Classification of Lichens

Lichens are classified based on their growth form, habitat, internal structure , and fungal partner.

Lichens actively contribute to ecosystems through their unique growth forms, specialized habitats, and reproductive strategies, demonstrating their ecological importance.

Classification Of Lichens

Lichens can be classified into different types based on their growth form, habitat, internal structure, and fungal partner.

Based on Growth Form

There are following classes of lichens based on their growth form:

Crustose Lichens

Crustose lichens have a flat, thin, and crust-like appearance without distinct lobes. They typically grow closely attached to stones, rocks, tree barks, and trunks. Examples include Haematomma puniceum and Graphis scripta.

Foliose Lichens

Foliose lichens are visually attractive and have a leaf-like structure. They are flat, broad, and often have crinkled and twisted edges. Foliose lichens possess a distinct upper and lower surface and are usually found attached to rocks and twigs using rhizoids. Cetraria, Cladonia, Parmelia, and Xanthoria are common examples of foliose lichens.

Fruticose Lichens

Fruticose lichens are characterized by their thin and freely branched growth form. They form larger and more attractive structures that stand out from tree branches, foliage, and rocks. Examples of fruticose lichens include Cladonia, Ramalina, and Usnea.

Based on Habitat

Here are the classes of lichens based on their habitat:

Lignicolous

These lichens inhabit woodlands and grow on decaying wood or dead tree branches.

Corticolous

Corticolous lichens grow on the bark of trees.

Saxicolous

Saxicolous lichens are found growing on stones or rocks.

Marine

Marine lichens grow on siliceous rocks near the shores of the sea.

Freshwater

Freshwater lichens grow on hard siliceous rocks, particularly in freshwater environments.

Terricolous

Terricolous lichens grow on the soil and are often referred to as terrestrial lichens.

Based on Internal Structure

Here are the types of lichens Based on Internal Structure:

Heteromerous Lichens

Heteromerous lichens have a distinct layering in their thallus, consisting of different fungal and algal layers.

Homoiomerous Lichens

Homoiomerous lichens lack a clear layering in their thallus and have a more uniform structure throughout.

Based on Fungal Partner

Here are the types of lichens Based on Fungal Partner:

 Ascolichens

In this case, lichens belong to Ascomycota Majority of the lichens belong to this group. It is further divided into two groups on the basis of fruiting bodies. These groups are Gymnocarpeae and pyrenocarpea.

Ascolichens have an ascomycete fungus as their primary fungal partner involved in the lichen symbiosis. They reproduce sexually using ascogonia and spermogonia.

Basidiolichens

Basidiolichens are a type of lichen that is a member of the Basidiomycota, which is a smaller group of lichens than the Ascomycota.

Basidiolichens have a basidiomycete fungus as their primary fungal partner. They reproduce sexually using basidia and spermatia.

Hymenolichens

Hymenolichens also have a basidiomycete fungus as their primary fungal partner. They form specialized reproductive structures called hymenial basidia, which produce basidiospores.

Species Of Lichens

The lichens are a combination of a fungus with algae or cyanobacteria. It has a very different form (morphology), physiology, and biochemistry than the parts growing by themselves. Thus lichens may be called species. But they are not single species like plants and animals. Lichens are combinations of species from two or three different biological kingdoms.

Thus they have no common lineage. By convention. lichens have the same scientific name as the fungus in them. They are not classified according to the species of the algae or cyanobacteria growing in them. The algae or cyanobacteria have their own, unique, scientific name. There are about 20,000 known species of lichens. Some lichens have the ability to reproduce sexually. But they are still taken as specie.

Common Naming Of Lichens

Common names for lichens may contain the word moss like Reindeer moss and Leeland moss. The lichens may superficially look like and grow with mosses. But lichens are not related to mosses or any plant. Lichens do not have roots that absorb water and nutrients like plants. Instead, they produce their food from sunlight, air, water, and minerals in their environment. Some lichens may grow on plants. Such lichens do not live as parasites. They use the plants only as a substrate.