The What, Where, and When Question
Every year at the fungus fair, all the species that are identified are painstakingly recorded and a list is put together (available at the MSSF website). These lists go back a long time, far into the seventies. What do these lists tell us?
The lists as such give some information on the mushroom species growing in the bigger San Francisco Bay area, and show which species are commonly fruiting at a certain time. They also can show trends; some species may suddenly appear on the lists, others might vanish.
More data than names are needed if we want to draw conclusions from the lists. Where were the mushrooms exactly collected? What dates were the fairs? What was the weather like before the collecting and during the summer months? Who went out in the field, and how many in each area, and who did the identification, what sources did they use, and were collections preserved to check the names?
A name, suddenly appearing on a list, does not necessarily mean that the species is new to the area. An expert in that particular group of mushrooms might have been present and introduced the locals to this species, or a key might have been published, making at last identification of Cortinarius species possible (to name a notoriously neglected group in the recording). If the lists went further back in time, perhaps twice as far as they do now, we would see Amanita phalloides make its first appearance, and could follow its subsequent spread.
Clearly there are various factors which determine the presence of names on a list—biotic factors (the species has recently arrived); abiotic factors (the weather was favourable for the fruiting of a certain species), and many human factors (such as the areas where people go, and the people who identify the mushrooms).
Fortunately, the MSSF website offers more than just those lists. At least for the years 2001-2004 catalogues are available, not only listing the species which have been identified, but also where they were found, and which species were new records. Mycology in our part of the USA is still very much in flux so the names we apply to species are not necessarily correct (among the plentiful examples: Leucoagaricus rubrotinctus only grows east of the Rocky Mountains, not in California; what was called Amanita rubescens until a few years ago was then described as a new species A. novinupta; Daldinia grandis, King Alfred’s cakes, appears to be very rare, and most collections under that name are now identified as Hypoxylon thouarsianum), and for many groups adequate keys are just not available. For all these reasons, it would be great to keep the collections from the fair, dry them and preserve them in a herbarium, so they are available later for morphological and molecular examination. In fact, herbaria exist for this purpose and people can still study the actual mushrooms that were collected by our distinguished mycological forebears back to the nineteenth century. For the fairs the time to do this, and the space to preserve the collections, are both in short supply, with the result that this has seldom been done. Only a few, rare or exceptional species have been conserved, depending on the interests of the people present.
The Point Reyes Mycoblitz, held this December 10, tried to fill some of the gaps. Organized by Prof. Bruns with the cooperation of the National Park Service, this event focused on one area only, and covered as many different habitats as possible from the dunes bordering Limantour beach to the pine clad top of Mount Vision, and south to the ridge just west of the San Andreas Fault. In all, around 200 collections were dried and will be preserved in the herbarium of UC-Berkeley along with photographs and much descriptive information. Many more collections were made but duplicates and the ones already collected from the area were discarded. Among the highlights were Amanita porphyria and an orange crust-forming polypore that has kept us intrigued (we are still working on its name). The mycoblitz will be repeated at the end of January for a second snapshot of the fungal diversity (look for details in the calendar section), and in the next few years.
Of course, the purpose of the mycoblitzes is to assess diversity systematically in one particular area, albeit a large one, while the focus at the fungus fairs is on showing fungi to the general public. Also, the participants of the mycoblitz diligently filled out the field labels with information on location, habitat, and substrate. This is hardly done for the fungus fair. Since 1997 NAMA, the North American Mycological Association, has kept good records of the species found during its annual forays. Collections of each species—known as vouchers—are photographed and kept in the Field Museum in Chicago. The data are entered into a database, which you can find on-line. Although the number of forays is still small, the sites are distributed over the country and the data are now easily accessible.
Naturally there is overlap in the species fruiting every year at the time of the fair, but in general there is huge variation in the lists. Only a few species at the fungus fairs are found in many locations. This phenomenon is very common in any inventory, whether it covers a whole country or just a small area; there are a few dominant species, found all the time and everywhere, and a huge number of species recorded only once or in one spot. The abundant ones at the Point Reyes Mycoblitz were members of the Gymnopus dryophilus group, which showed up everywhere (and also appeared a day later in several foray sites for the Yuba Watershed Institute event in North Columbia), and Inocybe sororia which you seemed to see whenever you put your basket down.
The absence of mushrooms (the fruitbodies) does not necessarily mean that the species is absent, but when we find the fruitbody we have foolproof evidence that the species is there. Other than conks, most fruitbodies have a very restricted lifespan, ranging from a few hours for fragile inky caps to perhaps a month or two for Sarcoscypha and other fleshy ascomycetes. To be in the right spot at the right time is a challenge, as every bolete hunter knows. We would like to know the size of the individual organism (the number of fruitbodies is no indication of the size of the below-ground part—many small apple trees can produce as many apples, as one old big trees) and its age. For both these aspects of fungal life we know very little, and that only for a few species in a few settings.
A meticulous Swiss study was set up to monitor the mycoflora in one forest. For 21 years, every week from May to December, the same protected plots were visited, and all fruitbodies were counted and identified to species. Individual fruitbodies were painted to avoid double counting. During all those years around 400 species were found, but only eight showed up consistently every year. Up to the end, the list was still growing with new species.
Since 1980 a mammoth recording project in the Netherlands has collected around 1.4 million meticulously identified and thoroughly documented records. Provided they meet its standards all collections are welcomed, whether they come from forays and mushroom weekends, systematic plot studies or are accidental finds. Even data from herbaria and the mycological literature have been incorporated into the database—the oldest record is from 1808. Each year new species are still added. With a totally different approach than the Swiss study, this project has produced distribution and temporal data on a national scale.
The big question is of course; how long and how intensively do we have to inventory mushrooms in a certain area to get a complete list of the species present? Are fruitbody inventories the best way to seek an answer, or are there other, molecularly-based methods which are more appropriate?
Today, it is indeed possible to do a large-scale sequencing project—just sample soil, grind it up, extract DNA out of the mess, and sequence every tiny bit. Then you compare the sequences with those in databases. When this was done in two plots in Duke Forest (NC), 412 sequence types for fungi were found. This is quite impressive, especially when compared with the outcome from the long-term and intensive Swiss study. This approach does have its limitations; not all species will have sufficient DNA and not all will do well with standard methods, while the current databases are under populated and of uncertain reliability. After all, putting a name on a sequence can only be done when someone has already identified it (correctly!) and provided a sequence for comparison. There is discussion about the feasibility of molecular “bar-codes” but, for the moment, the process still rests on traditional taxonomy, a skill slowly acquired.
Of course, another limitation of the molecular approach is that it does not say anything about fruiting patterns. Fruiting is important as an indication of the state of the environment. When forests which are naturally low in nitrogen get more and more of it, because of human activities, the trees eventually reduce the amount of carbohydrates they pass on to the ectomycorrhizal fungi, and this may prevent them from forming fruitbodies. In other words, changes in the environment change what we see above ground. Also, there will be a change in species composition, but that will also show up in studies of the underground world.
Similar studies to the Duke Forest inventory have been done for ectomycorrhizal fungi in one forest in the southern Sierra Nevada by sampling root tips which were ectomycorrhizal (i.e. they are covered by a fungal mantle), and comparing the sequences from those root tips with fruitbody sequences. There, 100 species were found, all growing with Abies sp., and one fifth of the species form hypogeous fruitbodies which are hard to find, when you just walk through and do not rake. So here we see a clear advantage of the molecular method. It should also be kept in mind that these dry forests do not produce fruitbodies on a regular basis.
All these data are extremely valuable, whether they have been collected by accidental encounters with fruitbodies, or systematic inventories of all substrates and careful matching of DNA sequences. They reveal the fungal diversity at a certain time and a certain place. Changes can be tracked with these data as reference. Distribution data can be inferred, management measures can be tracked by inventorying at a later date etc. etc. The data even gain value when they are easily accessible to others; here the NAMA data base, as a national project, sets a great example.
The data from the Swiss studies have been used for comparison with data collected in a similar way from nitrogen enriched plots, and from plots where the mushrooms were systematically picked. To reassure everybody, the conclusion is that even such picking does not influence in any way the formation of fruitbodies through the years. Trampling the forest floor, on the other hand, does have a negative effect on the fruiting. But, when the area is fenced off to keep people out, next year the mushrooms fruit normally again. The Dutch data have clearly shown human effects on a larger scale, notably that many ectomycorrhizal species have declined dramatically, due to nitrogen and acid deposition, and that, by contrast, many wood chip fungi have appeared and are flourishing.
So, give your mushrooming that extra value by recording and keeping specimens, by participating in mycoblitzes, collecting for the fair, and going to national forays!
Some further reading:
- Egli, S., M. Peter, C. Buser, W. Stahl & F. Ayer, 2006. Mushroom picking does not impair future harvests—results of a long-term study in Switzerland. Biological Conservation 129: 271-276. (PDF)
- Izzo, A., M. Meyer, J.M. Trappe, M. North & T.D. Bruns, 2005. Hypogeous ectomycorrhizal fungal species on roots and in small mammal diet in a mixed-conifer forest. Forestry science 51: 243-254. (PDF)
- Mueller, G.M., G.F. Bills & M.S. Foster (eds), 2004. Biodiversity of Fungi.
- O’Brien, H., J.L. Parrent, J.A. Jackson, J.-M. Moncalvo & R. Vilgalys, 2005. Fungal community analysis by large-scale sequencing of environmental samples. Applied and Environmental Microbiology 71: 5544-5550. (Abstract)
- Straatsma, G., F. Ayer & S. Egli, 2001. Species richness, abundance, and phenology of fungal fruit bodies over 21 years in a Swiss forest plot. Mycological Research 105: 515-523. (Abstract)