Le Péchon Timothée, Zhang Liang, He Hai, Zhou Xin-Mao, Bytebier Benny, Gao Xin-Fen, Zhang Li-Bing
Chengdu Institute of Biology, Chinese Academy of Sciences, P.O. Box 416, Chengdu, Sichuan 610041, China; School of Life Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg 3209, South Africa.
Chengdu Institute of Biology, Chinese Academy of Sciences, P.O. Box 416, Chengdu, Sichuan 610041, China.
Mol Phylogenet Evol. 2016 May;98:324-36. doi: 10.1016/j.ympev.2016.02.018. Epub 2016 Mar 2.
Intercontinental disjunctions in ferns have often been considered as the result of long-distance dispersal (LDD) events rather than of vicariance. However, in many leptosporangiate groups, both processes appear to have played a major role in shaping current geographical distribution. In this study, we reconstructed the phylogenetic relationships and inferred the ancestral distribution areas of the polystichoid ferns (Cyrtomium, Phanerophlebia, and Polystichum), to evaluate the relative impact of vicariance and LDD on the biogeography of this group. We used a molecular dataset including 3346 characters from five plastid loci. With 190 accessions our taxon coverage was about three times as large as any previous worldwide sampling. Biogeographical analyses were performed using S-DIVA and S-DEC and divergence times were estimated by integrating fossil and secondary calibrations. The polystichoid ferns are a monophyletic clade that may have originated in East Asia during the Eocene, an age much younger than previously estimated. Three transoceanic disjunctions between East Asia and New World were identified in the Paleogene: one for Phanerophlebia during late Eocene (34Ma, 19-51Ma), and two in Polystichum at the Eocene-Oligocene boundary (30Ma, 18-43Ma; 28Ma, 19-39Ma respectively). During the Neogene, further range expansions took place from Asia to Africa, Hawaii, and the Southwestern Indian Ocean region. Our results indicate that early transfers between the Old and the New World are compatible with a boreotropical migration scenario. After evolving in Asia during the Eocene, the polystichoid ferns reached the New World in independent migrations at the Eocene-Oligocene boundary through the boreotropical belt. However, although less likely, the alternative hypothesis of independent transoceanic dispersals from the Old to the New World cannot be ruled out. Further range expansion during the Neogene was most likely the result of long-distance dispersal (LDD).
蕨类植物的洲际间断分布通常被认为是长距离扩散（LDD）事件的结果，而非地理隔离的结果。然而，在许多薄囊蕨类植物类群中，这两个过程似乎在塑造当前地理分布方面都发挥了重要作用。在本研究中，我们重建了耳蕨类蕨类植物（贯众属、拟贯众属和耳蕨属）的系统发育关系，并推断其祖先分布区域，以评估地理隔离和长距离扩散对该类群生物地理学的相对影响。我们使用了一个分子数据集，包括来自五个质体基因座的3346个字符。我们的分类群覆盖范围有190个样本，大约是此前任何全球采样的三倍。使用S-DIVA和S-DEC进行生物地理学分析，并通过整合化石和二级校准来估计分歧时间。耳蕨类蕨类植物是一个单系类群，可能在始新世起源于东亚，这一年代比之前估计的要年轻得多。在古近纪发现了东亚和新世界之间的三次跨洋间断分布：一次是拟贯众属在始新世晚期（3400万年前，1900 - 5100万年前），另外两次是耳蕨属在始新世 - 渐新世边界（分别为3000万年前，1800 - 4300万年前；2800万年前，1900 - 3900万年前）。在新近纪，进一步的分布范围扩张从亚洲发生到非洲、夏威夷和印度洋西南部地区。我们的结果表明，旧世界和新世界之间的早期转移与北温带迁移情景相符。在始新世于亚洲进化后，耳蕨类蕨类植物在始新世 - 渐新世边界通过北温带带独立迁移到达新世界。然而，尽管可能性较小，但从旧世界到新世界独立跨洋扩散的另一种假设也不能排除。新近纪期间进一步的分布范围扩张很可能是长距离扩散（LDD）的结果。
