Abstract The pantropical Picrodendraceae produce mostly spheroidal to slightly oblate, echinate pollen grains equipped with narrow circular to elliptic pori that can be hard to identify to family level in both extant and fossil material using light microscopy only. Fossil pollen of the family have been described from the Paleogene of America, Antarctica, Australia, New Zealand, and Europe, but until now none have been reported from Afro-India. Extant pollen described here include representatives from all recent Picrodendraceae genera naturally occurring in Africa and/or Madagascar and south India and selected closely related tropical American taxa. Our analyses, using combined light microscopy and scanning electron microscopy, show that pollen of the Afro-Indian genera encompass three morphological types: Type 1, comprising only Hyaenanche; Type 2, including Aristogeitonia, Mischodon, Oldfieldia and Voatamalo; Type 3, comprising the remaining two genera, Androstachys and Stachyandra. Based on the pollen morphology presented here it is evident that some previous light microscopic accounts of spherical and echinate fossil pollen affiliated with Arecaceae, Asteraceae, Malvaceae, and Myristicaceae from the African continent could belong to Picrodendraceae. The pollen morphology of Picrodendraceae, fossil pollen records, a dated intra-familial phylogeny, seed dispersal modes, and the regional Late Cretaceous to early Cenozoic paleogeography, together suggest the family originated in the Americas and dispersed from southern America across Antarctica and into Australasia. A second dispersal route is believed to have occurred from the Americas into continental Africa via the North Atlantic Land Bridge and Europe.

中文翻译：

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Afro-Indian Picrodendraceae 的起源和分化：连接花粉形态、传播方式、化石记录、分子测年和古地理

摘要 泛热带的黄柏科产生的花粉粒大多呈球形至略扁圆形，带有细圆形至椭圆形孔，仅使用光学显微镜很难在现存和化石材料中鉴定到科水平。该科的花粉化石曾在美洲、南极洲、澳大利亚、新西兰和欧洲的古近纪被描述过，但到目前为止，还没有来自非洲-印度的报道。这里描述的现存花粉包括来自非洲和/或马达加斯加和印度南部自然发生的所有最近的 Picrodenderaceae 属的代表，以及选择的密切相关的热带美洲分类群。我们使用组合光学显微镜和扫描电子显微镜进行的分析表明，非洲-印度属的花粉包含三种形态类型：1 型，仅包含 Hyaenanche；类型 2, 包括 Aristogeitonia、Mischodon、Oldfieldia 和 Voatamalo；类型 3，包括其余两个属，Androstachys 和 Stachyandra。根据这里介绍的花粉形态，很明显，以前一些来自非洲大陆的属于槟榔科、菊科、锦葵科和肉豆蔻科的球形和刺状化石花粉的光镜记录可能属于 Picrodendraceae。Picrodendraceae 的花粉形态、花粉化石记录、过时的科内系统发育、种子传播模式以及区域晚白垩世至早新生代古地理，共同表明该科起源于美洲，并从南美洲扩散到南极洲和大洋洲。