“Lichens are fungi that have discovered agriculture” — lichenologist Trevor Goward
What Are Lichens
A lichen looks like a single organism, but it is actually a symbiotic relationship between different organisms. It is composed of a fungal partner (mycobiont) and one or more photosynthetic partners (photobiont). The photosynthetic partner is generally green algae or cyanobacteria. There are about 13,500 species of lichen on the Earth.
The algae provide nutrients, as they contain the pigment chlorophyll, which it uses during photosynthesis to produce carbohydrates the same way as green plants do. Thus the fungus obtains nutrients from the algae, the fungal tissue in turn provides shelter for the algae allowing it to grow in harsh conditions such as rock surfaces where it would otherwise be destroyed.
Lichens cover 6-8% of the Earth’s land surface, and more than 18,000 species of lichens have been identified worldwide. Theres been 1765 species recorded from NZ in 366 taxonomic groups, making up approximately 10% of the worlds known population.
Lichens are found in a wide range of habitats from the branches of tress to fence rails and rock and stone.
They are known from the Arctic and Antarctic and all regions between.
They have even survived 15 days exposed to the vacuum and near absolute zero (-273 deg. C) temperatures of space via a ride on a Soyuz rocket in 2005. When they returned to earth they were found to still be perfectly healthy.
To assist their survival in such inhospitable conditions, lichens are able to shut down metabolically during periods of unfavourable conditions then with the appropriate amount of light and moisture lichens will continue to grow.
Another method that helps with there survival is that lichens can produce an arsenal of more than 700 unique biochemical compounds that serve to control light exposure, repel herbivores, kill attacking microbes, and discourage competition from plants.
Reproduction
Lichen are capable of both sexual and asexual reproduction
Asexual Reproduction
Most lichens are very brittle when dry, some simply relying on breakage’s of the thallus to produce fragments that are dispersed by wind, rain, or insects and birds.
Lichen-forming fungi can reproduce sexually or asexually thus they have a number of different methods of reproduction.
They can also produce soredia, these are bundles of fungal filaments that are produced inside the lichen and rupture through the thallus, they then blow away to produce a new lichen.
They can also produce isidia, these develop on the surface of the lichen, they then break of and like soredia blow away to colonise new areas.
Sexual Reproduction
This is a far more complex process, descriptions of it involve many big words and concepts that are too complex to try and delve into.
Basically the fungal part of a lichen can reproduce sexually. The trick is that the new fungus that grows has to find an algal partner to form a new lichen. This happens by chance, the fungus produces a spore that is carried by the wind and water to a new site to germinate somehow it then has to find the right algae to become a new lichen.
In the lichens world sexual reproduction is no where near as successful as asexual reproduction.
Where to find them at Travis
On your wanders around Travis have a look on the trees and fence railings. The bird hide track is a good place.
You’ll find the grey green Ramalina with little “domes” on its surface, look closely and you will find 4 species of Ramalina. Groups of Usnea of which the aptly named old mans beard is a member.
Brightly coloured Golden-eye lichen and golden yellow Xanthoria add splashes of colour. If your lucky you may even find a Sexy pavement lichen.
Lichen are at their best after a rain they come alive and their colours shine.