Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, 830 North University Avenue, Ann Arbor, Michigan 48109-1048 USA.
Am J Bot. 2011 Sep;98(9):1486-503. doi: 10.3732/ajb.1000496. Epub 2011 Aug 29.
The Chamaesyce clade of Euphorbia is the largest lineage of C(4) plants among the eudicots, with 350 species including both narrow endemics and cosmopolitan weeds. We sampled this group worldwide to address questions about subclade relationships, the origin of C(4) photosynthesis, the evolution of weeds, and the role of hybridization and long-distance dispersal in the diversification of the group. •
Two nuclear (ITS and exon 9 of EMB2765) and three chloroplast markers (matK, rpl16, and trnL-F) were sequenced for 138 ingroup and six outgroup species. Exon 9 of EMB2765 was cloned in accessions with >1% superimposed peaks. •
The Chamaesyce clade is monophyletic and consists of three major subclades [1(2,3)]: (1) the Acuta clade, containing three North American species with C(3) photosynthesis and C(3)-C(4) intermediates; (2) the Peplis clade, mostly North American and entirely C(4); and (3) the Hypericifolia clade, all C(4), with both New World and Old World groups. Incongruence between chloroplast and ITS phylogenies and divergent cloned copies of EMB2765 exon 9 suggest extensive hybridization, especially in the Hawaiian Islands radiation. •
The Chamaesyce clade originated in warm, arid areas of North America, where it evolved C(4) photosynthesis. From there, it diversified globally with extensive reticulate evolution and frequent long-distance dispersals. Although many species are weedy, there are numerous local adaptations to specific substrates and regional or island radiations, which have contributed to the great diversity of this group.
大戟属的 chamaesyce 分支是真双子叶植物中最大的 C(4)植物谱系，包含 350 个种，包括狭窄的特有种和世界性的杂草。我们对这个组进行了全球采样，以解决关于亚分支关系、C(4)光合作用的起源、杂草的进化以及杂交和长距离扩散在该组多样化中的作用等问题。
对 138 种内群和 6 种外群种进行了两个核（ITS 和 EMB2765 exon 9）和三个叶绿体标记（matK、rpl16 和 trnL-F）的测序。在有>1%重叠峰的类群中克隆了 EMB2765 的 exon 9。
chamaesyce 分支是单系的，由三个主要的亚分支组成[1(2,3)]：（1）acuta 分支，包含三个具有 C(3)光合作用和 C(3)-C(4)中间产物的北美种；（2）peplis 分支，主要分布于北美，完全是 C(4)；和（3）hypericifolia 分支，全部是 C(4)，既有新世界组也有旧世界组。叶绿体和 ITS 系统发育之间的不一致以及 EMB2765 exon 9 的分歧克隆拷贝表明广泛的杂交，特别是在夏威夷群岛辐射中。
chamaesyce 分支起源于温暖、干旱的北美地区，在那里它进化出了 C(4)光合作用。从那里，它在全球范围内多样化，具有广泛的网状进化和频繁的长距离扩散。尽管许多物种是杂草，但有许多对特定基质的局部适应和区域或岛屿辐射，这为该组的多样性做出了贡献。
