Lichens primarily spread through fragmentation, where small pieces of the lichen body are dispersed.
Lichens have several strategies for dispersal, although sexual reproduction via fungal spores is less common. The most prevalent methods involve asexual reproduction, ensuring that both the fungal and algal (or cyanobacterial) partners are transferred together, which is essential for lichen survival.
Here's a breakdown of lichen dispersal methods:
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Fragmentation: This is the most common method. Small fragments of the lichen, containing both the fungal and algal components, break off and are dispersed by wind, water, or animals. If these fragments land in a suitable environment, they can begin to grow into new lichens.
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Soredia: Some lichens produce specialized structures called soredia. Soredia are powdery propagules consisting of a few algal cells surrounded by fungal hyphae. These are easily dispersed by wind and represent a more efficient method of asexual reproduction than simple fragmentation.
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Isidia: Similar to soredia, isidia are small, detachable, finger-like or cylindrical outgrowths on the lichen's surface. They contain both fungal and algal cells and can develop into new lichens when dispersed.
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Spore dispersal (less common): While the fungal partner can produce spores through sexual reproduction, this method is less effective for lichen dispersal. The spores need to land in an area where the appropriate algal partner is present, making successful lichen formation less likely. This reliance on finding a compatible alga/cyanobacteria makes dispersal less efficient than fragmentation or soredia.
Therefore, lichens predominantly rely on asexual methods that guarantee the dispersal of both fungal and algal partners, essential for establishing a new lichen thallus.
