ETH Zürich, Institute of Terrestrial Ecosystems, Ecosystem Management, CH-8092 Zürich, Switzerland.
Mol Ecol. 2011 Sep;20(18):3773-84. doi: 10.1111/j.1365-294X.2011.05228.x. Epub 2011 Aug 24.
Rare plant species are vulnerable to genetic erosion and inbreeding associated with small population size and isolation due to increasing habitat fragmentation. The degree to which these problems undermine population viability remains debated. We explore genetic and reproductive processes in the critically endangered long-lived tropical tree Medusagyne oppositifolia, an endemic to the Seychelles with a naturally patchy distribution. This species is failing to recruit in three of its four populations. We evaluate whether recruitment failure is linked to genetic problems associated with fragmentation, and if genetic rescue can mitigate such problems. Medusagyne oppositifolia comprises 90 extant trees in four populations, with only the largest (78 trees) having successful recruitment. Using 10 microsatellite loci, we demonstrated that genetic diversity is high (H(E) : 0.48-0.63; H(O) : 0.56-0.78) in three populations, with only the smallest population having relatively low diversity (H(E) : 0.26 and H(O) : 0.30). All populations have unique alleles, high genetic differentiation, and significant within population structure. Pollen and seed dispersal distances were mostly less than 100 m. Individuals in small populations were more related than individuals in the large population, thus inbreeding might explain recruitment failure in small populations. Indeed, inter-population pollination crosses from the large donor population to a small recipient population resulted in higher reproductive success relative to within-population crosses. Our study highlights the importance of maintaining gene flow between populations even in species that have naturally patchy distributions. We demonstrate the potential for genetic and ecological rescue to support conservation of plant species with limited gene flow.
珍稀植物物种易受到遗传侵蚀和近交的影响，这与小种群规模和隔离有关，因为栖息地的破碎化日益严重。这些问题在多大程度上破坏了种群的生存能力仍存在争议。我们探索了极度濒危的长寿热带树种 Medusagyne oppositifolia 的遗传和繁殖过程，该树种是塞舌尔的特有种，分布自然呈斑块状。该物种在其四个种群中的三个种群中无法繁殖。我们评估了繁殖失败是否与与破碎化相关的遗传问题有关，以及遗传拯救是否可以减轻这些问题。Medusagyne oppositifolia 由四个种群中的 90 棵现存树木组成，只有最大的种群（78 棵树）有成功的繁殖。使用 10 个微卫星基因座，我们证明了三个种群中的遗传多样性很高（H(E)：0.48-0.63；H(O)：0.56-0.78），只有最小的种群遗传多样性相对较低（H(E)：0.26 和 H(O)：0.30）。所有种群都有独特的等位基因、高度的遗传分化和显著的种群内结构。花粉和种子的扩散距离大多小于 100 米。小种群中的个体比大种群中的个体更相关，因此近交可能解释了小种群中的繁殖失败。事实上，来自大供体种群的种群间授粉杂交与种群内杂交相比，繁殖成功率更高。我们的研究强调了即使在自然呈斑块状分布的物种中，维持种群间基因流的重要性。我们证明了遗传和生态拯救有潜力支持具有有限基因流的植物物种的保护。
