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Summary      

 

ASSESSMENT OF LEVELS AND DYNAMICS OF INTRA-SPECIFIC GENETIC DIVERSITY OF TROPICAL TREES FOR CONSERVATION AND SUSTAINABLE MANAGEMENT

EU Contract Number: ERBIC18CT970149 

Objectives

The objectives of this study were to: 

  1. Quantify the level and distribution of genetic diversity within a range of economically and ecologically important tropical tree species 
  2. Describe the dynamics of this diversity (i.e gene flow and mating systems of the selected species) 
  3. Use the information to contribute to the development of in situ conservation strategies
  4. Identify suitable material for ex situ conservation in genebanks
  5. Evaluate the consequences of selected human impacts upon genetic diversity within tropical forests
  6. Develop universal molecular tools that are suitable for assessing gene diversity in tropical tree species.

 

Approach and methodologies

Molecular tools were  used to address questions concerning biodiversity, gene flow and mating systems in tree species specially selected for their ecological and/or economic importance, and model character.

Chloroplast and nuclear markers were used to assess levels of genetic diversity, seed flow and pollen flow, utilising maternally and biparentally transmitted markers. Attempts were made to develop universal markers as use of standardized tools would improve comparisons between studies.

 

Activities

The project analyzed the level and distribution of diversity inl tree species from different ecosystems, and evaluated the effects of human influence upon their diversity. Studies included species from forests in Central America, the Caribbean, the Brazilian Amazonian and Atlantic rainforests. The selected species were characterized by a broad range of life history attributes (dispersion mechanisms and spatial distribution patterns) which are suspected to affect levels of diversity. Underpinning all these activities, was the development of molecular and statistical techniques, which were an essential component of this project.

 

Results and  conclusions

Chloroplast DNA studies indicated that cpDNA variation was usually low, and often showed strong structuring related to population, geographic region and (possibly) ancient geological events. However, one species, Symphonia globulifera, showed very high variation and it is thought that cpDNA inheritance in this species may not be strictly maternal, as is usually the case. 

Microsatellite studies of Vochysia ferruginea and Swietenia macrophylla indicated that logging and forest disturbance reduced genetic diversity, and with the latter species, studies at one site indicated that genetic diversity is unlikely to recover through long distance gene flow. With the former species, studies on a completely cleared and regenerated site indicated the importance of the soil seedbank and the presence of mother trees in adjacent undisturbed forest blocks in determining the genetic structure and diversity of the regenerated forest.

Genetic diversity could not be predicted from pollinator or population density; studies on Symphonia globulifera indicated that territorial behaviour of pollinators and flowering patterns should not be overlooked. While bird pollinated Symphonia had low outcrossing rates, bat pollinated Ceiba pentandra showed long pollination distances (~18 km) and highlighted the influence of bat populations on genetic diversity.

These results are only a small subset of those obtained within the project. They highlight the value of molecular approaches for developing conservation and land management strategies: they have shown important differences between populations and the level of genetic structuring within populations, and have indicated the role of different breeding systems and colonising strategies in determining diversity.  Thus when challenged by different types of environmental change, species will respond differently. S. macrophylla (mahogany) was studied in greater depth than other species and results indicate that this commercially important and heavily logged species is very sensitive to disturbance, and populations may take generations (100s of years) to recover. Careful management is crucial to prevent populations descending into a downard spiral of genetic resource loss.  Results are being published and steps are being taken to inform and involve conservation agencies in the application of this data.  

1 November 1997 - 31 July 2001

 

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Last modified: November 20, 2002