Perron M, Perry D J, Andalo C, Bousquet J
Centre de Recherche en Biologie Forestière, Université Laval, Sainte-Foy, QC, Canada G1K 7P4.
Proc Natl Acad Sci U S A. 2000 Oct 10;97(21):11331-6. doi: 10.1073/pnas.200417097.
Black spruce (Picea mariana [B.S.P.] Mill.) and red spruce (Picea rubens Sarg.) are two conifer species known to hybridize naturally in northeastern North America. We hypothesized that there is a progenitor-derivative relationship between these two taxa and conducted a genetic investigation by using sequence-tagged-site markers of expressed genes. Based on the 26 sequence-tagged-site loci assayed in this study, the unbiased genetic identity between the two taxa was quite high with a value of 0.920. The mean number of polymorphic loci, the mean number of alleles per polymorphic locus, and the average observed heterozygosity were lower in red spruce (P = 35%, A(P) = 2.1, H(o) = 0.069) than in black spruce (P = 54%, A(P) = 2.9, H(o) = 0.103). No unique alleles were found in red spruce, and the observed patterns of allele distribution indicated that the genetic diversity of red spruce was essentially a subset of that found in black spruce. When considered in combination with ecological evidence and simulation results, these observations clearly support the existence of a progenitor-derivative relationship and suggest that the reduced level of genetic diversity in red spruce may result from allopatric speciation through glaciation-induced isolation of a preexisting black spruce population during the Pleistocene era. Our observations signal a need for a thorough reexamination of several conifer species complexes in which natural hybridization is known to occur.
黑云杉（Picea mariana [B.S.P.] Mill.）和红云杉（Picea rubens Sarg.）是已知在北美东北部自然杂交的两种针叶树种。我们假设这两个分类群之间存在祖先 - 衍生关系，并使用表达基因的序列标签位点标记进行了遗传研究。基于本研究中检测的26个序列标签位点，两个分类群之间的无偏遗传同一性相当高，值为0.920。红云杉（P = 35%，A(P) = 2.1，H(o) = 0.069）的多态性位点平均数、每个多态性位点的等位基因平均数和平均观察杂合度低于黑云杉（P = 54%，A(P) = 2.9，H(o) = 0.103）。在红云杉中未发现独特的等位基因，观察到的等位基因分布模式表明红云杉的遗传多样性基本上是黑云杉遗传多样性的一个子集。结合生态证据和模拟结果考虑，这些观察结果明确支持祖先 - 衍生关系的存在，并表明红云杉遗传多样性水平降低可能是由于更新世时期冰川作用导致先前存在的黑云杉种群隔离而形成的异域物种形成所致。我们的观察结果表明需要对已知发生自然杂交的几个针叶树种复合体进行全面重新审视。
