Lichen symbioses are stable mutualistic associations in which eukaryotic algae and/or cyanobacteria provide carbohydrates for heterotrophic fungi. This represents a highly successful nutritional strategy, which allows symbiotic organisms to greatly expand their ecological ranges. During their diverse evolutionary history lichen symbioses have evolved a plethora of different growth forms and habitat ecologies, and today lichens are found in most terrestrial ecosystems from the tropics to polar regions. Generally, lichen fungi (mycobionts) are highly selective toward their phototrophic symbionts (photobionts).
The application of modern molecular methods to lichen systematics has recently revealed unprecedented levels of genetic diversity in many lineages of lichen-symbiotic organisms. While some groups of boreal and temperate macrolichens are relatively well known, very little is still known about tropical lineages and hundreds of new lichen species have recently been identified from the Neotropics alone. Our knowledge of African lichens is particularly poor and mainly comes from the pre-molecular era. The DNA-based methods have clearly shown that many traditional species concepts and nomenclature need critical updating and revision, but such methods have so far only been applied to very few lichen specimens collected from scattered locations within tropical Africa.
The specific research objectives of this project are 1) to provide the first account of lichen symbiont diversity in tropical mountains, including surveys (a) of remnant forest patches in a global biodiversity hot spot and (b) along a steep natural climatic gradient on the slopes of a high tropical volcano; and 2) to elucidate the effects of human induced environmental change to lichen symbiotic organisms, including the effects of (a) dwindling and fragmentation of indigenous forests, (b) expansion of agricultural and other disturbed ecosystems, and (c) changing climate studied along a naturally existing gradient.
The study areas of this project are located in tropical mountains of Kenya and Tanzania. Taita Hills in southeast Kenya is part of a well-known biodiversity hotspot and home to a high diversity of endemic species, while the more recently formed dormant volcano Mt. Kilimanjaro in the northeast Tanzania provides pronounced altitudinal zonation of vegetation on its slopes. Currently these African montane forests are threatened by human activities, including land clearing, firewood collection, introduction of foreign species, and recently also the effects of climate change. Still the remaining cloud forests function as ‘natural water towers’ for the semiarid plains around the mountains, and also epiphytic lichens play their own role in maintaining this ecosystem service.
