EPISODIC MIGRATION OF OAKS TO ICELAND: EVIDENCE FOR A NORTH ATLANTIC "LAND BRIDGE" IN THE LATEST MIOCENE
EPISODIC MIGRATION OF OAKS TO ICELAND: EVIDENCE FOR A NORTH ATLANTIC "LAND BRIDGE" IN THE LATEST MIOCENE
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DOI：
10.3732/ajb.0900195
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发表时间：
2010-02-01
影响因子：
3
通讯作者：
Zetter, Reinhard
中科院分区：
文献类型：
--
作者：
Denk, Thomas;Grimsson, Fridgeir;Zetter, Reinhard
确定北大西洋陆桥（NALB）的沉降历史对于理解北方温带树木的洲际分离至关重要。传统上，NALB一直被认为是作为一个走廊的植物迁移，只有在新生代早期，但最近的植物化石的发现和分子研究的推论是挑战这一观点。在这里，我们报告分散花粉栎晚中新世沉积物在冰岛，表现出与现存的北方半球白色橡树和北美红橡树的亲和力。年龄较大（15至10马）的沉积物不包含花粉的栎属表明它到达后，时间。花粉从9-8马Hrutagil地方是无法区分的形态之间常见的白色和红色橡树。相比之下，花粉从5.5马Selargil地方有一个顶盖，目前仅限于北美白色和红橡树，表明第二集迁移到冰岛。这些发现表明，温带植物类群的跨大西洋迁移可能并没有受到中新世期间广阔海域或寒冷气候的限制。此外，我们的研究结果提供了一个合理的解释现代间断欧洲和北美橡树之间的遗传分化程度非常低。
Dating the subsidence history of the North Atlantic Land Bridge (NALB) is crucial for understanding intercontinental disjunctions of northern temperate trees. Traditionally, the NALB has been assumed to have functioned as a corridor for plant migration only during the early Cenozoic, but recent findings of plant fossils and inferences from molecular studies are challenging this view. Here, we report dispersed pollen of Quercus from Late Miocene sediments in Iceland that shows affinities with extant northern hemispheric white oaks and North American red oaks. Older (15 to 10 Ma) sediments do not contain pollen of Quercus suggesting it arrived after that time. Pollen from the 9-8 Ma Hrutagil locality is indistinguishable from morphotypes common among white and red oaks. In contrast, pollen from the 5.5 Ma Selargil locality has a tectum that is at present confined to North American white and red oaks, indicating a second episode of migration to Iceland. These findings suggest that transatlantic migration of temperate plant taxa may not have been limited by vast areas of sea or by cold climates during the Miocene. Furthermore, our results offer a plausible explanation for the remarkably low degree of genetic differentiation between modern disjunct European and North American oaks.