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Evaluating Alternative Metacommunity Hypotheses for Diatoms in the McMurdo Dry Valleys Using Simulations and Remote Sensing Data
Frontiers in Ecology and Evolution ( IF 2.4 ) Pub Date : 2020-09-25 , DOI: 10.3389/fevo.2020.521668
Eric R. Sokol , J. E. Barrett , Tyler J. Kohler , Diane M. McKnight , Mark R. Salvatore , Lee F. Stanish

Diatoms are diverse and widespread freshwater Eukaryotes that make excellent microbial subjects for addressing questions in metacommunity ecology. In the McMurdo Dry Valleys of Antarctica, the simple trophic structure of glacier-fed streams provides an ideal outdoor laboratory where well-described diatom assemblages are found within two cyanobacterial mat types, which occupy different habitats and vary in coverage within and among streams. Specifically, black mats of Nostoc spp. occur in marginal wetted habitats, and orange mats (Oscillatoria spp. and Phormidium spp.) occur in areas of consistent stream flow. Despite their importance as bioindicators for changing environmental conditions, the role of dispersal in structuring dry valley diatom metacommunities remains unclear. Here, we use MCSim, a spatially explicit metacommunity simulation package for R, to test alternative hypotheses about the roles of dispersal and species sorting in maintaining the biodiversity of diatom assemblages residing in black and orange mats. The spatial distribution and patchiness of cyanobacterial mat habitats was characterized by remote imagery of the Lake Fryxell sub-catchment in Taylor Valley. The available species pool for diatom metacommunity simulation scenarios was informed by the Antarctic Freshwater Diatoms Database, maintained by the McMurdo Dry Valleys Long Term Ecological Research program. We used simulation outcomes to test the plausibility of alternative community assembly hypotheses to explain empirically observed patterns of freshwater diatom biodiversity in the long-term record. The most plausible simulation scenarios suggest species sorting by environmental filters, alone, was not sufficient to maintain biodiversity in the Fryxell Basin diatom metacommunity. The most plausible scenarios included either (1) neutral models with different immigration rates for diatoms in orange and black mats or (2) species sorting by a relatively weak environmental filter, such that dispersal dynamics also influenced diatom community assembly, but there was not such a strong disparity in immigration rates between mat types. The results point to the importance of dispersal for understanding current and future biodiversity patterns for diatoms in this ecosystem, and more generally, provide further evidence that metacommunity theory is a useful framework for testing hypotheses about microbial community assembly.

中文翻译:

使用模拟和遥感数据评估麦克默多干谷硅藻的替代元群落假设

硅藻是多种多样且分布广泛的淡水真核生物,它们是解决元群落生态学问题的优秀微生物课题。在南极洲的麦克默多干谷,冰川喂养的溪流的简单营养结构提供了一个理想的室外实验室,在那里可以在两种蓝藻垫类型中发现充分描述的硅藻组合,它们占据不同的栖息地,并且在溪流内和溪流之间的覆盖范围不同。具体来说,Nostoc spp 的黑色垫子。发生在边缘湿润的栖息地,橙色垫子(Oscillatoria spp. 和 Phormidium spp.)出现在河流流量一致的地区。尽管它们作为改变环境条件的生物指标很重要,但分散在构建干谷硅藻元群落中的作用仍不清楚。在这里,我们使用 MCSim,R 的空间明确的元群落模拟包,用于测试关于散布和物种分类在维持居住在黑色和橙色垫子中的硅藻组合的生物多样性方面的作用的替代假设。蓝藻垫栖息地的空间分布和斑驳性以泰勒谷 Fryxell 湖子集水区的远程图像为特征。用于硅藻元群落模拟场景的可用物种库来自南极淡水硅藻数据库,该数据库由麦克默多干谷长期生态研究计划维护。我们使用模拟结果来测试替代群落组装假设的合理性,以解释长期记录中经验观察到的淡水硅藻生物多样性模式。最合理的模拟场景表明,单独通过环境过滤器进行物种分类不足以维持 Fryxell 盆地硅藻元群落的生物多样性。最合理的情况包括(1)橙色和黑色垫中硅藻具有不同迁移率的中性模型,或(2)通过相对较弱的环境过滤器对物种进行分类,这样扩散动态也影响了硅藻群落的组装,但没有这样的垫子类型之间的移民率存在很大差异。结果表明扩散对于理解该生态系统中硅藻当前和未来的生物多样性模式的重要性,更一般地说,提供了进一步的证据,证明元群落理论是检验微生物群落组装假设的有用框架。单独,不足以维持 Fryxell 盆地硅藻元群落的生物多样性。最合理的情况包括(1)橙色和黑色垫中硅藻具有不同迁移率的中性模型,或(2)通过相对较弱的环境过滤器对物种进行分类,这样扩散动态也影响了硅藻群落的组装,但没有这样的垫子类型之间的移民率存在很大差异。结果表明扩散对于理解该生态系统中硅藻当前和未来的生物多样性模式的重要性,更一般地说,提供了进一步的证据,证明元群落理论是检验微生物群落组装假设的有用框架。单独,不足以维持 Fryxell 盆地硅藻元群落的生物多样性。最合理的情况包括(1)橙色和黑色垫中硅藻具有不同迁移率的中性模型,或(2)通过相对较弱的环境过滤器对物种进行分类,这样扩散动态也影响了硅藻群落的组装,但没有这样的垫子类型之间的移民率存在很大差异。结果表明扩散对于理解该生态系统中硅藻当前和未来的生物多样性模式的重要性,更一般地说,提供了进一步的证据,证明元群落理论是检验微生物群落组装假设的有用框架。最合理的情况包括(1)橙色和黑色垫中硅藻具有不同迁移率的中性模型,或(2)通过相对较弱的环境过滤器进行物种分类,这样扩散动态也影响了硅藻群落的组装,但没有这样的垫子类型之间的移民率存在很大差异。结果表明扩散对于理解该生态系统中硅藻当前和未来的生物多样性模式的重要性,更一般地说,提供了进一步的证据,证明元群落理论是检验微生物群落组装假设的有用框架。最合理的情况包括(1)橙色和黑色垫中硅藻具有不同迁移率的中性模型,或(2)通过相对较弱的环境过滤器对物种进行分类,这样扩散动态也影响了硅藻群落的组装,但没有这样的垫子类型之间的移民率存在很大差异。结果表明扩散对于理解该生态系统中硅藻当前和未来的生物多样性模式的重要性,更一般地说,提供了进一步的证据,证明元群落理论是检验微生物群落组装假设的有用框架。这样,扩散动态也影响了硅藻群落的组装,但垫类型之间的迁移率没有如此大的差异。结果表明扩散对于理解该生态系统中硅藻当前和未来的生物多样性模式的重要性,更一般地说,提供了进一步的证据,证明元群落理论是检验微生物群落组装假设的有用框架。这样,扩散动态也影响了硅藻群落的组装,但垫类型之间的迁移率没有如此大的差异。结果表明扩散对于理解该生态系统中硅藻当前和未来的生物多样性模式的重要性,更一般地说,提供了进一步的证据,证明元群落理论是检验微生物群落组装假设的有用框架。
更新日期:2020-09-25
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