PhD defense: Ida Hartvig Larsen

Title: Conservation genetics of threatened Dalbergia timber species in Indochina

Principal supervisor

Associate professor Lene Rostgaard Nielsen (chair)
Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, DK

Co-supervisor

Professor Erik Dahl Kjær
Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, DK

Co-supervisor

Senior researcher Ida Theilade
Department of Food and Resource Economics, Faculty of Science, University of Copenhagen, DK 

Assessment Committee

Associate professor Anders Ræbild (chair)
Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, DK

Associate professor Siri Fjellheim
Norwegian University of Life Sciences (UMB), Norway

Researcher Santiago C. Gonzalés-Martinez
University of Lausanne, France

Summary

Tropical forests all over the world are disappearing at high rates primarily due to anthropogenic ecosystem changes. A high number of tropical tree species is threatened with extinction due to deforestation and unsustainable levels of logging, and the implementation of effective conservation plans is often hindered by the lack of basic knowledge of their biology.

This study represents the first region-wide analysis of population genetic diversity for tree species in Indochina and provides valuable knowledge on how threatened tree species are affected by landscape features, ancient or recent habitat changes and logging.  Molecular tools in the form of DNA barcoding and population genetic markers were applied to two threatened Dalbergia timber species from Indochina, D. cochinchinensis and D. oliveri (Fabaceae), in order to provide knowledge on species delimitation, genetic structure and mating systems of the two species. The study was based on field samples from Laos, Thailand, Cambodia and Vietnam as well as samples from herbarium specimens.

DNA barcoding markers proved very efficient in discriminating among Dalbergia species, confirmed the monophyly of D. oliveri, which was previously recognized as several separate species and accurately identified the CITES-listed D. cochinchinensis. The results can be used to update threat assessments with correct taxonomic information and the method can be implemented as an identification tool in field studies as well as in enforcement of CITES regulations.

The population genetic analyses revealed that both species reproduce clonally by root suckers, and that D. oliveri is outcrossing, while D. cochinchinensis exhibits some levels of selfing. Populations of D. oliveri were more genetically diverse than D. cochinchinensis, which can be attributed to differences in mating systems and dispersal abilities, or be due to higher levels of logging of D. cochinchinensis. Likely recent impacts of severe habitat loss and logging was detected in a higher selfing rate for D. cochinchinensis compared to earlier studies, and a lower level of genetic diversity for both species in the countries with the longest history of deforestation. Differences in genetic diversity levels among countries could though also reflect ancient population demographic changes, as both species showed signs of ancient bottlenecks. Level of differentiation among populations was high for both species, and landscape features such as rivers, lakes and non-forest areas were important factors affecting their genetic structure.

The obtained knowledge on genetic structure and mating system can be used to guide conservation and future breeding plans of the two Dalbergia species. The molecular markers can also be applied in forensics, as they can be used to identify both the species identity and the geographic origin of illegally traded timber. 

After the PhD defense there will be a reception at Rolighedsvej 23, in the canteen (common area) on ground floor in the new building