Tropical Diversity Studies

Sustainable exploitation and efficient management of a tropical rain forest requires a thorough insight into the structure and dynamics of this ecosystem. The stability of an ecosystem is largely determined by the intraspecific genetic diversity of the different interacting species, because this diversity holds a reservoir of potential adaptations to changing environmental conditions. Although the measurement of visual traits reveals the existence of genetic variation, it does not give a good indication of the structure of diversity within populations or how this diversity is maintained.7 Progress in molecular biology has recently offered new, more powerful tools based on the polymerase chain reaction. DNA analysis visualizes the genetic information directly, independently of environmental factors, tissue or developmental stage. For this reason, molecular techniques are used more and more for the study of genetic structures of tropical ecosystems. Applications include the use of molecular markers for species identification and for the development of general sets of molecular markers with which to assess genetic diversity.

The Department of Plant Genetics (University of Gent, Gent, Belgium) has initiated a collaboration project with Silvolab (French Guyana) and INRA-Bordeaux (France) in order to introduce and adapt DNA marker technology for tropical forest studies. The main objective of the project is to describe the levels and distribution of genetic diversity in a selected number of tropical tree species that display contrasting life history traits and to analyze the dynamics of this diversity. The marker methods used are AFLP and microsatellites which, combined, can reveal almost all aspects of genetic diversity and gene flow. The further development and use of sets of molecular markers will greatly facilitate future diversity studies on a large scale.

Microorganisms are another crucial component of tropical forest ecosystems. Indeed, trees of tropical forests are usually dependent on obligate root symbioses, such as mycorrhizae, for water and nutrient acquisition, and for protection against soil-borne pathogens. In a recent study, the conclusion was that the mycorrhizal fungal diversity determines the plant biodiversity, as well as the ecosystem variability and productivity.8 The same molecular techniques, as applied to trees, can be used for microorganisms. This study will lead to a deeper insight into the dynamics and stability of soil beneficial organisms in their interaction with trees of tropical forests. This is essential for sustainable forest management, in protected reserves and sanctuaries or for a sustainable use of diversity.

It will be also very useful for reforestation and agroforestry.

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