Areography, environmental heterogeneity and spatial models explain patterns of past and present diversity in Edraianthus (Campanulaceae)

Our study aims to shed light on distribution patterns and the relationship between species diversity and environmental heterogeneity of 17 <em>Edraianthus</em> taxa. We examined present-day and past distribution (Last Glacial Maximum) by applying ecological niche modelling. The environmental space occupied by the taxa was analysed using niche comparison methods. The results support the idea that the central and southern Dinaric Alps represent a centre of diversity and endemism in the western Balkan Peninsula. <em>Edraianthus</em> diversity is best explained by topographic (slope) and bioclimatic predictors (maximum temperature of warmest month, precipitation seasonality, precipitation of warmest quarter, precipitation of coldest quarter), suggesting that mountain areas with the most diversified relief have higher diversity. Niche modelling results suggest considerable range dynamics during the climatically unstable Quaternary. Thermophitic and lowland taxa responded with longitudinal shifts to ecologically suitable areas farther south, while high mountain taxa responded mainly with elevational shifts. The greatest niche similarity is found among phylogenetically closely related taxa and among ecologically similar and often sympatric taxa. The least similarity was observed in species with marked differences in habitat elevation and in more geographically isolated species. Our results suggest that the extent of range and niche overlap varied among some taxa throughout their evolutionary history, which may have led to diversification at both allopatric and sympatric levels. The correlation between the genetic diversity of the most widespread taxon and the richness of taxa could be a consequence of past and present contacts. On the other hand, alternate periods of isolation may have favoured the emergence of taxa that are reproductively isolated and ecologically specialised.本研究旨在阐明17个球果风铃草属（Edraianthus）类群的分布格局及其物种多样性与环境异质性之间的关联。本研究采用生态位建模（ecological niche modelling）方法，分析了类群当前及末次冰盛期（Last Glacial Maximum）的历史分布情况，并通过生态位比较方法解析了该属类群所占据的环境空间。研究结果支持“迪纳里克阿尔卑斯山脉中部与南部是巴尔干半岛西部的物种多样性与特有性中心”这一观点。球果风铃草属的物种多样性最优可由地形因子（坡度）与生物气候预测因子（最热月最高温、降水季节性、最热季降水量、最冷季降水量）解释，这表明地形起伏最为多样的山地区域拥有更高的物种多样性。生态位建模结果显示，在气候不稳定的第四纪时期，类群的分布范围发生了显著的动态变化。其中，嗜热类群与低地类群通过沿经度方向迁移至更靠南的适宜生态区域做出响应，而高山类群则主要通过海拔梯度上的迁移完成分布调整。系统发育关系密切的类群之间、生态特征相似且通常同域分布（sympatric）的类群之间，生态位相似度最高；而生境海拔差异显著的物种以及地理隔离程度更高的物种，其生态位相似度则最低。本研究结果表明，部分类群在其演化历史中，分布范围与生态位重叠程度存在差异，这可能推动了异域分化（allopatric）与同域分化两种模式下的物种多样化进程。分布最广的类群的遗传多样性与类群丰富度之间的相关性，可能是过去与当前类群间基因交流的结果。另一方面，周期性的隔离时期可能促进了生殖隔离且生态特化的类群的形成。