Hardseededness is a common trait in Mediterranean plant communities, although the origin of its selection is controversial. It may be a mechanism of persistence to fire temperatures, but could also form part of a gap-detecting mechanism to provide germination cues under arid conditions. To disentangle this, we studied the phylogenetic structure of plant communities against fire frequency and aridity gradients. The phylogenetic structure in Mediterranean Basin ecosystems was analysed for the hardseededness trait as a whole and was separated by the families composing this trait (Fabaceae and Cistaceae). This study focused on woody perennial species. The phylogenetic structure was also contrasted against soil classes. Hardseededness on the whole, and for the Fabaceae family alone, showed phylogenetic clustering as aridity increased. Cistaceae displayed the opposite pattern with phylogenetic clustering in most humid areas, together with a significant soil effect. Surprisingly, fire frequency had no influence in any case. This climate-driven phylogenetic clustering indicates that the hardseededness trait could confer some fitness advantage under dry conditions. For this reason, coexisting species were more closely related in the community with increasing aridity. This effect was especially evident for the Fabaceae family. These results shed some light on the evolutionary selection of this adaptive trait under Mediterranean conditions. Our results question the role of fire in the selection of the hardseededness trait in Mediterranean Basin ecosystems and indicates that climate is the most important factor. Therefore, we should be cautious in assigning to fire a preponderant role in the selection of some plant traits.

硬种子是地中海植物群落的一个共同特征，尽管其选择的起源是有争议的。它可能是对火灾温度持续存在的一种机制，但也可能构成间隙检测机制的一部分，以在干旱条件下提供发芽线索。为了解决这个问题，我们研究了植物群落对火频和干旱梯度的系统发育结构。对地中海盆地生态系统的种系结构进行了整体硬种子性状分析，并由构成该性状的科（Fabaceae和Cistaceae）分开。这项研究的重点是多年生木本植物。系统发育结构也与土壤类别形成对比。整体上，以及仅对豆科植物而言，硬种子显示出随着干旱增加，系统发生聚类。在大多数湿润地区，Cistaceae表现出相反的格局，并带有系统发育簇，并具有显着的土壤效应。令人惊讶的是，开火频率在任何情况下都没有影响。这种气候驱动的系统发育聚类表明，硬种子性状可以在干燥条件下赋予某些健身优势。因此，社区中共存的物种与干旱的增加有着更紧密的联系。对于豆科（Fabaceae）家族而言，这种效果尤为明显。这些结果为地中海条件下该适应性状的进化选择提供了一些启示。我们的结果质疑火在地中海盆地生态系统硬种子性状选择中的作用，并表明气候是最重要的因素。因此，