycologia 98 (6): 1029-1040.

Kimbrough, J. W., L.-T. Li & C.-G. Wu. 1996. Ultrastructural evidence for the placement of the truffle Barssia in the Helvellaceae (Pezizales). Mycologia 88 (1): 38-46.

Lumbsch, H. T., & S. M. Huhndorf (eds) 2007. Outline of Ascomycota—2007. Myconet 13: 1-58.

Percudani, R., A. Trevisi, A. Zambonelli & S. Ottonello. 1999. Molecular phylogeny of truffles (Pezizales: Terfeziaceae, Tuberaceae) derived from nuclear rDNA sequence analysis. Molecular Phylogenetics and Evolution 13 (1): 169-180.

Underwood, L. M. 1896. On the distribution of the North American Helvellales. Minnesota Botanical Studies Bulletin 9 (8): 483-500.