Abstract Calycanthus (Calycanthaceae), a genus for which three species are described, belongs to an early diverging lineage of angiosperms. As far as known, all species have highly specialized sap beetle (Nitidulidae) pollination systems. While the floral scent is likely to play a key role in attracting the beetles to the flowers, its chemistry is not known for any of the species of this genus. Herein, we analyzed the floral scent of the species Calycanthus occidentalis by dynamic headspace and gas chromatography / mass spectrometry (GC/MS), and determined its floral visitors in plants cultivated in the Botanical Garden of the University of Ulm. The protogynous flowers had one-to-two days lasting anthesis, similar to what was previously reported for native stands in California. More than ten pollinating beetle species, mainly Nitidulidae and Staphylinidae, were collected from the floral chambers of pistillate-stage flowers and identified to species level by DNA barcoding. The high number of beetle species inside the flowers was surprising, especially considering that only the nitidulid species Colopterus truncatus was known so far as pollinator in native habitats. In addition, we observed some drosophilid flies on, but not inside the flowers, which suggests that they are not pollinators. The scent of flowers had a strong alcoholic note, especially in the pistillate phase. The GC/MS data revealed that the most prominent scent compounds were ethanol, ethyl acetate, acetoin, 2,3-butanediol isomers, acetoin acetate, 2,3-butandiol monoacetate, and 2,3-butandiol diacetate. Interestingly, besides scent compounds that were previously found in plants pollinated by nitidulid and staphylinid beetles, some other compounds, including acetoin acetate and 2,3-butandiol monoacetate, were observed for the first time as floral scent of plants attracting such beetles. However, further studies will be required to investigate whether the stereoisomeric pattern of these compounds differs among plant species and whether the stereoisomers attract different pollinator species. Overall, the scent of C. occidentalis is similar to that of other plant species that release scents reminiscent of fermenting fruits and are pollinated by beetles and/or drosophilid flies, such as Asimina triloba, Ceropegia crassifolia and Arum palaestinum.

中文翻译：

---

仿甲虫授粉的 Calycanthus occidentalis (Calycanthaceae) 发酵果实

摘要 Calycanthus (Calycanthaceae) 属于被子植物的早期分化谱系，共有三个物种。众所周知，所有物种都具有高度专业化的树液甲虫（Nitidulidae）授粉系统。虽然花香可能在将甲虫吸引到花朵中发挥关键作用，但该属的任何物种都不知道其化学成分。在此，我们通过动态顶空和气相色谱/质谱 (GC/MS) 分析了 Calycanthus occidentalis 的花香，并确定了乌尔姆大学植物园栽培植物中的花香访客。原始花有 1 到 2 天的持续开花期，类似于之前报道的加利福尼亚本地林分。十余种授粉甲虫，主要是 Nitidulidae 和 Staphylinidae，从雌蕊花的花室中收集，并通过 DNA 条形码鉴定到物种水平。花中甲虫的数量之多令人惊讶，特别是考虑到目前只有 nitidulid 物种 Colopterus truncatus 被认为是原生栖息地的传粉者。此外，我们观察到一些果蝇在花上，但不在花内，这表明它们不是传粉者。花香有强烈的酒精味，尤其是在雌蕊阶段。GC/MS 数据显示，最突出的气味化合物是乙醇、乙酸乙酯、乙偶姻、2,3-丁二醇异构体、乙偶姻乙酸酯、2,3-丁二醇单乙酸酯和 2,3-丁二醇二乙酸酯。有趣的是，除了先前在由 nitidulid 和 staphylinid 甲虫授粉的植物中发现的气味化合物外，还首次观察到一些其他化合物，包括醋酸乙偶姻和 2,3-丁二醇单乙酸酯，作为吸引此类甲虫的植物的花香。然而，需要进一步研究来调查这些化合物的立体异构模式是否因植物物种而异，以及立体异构体是否吸引不同的传粉物种。总体而言，C. occidentalis 的气味类似于其他植物物种的气味，这些植物释放出让人联想到发酵果实的气味，并由甲虫和/或果蝇授粉，例如 Asimina triloba、Ceropegia crassifolia 和 Arum palaestinum。首次观察到植物的花香吸引了这种甲虫。然而，需要进一步研究来调查这些化合物的立体异构模式是否因植物物种而异，以及立体异构体是否吸引不同的传粉物种。总体而言，C. occidentalis 的气味类似于其他植物物种的气味，这些植物释放出让人联想到发酵果实的气味，并由甲虫和/或果蝇授粉，例如 Asimina triloba、Ceropegia crassifolia 和 Arum palaestinum。首次观察到植物的花香吸引了这种甲虫。然而，需要进一步研究来调查这些化合物的立体异构模式是否因植物物种而异，以及立体异构体是否吸引不同的传粉物种。总体而言，C. occidentalis 的气味类似于其他植物物种的气味，这些植物释放出让人联想到发酵果实的气味，并由甲虫和/或果蝇授粉，例如 Asimina triloba、Ceropegia crassifolia 和 Arum palaestinum。