Geographical patterns of ferns species diversity: comparing the latitudinal and elevational gradients to disentangle climatic drivers of species diversity

为了加深对蕨类生物多样性地理分布的认识，本文比较了东亚岛屿上赤道和43°N之间蕨类物种丰富度的纬度和海拔梯度。为了解开限制物种丰富度地理分布的众多潜在驱动因素，这两种梯度都越来越受欢迎。通过特别关注气候成分，我们将回答这个问题：当物种从热带气候扩散到温带气候时，必须适应的主要气候限制是什么？目前尚不清楚生物体必须主要适应气候条件的哪一部分，是极端气候还是气候条件的变化（例如季节性）。由于它们不能单独沿着纬度梯度解开，我将使用纬度梯度和海拔梯度的组合。在两极，气候条件的变化增加，但不沿海拔梯度，而极端气候的变化方式相同。因此，这种综合方法可以解开限制物种丰富度地理分布的气候限制因素和结论。这些数据进一步验证了一种假设，即系统发育组合的模式也反映了蕨类植物类群从热带温暖气候向高高山/温带气候扩散的进化史。作为前一项研究的结果，已在梯度的热带部分对计划的20个研究地点中的15个进行了取样。拟议的项目将完成这些数据到北纬带的完整纬度梯度，并且是第一个直接联系两种基本梯度类型的项目，以加深我们对气候限制蕨类生物多样性地理分布的理解。

To contribute to the increasing understanding of the geographical distribution of fern biodiversity, I aim to compare latitudinal and elevational gradients of fern species richness between the equator and 43°N on East Asian islands. Both gradients have become increasingly popular in order to disentangle the numerous potential drivers limiting the geographical distribution of species richness. By focusing specifically on the climatic component, we will answer the question: What are the main climatic constraints species have to adapt to when dispersing from the tropics to temperate climates? It is still unclear which component of climatic conditions organisms have to adapt primarily to, climatic extremes or the variation in climatic conditions (e.g. seasonality). Since they cannot be disentangled along the latitudinal gradient alone, I will use a combination of latitudinal and elevational gradients. Towards the poles, variation in climatic conditions increases but not along elevational gradients, whereas climatic extremes change the same way. This combined approach therefore allows to disentangle both factors and conclusions on the climatic constraints limiting the geographical distribution of species richness. Further these data permit to test the hypothesis that patterns of phylogenetic assemblies also reflect the evolutionary history of fern taxa in spreading from tropical-warm to high-alpine-/ temperate climates.As an outcome of a former study, 15 of the planed 20 study localities have already been sampled on the tropical part of the gradient. The proposed project will complete this data to a full latitudinal gradient up to boreal zones and is the first to directly link two basic types of gradients in order to deepen our understanding of the climatic constraints on the geographical distribuition of fern biodiversity.