334 Math & Natural Science Building, Department of Biology, Lincoln Memorial University, 6965 Cumberland Gap Parkway, Harrogate, Tennessee 37752 USA.
Am J Bot. 2013 Oct;100(10):2092-101. doi: 10.3732/ajb.1300037. Epub 2013 Oct 2.
Narrow-ranging, rare species often exhibit levels of genetic diversity lower than more common or widespread congeners. These taxa are at increased risk of extinction due to threats associated with natural as well as anthropogenic events. We assessed genetic variation in three federally endangered Sarracenia species. We discuss maintenance of genetic diversity and evolutionary implications of rarity. •
We analyzed three noncoding chloroplast regions and nine microsatellite loci in populations spanning the geographic ranges of S. oreophila, S. alabamensis, and S. jonesii. The same microsatellite loci were used to examine a single field site of three more widespread species (S. alata, S. leucophylla, and S. rubra subsp. wherryi). •
All three endangered species have experienced reductions in population size and numbers. All show considerably less variation than more widespread members of the genus. Sarracenia alabamensis maintains the greatest microsatellite variation but has the fewest remaining populations and may be under the greatest threat. More widespread S. oreophila maintains surprising chloroplast diversity, yet exhibits little microsatellite diversity. Sarracenia jonesii lacks chloroplast diversity, yet maintains greater microsatellite diversity than S. oreophila. •
The three endangered species differ in levels and structure of diversity, yet not in predictable ways, emphasizing that unique demographic and ecological histories, rather than current distribution and population size, best explain present patterns of genetic variation. Maintenance of remaining genetic variation is important, but preventing further habitat loss and degradation is critical.
范围狭窄、罕见的物种通常表现出的遗传多样性水平低于更为常见或广泛分布的近缘种。由于与自然和人为事件相关的威胁，这些类群灭绝的风险更高。我们评估了三种受联邦保护的猪笼草物种的遗传变异。我们讨论了遗传多样性的维持以及稀有性的进化意义。
我们分析了跨越 oreophila、alabamensis 和 jonesii 三种猪笼草地理范围的种群的三个非编码叶绿体区域和九个微卫星位点。同样的微卫星位点被用来研究三个分布更广泛的物种（alata、leucophylla 和 rubra subsp. wherryi）的一个单一野外地点。
所有三种受威胁的物种都经历了种群规模和数量的减少。所有这些物种的遗传变异都明显低于属内更广泛的成员。alabamensis 保持了最大的微卫星变异，但剩余的种群数量最少，可能面临最大的威胁。分布更为广泛的 oreophila 保持了惊人的叶绿体多样性，但表现出很少的微卫星多样性。jonesii 缺乏叶绿体多样性，但保持了比 oreophila 更大的微卫星多样性。
这三种受威胁的物种在多样性的水平和结构上存在差异，但不是以可预测的方式，这强调了独特的人口和生态历史，而不是当前的分布和种群规模，最能解释目前遗传变异的模式。维持剩余的遗传多样性很重要，但防止进一步的栖息地丧失和退化至关重要。
