Palaeoecology of Macroneuropteris scheuchzeri, and its implications for resolving the paradox of ‘xeromorphic’ plants in Pennsylvanian wetlands
Palaeoecology of Macroneuropteris scheuchzeri, and its implications for resolving the paradox of ‘xeromorphic’ plants in Pennsylvanian wetlands
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DOI：
10.1016/j.palaeo.2012.03.019
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发表时间：
2012-05
期刊：
影响因子：
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通讯作者：
Gregory W. Stull;W. DiMichele;H. Falcon-Lang;W. Nelson;Scott D. Elrick
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作者：
Gregory W. Stull;W. DiMichele;H. Falcon-Lang;W. Nelson;Scott D. Elrick
有髓蕨类植物Macroneuropteris scheuchzeri（Hoffmann）Cleal，Shute & Zodrow广泛分布于热带泛古陆的宾夕法尼亚纪中晚期森林中。根据其厚的表皮，很少的正面气孔，凹陷的气孔，和密集的毛状体，它已被推断为旱生植物。在这里，我们通过分析它的相分布，特别是与煤的关系，在华盛顿，华盛顿特区史密森国家自然历史博物馆的约45个地层中收集了273个地点，这些标本集代表了大部分（部分）本地的组合，并覆盖了泛大陆中西部阿巴拉契亚山脉以西的该分类群的完整已知的时间范围。相产状资料的卡方分析表明，M。scheuchzeri有一个强烈的偏好矿物质丰富的湿地，立即之前和之后的泥炭沼泽和沼泽（煤）的发展，特别是在晚中宾夕法尼亚州（晚莫斯科）的时间，符合一个时期的减少极地冰量。在晚宾夕法尼亚世，随着全球变暖和热带湿地重组，古赤道气候转向整体干燥模式。这是伴随着M的消失。scheuchzeri从欧洲及其限制，西部的阿巴拉契亚山脉，以最潮湿的栖息地的景观。因此，我们的数据证伪了M. scheuchzeri是一个传统的旱生植物，但突出了一个明显的旱生植物特征局限于湿地栖息地的矛盾。我们认为这种关联有几种可能的解释：（1）对营养缺乏的反应，（2）对基质盐度的反应（由于沿海红树林栖息地的生长），（3）对古生代大气成分的反应，（4）投资回报（长叶寿命），（5）反映祖先条件的系统发育限制。我们的研究结果有更广泛的意义，解释各种各样的其他宾夕法尼亚州的湿地植物，同样显示出“旱生”的功能。
The medullosan pteridosperm Macroneuropteris scheuchzeri (Hoffmann) Cleal, Shute & Zodrow was widespread and abundant in the Middle to Late Pennsylvanian forests of tropical Pangaea. On the basis of its thick cuticles, few adaxial stomata, sunken stomata, and dense trichomes, it has been inferred to be a xeromorphic plant. Here we test that hypothesis by analyzing its facies distribution, especially in relation to coals, at 273 site collections from ~45 stratigraphic horizons accessioned in the Smithsonian National Museum of Natural History, Washington, D.C., U.S.A. The collections represent mostly (par)autochthonous assemblages and cover the taxon's complete known temporal range west of the Appalachians in west-central Pangaea. Chi-square analysis of facies-occurrence data indicates that M. scheuchzeri had a strong preference for mineral-enriched wetlands that immediately preceded and followed the development of peat swamps and mires (coals), particularly during the late Middle Pennsylvanian (late Moscovian) times, coincident with a period of reduced polar ice volume. In the Late Pennsylvanian, following an interval of global warming and tropical wetland reorganization, palaeoequatorial climate shifted to an overall drier mode. This was accompanied by the disappearance of M. scheuchzeri from Europe and its limitation, west of the Appalachians, to the wettest available habitats on the landscape. Thus, our data falsify the hypothesis that M. scheuchzeri was a conventional xerophyte, but highlight the paradox of a plant with apparent xeromorphic features confined to a wetland habitat. We consider several possible explanations for this association: (1) response to nutrient deficiency, (2) response to substrate salinity (due to growth in coastal mangrove habitats), (3) response to the composition of the Palaeozoic atmosphere, (4) return on investment (long leaf lifespan), and (5) phylogenetic constraint reflecting ancestral conditions. Our findings have broader implications for interpreting a wide variety of other Pennsylvanian wetland plants, which similarly show ‘xermorphic’ features.