Comparing genetic diversity in agroforestry systems with natural forest: a case study of the important timber tree Vitex fischeri in central Kenya |
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Authors: | Ard G. Lengkeek Alice Muchugi Mwangi Caroline A. C. Agufa Joseph O. Ahenda Ian K. Dawson |
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Affiliation: | (1) World Agroforestry Centre (ICRAF), P.O. Box 30677 Nairobi, Kenya;(2) Biosystematics Group, Wageningen University and Research centre, P.O. Box 8010, 6700 ED Wageningen, The Netherlands;(3) Kenya Forest Seed Centre, Muguga, P.O. Box 20412, Nairobi, Kenya |
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Abstract: | It is possible that current tree domestication practices undertaken by farmers reduce the genetic base of tree resources on farms, raising concerns regarding the productivity, sustainability and conservation value of agroforestry ecosystems. Here, we assessed possible changes in genetic variation during domestication in the important and heavily utilised timber species, Vitex fischeri Gürke (syn. Vitex keniensis), by comparing geographically proximate forest and farm material in central Kenya. Employing RAPD analysis, a total of 104 polymorphic markers revealed by five arbitrary primers were scored in a total of 65 individuals, 32 from forest and 33 from farmland. Despite concerns of possible genetic erosion, forest and farm stands did not differ significantly in levels of genetic variation, with H values of 0.278 and 0.269, respectively. However, Mantel tests did reveal greater geographically related associative genetic structure among individuals in farm rather than forest material, with r M values of 0.217 and 0.114, respectively. A more detailed analysis of structure suggested this could be due to local variation in origin of some on-farm trees. Implications of data for the genetic management of V. fischeri stands during farmer-led tree domestication activities are discussed. At present, there appears little reason to reject on-farm V. fischeri as a source of germplasm for future on-farm planting or for conservation purposes, although this situation may change and will require monitoring. |
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Keywords: | Conservation Genetic erosion RAPD Tree domestication Vitex keniensis |
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