Floristic distinctiveness and endemic richness of woody plants highlight the biodiversity value of the <i>herriza</i> among all Mediterranean heathlands

<b><i>Background</i></b>: Heathlands are relatively abundant in the landscape of the western Mediterranean region, especially in the Strait of Gibraltar region, where it is locally known as herriza. They are associated with a mild Mediterranean climate regime and with acid, nutrient-poor soils. They harbour a high plant diversity, often viewed as a consequence of the transition between European Atlantic heathland and Mediterranean sclerophyllous shrubland floras. <b><i>Aims</i></b>: To determine whether species-rich Mediterranean heathlands, including the herriza, constitute distinct heathland formations rather than transitional vegetation units between Atlantic heathlands and Mediterranean garrigue shrublands. <b><i>Methods</i></b>: We quantified species richness, endemism and analysed the β-diversity of the woody component of Mediterranean heathland communities throughout its geographic range, with special emphasis on the Strait of Gibraltar region. <b><i>Results</i></b>: Mediterranean heathlands, including the herriza, are not transitional communities between Atlantic heathlands and Mediterranean shrublands. Woody species richness and, particularly, endemic richness was the highest in the herriza. <b><i>Conclusions</i></b>: The high biodiversity values of the herriza are a likely consequence of the ecological singularity of the Strait of Gibraltar region and its known role as a glacial refugium. Despite its treeless feature, the herriza deserves special recognition and protection from both in its European and North African extension.<b><i>背景</i></b>：石楠灌丛在西地中海地区的景观中分布相对广泛，尤以直布罗陀海峡区域为甚，该区域内的石楠灌丛在当地被称为herriza。这类灌丛适宜于温和的地中海气候与酸性低营养土壤，拥有极高的植物多样性，这一特征通常被认为是欧洲大西洋石楠灌丛与地中海硬叶灌丛植物区系之间过渡的结果。<b><i>目标</i></b>：明确包括herriza在内的物种丰富型地中海石楠灌丛是否属于独立的石楠灌丛群落类型，而非大西洋石楠灌丛与地中海嘎利哥灌丛之间的过渡性植被单元。<b><i>方法</i></b>：本研究对地中海石楠灌丛群落整个分布范围内的木本组分的物种丰富度、特有性进行了量化，并分析了其β多样性，重点聚焦直布罗陀海峡区域。<b><i>结果</i></b>：包括herriza在内的地中海石楠灌丛并非大西洋石楠灌丛与地中海嘎利哥灌丛之间的过渡性群落。其中，木本物种丰富度，尤其是特有物种丰富度，在herriza中达到最高水平。<b><i>结论</i></b>：herriza所具备的高生物多样性价值，大概率源于直布罗陀海峡区域的生态独特性，以及该区域作为冰期避难所的已知功能。尽管herriza无乔木覆盖，但其在欧洲与北非的分布范围均应得到特别的关注与保护。