RAPD variation in a germplasm collection of Myracrodruon urundeuva (anacardiaceae), an endangered tropical tree: recommendations for conservation

RAPD markers were used to investigate the distribution of genetic variability in a germplasm collection of the dioecious tropical tree Aroeira (Myracrodruon urundeuva) composed of open pollinated maternal half-sib families collected from trees at least 300 meters apart and grouped in nine collection areas throughout its geographical range in Brazil. Open pollinated families from nearby trees from two natural populations were also included in the study. A Principal Coordinate Analysis (PCO) based on genetic similarities estimated with 83 RAPD markers showed no defined clustering among individuals from the same collection areas. However, a matrix correlation test showed low, but significant correlation between genetic and geographic distances (r 5 0.17; p , 0.02). An AMOVA showed that 92% of the genetic variation is found within collection areas. Significant variation was found both between regions and between areas within regions although only 3.54 and 4.44% of the variation was found at these levels respectively. An AMOVA on the individuals from the two natural populations resulted in a pattern of distribution congruent to the one found for the collection areas, with 97% of variability within populations. An analysis of 10 open-pollinated half-sib families revealed that between 75% and 89% of the variability is contained within families, suggesting that seeds from one tree represent a significant proportion of the variability found in the population. These results indicate that, either for the establishment of in situ genetic reserves or for ex situ conservation, efforts should be directed to the conservation of several individual trees or collection of open pollinated seed families in a few distant sites. In addition, if resources are available to enlarge the genetic base of the existing collection, expeditions should prioritize collection sites located in areas at significant distances to those already sampled