Questions

Question-
To what extent are fungi species geographically localised. I ask because it would seem likely that their spores could be carried around the world on the winds.

Spores travel far — but not every spore succeeds

It's true that fungal spores are microscopic and incredibly numerous — some species release billions of spores, and a small proportion do travel enormous distances, crossing oceans and continents on high‑altitude winds. In that sense, the world really is their oyster. But — and this is the crucial "but" — arriving somewhere is not the same thing as surviving and growing there.

The "Everything is everywhere, but the environment selects" debate

For decades, biologists thought microbes and fungi were basically everywhere, and only stopped you seeing them where conditions didn't suit. We now know this is only partly true:

• Many common, wind‑dispersed species really are very widespread — things like the Shaggy Ink Cap or Common Puffball turn up across continents. Their spores are abundant, tough, and find suitable habitat readily

• But a surprising number of fungi are genuinely restricted — some only grow on one particular tree species, in one type of soil, at the right altitude and rainfall, and with the right partner trees nearby. Even if spores arrive, if the specific conditions aren't exactly right, they simply cannot establish

Why so many fungi stay local

Several things limit them:

• Specific partnerships: Mycorrhizal fungi can only survive by hooking up with the exact right tree or plant — spores can land on the wrong continent all day long; without that partner, they die

• Habitat specialism: Some fungi need ancient woodland, undisturbed peat, or particular rock types — habitats that themselves are patchy and isolated

• Spores aren't invincible: Most spores don't survive the journey — UV radiation, extreme cold, and dry air kill them high up. Only a tiny fraction travel thousands of kilometres intact

• Slow colonisers: Even when spores do arrive successfully, many fungi — especially those forming long‑lived partnerships — spread only very slowly once established

What this means in practice

• Generalist saprotrophs that eat dead material are the most widespread — their spores travel well and they don't need a partner

• Host‑specific mycorrhizal fungi are the most likely to be genuinely local — some are even found only on single mountains or in one valley system

• Ancient woodland indicator fungi can be remarkably stationary — some have barely moved since the last Ice Age, even though their spores could theoretically go much further

So the short answer is: spores can go almost anywhere, but a fungus only stays where the whole ecosystem welcomes it. Wind gives them the ticket — but the local environment decides if they get to stay. 

Question -
Are fungal mycelia and hyphae which exist out of the light particularly susceptible to ultraviolet light, but the fruiting bodies (Toadstools)are not, as they have to be in the open? Following on from this question can UV be used to cure fungal diseases such as athletes foot, trench foot or psoriasis (which maybe has a fungal component?) ?

 Mycelium vs. Fruiting Bodies — your intuition is partly right

Mycelium (the hidden, feeding network):

• This is indeed far more vulnerable to UV damage. It grows in the dark — underground, inside wood, or deep within soil — and has evolved with almost no exposure to direct sunlight. Its thin, delicate threads have little or no protective pigmentation, so UV radiation damages its DNA quickly, killing cells or stopping growth

• Because it's made of fine, spreading threads, UV can penetrate and damage it quite effectively

Fruiting bodies (toadstools):

• These are more resistant — but not immune. They often do grow in the open, and many have protective adaptations: thick outer layers, melanin or other pigments in their surface cells that act like a natural sunscreen

• However, UV will still damage them given enough time — they're just built to survive moderate exposure, not to be indestructible

The key difference: It's not that fruiting bodies need UV protection and mycelia don't — it's that mycelia never evolved to cope with it, while fruiting bodies are structured to survive just enough sunlight to release their spores before being damaged.

Can UV light be used to treat infections?

Athlete's foot and fungal skin infections — YES, sometimes

UV light — particularly UVC (the germicidal wavelength around 254nm) — is very effective at killing fungi. It works by breaking their DNA so they can't reproduce. Medical devices using UVC are sometimes used as an additional treatment for stubborn fungal skin infections like athlete's foot, alongside creams and powders.

BUT — important limitations:

• UV light cannot penetrate into the nail bed or deep into skin tissue — so it works best on surface infections

• It won't kill fungus deep in the dermis

• Over-exposure damages your own skin cells and increases cancer risk, so it must be used carefully and at the right dose

Trench foot — NO, it's not a fungal disease

Trench foot is caused by prolonged exposure to cold and wet conditions, not infection. It damages blood vessels and nerves in the feet. UV light would not help at all — the treatment is warmth, drying, and rest.

 Psoriasis — complicated

Psoriasis is not caused by a fungus. It's an autoimmune condition where your skin cells grow too quickly. Interestingly, UVB light therapy IS a standard, effective treatment for psoriasis — but it works by calming the immune system and slowing cell growth, not by killing anything. The idea that psoriasis might have a fungal cause is an old theory that's generally not supported by modern research, even though antifungal treatments are sometimes tried experimentally.