Arnaud-Haond S, Teixeira S, Massa S I, Billot C, Saenger P, Coupland G, Duarte C M, Serrão E A
CCMAR-CIMAR Laboratório Associado, Universidade do Algarve, Gambelas, 8005-139, Faro, Portugal.
Mol Ecol. 2006 Oct;15(12):3515-25. doi: 10.1111/j.1365-294X.2006.02997.x.
Understanding the genetic composition and mating systems of edge populations provides important insights into the environmental and demographic factors shaping species' distribution ranges. We analysed samples of the mangrove Avicennia marina from Vietnam, northern Philippines and Australia, with microsatellite markers. We compared genetic diversity and structure in edge (Southeast Asia, and Southern Australia) and core (North and Eastern Australia) populations, and also compared our results with previously published data from core and southern edge populations. Comparisons highlighted significantly reduced gene diversity and higher genetic structure in both margins compared to core populations, which can be attributed to very low effective population size, pollinator scarcity and high environmental pressure at distribution margins. The estimated level of inbreeding was significantly higher in northeastern populations compared to core and southern populations. This suggests that despite the high genetic load usually associated with inbreeding, inbreeding or even selfing may be advantageous in margin habitats due to the possible advantages of reproductive assurance, or local adaptation. The very high level of genetic structure and inbreeding show that populations of A. marina are functioning as independent evolutionary units more than as components of a metapopulation system connected by gene flow. The combinations of those characteristics make these peripheral populations likely to develop local adaptations and therefore to be of particular interest for conservation strategies as well as for adaptation to possible future environmental changes.
了解边缘种群的遗传组成和交配系统，有助于深入洞察塑造物种分布范围的环境和人口因素。我们使用微卫星标记分析了来自越南、菲律宾北部和澳大利亚的红树林白骨壤样本。我们比较了边缘种群（东南亚和澳大利亚南部）和核心种群（澳大利亚北部和东部）的遗传多样性和结构，并将我们的结果与之前发表的核心和南部边缘种群的数据进行了比较。比较结果显示，与核心种群相比，两个边缘地区的基因多样性显著降低，遗传结构更高，这可归因于分布边缘地区非常低的有效种群大小、传粉者稀缺和高环境压力。与核心种群和南部种群相比，东北部种群的近亲繁殖估计水平显著更高。这表明，尽管近亲繁殖通常与高遗传负荷相关，但由于生殖保证或局部适应的可能优势，近亲繁殖甚至自交在边缘栖息地可能是有利的。极高的遗传结构和近亲繁殖水平表明，白骨壤种群更像是独立的进化单元，而不是通过基因流动连接的集合种群系统的组成部分。这些特征的组合使得这些边缘种群有可能形成局部适应，因此对于保护策略以及适应未来可能的环境变化特别有意义。
