Data from: Phylogeny and circumscription of Cephalocereus (Cactaceae) based on molecular and morphological evidence

Cephalocereus, Neobuxbaumia, and Pseudomitrocereus (Cactaceae, Cactoideae, Echinocereeae) are related genera of columnar cacti native to Mexico with current ambiguous circumscription. We applied maximum parsimony and Bayesian inference methods to reconstruct the phylogeny of the Cephalocereus group using molecular data from seven chloroplast regions (petL-psbE, psbA-trnH, rpl16, rpl32-trnLUAG, trnL-F, trnQrps16, andycf1), simple coded indels, and 46 structural characters. The Cephalocereus group was recovered as monophyletic with high support values, whereas Neobuxbaumia appeared as paraphyletic, due to the polyphyly of Cephalocereus and the derived position of Pseudomitrocereus within this group. Topology was mostly congruent among the different phylogenetic methods explored, and three pervasive clades were observed. Two structural characters were confirmed as synapomorphies for the Cephalocereus group: prismatic crystals in the dermal system and a perianth woody cap persistent in the fruit. The derived position of Pseudomitrocereus suggests that new hypotheses must be explored regarding the possible hybrid origin of this taxon. We propose the transfer of all species of Neobuxbaumia, Cephalocereus, and Pseudomitrocereus to a single genus, in which Cephalocereus takes priority over the other names. Based on our results, a new circumscription for Cephalocereus is proposed, including a taxonomic synthesis, two new combinations (Cephalocereus multiareolatus and Cephalocereus sanchezmejoradae), and a key for species.

翁柱属（Cephalocereus）、新柱属（Neobuxbaumia）与假米柱属（Pseudomitrocereus）为原产于墨西哥的柱状仙人掌近缘属，隶属于仙人掌科（Cactaceae）、仙人掌亚科（Cactoideae）、仙人柱族（Echinocereeae），目前其分类界定仍存在歧义。本研究采用最大简约法（maximum parsimony）与贝叶斯推断法（Bayesian inference），基于7个叶绿体区域（petL-psbE、psbA-trnH、rpl16、rpl32-trnLUAG、trnL-F、trnQ-rps16及ycf1）的分子数据、简单编码的插入缺失变异（indels）以及46个形态结构性状，对翁柱属类群开展系统发育重建。系统发育分析结果显示，翁柱属类群为单系群（monophyletic）且支持度较高；而新柱属呈现并系群（paraphyletic）特征，这源于翁柱属本身为多系群（polyphyly），且假米柱属在该类群中处于衍生演化位置。不同系统发育分析方法得到的拓扑结构整体一致性良好，共识别出3个稳定的演化支。本研究确认了两个结构性状可作为翁柱属类群的共源性状（synapomorphies）：表皮系统中的棱柱状晶体，以及留存于果实上的花被木质化帽状体。假米柱属的衍生演化位置提示，需针对该类群可能的杂交起源探索新的研究假说。本研究提议将新柱属、翁柱属与假米柱属的所有物种合并至单一属中，依据命名优先法则，采用翁柱属（Cephalocereus）作为该合并属的合法名称。基于本研究结果，我们提出翁柱属新的分类界定方案，包含分类学综述、2个新组合（Cephalocereus multiareolatus与Cephalocereus sanchezmejoradae）以及该属物种的检索表。