Bilobate leaves of Bauhinia (Leguminosae, Caesalpinioideae, Cercideae) from the middle Miocene of Fujian Province, southeastern China and their biogeographic implications.
Bilobate leaves of Bauhinia (Leguminosae, Caesalpinioideae, Cercideae) from the middle Miocene of Fujian Province, southeastern China and their biogeographic implications.
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中国东南部福建省中新世中期紫荆花（豆科、云实亚科、芹科）的双叶叶及其生物地理学意义
DOI：
10.1186/s12862-015-0540-9
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发表时间：
2015-11-16
影响因子：
3.4
通讯作者：
Li Z
中科院分区：
文献类型：
--
作者：
Lin Y;Wong WO;Shi G;Shen S;Li Z
形态学和分子系统发育研究表明，泛热带的广义羊蹄甲属（Bauhinia L. s.l.，羊蹄甲亚族，紫荆族，豆科）是并系类群，或许可细分为9个属，其中包括狭义羊蹄甲属（Bauhinia L. s.s. ）及其近缘属。它们的叶子通常具有明显的二裂特征，因此在化石记录中很容易识别。这为在形态学和分子研究框架下，从历史角度了解羊蹄甲属植物的早期演化、多样化以及生物地理历史提供了契机。
本文详细总结了羊蹄甲属及其近缘属在全球的分类、分布和叶结构，这构成了对二裂叶化石进行分类以及评估羊蹄甲属化石记录和生物地理学的基础。在中国东南部福建省中新世中期的佛昙群中描述了两种羊蹄甲属植物。新种类蹄羊蹄甲（Bauhinia ungulatoides sp. nov.）的特征为叶浅至中度二裂，具叶枕，基部浅心形，每裂片先端锐尖，气孔复合体为平列型。修订后的佛昙羊蹄甲（Bauhinia fotana F.M.B. Jacques et al. emend. ）具有中度二裂、具叶枕的叶子，基部中至深心形，每裂片先端锐尖或略钝。
二裂叶化石类蹄羊蹄甲和佛昙羊蹄甲，以及中国晚古近纪 - 早新近纪该属的其他记录表明，到晚古近纪时羊蹄甲属在中国南方已经具有多样性。它们分别与南美洲和南亚的一些物种极为相似，这意味着羊蹄甲属可能在中新世期间或之前经历了广泛的扩散和多样化。化石记录、现存物种多样性以及分子系统发育分析表明，羊蹄甲亚族可能起源于特提斯海东缘低纬度地区的古近纪。它们向南扩散至非洲，在渐新世期间通过北大西洋陆桥或漂浮岛屿从欧亚大陆迁移到北美洲。然后，自中新世起，该属可能通过巴拿马地峡扩散至南美洲，并在新近纪气候变冷期间在中高纬度的热带北缘地区经历了区域性灭绝。因此，羊蹄甲属目前呈现出泛热带洲际间断分布。
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BackgroundMorphological and molecular phylogenetic studies suggest that the pantropical genusBauhiniaL. s.l. (Bauhiniinae, Cercideae, Leguminosae) is paraphyletic and may as well be subdivided into nine genera, includingBauhiniaL. s.s. and its allies. Their leaves are usually characteristic bilobate and are thus easily recognized in the fossil record. This provides the opportunity to understand the early evolution, diversification, and biogeographic history of orchid trees from an historical perspective under the framework of morphological and molecular studies.ResultsThe taxonomy, distribution, and leaf architecture ofBauhiniaand its allies across the world are summarized in detail, which formed the basis for classifying the bilobate leaf fossils and evaluating the fossil record and biogeography ofBauhinia. Two species ofBauhiniaare described from the middle Miocene Fotan Group of Fujian Province, southeastern China.Bauhinia ungulatoidessp. nov. is characterized by shallowly to moderately bilobate, pulvinate leaves with shallowly cordate bases and acute apices on each lobe, as well as paracytic stomatal complexes.Bauhinia fotanaF.M.B. Jacques et al. emend. possesses moderately bilobate, pulvinate leaves with moderately to deeply cordate bases and acute or slightly obtuse apices on each lobe.ConclusionsBilobate leaf fossilsBauhinia ungulatoidesandB. fotanatogether with other late Paleogene – early Neogene Chinese record of the genus suggest thatBauhiniahad been diverse in South China by the late Paleogene. Their great similarities to some species from South America and South Asia respectively imply thatBauhiniamight have undergone extensive dispersals and diversification during or before the Miocene. The fossil record, extant species diversity, as well as molecular phylogenetic analyses demonstrate that the Bauhiniinae might have originated in the Paleogene of low-latitudes along the eastern Tethys Seaway. They dispersed southwards into Africa, migrated from Eurasia to North America via the North Atlantic Land Bridge or floating islands during the Oligocene. Then the genus spread into South America probably via the Isthmus of Panama since the Miocene onward, and underwent regional extinctions in the Boreotropics of mid-high-latitudes during the Neogene climatic cooling. Hence,Bauhiniapresently exhibits a pantropical intercontinental disjunct distribution.