Data from: Woody flora types to describe phytogeographic units: an insight along a west–east transect in central Italy

To improve the phytogeographic characterization of peninsular Italy, we analysed and compared the spatial distribution of woody flora at species and genus levels along an approximate 160 km west–east transect within the central peninsula. Sampling sites were selected using a subjective stratified sampling design. A total of 1710 occurrence data, 138 species, and 74 genera from 153 floristic relevés was used. The congruence in species and genera patterns, supported by Mantel and Procrustes tests, confirmed the validity of the higher-taxon approach to analyse woody flora patterns. Nonmetric multidimensional scaling and Pearson's chi square test pointed out that elevation and related bioclimatic factors were the most important drivers of woody species composition. Three well defined woody flora types (coastal low-elevation, inland middle-elevation, and inland high-elevation) were identified using partition around medoids clustering; the species-rich inland middle-elevation type supports the recently described Transition unit between the Mediterranean and Eurosiberian Regions. Contrary to previous assumptions by other authors, floristic and chorological differences between the Tyrrhenian and the Adriatic subtypes were detected only in the inland high-elevation type and not in the coastal low-elevation one. The adopted methodological approach, based on higher-taxon approach, on clustering and on ordination of floristic relevés, resulted to be valuable to detect woody flora distribution patterns and to delineate the phytogeographic characters of a very heterogeneous and biodiverse area.为完善意大利半岛的植物地理区划研究，我们针对半岛中部一条长约160km的东西向样带，开展了木本植物区系在物种和属级阶元上的空间分布格局分析与对比。采样点位采用主观分层抽样方案选取。本研究共使用了来自153个植物区系样方的1710条分布记录、138个物种及74个属。经曼特尔检验（Mantel test）与普洛克鲁斯忒斯检验（Procrustes test）验证的物种与属级分布格局一致性，证实了利用高阶元类群分析木本植物区系格局的有效性。非度量多维标度分析（Nonmetric Multidimensional Scaling）与皮尔逊卡方检验结果显示，海拔及其相关的生物气候因子是驱动木本植物物种组成的最关键因素。通过围绕中心点的划分聚类法（Partition Around Medoids），本研究识别出三类特征鲜明的木本植物区系类型：沿海低海拔型、内陆中海拔型与内陆高海拔型。其中物种丰富度较高的内陆中海拔型，佐证了近期被提出的地中海区与欧西伯利亚区之间的过渡单元。与此前其他学者的推论相悖，本研究仅在内陆高海拔型中检测到第勒尼安亚型与亚得里亚亚型间的区系及分布区类型差异，而沿海低海拔型并无此类差异。本研究采用的基于高阶元类群分析、植物区系样方聚类与排序的方法论，可有效揭示木本植物区系的分布格局，并为高度异质且生物多样性丰富的区域划定植物地理特征提供可靠支撑。