Data from: Global biogeography and diversification of palms sheds light on the evolution of tropical lineages. I. Historical biogeography

AIM: Palms (Arecaceae/Palmae) are a model group for evolutionary studies in the tropics. Family-wide data on taxonomy, phylogenetics and distribution are now available, but a general framework of palm evolution is still lacking. The overall aim of this study, published in two companion papers, is to seek evolutionary explanations for the geographical distribution of palm lineages and species diversity patterns at global and regional levels. In this first paper we undertake a detailed analysis of palm biogeography for all major lineages in a global context, comparing our results to the fossil record, molecular dating studies and previously established biogeographical hypotheses for the family. LOCATION: Global. METHODS: A dated phylogeny of all palm genera and distributional data were used to infer ancestral areas. A global model of area evolution for tropical lineages was formulated and ancestral areas were reconstructed using a maximum likelihood approach under the dispersal–extinction–cladogenesis model. RESULTS: The crown node divergence of palms and divergences of all five subfamilies occurred before the end of the Cretaceous within Laurasian regions. Early range expansions into South America took place in the stem lineages of subfamilies Arecoideae and Ceroxyloideae, and into Africa and South America in Cretaceous lineages within subfamily Calamoideae. The largest subfamily Arecoideae underwent its early diversification history in South America and has been an important source of lineages expanding into other regions, notably in the major Indo-Pacific tribe Areceae. In contrast, the history of subfamily Coryphoideae was primarily Laurasian, supporting earlier boreotropical hypotheses for the group. Dispersals across Wallace's Line are prevalent in major groups of Arecoideae, Calamoideae and Coryphoideae, both before and after the Miocene geological evolution of the Malesian Archipelago. MAIN CONCLUSIONS: We present the first robust biogeographical hypothesis for the evolution of palms in space and time. Although palms show evidence of dispersal limitation, our findings highlight the role of long-distance dispersal events in the establishment of major biogeographical patterns of palm clades. This is consistent with the growing evidence for long-distance dispersal as a major mechanism underpinning the distribution of tropical lineages.

研究目标：棕榈科（Arecaceae/Palmae）是热带地区进化生物学研究的经典模式类群。目前学界已获取该科全科范围的分类学、系统发育学与分布数据，但仍缺乏一套通用的棕榈演化研究框架。本研究以两篇姊妹论文的形式发表，其整体研究目标是阐释棕榈支系的地理分布格局，以及全球与区域尺度下物种多样性模式的进化成因。在本第一篇论文中，我们基于全球尺度对所有主要棕榈支系开展了详尽的生物地理学分析，并将研究结果与化石记录、分子定年研究以及先前提出的该科生物地理学假说进行比对。
研究区域：全球范围。
研究方法：本研究通过所有棕榈属的带时间标度的系统发育树与分布数据，推断祖先分布区。我们构建了热带支系的全球分布区演化模型，并基于扩散-灭绝-分支（dispersal–extinction–cladogenesis, DEC）模型，采用最大似然法重建祖先分布区。
研究结果：棕榈科冠群的分化以及全部5个亚科的分化事件均发生于白垩纪末期之前的劳亚古陆区域。早期向南美洲的分布扩张发生于槟榔亚科（Arecoideae）和蜡椰亚科（Ceroxyloideae）的基干支系；而向非洲与南美洲的分布扩张则发生于省藤亚科（Calamoideae）内的白垩纪支系。最大的亚科——槟榔亚科（Arecoideae）的早期多样化过程起源于南美洲，且该亚科是向其他区域扩散支系的重要来源，尤其是在印太地区主要类群槟榔族（Areceae）中。与之相对，扇叶椰亚科（Coryphoideae）的演化历史主要局限于劳亚古陆，这支持了该类群先前的北热带生物地理假说。跨华莱士线（Wallace's Line）的扩散事件在槟榔亚科、省藤亚科与扇叶椰亚科的主要类群中均普遍存在，且发生于马来群岛中新世地质演化的前后。
主要结论：本研究首次提出了棕榈科在时空尺度下演化的可靠生物地理学假说。尽管棕榈类群表现出扩散限制的特征，但本研究结果凸显了长距离扩散事件在塑造棕榈支系主要生物地理分布格局中的关键作用。这一结论与日益增多的研究证据相吻合——长距离扩散是支撑热带类群地理分布的核心机制。