Acarospora thamnina is a species of crustose lichen belonging to the family Acarosporaceae. It is a widespread and relatively common lichen, typically found growing on siliceous rocks. Like all lichens, it is a symbiotic organism composed of a fungus (mycobiont) and one or more photosynthetic partners (photobionts), in this case, green algae.
Classification
- Kingdom: Fungi
- Phylum: Ascomycota
- Class: Lecanoromycetes
- Order: Acarosporales
- Family: Acarosporaceae
- Genus: Acarospora
- Species: A. thamnina
Description Acarospora thamnina forms a crustose thallus that is tightly adnate (closely attached) to its substrate. The thallus is typically a yellowish-green to dull greenish-grey color, sometimes appearing quite pale. It can be continuous or minutely cracked (areolate), and the surface is often smooth or slightly granular. The margins of the thallus are usually indistinct.
The reproductive structures, called apothecia, are immersed within the thallus or slightly emergent. They are typically numerous, small, and often irregular in shape, ranging from rounded to angular. The apothecial discs are usually darker than the thallus, often brown to reddish-brown or blackish. A key characteristic for the genus Acarospora is the production of numerous, very small, ellipsoid spores within each ascus (spore sac), often 100 or more per ascus, a feature not common in many other lichen genera.
Habitat and Distribution This species primarily inhabits exposed, non-calcareous (siliceous) rocks, such as granite, quartzite, and sandstone, in various environments. It can be found in sunny, open habitats, often in association with other saxicolous (rock-dwelling) lichens. Its distribution is quite broad, occurring in temperate and boreal regions across North America, Europe, and parts of Asia. It is particularly common in mountainous and coastal areas where suitable rock substrates are prevalent.
Ecology As a saxicolous lichen, Acarospora thamnina plays a role in the initial stages of soil formation by contributing to the weathering of rock surfaces through the secretion of organic acids. It is a resilient organism, capable of tolerating harsh conditions including desiccation and extreme temperatures, which allows it to thrive in exposed rocky environments. Its presence can indicate long-term stability of the rock substrate.
Distinguishing Features Acarospora thamnina can be distinguished from other Acarospora species by a combination of its yellowish-green thallus, typically immersed and often angular apothecia with dark discs, and its preference for siliceous rocks. Differentiation from closely related species often requires microscopic examination of spore characteristics and sometimes chemical spot tests, though these usually yield negative results (K-, C-, P-) for the thallus of A. thamnina.