Molecular, quantitative and abiotic variables for the delineation of evolutionary significant units: case of sandalwood (Santalum austrocaledonicum Vieillard) in New Caledonia
Various approaches have been developed to define conservation units for plant and animal species. In this study we combined nuclear microsatellites (from a previous published study) and chloroplast microsatellites (assessed in the present study), leaf and seed morphology traits and abiotic variables (climate and soil) to define evolutionary significant units (ESU) of Santalum austrocaledonicum, a tree species growing in New Caledonia. Results for chloroplast microsatellites showed that the total population heterozygosity was␣high, (H cp = 0.84) but varied between islands. Differentiation was strong in the total population (F stcp = 0.66) but also within the main island Grande Terre (F stcp = 0.73) and within Iles Loyauté (F stcp = 0.52), highlighting a limited gene flow between populations. These results confirmed those obtained with nuclear microsatellites. The cluster analysis on molecular markers discriminated two main groups constituted by the populations of Grande Terre and the populations of Iles Loyauté. A principal component analysis of leaf and seed morphology traits singled out the populations of Iles Loyauté and the western populations of Grande Terre. Quantitative genetic analyses showed that the variation between populations was under genetic control (broad sense heritability close to 80%). A high correlation between rainfall and morphological traits suggested an impact of climate on this variation. The integration of these results allows to define two ESUs, one corresponding to Grande Terre and Ile des Pins and the other the Iles Loyauté archipelago. This study stresses the need to restore some populations of Grande Terre that are currently threatened by their small size.
KeywordsSantalum austrocaledonicum Nuclear microsatellites Chloroplastic microsatellites Morphological traits Evolutionary significant units
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These results are part of Lorraine Bottin 9s PhD thesis on the analysis of genetic diversity of Santalum austrocaledonicum. This study was supported by the sandalwood project funded by the MEDD, the French Ministry of Ecology and Sustainable Development. The laboratory work and analyses were done in the Forest Department of Cirad in Montpellier, France, where J.M. Bouvet is the head of the “Forest Genetics” research unit. We would like to thank Alexandre Vaillant for laboratory work, and Alexandre Lagrange and Géraldine Derroire for field work in New Caledonia. Many thanks go to IAC (Institut Agronomique néo-Calédonien) and to the Development Services of the Provinces of Islands, North and South which facilitated the field operation.
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