Department of Genetics, Institute of Experimental Biology, Kazimierz Wielki University, Bydgoszcz, Poland.
Heredity (Edinb). 2011 Dec;107(6):589-600. doi: 10.1038/hdy.2011.51. Epub 2011 Jun 29.
Habitat fragmentation can have severe genetic consequences for trees, such as increased inbreeding and decreased effective population size. In effect, local populations suffer from reduction of genetic variation, and thus loss of adaptive capacity, which consequently increases their risk of extinction. In Europe, Taxus baccata is among a number of tree species experiencing strong habitat fragmentation. However, there is little empirical data on the population genetic consequences of fragmentation for this species. This study aimed to characterize local genetic structure in two natural remnants of English yew in Poland based on both amplified fragment length polymorphism (AFLP) and microsatellite (SSR) markers. We introduced a Bayesian approach that estimates the average inbreeding coefficient using AFLP (dominant) markers. Results showed that, in spite of high dispersal potential (bird-mediated seed dispersal and wind-mediated pollen dispersal), English yew populations show strong kinship structure, with a spatial extent of 50-100 m, depending on the population. The estimated inbreeding levels ranged from 0.016 to 0.063, depending on the population and marker used. Several patterns were evident: (1) AFLP markers showed stronger kinship structure than SSRs; (2) AFLP markers provided higher inbreeding estimates than SSRs; and (3) kinship structure and inbreeding were more pronounced in denser populations regardless of the marker used. Our results suggest that, because both kinship structure and (bi-parental) inbreeding exist in populations of English yew, gene dispersal can be fairly limited in this species. Furthermore, at a local scale, gene dispersal intensity can be more limited in a dense population.
生境破碎化会对树木造成严重的遗传后果，例如增加近亲繁殖和降低有效种群大小。实际上，当地种群的遗传变异减少，适应能力丧失，从而增加了灭绝的风险。在欧洲，红豆杉是经历强烈生境破碎化的树种之一。然而，关于该物种因破碎化而导致的种群遗传后果的实证数据很少。本研究旨在基于扩增片段长度多态性 (AFLP) 和微卫星 (SSR) 标记，对波兰两个自然红豆杉残余物的局部遗传结构进行特征描述。我们采用了一种贝叶斯方法，该方法使用 AFLP（显性）标记来估计平均近交系数。结果表明，尽管具有较高的扩散潜力（鸟类介导的种子扩散和风力介导的花粉扩散），但英国紫杉种群仍表现出强烈的亲缘关系结构，其空间范围为 50-100m，具体取决于种群。估计的近交水平范围为 0.016 至 0.063，具体取决于种群和使用的标记。有几种模式明显存在：(1)AFLP 标记比 SSRs 显示出更强的亲缘关系结构；(2)AFLP 标记比 SSRs 提供更高的近交估计值；(3)无论使用哪种标记，在密度较高的种群中，亲缘关系结构和近交程度更为明显。我们的研究结果表明，由于英国紫杉种群中既存在亲缘关系结构又存在（双亲）近交，因此基因扩散在该物种中可能相当有限。此外，在局部尺度上，在密度较高的种群中，基因扩散强度可能更有限。
