Gómez Africa, Hughes Roger N, Wright Peter J, Carvalho Gary R, Lunt David H
Department of Biological Sciences, University of Hull, Cottingham Road, Hull HU6 7RX, UK.
Mol Ecol. 2007 May;16(10):2173-88. doi: 10.1111/j.1365-294X.2007.03308.x.
The marine bryozoan Celleporella hyalina is a species complex composed of many highly divergent and mostly allopatric genetic lineages that are reproductively isolated but share a remarkably similar morphology. One such lineage commonly encrusts macroalgae throughout the NE Atlantic coast. To explore the processes leading to geographical diversification, reproductive isolation and speciation in this taxon, we (i) investigated NE Atlantic C. hyalina mitochondrial DNA phylogeography, and (ii) used breeding trials between geographical isolates to ascertain reproductive isolation. We find that haplotype diversity is geographically variable and there is a strong population structure, with significant isolation by distance. NE Atlantic C. hyalina is structured into two main parapatric lineages that appear to have had independent Pleistocene histories. Range expansions have resulted in two contact zones in Spain and W Ireland. Lineage 1 is found from Ireland to Spain and has low haplotype diversity, with closely related haplotypes, suggesting a recent population expansion into the Irish Sea, S Ireland, S England and Spain. Lineage 2 is found from Iceland to Spain and has high haplotype diversity. Complete reproductive isolation was found between some geographical isolates representing both lineages, whereas it was incomplete or asymmetric between others, suggesting these latter phylogeographical groups probably represent incipient species. The phylogeographical distribution of NE Atlantic C. hyalina does not fall easily into a pattern of southern refugia, and we discuss likely differences between terrestrial and marine system responses to Pleistocene glacial cycles.
海洋苔藓虫类的透明格苔藓虫（Celleporella hyalina）是一个物种复合体，由许多高度分化且大多异域分布的遗传谱系组成，这些谱系生殖隔离，但形态却极为相似。其中一个谱系通常附着在整个东北大西洋海岸的大型藻类上。为了探究导致该分类群地理分化、生殖隔离和物种形成的过程，我们（i）研究了东北大西洋透明格苔藓虫的线粒体DNA系统地理学，以及（ii）利用地理隔离种群之间的杂交试验来确定生殖隔离。我们发现单倍型多样性在地理上存在差异，且有很强的种群结构，存在显著的距离隔离。东北大西洋透明格苔藓虫分为两个主要的邻域谱系，它们似乎有着独立的更新世历史。分布范围的扩张在西班牙和爱尔兰西部形成了两个接触带。谱系1分布于从爱尔兰到西班牙的区域，单倍型多样性较低，单倍型之间亲缘关系密切，这表明最近有一个种群扩张到了爱尔兰海、爱尔兰南部、英格兰南部和西班牙。谱系2分布于从冰岛到西班牙的区域，单倍型多样性较高。在代表两个谱系的一些地理隔离种群之间发现了完全生殖隔离，而在其他种群之间则是不完全或不对称的生殖隔离，这表明后一类系统地理学群体可能代表着初始物种。东北大西洋透明格苔藓虫的系统地理分布并不容易归入南方避难所模式，我们还讨论了陆地和海洋系统对更新世冰川周期反应可能存在的差异。
