Rawson Paul D, Hilbish Thomas J
Department of Biological Sciences, University of South Carolina, Columbia, South Carolina, 29208.
Evolution. 1998 Feb;52(1):100-108. doi: 10.1111/j.1558-5646.1998.tb05142.x.
-Mytilus edulis and M. galloprovincialis are two blue mussel species that coexist in western Europe. Previously, we reported that M. galloprovincialis populations contain female and male haplotypes that are fixed in M. edulis populations as well as unique haplotypes. This study assesses whether paraphyly for these species is due to introgression or incomplete lineage extinction. The lineage extinction hypothesis predicts that the shared mtDNA haplotypes in M. galloprovincialis will be significantly diverged from those in M. edulis and form distinct sequence clades. In contrast, the introgression hypothesis proposes that M. edulis haplotypes have only recently been introduced into M. galloprovincialis through hybridization with relatively little divergence accumulating between the shared RFLP haplotypes. We examined 80 mtl6S gene sequences for both the maternal and paternal mtDNA lineages from mussels sampled from various European populations and found strong support for the introgression hypothesis. In addition, we found that M. edulis mtDNA haplotypes appear to be introgressing into mussel populations in the Baltic Sea, which have predominantly M. trossulus nuclear genotypes, indicating that introgressive hybridization is prevalent among European mussel populations.
紫贻贝和地中海贻贝是共存于西欧的两种蓝贻贝物种。此前，我们报道过地中海贻贝种群中包含在紫贻贝种群中固定存在的雌性和雄性单倍型以及独特的单倍型。本研究评估这些物种的并系发生是由于基因渗入还是不完全谱系灭绝。谱系灭绝假说预测，地中海贻贝中共享的线粒体DNA单倍型将与紫贻贝中的单倍型有显著差异，并形成不同的序列分支。相比之下，基因渗入假说提出，紫贻贝单倍型是最近通过杂交才引入到地中海贻贝中的，共享的限制性片段长度多态性单倍型之间积累的差异相对较小。我们检测了来自欧洲不同种群的贻贝的母系和父系线粒体DNA谱系的80个线粒体16S基因序列，并发现有力支持基因渗入假说。此外，我们发现紫贻贝的线粒体DNA单倍型似乎正在渗入到波罗的海的贻贝种群中，这些种群主要具有格氏贻贝的核基因型，这表明渐渗杂交在欧洲贻贝种群中很普遍。
