Keyghobadi Nusha, Roland Jens, Matter Stephen F, Strobeck Curtis
Department of Biology, Okanagan University College, 3333 University Way, Kelowna, British Columbia, Canada V1V 1V7.
Proc Biol Sci. 2005 Mar 7;272(1562):553-60. doi: 10.1098/rspb.2004.2976.
Habitat fragmentation is a ubiquitous by-product of human activities that can alter the genetic structure of natural populations, with potentially deleterious effects on population persistence and evolutionary potential. When habitat fragmentation results in the subdivision of a population, random genetic drift then leads to the erosion of genetic diversity from within the resulting subpopulation, random genetic drift then leads to the erosion of genetic diversity from within the resulting subpopulations and greater genetic divergence among them. Theoretical and simulation analyses predict that these two main genetic effects of fragmentation, greater differentiation among resulting subpopulation and reduced genetic diversity within them, will proceed at very different rates. Despite important implications for the interpretation of genetics data from fragmented populations, empirical evidence for this phenomenon has been lacking. In this analysis, we carry out an empirical study in population of an alpine meadow-dwelling butterfly, which have become fragmented increasing forest cover over five decades. We show that genetic differentiation among subpopulations (G(ST)) is most highly correlated with contemporary forest cover, while genetics diversity within subpopulation (expected heterozygosity) is better correlated with the spatial pattern of forest cover 40 years in the past. Thus, where habitat fragmentation has occurred in recent decades, genetic differentiation among subpopulation can be near equilibrium while contemporary measures of within subpopulation diversity may substantially overestimate the equilibrium values that will eventually be attained.
栖息地破碎化是人类活动普遍存在的一种副产品，它能够改变自然种群的遗传结构，对种群的持久性和进化潜力产生潜在的有害影响。当栖息地破碎化导致种群细分时，随机遗传漂变会致使由此产生的亚种群内部的遗传多样性受到侵蚀，进而导致亚种群之间的遗传差异增大。理论分析和模拟研究预测，破碎化产生的这两种主要遗传效应，即亚种群之间的差异增大以及亚种群内部遗传多样性降低，其发展速率会大不相同。尽管这一现象对于解释来自破碎化种群的遗传学数据具有重要意义，但一直缺乏相关的实证证据。在本分析中，我们对一种栖息于高山草甸的蝴蝶种群进行了实证研究，该种群在过去五十多年间因森林覆盖面积增加而出现了栖息地破碎化。我们发现，亚种群之间的遗传分化（G(ST)）与当前的森林覆盖面积相关性最高，而亚种群内部的遗传多样性（预期杂合度）与40年前森林覆盖的空间格局相关性更好。因此，在近几十年发生栖息地破碎化的地区，亚种群之间的遗传分化可能已接近平衡状态，而当前对亚种群内部多样性的测量可能会大幅高估最终将达到的平衡值。
