Erica comprises ~860 species of evergreen shrubs and trees ranged from Europe to southern Africa and Madagascar. Wood structure of the around 20 European species is well studied, but despite its relevance to adaptation across the wider geographic range, it has not yet been explored across the much greater diversity, particularly of southern African lineages. In this study, we examine wood structure of 28 Erica species from southern Africa. In the African Erica clade, loss of scalariform perforation plates could be driven by increased aridity and seasonality in the mid-Miocene, and its re-gain can represent an adaptation to freezing in the high elevation species E. nubigena. As vessels in Erica are mostly solitary, imperforate tracheary elements probably form a subsidiary conduit network instead of vessel groups. Increase of ray frequency in habitats with a prominent dry and hot season probably facilitates refilling of vessels after embolism caused by water stress. Wider rays are ancestral for the lineage comprising African Erica and the Mediterranean E. australis. The negative correlation between ray width and expression of summer drought is consistent with Ojeda’s model explaining the diversification of seeders and resprouters among southern African Erica.

中文翻译：

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火灾、霜冻和干旱限制了南部非洲埃里卡（杜鹃花科）木材的结构多样性

埃里卡 (Erica) 包含约 860 种常绿灌木和树木，分布范围从欧洲到南部非洲和马达加斯加。大约 20 种欧洲物种的木材结构已得到充分研究，但尽管其与更广泛地理范围内的适应相关，但尚未在更大的多样性中进行探索，特别是南部非洲谱系。在这项研究中，我们研究了来自南部非洲的 28 种埃里卡树种的木材结构。在非洲埃里卡进化枝中，阶梯状穿孔板的损失可能是由于中新世中期干旱和季节性的增加造成的，而其重新获得可能代表了高海拔物种埃里卡（E. nubigena）对冰冻的适应。由于埃里卡的血管大多是孤立的，无孔气管元件可能形成辅助导管网络而不是血管群。干燥和炎热季节明显的栖息地中射线频率的增加可能有利于因水分胁迫引起的栓塞后血管的重新填充。较宽的鳐鱼是包括非洲艾丽卡和地中海艾丽卡的谱系的祖先。射线宽度与夏季干旱表达之间的负相关性与奥赫达模型一致，该模型解释了南部非洲埃里卡播种者和再发芽者的多样化。