Data from: Evolution of woody life form on tropical mountains in the tribe Spermacoceae (Rubiaceae)

Spermacoceae are mainly an herbaceous group in the Rubiaceae. However, a few lineages are woody, and are found in a diverse range of habitat types. Three of the largest woody lineages (Arcytophyllum, Hedyotis, and Kadua) are characterized by their distribution in the moist tropical mountains, and have disjunct distribution patterns with respect to their closest relatives. In this study, we explore the cases of derived woodiness in these three lineages and their diversification dynamics in the tropical mountains of Asia, the Pacific, and the Americas. By combining phylogenetic results with wood anatomical studies, we estimated timing of origin of the three woody groups, inferred their ancestral traits and ancestral distribution ranges, analyzed their associations with the tropical upland habitat, and elucidated their diversification across tropical mountains.
The three woody clades originated and diversified from herbaceous ancestors in close association with the tropical upland habitat during the Miocene. The ancestral range for Asian-Pacific Hedyotis and Pacific Kadua is Africa/Madagascar and continental Asia respectively. The complex geological history of tropical Asia allowed Hedyotis to diversify faster and create narrow endemics near oceans in the highlands of Western Ghats (India), Sri Lanka, Southeast Asia including southeastern China, and New Guinea. The three major woody clades in Spermacoceae have gained their woodiness independently from one another, subsequent to colonization by their ancestors from a different geographic environment. The evolution and diversification along the tropical mountain orogeny is strongly linked with the formation of woody habit and many narrow endemic species.

耳草族（Spermacoceae）是茜草科（Rubiaceae）中主要为草本的类群。但有少数支系演化出木本性状，且分布于多样的生境类型中。其中三个最大的木本支系（Arcytophyllum属、耳草属Hedyotis、卡杜阿属Kadua）以分布于湿润热带山地为典型特征，且与其近缘类群呈现出间断分布格局。本研究聚焦这三个支系的次生木质化现象，以及它们在亚洲、太平洋及美洲热带山地的演化动态。研究结合系统发育结果与木材解剖学研究，估算了这三个木本类群的起源时间，推断了它们的祖先性状与祖先分布范围，分析了其与热带高地生境的关联，并阐明了它们在热带山地间的演化分化过程。
这三个木本支系均起源于草本祖先，并在中新世时期与热带高地生境紧密结合的背景下发生演化分化。亚太耳草属（Hedyotis）与太平洋卡杜阿属（Kadua）的祖先分布范围分别为非洲/马达加斯加与大陆亚洲。热带亚洲复杂的地质历史使得耳草属的演化分化速率更快，并在西高止山脉（印度）、斯里兰卡、包括中国东南部的东南亚以及新几内亚的滨海高地形成了众多狭域特有种。耳草族的三个主要木本支系均独立演化出木质化性状，其祖先均来自不同的地理环境并完成定殖后才发生这一转变。热带山地造山运动伴随的演化与分化过程，与木质化习性的形成以及众多狭域特有种的产生密切相关。