Zartman Charles E, McDaniel Stuart F, Shaw A Jonathan
Department of Biology, Duke University, Box 90338, Durham, North Carolina 27707, USA.
Mol Ecol. 2006 Aug;15(9):2305-15. doi: 10.1111/j.1365-294X.2006.02929.x.
Habitat fragmentation increases the migration distances among remnant populations, and is predicted to play a significant role in altering both demographic and genetic processes. Nevertheless, few studies have evaluated the genetic consequences of habitat fragmentation in light of information about population dynamics in the same set of organisms. In a 10,000-km(2) experimentally fragmented landscape of rainforest reserves in central Amazonia, we examine patterns of genetic variation (amplified fragment length polymorphisms, AFLPs) in the epiphyllous (e.g. leaf-inhabiting) liverwort Radula flaccida Gott. Previous demographic work indicates that colonization rates in this species are significantly reduced in small forest reserves. We scored 113 polymorphic loci in 86 individuals representing five fragmented and five experimentally unmanipulated populations. Most of the variation (82%) in all populations was harboured at the smallest (400 m(2)) sampling unit. The mean ((+/-) SD) within-population genetic diversity (Nei's), of forest remnants (0.412 +/- 0.2) was indistinguishable from continuous (0.413 +/- 0.2) forests. Similarly, F(ST) was identical among small (1- and 10-ha) and large (> or = 100-ha) reserves (0.19 and 0.18, respectively), but linkage disequilibrium between pairs of loci was significantly elevated in fragmented populations relative to those in continuous forests. These results illustrate that inferences regarding the long-term viability of fragmented populations based on neutral marker data alone must be viewed with caution, and underscore the importance of jointly evaluating information on both genetic structure and demography. Second, multilocus analyses may be more sensitive to the effects of fragmentation in the short term, although the effects of increasing linkage disequilibrium on population viability remain uncertain.
栖息地破碎化增加了残余种群之间的迁移距离，并预计在改变人口统计学和遗传过程中发挥重要作用。然而，很少有研究根据同一组生物体的种群动态信息来评估栖息地破碎化的遗传后果。在亚马逊中部一片面积达10000平方公里的热带雨林保护区实验性破碎化景观中，我们研究了附生（如叶栖）地钱Radula flaccida Gott的遗传变异模式（扩增片段长度多态性，AFLP）。先前的人口统计学研究表明，在小型森林保护区中，该物种的定殖率显著降低。我们对代表五个破碎化种群和五个实验未处理种群的86个个体中的113个多态性位点进行了评分。所有种群中大部分变异（82%）存在于最小（400平方米）的采样单元中。森林残余种群（0.412±0.2）的种群内遗传多样性（Nei氏指数）均值与连续森林（0.413±0.2）无显著差异。同样，小型（1公顷和10公顷）和大型（≥100公顷）保护区之间的F(ST)相同（分别为0.19和0.18），但相对于连续森林中的种群，破碎化种群中位点对之间的连锁不平衡显著升高。这些结果表明，仅基于中性标记数据推断破碎化种群的长期生存能力时必须谨慎，并强调了联合评估遗传结构和人口统计学信息的重要性。其次，多基因座分析在短期内可能对破碎化的影响更敏感，尽管连锁不平衡增加对种群生存能力的影响仍不确定。
