GENETIC-VARIATION IN COSTA-RICAN POPULATIONS OF THE TROPICAL TIMBER SPECIES CEDRELA-ODORATA L., ASSESSED USING RAPD

Cedrela odorata L. (Spanish cedar), an economically important timber s pecies native to the American tropics, is the focus of increasing cons ervation concern due to high rates of deforestation within its native range. To assess the extent of the genetic diversity within and betwee n populations of this species, samples were obtained from 10 widely di spersed populations within Costa Pica and analysed for random amplifie d polymorphic DNA (RAPD) variation. Fourteen 10-mer primers were used to generate 97 polymorphic RAPD bands. Presence/absence data for all b ands were subjected to a pairwise genetic distance analysis,, accordin g to Jaccard's coefficient, then neighbour-joining cluster analysis wa s performed on these distances, as was an analysis of molecular varian ce (AMOVA), to assess levels of differentiation between populations an d regions, and Shannon's Diversity Index was used to quantify levels o f diversity within and between populations. Results indicated highly s ignificant genetic differentiation (P < 0.004, AMOVA) between populati ons originating from the North Pacific and Atlantic/South Pacific regi ons of Costa Rica, with 35.3% of the total variation attributable to a difference between these areas. Little differentiation was recorded b etween populations from within the same region (P = 0.757, AMOVA), and 65.1% of the total variance was attributable to variation within popu lations. Estimated values for within-population diversity, calculated as H-pop/H-sp by means of Shannon's Diversity Index, were found to var y greatly between primers, but the overall within-population component of genetic diversity was 0.45. Possible reasons for the high degree o f intraspecific genetic variation within this species are discussed an d the implications of these results for the conservation and use of it s genetic resources are described.