Molecular Ecology Laboratory, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, 8140 New Zealand.
Syst Biol. 2012 May;61(3):461-89. doi: 10.1093/sysbio/syr130. Epub 2012 Jan 4.
The Guiana Shield (GS) is one of the most pristine regions of Amazonia and biologically one of the richest areas on Earth. How and when this massive diversity arose remains the subject of considerable debate. The prevailing hypothesis of Quaternary glacial refugia suggests that a part of the eastern GS, among other areas in Amazonia, served as stable forested refugia during periods of aridity. However, the recently proposed disturbance-vicariance hypothesis proposes that fluctuations in temperature on orbital timescales, with some associated aridity, have driven Neotropical diversification. The expectations of the temporal and spatial organization of biodiversity differ between these two hypotheses. Here, we compare the genetic structure of 12 leaf-litter inhabiting frog species from the GS lowlands using a combination of mitochondrial and nuclear sequences in an integrative analytical approach that includes phylogenetic reconstructions, molecular dating, and Geographic Information System methods. This comparative and integrated approach overcomes the well-known limitations of phylogeographic inference based on single species and single loci. All of the focal species exhibit distinct phylogeographic patterns highlighting taxon-specific historical distributions, ecological tolerances to climatic disturbance, and dispersal abilities. Nevertheless, all but one species exhibit a history of fragmentation/isolation within the eastern GS during the Quaternary with spatial and temporal concordance among species. The signature of isolation in northern French Guiana (FG) during the early Pleistocene is particularly clear. Approximate Bayesian Computation supports the synchrony of the divergence between northern FG and other GS lineages. Substructure observed throughout the GS suggests further Quaternary fragmentation and a role for rivers. Our findings support fragmentation of moist tropical forest in the eastern GS during this period when the refuge hypothesis would have the region serving as a contiguous wet-forest refuge.
圭亚那地盾（GS）是亚马逊地区最原始的地区之一，也是地球上生物多样性最丰富的地区之一。这种巨大的多样性是如何以及何时产生的，仍然是一个相当有争议的话题。第四纪冰川避难所的主流假说是，GS 的东部地区与亚马逊地区的其他地区一样，在干旱时期是稳定的森林避难所。然而，最近提出的干扰-分歧假说认为，轨道时间尺度上的温度波动，伴随着一些相关的干旱，推动了新热带地区的多样化。这两种假说对生物多样性的时间和空间组织的期望不同。在这里，我们使用线粒体和核序列的组合，在一个包括系统发育重建、分子年代测定和地理信息系统方法的综合分析方法中，比较了来自 GS 低地的 12 种叶栖蛙类的遗传结构。这种比较和综合的方法克服了基于单一物种和单一基因座的系统地理学推断的众所周知的局限性。所有的焦点物种都表现出独特的系统地理学模式，突出了特定分类单元的历史分布、对气候干扰的生态容忍度和扩散能力。然而，除了一种之外，所有物种在第四纪期间都表现出在 GS 东部的碎裂/隔离历史，物种之间存在时空一致性。在更新世早期，法属圭亚那北部的隔离特征尤为明显。近似贝叶斯计算支持了法属圭亚那北部与其他 GS 谱系之间的分歧的同步性。在整个 GS 中观察到的亚结构表明进一步的第四纪碎裂作用和河流的作用。我们的研究结果支持了在这个时期东部 GS 湿润热带森林的碎裂化，当时避难所假说认为该地区是一个连续的湿润森林避难所。
