XVI International Botanical Congess

The consideration of lichens as long-lived organisms does not apply to those inhabiting leaves of vascular plants in tropical rainforests. Leaves represent a highly ephemerous substrate, they are mostly shed after 1-3 years. Foliicolous lichens are not particularly fast-growing, but their reproduction takes place soon after their establishment, often within 6-12 months, and mature thalli rarely exceed 20 mm. These tiny organisms are abundant in the forest under storey which is characterized by high temperature and low light intensity and requires low photosynthetic compensation, achieved by reduced thallus morphology. Damage to the leaf would prejudice successful reproduction by increasing the probability of parasite attack. and leaf shedding. Therefore, foliicolous lichens adhere by mucilage and are easily detached by mechanical forces. In spite of these shortcomings, they develop a remarkably high diversity, particularly on the small scale. Up to 300 of the 550 species known world-wide are found at a single site, and 50-80 species, i.e. 10-15% of the world=s diversity, are conserved on single leaves! Foliicolous lichens are therefore appropriate for studying the mechanisms that maintain high vegetative diversity in tropical rainforests. They also are excellent indicators of microclimate dependent microsites and anthropogenic disturbances.