Author: Stefan Blaser
In the SwissFungi distribution atlas, a heart can be found in the spruce needle cast (Lirula macrospora). The background is not the love for this fungal species. In addition to presenting this "courageous" fungus, this whole story is intended to show why the actual distribution of fungal species is often not visible in the atlas.
The SwissFungi atlas is an important source for the public to estimate the frequency and distribution of fungi in Switzerland or to obtain ecological information on the species (phenology, choice of substrate, etc.). It should always be clear that the apparent distribution is often misleading. This phenomenon in available data is referred to as "bias", which can be translated as "distortion". This bias in the distribution data is easy to explain, as most of the data in SwissFungi does not come from systematic studies, but from voluntary reporters with different places of residence and different preferences with regard to the mushrooms studied. This often results in completely false pictures of the distribution of species.
If we take a look at the distribution of the holly dumbbell mushroom(Vialaea insculpta) (Fig. 2), we can see that the species apparently feels particularly at home in the canton of Bern (which the author can certainly understand). The fungus is very inconspicuous: the fruiting bodies, which are a maximum of 0.5 mm (!) in size, grow sunken into thin, dead branches of the holly (Fig. 3). Hobby mycologists must therefore first be aware of the species in order to search for it. On the distribution map we can therefore see the hunting ground of those hobby mycologists who have the relevant knowledge and sufficient interest to pursue the fungus. Incidentally, microscopists are rewarded with the very special spores of the fungus (Fig. 4).
However, this is not about the holly dumbbell spore ball fungus, but about playing a little more mischief with this data distortion. A little over a year ago, I asked myself the question: Is it possible to create a figure, for example a heart, using found points for a certain type of mushroom?
For this I needed a free "drawing area" in my hunting area (no finds in the Emmental) and it still had to be a very common type of mushroom (I don't like searching...). The spruce needle scab(Lirula macrospora) fulfilled these conditions. Now I just had to define 14 find squares and inspire my family for more or less nice weekend trips... (Thanks for your cooperation!). In any case, the final result can be seen in Fig. 5 (for "eternity") or here (ephemeral...).
This "work of art" should soon be a thing of the past - thanks to the numerous finds reported. For this reason, the target fungus species is presented in detail below.
Spruce needle cast (Lirula macrospora (R. Hartig) Darker)
Macroscopic description:
Infested, light brown needles sit singly or in small groups on green needled twigs. On the underside of infested needles, up to 8 mm long, shiny black, narrow beads can be seen. In very humid weather or in the humidity chamber at home, the bulges open in a lip shape and a whitish-colored fruiting layer (apothecia disc) becomes visible. Characteristic of infested needles is a clear, black demarcation line at the base (growth point).
Microscopic description:
Spores hyaline, smooth, acicular, with thick mucilaginous sheath, 75-86 x 3.0-3.5 µm (measurement without mucilaginous sheath). Asci cylindrical, but mostly slightly bulbous (elongate spindle-shaped; fig. 6). Paraphyses filamentous, slightly thickened at the front, surrounded by a thick mucilaginous sheath similar to the spores. As a result, the fruit layer shrinks considerably when it dries out and swells accordingly when wet.
Ecology (according to Butin 2019): The infested needles die off in the year of infestation and turn a conspicuous light brown. At the base, the fungus forms a black line of phenolic deposits, which prevents the needle from being shed. In the following year, an elliptical conidial fruiting body forms (not yet observed by the author). Only a few months to 1 year later, the elongated, sexual fruiting bodies described above form. During periods of rain, the ascospores can be spread and infect fresh needles. The needle disease is usually only mild, but can become more severe in extreme weather conditions. Especially on young spruce trees in the forest interior, somewhat more severe infestations may occasionally be visible on the lower branches (own observation).
Distribution: The species probably largely follows the distribution of spruce as a host plant and is hardly ever absent from a spruce stand in Switzerland.
Fir needle scab (Lirula nervisequia (DC.: Fr.) Darker) - Another species with a lot of free "drawing area"
For the sake of completeness, it should also be pointed out that there is a closely related species, the fir needle scab(Lirula nervisequia), on the silver fir and its needles. The appearance and the fruiting bodies on the underside are very similar. According to Butin 2019, the spores are slightly longer (57-90 µm, according to Butin 2019), which I could not reproduce in my own measurements. My measurement showed 65 - 70 x 4.0 - 4.5 µm, even slightly shorter but slightly wider spores. However, the spores may not have been fully ripe. In any case, the species can be distinguished by the choice of host.
Literature:
Butin, Heinz. 2019. Krankheiten der Wald- und Parkbäume. Stuttgart (Hohenheim): Ulmer, 2., aktualisierte Auflage.