CNRS, Université Paul Sabatier, IRD, UMR 5174 EDB (Laboratoire Évolution & Diversité Biologique), 118 route de Narbonne, F-31062 Toulouse, France.
Claude E. Phillips Herbarium, Delaware State University, 1200 North DuPont Highway, Dover, DE 19901, USA.
Ann Bot. 2024 Oct 30;134(4):577-592. doi: 10.1093/aob/mcae100.
Progress in the systematic studies of the olive family (Oleaceae) during the last two decades provides the opportunity to update its backbone phylogeny and to investigate its historical biogeography. We also aimed to understand the factors underlying the disjunct distribution pattern between East Asia and both West Asia and Europe that is found more commonly in this family than in any other woody plant family.
Using a sampling of 298 species out of ~750, the largest in a phylogenetic study of Oleaceae thus far, with a set of 36 plastid and nuclear markers, we reconstructed and dated a new phylogenetic tree based on maximum likelihood and Bayesian methods and checked for any reticulation events. We also assessed the relative support of four competing hypotheses [Qinghai-Tibet Plateau uplift (QTP-only hypothesis); climatic fluctuations (climate-only hypothesis); combined effects of QTP uplift and climate (QTP-climate hypothesis); and no effects (null hypothesis)] in explaining these disjunct distributions.
We recovered all tribes and subtribes within Oleaceae as monophyletic, but uncertainty in the position of tribe Forsythieae remains. Based on this dataset, no reticulation event was detected. Our biogeographical analyses support the QTP-climate hypothesis as the likely main explanation for the East-West Eurasian disjunctions in Oleaceae. Our results also show an earlier origin of Oleaceae at ~86 Mya and the role of Tropical Asia as a main source of species dispersals.
Our new family-wide and extensive phylogenetic tree highlights both the stable relationships within Oleaceae, including the polyphyly of the genus Chionanthus, and the need for further systematic studies within the largest and most undersampled genera of the family (Chionanthus and Jasminum). Increased sampling will also help to fine-tune biogeographical analyses across spatial scales and geological times.
过去二十年中，对橄榄科（Oleaceae）系统研究的进展为更新其系统发育框架和研究其历史生物地理学提供了机会。我们还旨在了解该科中常见的东亚与西亚和欧洲之间的间断分布模式的背后因素，这比任何其他木本植物科更为常见。
利用迄今橄榄科系统发育研究中最大的样本（约 750 种中的 298 种），使用一套 36 个质体和核标记，我们基于最大似然法和贝叶斯法重建和测定了一个新的系统发育树，并检查了任何网状进化事件。我们还评估了四个竞争假说[青藏高原隆起（仅青藏高原假说）；气候波动（仅气候假说）；青藏高原隆起和气候的综合影响（青藏高原-气候假说）；和无影响（无效假说）]在解释这些间断分布中的相对支持。
我们恢复了橄榄科中的所有族和亚族为单系，但 Forsythieae 族的位置仍存在不确定性。基于这个数据集，没有检测到网状进化事件。我们的生物地理学分析支持青藏高原-气候假说作为橄榄科东亚-西欧亚间断分布的主要解释。我们的结果还表明，橄榄科的起源更早，约为 8600 万年前，热带亚洲是物种扩散的主要来源。
我们的新的全家族广泛的系统发育树突出了橄榄科内部的稳定关系，包括 Chionanthus 属的多系性，以及在科中最大和采样最少的属（Chionanthus 和 Jasminum）中进行进一步系统研究的必要性。增加采样也将有助于在空间尺度和地质时间上微调生物地理学分析。
