Department of Botany, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden.
Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
Ann Bot. 2022 Dec 16;130(6):849-867. doi: 10.1093/aob/mcac121.
The tribe Danaideae (Rubiaceae) is almost exclusively endemic to the Western Indian Ocean Region (WIOR), and encompasses the genera Danais, Payera and Schismatoclada that occur in humid, sub-humid and mountain and mountain bio climate zones. Much of the species diversity is endemic to restricted, remote and/or mountainous areas of Madagascar and recent field work on the island indicates substantial unknown diversity of the Danaideae. Furthermore, the monophyly of the Malagasy genera Payera and Schismatoclada has been questioned in previous work, species delimitations and phylogenetic relationships within the genera are poorly understood, and the distribution and evolution of gross morphological features have not been assessed.
We conducted morphological investigations, and produced robust phylogenies of Danaideae based on nuclear and plastid sequence data from 193 terminals. Ample plant material has been newly collected in the WIOR for the purpose of the present study, including potentially new species unknown to science. We performed Bayesian non-clock and relaxed-clock analyses employing three alternative clock models of a dataset with a dense sample of taxa from the entire geographical ranges of Danaideae. Based on the results, we discuss species diversity and distribution, relationships, and morphology in Danaideae.
Our results demonstrate the monophyly of Danaideae, its three genera and 42 species. Nine species are resolved as non-monophyletic. Many geographically distinct but morphologically heterogeneous lineages were identified, and morphological features traditionally considered diagnostic of subgroups of the genera, used for example in species identification keys, are not clade-specific.
Our results demonstrate that Madagascar contains ample previously undocumented morphological and species diversity of Danaideae. Our novel approach to molecular phylogenetic analyses as a precursor to taxonomic revisions provides numerous benefits for the latter. There are tentative indications of parallel northward diversification in Payera and Schismatoclada on Madagascar, and of geographical phylogenetic clustering despite the anemochorous condition of Danaideae.
Danaideae 族（茜草科）几乎完全局限于西印度洋地区（WIOR），包括 Danais、Payera 和 Schismatoclada 属，它们分布在潮湿、半湿润和山地及山地生物气候带。该族的大部分物种多样性是马达加斯加特有种，局限于偏远和/或多山地区，最近在该岛上的实地考察表明，Danaideae 具有大量未知的多样性。此外，在以前的研究中，马达加斯加的 Payera 和 Schismatoclada 属的单系性受到质疑，属内的物种界限和系统发育关系理解甚少，宏观形态特征的分布和进化尚未得到评估。
我们进行了形态学研究，并基于核和质体序列数据，对来自 193 个终端的 Danaideae 进行了稳健的系统发育分析。为了本研究的目的，在西印度洋地区新采集了大量植物材料，包括科学界未知的潜在新物种。我们对具有 Danaideae 整个地理分布范围的大量分类群的数据集，使用三种替代时钟模型，进行了贝叶斯非时钟和松弛时钟分析。基于这些结果，我们讨论了 Danaideae 的物种多样性和分布、关系和形态。
我们的结果表明 Danaideae、其三个属和 42 个种是单系的。有 9 个种是非单系的。鉴定出许多在地理上不同但形态上异质的谱系，并且传统上被认为是分组特征的形态特征，例如在物种鉴定钥匙中使用的特征，不是分支特异性的。
我们的研究结果表明，马达加斯加含有大量以前未记录的 Danaideae 形态和物种多样性。我们对分子系统发育分析的新方法作为分类修订的前奏，为后者提供了许多好处。在马达加斯加，Payera 和 Schismatoclada 有向北多样化的迹象，尽管 Danaideae 是风媒传粉的，但地理上的系统发育聚类也有迹象。
