Azevedo Vânia C R, Kanashiro Milton, Ciampi Ana Y, Grattapaglia Dario
Embrapa Recursos Genéticos e Biotecnologia, PqEB final W5 Norte, CEP 70770-900, PO Box 02372, Brasília DF, Brazil.
J Hered. 2007 Nov-Dec;98(7):646-54. doi: 10.1093/jhered/esm074. Epub 2007 Sep 14.
In this work, we report on the population genetic structure of the endangered tree species Manilkara huberi, an Amazonian tree species intensely exploited due to the high density and resistance of its wood. We investigated the patterns of spatial distribution, genetic structure, and mating system using 7 microsatellite loci and here discuss the consequences for conservation and management of the species. To examine the population genetic structure, 481 adult trees and 810 seedlings were sampled from an area of 200 ha from a natural population in FLONA Tapajós, PA, Brazil. We found relatively high and consistent inbreeding levels (intrapopulation fixation index [f] 0.175 and 0.240) and a significant spatial genetic structure up to a radius of approximately 300 m, most likely due to a limited seed and pollen flow. The multilocus (tm) population outcrossing rate was high (0.995), suggesting that the species is predominantly allogamous with a pollen flow restricted to 47 m. These results suggest that M. huberi is spatially structured, consistent with a model of isolation by distance. Fragmentation may therefore cause the loss of subpopulations, suggesting that management programs for production and conservation should include large areas. The genetic data also revealed that for ex situ conservation, seeds should be collected from more than 175 maternal trees, in order to keep an effective population size of 500. Furthermore, as the species is widely distributed across the Amazon Forest, samples should include several populations in order to represent the highest genetic diversity possible. These results provide a blueprint to guide the production and conservation management policies of this valuable timber species.
在本研究中，我们报告了濒危树种亚马孙牛奶树（Manilkara huberi）的种群遗传结构。由于其木材密度高且坚固，这种亚马孙树种遭到了过度采伐。我们使用7个微卫星位点研究了其空间分布模式、遗传结构和交配系统，并在此讨论这些结果对该物种保护和管理的影响。为了研究种群遗传结构，我们从巴西帕拉州托帕若斯国家森林（FLONA Tapajós）一片200公顷的天然种群区域中，采集了481株成年树木和810株幼苗的样本。我们发现其近亲繁殖水平相对较高且较为一致（种群内固定指数[f]分别为0.175和0.240），并且在半径约300米的范围内存在显著的空间遗传结构，这很可能是由于种子和花粉传播受限所致。多位点（tm）种群异交率较高（0.995），表明该物种主要为异花授粉，花粉传播距离限制在47米以内。这些结果表明，亚马孙牛奶树具有空间结构，符合距离隔离模型。因此，森林碎片化可能导致亚种群的丧失，这表明生产和保护管理计划应涵盖大面积区域。遗传数据还显示，为了进行迁地保护，应从175株以上母树上采集种子，以维持500的有效种群大小。此外，由于该物种广泛分布于亚马孙森林，样本应包括多个种群，以尽可能代表最高的遗传多样性。这些结果为指导这种珍贵木材物种的生产和保护管理政策提供了蓝图。
