Biology
Collema dichotomum - section of thallus showing medulla in centre and cyanobacteria layers below the upper and lower surface.
Lichens are the symbiotic type of specialised fungi which form their highly structured thalli only when growing together with a compatible algal partner.
Like many other lichenised fungi the river jelly lichen develops disk-like fruiting bodies, the apothecia. In these structures it produces spores, which are its principal mean of dispersal. However, in many populations of Collema dichotomum, especially in the southern part of its distribution range, apothecia are poorly developed. We currently do not know if this phenomenon poses a risk for the survival of this lichen. The question arises whether fragmentation of the thallus contributes to the dispersal of the species in the wild.