Evolutionary biogeography of Manihot (Euphorbiaceae), a rapidly radiating Neotropical genus restricted to dry environments
Evolutionary biogeography of Manihot (Euphorbiaceae), a rapidly radiating Neotropical genus restricted to dry environments
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DOI：
10.1111/j.1365-2699.2011.02474.x
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发表时间：
2011-06-01
影响因子：
3.9
通讯作者：
McKey, Doyle
中科院分区：
文献类型：
--
作者：
Duputie, Anne;Salick, Jan;McKey, Doyle
目的 本研究的目的是重建木薯属（一种仅限于季节性干旱地区的新热带属）的系统发育，以深入了解其生物地理历史，并确定一种广泛种植但鲜为人知的作物：木薯（Manihot esculenta）的最接近的野生近缘种。地点中美洲和南美洲的干燥和季节性干旱地区。方法我们收集了 101 个木薯样本，代表 52 个物种，大部分来自植物标本室和两个外类群（麻疯树和 Cnidoscolus urens）。我们的研究涵盖了目前公认的木薯物种的一半以上；我们的采样涵盖了该属的整个原生范围及其大部分表型和生态变异。我们使用两个核基因和一个非编码叶绿体区域的序列重建了木薯物种之间的系统发育关系。然后我们重建了与生长形态、扩散生态和再生能力相关的性状的历史。结果中美洲的木薯物种形成了基础至南美洲的等级。后一物种表现出强烈的生物地理集群：来自塞拉多的物种形成了明确的分支，来自巴西东北部卡廷加的物种形成了另一个分支，仅限于亚马逊盆地边缘森林间隙的物种也是如此。藤本植物和树木的生长习性在该属中反复进化，果实不裂和蚂蚁介导的种子传播丧失也是如此。主要结论木薯属可能起源于中美洲，在殖民南美洲之前就在那里多样化。在南美洲，几个群体随后在各种季节性干燥的低地栖息地内向南和向东辐射。有些物种还适应了更潮湿的环境，例如亚马逊盆地边缘的森林间隙。鉴于木薯物种的扩散能力有限，我们认为这种辐射很可能仅在巴拿马地峡完成之后或之前不久（大约 3.5 Ma）发生。我们的结果与亚马逊流域或南美东部海岸过去存在的干燥植被走廊一致。此外，我们的系统发育可以识别木薯最近的野生近缘种。
Aim The aims of this study were to reconstruct the phylogeny of Manihot, a Neotropical genus restricted to seasonally dry areas, to yield insight into its biogeographic history, and to identify the closest wild relatives of a widely grown, yet poorly known, crop: cassava (Manihot esculenta).Location Dry and seasonally dry regions of Meso- and South America.Methods We collected 101 samples of Manihot, representing 52 species, mostly from herbaria, and two outgroups (Jatropha gossypiifolia and Cnidoscolus urens). More than half of the currently accepted Manihot species were included in our study; our sampling covered the whole native range of the genus, and most of its phenotypic and ecological variation. We reconstructed phylogenetic relationships among Manihot species using sequences for two nuclear genes and a non-coding chloroplast region. We then reconstructed the history of traits related to growth form, dispersal ecology and regeneration ability.Results Manihot species from Mesoamerica form a grade basal to South American species. The latter species show a strong biogeographic clustering: species from the cerrado form well defined clades, species from the caatinga of north-eastern Brazil form another, and so do species restricted to forest gaps along the rim of the Amazon basin. Vine and tree growth habits evolved repeatedly in the genus, as did fruit indehiscence and loss of ant-mediated seed dispersal.Main conclusions The genus Manihot probably originated in Mesoamerica, where it diversified prior to colonizing South America. Within South America, several groups then radiated southwards and eastwards within all kinds of seasonally dry lowland habitats. Some species also adapted to more humid environments, such as forest gaps, around the rim of the Amazon basin. Given the limited dispersal abilities of Manihot species, we propose that this radiation is most likely to have occurred only after, or shortly before, the completion of the Isthmus of Panama, around 3.5 Ma. Our results are in agreement with the past existence of a corridor of dry vegetation through Amazonia or along the eastern South American coast. In addition, our phylogeny allows identification of cassava's closest wild relatives.