Subproject E10

Dr. Manfred Kraemer, Zoological Research Institute and Museum Alexander Koenig, Adenauerallee 160, 53113 Bonn, Germany

Effects of rainforest fragmentation on plant-insect and plant-pollinator interactions in Kakamega forest

Summary
Almost 100 percent of the flowering plant species in tropical forests are pollinated by animals, with bees and birds being among the most important pollinators. The conversion of formerly continuous forests into small-scaled fragments is assumed to lead to a disruption of mutualistic pollinator-plant interactions. Consequently, certain species of plants and pollinators may not survive in fragments. In the long term, this may lead to extinction cascades due to the web-like structure of plant-pollinator systems, and thus cause a severe collapse of biodiversity. Comparing samples from different-sized forest fragments to continuous forests, we want to analyse the effects of habitat fragmentation on the diversity and abundance of pollinators showing different grades of mobility. The main focus of this study will be the consequences of such alterations on the pollination success, that is, plants´ seed production. The results are to be discussed with reference to the degree of specialization of plants and pollinators, and refering to the different abilities of the pollinating agents to disperse and thus to colonize fragments.

Methods
The study will concentrate on plants which are abundant enough to allow statistically correct data sampling. Most methods to be used are quite simple and non-invasive, like observations on pollinator behaviour (flower visits), counting of pollination events, counting of flowers and fruits, sampling and measuring of nectar and pollen. Insect sampling will be done using malaise traps, colour pans, and insect nets.

Dr. Thomas Wagner, Wolfram Freund Zoological Research Institute and Museum Alexander Koenig, Adenauerallee 160, 53113 Bonn, Germany

Effects of fragmentation and degradation of Kenyan forests on the diversity structure of leaf beetle communities (Coleoptera, Chrysomelidae)

Summary
This study project will focus on the effect of man-made change on the biodiversity of insects in Kakamega Forest and, lateron, on forests at Mt. Kenya. Assemblages of canopy dwelling species of phytophagous beetles will be analysed quantitatively in primary forests, secondary forests and adjacent forest fragments. Due to their species richness and abundance leaf beetles (Chrysomelidae) represent an excellent target group as one of the dominating groups of arthropods in tropical forests with a key position between plants and first order consumers. Furthermore, the material sampled will allow to analyse the degree of specialisation of phytophagous insects in tropical systems, and the influence of habitat change, habitat structure and abiotic components. On that account, leaf beetles form an excellent indicator group for the evaluation of man-made habitat changes and for developing concepts for a sustainable use of tropical forest ecosystems.

Methods
The studies shall be carried out at two different sites in Kenya, at Kakamega Forest and at Mt. Kenya. At both sites, characteristic tree species should be investigated in standardized plots of primary and secondary forests, and adjacent forest fragments. Material will be collected using the tree fogging method which allows a quantitative allocation of leaf beetles adaequate for statistical analysis. At all study sites remaining primary forest plots are available next to secondary forests, differently sized forest fragments in a forest-savanna-mosaic at the forest edges. With respect to our previous studies, the tree Teclea nobilis (Rutaceae) will be selected for Kakamega Forest and the montane rain forest at Mt. Kenya, and Podocarpus latifolius (Podocarpaceae) at Mt. Kenya. The latter species is distributed along a gradient of more than 1000 metres, which will allow first data on changes along an altitudinal gradient.