Foliicolous lichens and the phyllosphere
A microcosmos in tropical rain Forests
Quartier Vallée 1 - Chemin de la Vallée, 4
4000 Liège (Sart Tilman) See the map
Dans le cadre de sa venue à Liège, le Dr. Robert Lücking (Botanischer Garten, Freie Universität, Berlin) donnera une conférence en anglais intitulée : "Foliicolous lichens and the phyllosphere: A microcosmos in tropical rain Forests".
Foliicolous lichens inhabit the surface of living leaves of vascular plants. Together with bryophytes, green algae, cyanobacteria, superficial fungi, bacteria, and invertebrates (psocids, mites, insect larvae, nematodes), they constitute the phyllospere, a diverse miniature ecosystem best developed in tropical rain forests. Notable features of foliicolous lichens include their short life cycles, in combination with often diminutive thalli, fixed to the substrate by a thin layer of mucilage, as well as specialized reproductive structures. Many species are believed to be widely and even pantropically distributed, presumably reflecting long-distance dispersal or high phylogenetic age. However, molecular phylogenetic studies suggest a high level of endemism and a high degree of cryptic speciation. There is a strong decline of species richness with increasing altitude and seasonality, most taxa being confined to lowland rain forests. A single leaf the size of a hand may support up to 50 species and more than 300 species may occur within a single locality. This impressive small-scale diversity, together with the high community dynamics, provide an excellent model to investigate mechanisms that maintain high small-scale diversity in tropical ecosystems, such as the Huston-Connell intermediate disturbance model and density-dependent feedback interactions. Within the rain forest, three associations of foliicolous lichens can be distinguished: in the shady understory, in natural light gaps, and in the canopy. The nature of the phorophyte has little influence on species composition but affects diversity. Closely related species are often ecologically equivalent and co-occur side-by-side on the same leaves, a phenonemon possibly explained by an evolutionary species pump mechanism. Due to their sensitivity to abiotic factors and environmental changes, foliicolous lichens can be used to indicate microclimatic parameters, as well as the degree of disturbance of a rain forest site. Species of certain genera, such as Badimia, are excellent indicators of well-preserved rain forest.
Robert Lücking est un expert mondial des lichens, en particulier dans les milieux tropicaux. C'est sans doute le plus grand spécialiste des lichens foliicoles, des organismes fascinants mais méconnus qui forment des écosystèmes miniatures à la surface des feuilles dans les forêts tropicales.