Department of Plant Biology, Southern Illinois University, Carbondale, IL, 62901-6509, USA.
Department of Zoology, Southern Illinois University, Carbondale, IL, 62901-6509, USA.
Am J Bot. 2019 Mar;106(3):402-414. doi: 10.1002/ajb2.1250. Epub 2019 Mar 11.
The sandalwood order (Santalales) includes members that present a diverse array of inflorescence types, some of which are unique among angiosperms. This diversity presents not only interpretational challenges but also opportunities to test fundamental concepts in plant morphology. Here we used modern phylogenetic approaches to address the evolution of inflorescences in the sandalwood order.
Phylogenetic analyses of two nuclear and three chloroplast genes were conducted on representatives of 146 of the 163 genera in the order. A matrix was constructed that scored nine characters dealing with inflorescences. One character, "trios", that encompasses any grouping of three flowers (i.e., both dichasia and triads) was optimized on samples of the posterior distribution of trees from the Bayesian analysis using BayesTraits. Three nodes were examined: the most recent common ancestors of (A) all ingroup members, (B) Loranthaceae, and (C) Opiliaceae, Santalaceae s.l., and Viscaceae.
The phylogenetic analysis resulted in many fully resolved nodes across Santalales with strong support for 18 clades previously named as families. The trios character was not supported for nodes A and C, whereas it was supported for node B where this partial inflorescence type is best described as a triad.
Essentially every major inflorescence type can be found in Santalales; however, the dichasium, a type of partial inflorescence, is rarely seen and is not plesiomorphic for the order. In the family Erythropalaceae, inflorescences are mostly in small, axillary fascicles or cymes. Successive families show both cymose and racemose types and compound systems (e.g., thyrses). Inflorescences in Amphorogynaceae and Viscaceae are not dichasial and in general are difficult to compare to "standard" inflorescences.
檀香目（檀香目）包括呈现出多种多样花序类型的成员，其中一些在被子植物中是独特的。这种多样性不仅带来了解释上的挑战，也为检验植物形态学的基本概念提供了机会。在这里，我们使用现代系统发育方法来解决檀香目植物花序的演化问题。
对檀香目中 163 个属中的 146 个代表进行了两个核和三个叶绿体基因的系统发育分析。构建了一个矩阵，该矩阵对涉及花序的九个特征进行了评分。一个特征“trios”，它包含任何三个花的组合（即，二分花序和三联体），是在贝叶斯分析中基于后验树样本使用 BayesTraits 对其进行优化的。检查了三个节点：（A）所有内群成员、（B）桑寄生科和（C）檀香科、桑寄生科和西番莲科的最近共同祖先的共同祖先。
系统发育分析导致檀香目中许多完全解决的节点具有强烈的支持，共有 18 个分支被命名为科。trios 特征不支持节点 A 和 C，而支持节点 B，在该节点中，这种部分花序类型最好被描述为三联体。
基本上，檀香目中可以找到每一种主要的花序类型；然而，二分花序，一种部分花序类型，很少见，并且不是该目的原始特征。在 Erythropalaceae 科中，花序大多是小的、腋生的束或聚伞花序。连续的科都显示出聚伞状和总状类型和复合系统（例如，复伞形花序）。Amphorogynaceae 和 Viscaceae 的花序不是二分的，通常难以与“标准”花序进行比较。
