Lichens & Algae
Lichens are a type of fungi which have evolved a specialised mode of nutrition: symbiosis with a photosynthetic partner. Lichens are primary colonisers in plant successions and are found, in NZ, in a wide variety of habitats from sea level to the summit rocks of our mountains. Lichen is not a single organism the way most other living things are, but rather it is a combination of two organisms which live together intimately. Most of the lichen is composed of fungal filaments called the 'mycobiont', but living among the filaments are algal cells, usually from a green alga or a cyanobacterium called the 'photobiont'.
In many cases the fungus and the algae which together make the lichen may each be found living in nature without its partner, but many other lichens include a fungus which cannot survive on its own -- it has become dependent on its algal partner for survival. In all cases though, the appearance of the fungus in the lichen is quite different from its morphology as a separately growing individual.
The body (thallus) of most lichens is quite different from those of either the fungus or alga growing separately, and may strikingly resemble simple plants in form and growth. The fungus surrounds the algal cells, often enclosing them within complex fungal tissues unique to lichen associations.
Lichens are poikilohydric, capable of surviving extremely low levels of water content.
Many lichens reproduce asexually, either by vegetative reproduction or through the dispersal of diaspores containing algal and fungal cells, some photos lichens.
Lichens are informally classified by growth form into:
Crustose (paint-like, flat),
Squamulose (consisting of small scale-like structures, lacking a lower cortex)
Gelatinous lichens in which the cyanobacteria produces a polysaccharide which absorbs and retains water.
Squamulose lichens have scale-like lobes called squamules that are usually small and overlapping.
Crustose lichens are found on all substrate types: bark, soil, rocks, other lichens, mosses, with variations or stratification of such habitats.
Identification for many species requires chemical tests and examination of tiny spores, making field identification next to impossible for many species, particularly the crustose species. Lichens grow on just about every substrate: bark, soil, rocks, other lichens, mosses, with variations or stratification of such habitats.
Foliicolous lichens: (Lichens colonising leaf surfaces).
Terricolous: Soil lichens
Saxicolous: Rock lichens.
Corticolous: Bark lichens
Lignicolous: lichens growing on non-living wood [lignum]
Terricolous and saxicolous lichens help control erosion by holding soil and rock particles together. Lichens also provide habitat and food for a number of wildlife, mostly invertebrates, such as tartegrades.(Tiny segmented animals with eight legs). Many native peoples use lichens for sources of dye.
Algae (Trentepohlia spp)
Cladinia (Reindeer lichens)
Cladonia coccifera (Red pixie cup)
Cladonia floerkeana (Devils matchstick)
Cladonia pyxidata (a cup lichen)
Cladia retipora (Coral lichen)
Ramalina geniculata (a tufted lichen)
Usnea lichens (Beard lichens)
Xanthoria elegans (Elegant sunburst lichen)
Xanthoria parietina (Maritime sunburst lichen)
Some more lichen species
Lichen on rock
Black lichen on tree trunk
Lichen on dead branch
NZ Lichens by W.Martin & J. Childs
The Forest Carpet by B & N Malcolm