Phylogenetic placement of the enigmatic angiosperm Hydrostachys
Phylogenetic placement of the enigmatic angiosperm Hydrostachys
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作者：
Albach, DC;Soltis, DE;Soltis, PS
水螅属（Hydrostachys）是一种分布于马达加斯加和非洲南部至中部的神秘水生植物属，胚胎学研究表明它与Lamiales有亲缘关系，而rbcL序列则表明它与绣球科（Cornales）有亲缘关系。我们将rbcL与atpB和ndhF序列结合，并在绣球科增加分类单元取样，对这些假设进行了验证。分子进化的速率和模式在不同的ndhF中不同，3 ‘部分的结果与5 ’部分的结果不同。Hydrostachys高度分化的序列使得系统发育定位困难，但对组合数据集的最大简约性和最大似然分析一致认为Hydrostachys属于绣球科，对rbcL， atpB和ndhF的5 '部分的单独分析也是如此。很少有形态学和胚胎学特征支持这种关系。
Hydrostachys, an enigmatic aquatic plant genus from Madagascar and southern to central Africa, has been suggested to be related to Lamiales based on embryology, whereas rbcL sequences have indicated a relationship with Hydrangeaceae (Cornales). We investigated these hypotheses by combining rbcL with atpB and ndhF sequences and increased taxon sampling in Hydrangeaceae compared to previous analyses. Rates and patterns of molecular evolution vary across ndhF with the 3 ' portion giving a different result than the 5 ' portion. The highly divergent sequences of Hydrostachys make phylogenetic placement difficult, but maximum parsimony and maximum likelihood analyses of combined data sets agree in placing Hydrostachys within Hydrangeaceae, as do separate analyses of rbcL, atpB, and the 5 ' portion of ndhF. Few morphological and embryological characters support this relationship.