Molecular Phylogenetics of Alternanthera (Gomphrenoideae, Amaranthaceae): Resolving a Complex Taxonomic History Caused by Different Interpretations of Morphological Characters in a Lineage with C4 and C3-C4 Intermediate Species
Molecular Phylogenetics of Alternanthera (Gomphrenoideae, Amaranthaceae): Resolving a Complex Taxonomic History Caused by Different Interpretations of Morphological Characters in a Lineage with C4 and C3-C4 Intermediate Species
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DOI：
10.1111/j.1095-8339.2012.01248.x
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发表时间：
2012-07
影响因子：
2.4
通讯作者：
I. Pino;T. Motley;T. Borsch
中科院分区：
文献类型：
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作者：
I. Pino;T. Motley;T. Borsch
苋属（苋科）是一个种类繁多的属（80-200种），主要局限于美洲热带地区。与Pedersenia和Tidestromia一起，它构成了Gomphrenoideae的“交替进化支”。核（ITS）和质体（rpl16, trnL-F）核苷酸序列及形态特征的简约分析和贝叶斯分析表明，互花属柱头状花序是互花属内的一种突触形态。在互花属中，两个主要分支均以雌蕊同质性特征为标志：分支A [99% jackknife (JK)]；后验概率为1.0 (PP)] 9种，B枝（60% JK; 0.98 PP） 22种。在b枝中鉴定出4个亚支（B1-B4），在统计学上得到了强有力的支持。大多数主要谱系的核和质体数据一致，但nrITS和质体系统发育树之间的一些不一致表明杂交可能在交替种的猖獗物种形成中发挥了作用。虽然C4光合作用似乎是在单一进化枝中进化而来，但在这一进化枝中，a . littoralis var. maritima （C3）的位置可能是由杂交物种形成来解释的，而不是由C4到C3的逆转。所有C3 - c4中间体都属于一个不同的分支，其中也包含C3物种，但物种限制，包括广泛研究的a . tenella，尚不清楚。包括A. tenella和A. halimifolia的进化支包含了加拉帕戈斯群岛特有的大多数物种，而A. nesiotes也是岛上特有的，在广泛的美洲分类群中筑巢。这表明Alternanthera的加拉帕戈斯辐射可能起源于至少两次独立的殖民事件，随后是前谱系的后续辐射。©2012伦敦林奈学会，林奈学会植物学杂志，2012,169,493-517。
Alternanthera (Amaranthaceae) is a diverse genus (80–200 species) largely restricted to the American Tropics. With Pedersenia and Tidestromia, it makes up the ‘Alternantheroid clade’ in Gomphrenoideae. Parsimony and Bayesian analyses of nucleotide sequences of nuclear (ITS) and plastid (rpl16, trnL-F) and morphological characters identify that the capitate stigma of Alternanthera is a synapomorpy within the Alternantheroids. Within Alternanthera, two major clades were resolved, both of which were marked by otherwise homoplasious characters of the gynoecium: Clade A [99% jackknife (JK); 1.0 posterior probability (PP)] with nine species and Clade B (60% JK; 0.98 PP) with 22 species. Four subclades (B1–B4), strongly supported statistically, were identified in Clade B. Previous subgeneric classifications of Alternanthera appear artificial in light of our new molecular phylogenetic analyses. Most major lineages are congruently resolved by nuclear and plastid data but some incongruence between the nrITS and plastid phylogenetic trees suggests hybridization may have played a role in the rampant speciation in Alternanthera. Whereas C4 photosynthesis appears to have evolved in a single clade, the position of A. littoralis var. maritima (C3) in this clade may be explained by hybrid speciation rather than a reversal from C4 to C3. All C3–C4 intermediates belong to a different clade that also contains C3 species, but species limits, including the widely studied A. tenella, are unclear. The clade including A. tenella and A. halimifolia contains most of the species endemic to the Galapagos whereas A. nesiotes, also endemic to the islands, is nested among widespread American taxa. This suggests that the Galapagos radiation of Alternanthera may have arisen from at least two independent colonization events followed by a subsequent radiation in the former lineage. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 493–517.