Sumner Joanna, Jessop Tim, Paetkau David, Moritz Craig
Department of Zoology and Entomology and the Rainforest CRC, University of Queensland, St Lucia, Qld 4072, Australia.
Mol Ecol. 2004 Feb;13(2):259-69. doi: 10.1046/j.1365-294x.2003.02056.x.
To examine the effects of recent habitat fragmentation, we assayed genetic diversity in a rain forest endemic lizard, the prickly forest skink (Gnypetoscincus queenslandiae), from seven forest fragments and five sites in continuous forest on the Atherton tableland of northeastern Queensland, Australia. The rain forest in this region was fragmented by logging and clearing for dairy farms in the early 1900s and most forest fragments studied have been isolated for 50-80 years or nine to 12 skink generations. We genotyped 411 individuals at nine microsatellite DNA loci and found fewer alleles per locus in prickly forest skinks from small rain forest fragments and a lower ratio of allele number to allele size range in forest fragments than in continuous forest, indicative of a decrease in effective population size. In contrast, and as expected for populations with small neighbourhood sizes, neither heterozygosity nor variance in allele size differed between fragments and sites in continuous forests. Considering measures of among population differentiation, there was no increase in FST among fragments and a significant isolation by distance pattern was identified across all 12 sites. However, the relationship between genetic (FST) and geographical distance was significantly stronger for continuous forest sites than for fragments, consistent with disruption of gene flow among the latter. The observed changes in genetic diversity within and among populations are small, but in the direction predicted by the theory of genetic erosion in recently fragmented populations. The results also illustrate the inherent difficulty in detecting genetic consequences of recent habitat fragmentation, even in genetically variable species, and especially when effective population size and dispersal rates are low.
为了研究近期栖息地破碎化的影响，我们对一种雨林特有蜥蜴——多刺森林石龙子（Gnypetoscincus queenslandiae）的遗传多样性进行了分析。该蜥蜴来自澳大利亚昆士兰州东北部阿瑟顿高原的七个森林碎片和五个连续森林区域。该地区的雨林在20世纪初因伐木和开垦奶牛场而破碎化，大多数研究的森林碎片已隔离了50 - 80年，即九到十二代石龙子。我们对411个个体的九个微卫星DNA位点进行了基因分型，发现来自小型雨林碎片的多刺森林石龙子每个位点的等位基因较少，且森林碎片中等位基因数量与等位基因大小范围的比率低于连续森林，这表明有效种群数量减少。相反，正如对邻域大小较小的种群所预期的那样，连续森林中的碎片和区域之间的杂合度和等位基因大小方差均无差异。考虑到种群分化的衡量指标，碎片之间的FST没有增加，并且在所有12个位点中都识别出了显著的距离隔离模式。然而，连续森林区域的遗传距离（FST）与地理距离之间的关系比碎片区域显著更强，这与后者之间基因流的中断一致。观察到的种群内部和种群之间遗传多样性的变化很小，但方向符合近期破碎化种群遗传侵蚀理论的预测。结果还表明，即使在遗传可变的物种中，尤其是当有效种群数量和扩散率较低时，检测近期栖息地破碎化的遗传后果存在内在困难。
