PHYLOGEOGRAPHIC PATTERNS INDICATE TRANSATLANTIC MIGRATION FROM EUROPE TO NORTH AMERICA IN THE RED SEAWEED CHONDRUS CRISPUS (GIGARTINALES, RHODOPHYTA)1

Inferring how the Pleistocene climate oscillations have repopulated the extant population structure of Chondrus crispus Stackh. in the North Atlantic Ocean is important both for our understanding of the glacial episode promoting diversification and for the conservation and development of marine organisms. C. crispus is an ecologically and commercially important red seaweed with broad distributions in the North Atlantic. Here, we employed both partial mtDNA Cox1 and nrDNA internal transcribed spacer region 2 (ITS2) sequences to explore the genetic structure of 17 C. crispus populations from this area. Twenty-eight and 30 haplotypes were inferred from these two markers, respectively. Analysis of molecular variance (AMOVA) and of the population statistic Theta(ST) not only revealed significant genetic structure within C. crispus populations but also detected significant levels of genetic subdivision among and within populations in the North Atlantic. On the basis of high haplotype diversity and the presence of endemic haplotypes, we postulate that C. crispus had survived in Pleistocene glacial refugia in the northeast Atlantic, such as the English Channel and the northwestern Iberian Peninsula. We also hypothesize that C. crispus from the English Channel refugium repopulated most of northeastern Europe and recolonized northeastern North America in the Late Pleistocene. The observed phylogeographic pattern of C. crispus populations is in agreement with a scenario in which severe Quaternary glaciations influenced the genetic structure of North Atlantic marine organisms with contiguous population expansion and locally restricted gene flow coupled with a transatlantic dispersal in the Late Pleistocene.

Molecular evidence for the sister relationship of the eastern Asia-North American intercontinental species pair in the Podophyllum group (Berberidaceae)

The presumed pair relationships of intercontinental vicariad species in the Podophyllum group (Sinopodophyllum hexandrum vs. Podophyllum pelatum and Diphylleia grayi vs. D. cymosa) were recently, considered to be paraphyletic. In the present paper, the trnL-F and ITS gene sequences of the representatives were used to examine the sister relationships of these two vicariad species. A heuristic parsimony analysis based on the trnLF data identified Diphylleia as the basal clade of the other three genera, but provided poor resolution of their inter-relationships. High sequence divergence was found in the ITS data. ITS1 region, more variable but parsimonyuninformative. has no phylogenetic value, Sequence divergence of the ITS2 region provided abundant, phylogenetically informative variable characters. Analysis of ITS2 sequences confirmeda sister relationship between the presumable vicariad species, in spite of a low bootstrap support for Sinopodophyllum hexandrum vs. Podophyllum pelatum. The combined ITS2 and trnL-F data enforced a sister relationship between Sinopodophyllum hexandrum and Podophyllum pelatum with an elevated bootstrap support of 100%. Based on molecular phylogeny, the morphological evolution of this group was discussed. The self-pollination might have evolved from cross-fertilization two times in this group. The different pollination and seed dispersal systems of Sinopodophyllum hexandrum and Podophlyllum pelatum resulted from their adaptations to different ecological habitats. The divergence time of Sinopodophyllum hexandrum-Podophyllum pelatum is estimated to be 6.52+/-1.89 myr based on the ITS divergence. The divergence of this species pair predated or co-occurred with the recent uplift of the Himalayas 4-3 myr during the late Miocene and the formation of the alpine habitats. Sinopodophyllum hexandrum developed a host of specialized characters in its subsequent adaptation to the arid alpine surroundings. The present study confirmed the different patterns of species relationship between Asian-North American disjuncts. The isolation of plant elements between North America and eastern Asia must have been a gradual process, resulting in the different phylogenetic patterns and divergence times of the disjuncts.

土圞儿属和旋花豆属的系统学研究

土圞儿属（含8种）和旋花豆属（含2种）隶属于豆科、菜豆族、刺桐亚族。土圞儿属呈东亚-北美间断分布，旋花豆属分布于喜玛拉雅地区。传统上，这两个属被认为系统关系非常近。目前对于土圞儿属中种的划分和分类问题缺乏世界范围内的深入研究，因此该属应予以修订。另外，土圞儿属内种间和土圞儿属与旋花豆属间的系统关系也需要进一步研究。本文对这两个属进行了世界范围内的分类学修订。同时，基于形态学、解剖学、孢粉学特征和分子系统学方面的研究，对土圞儿属内部和这两个属之间的系统发育关系进行了探讨。结果如下： 1. 形态学 在标本室研究和野外考查的基础上，对土圞儿属和旋花豆属植物形态性状的变异式样及其分类学意义进行了分析，发现块茎的形态、小叶的大小和形态、花序的类型和花冠的形态等特征在种内稳定，是比较可靠的分类学性状。通过对花序的研究，认为花序的类型可能反映了土圞儿属内各种之间的演化关系，推测肉色土圞儿可能是土圞儿属中较为进化的种类，而云南土圞儿和纤细土圞儿则可能较为原始。 2. 叶表皮特征 首次在光学显微镜和扫描电子显微镜下，对土圞儿属和旋花豆属全部8种植物的叶表皮进行了观察。发现这两个属叶表皮的性状，特别是表皮细胞的形状、垂周壁的式样和蜡质纹饰的特征，对于理解土圞儿属内和这两个属之间的系统关系有重要意义。叶表皮的特征支持以下结论：纤细土圞儿是一个独立的种，而不是云南土圞儿之下的一个变种;对于土圞儿属进行亚属的划分是不合理的。 3. 孢粉学 在光学显微镜和扫描电子显微镜下，对7种土圞儿属和旋花豆属植物的花粉进行了观察。这两个属的花粉均为三孔沟，三角球形或球形。土圞儿属的花粉可划分为两种类型：肉色土圞儿的花粉外壁为典型的网状纹饰;其他的种花粉外壁较光滑，具颗粒状或短条纹状纹饰。肉色土圞儿花粉外壁纹饰的类型可能反映了其在Apios属中较进化的位置。旋花豆属的花粉特征和肉色土圞儿相似，这也许说明了两者之间的亲缘关系较近。 4. 分子系统学 通过对土圞儿属和旋花豆属6种植物的两个DNA片段ITS和H3D进行简约性分析，构建了这两个属之间的系统关系树。结果如下：土圞儿属和旋花豆属是亲缘关系较近的姐妹群;土圞儿属自身组成一个单系群，是一个自然的类群;北美的土圞儿聚成一支，隐藏在东亚的种里。分子证据和花序类型、花粉形态等重要的形态学证据相吻合。基于上述证据，我们对土圞儿属东亚-北美间断分布的格局及其可能的成因进行了初步探讨。 5. 分类修订 对土圞儿属和旋花豆属进行了分类修订，考证了关于这两个属曾发表过的所有的名称。确认了土圞儿属应包含6种，旋花豆属有2种。排除了5个不包括在土圞儿属内的种名。此外，本文还给出了这两个属各个种的地理分布图、分种检索表、形态描述和插图。

黄杉属的分子系统发育与生物地理学

松科植物的叶绿体和线粒体基因分别为父系和母系遗传，二者的联合分析为系统发育重建，特别是揭示网状进化过程提供了便利条件。此外，松科中的多个属（如黄杉属、铁杉属等）呈洲际间断分布，是研究生物地理学问题的良好试材。 本文选择来自于叶绿体和线粒体基因组的5个DNA片段，通过序列分析对黄杉属的所有8个种进行了系统发育重建;同时结合已有的对黄杉属的各方面研究，讨论了该属典型的东亚-北美间断分布式样的形成过程。主要结果如下： (1) 叶绿体DNA片段trnfM-trnS、rpl20和trnP的序列分析 无论叶绿体基因两两组合分析还是3个叶绿体片段的联合分析均强烈支持东亚的6种黄杉属植物聚为一支（支持率>96%），其中日本黄杉位于最基部，其他分布于中国的5个种聚在一起。 (2) 线粒体基因nad5和cox1的序列分析 线粒体基因序列的进化速率较慢，信息位点相对较少，因此分辨率较低。本文中线粒体DNA序列在黄杉属的东亚物种间几乎没有分辨率，但是仍以>60%的Bootstrap支持率将该属分为东亚与北美两个姐妹支。 (3) 5个DNA片段的联合分析 5个细胞质DNA片段(trnfM-trnS, rpl20, trnP, nad5, cox1)的联合数据矩阵长4351 bp，其中含变异位点129个（3.0%），信息位点109个（2.5%）。利用最大简约法进行的系统发育分析表明：黄杉属分成北美和东亚两支，与地理分布相吻合，并分别得到了66%和100%的支持;中国的5个物种形成一个单系分支，该分支与日本黄杉为姐妹群关系。 根据上述叶绿体和线粒体DNA片段的序列分析结果，并结合前人的研究资料，我们认为黄杉属通过白令陆桥扩散后，在北美和东亚独立进化，但该属的起源地尚需要进一步研究。