González-Carrera Santiago, Fernández-Fuentes Alejandro, Escudero Alfonso, García-Estévez Ignacio, Martínez-Ortega Montserrat, Mediavilla Sonia
Department of Ecology, Faculty of Biology, University of Salamanca, c/ Licenciado Méndez Nieto, s/n, Salamanca 37071, Spain.
Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Pharmacy, University of Salamanca, c/ Licenciado Méndez Nieto, s/n, Salamanca 37071, Spain.
Tree Physiol. 2025 Jan 25;45(1). doi: 10.1093/treephys/tpae170.
Insect herbivory has attracted enormous attention from researchers due to its effects on plant fitness. However, there remain questions such as what are the most important leaf traits that determine consumption levels, whether there are latitudinal gradients in herbivore pressure, or whether there are differences in susceptibility between hybrids and their parental species. In this work, we address all these issues in two species of Mediterranean Quercus (Quercus faginea subsp. faginea Lam. and Quercus pyrenaica Wild.) and their hybrids. Over 2 years, we analyzed leaf emergence and 11 leaf traits (biomechanical, chemical and morphological), as well as the levels of herbivory by insects in leaves of the three genetic groups in different locations distributed along a climatic gradient. The hybrids showed intermediate values between both species in leaf emergence, chemical traits and structural reinforcement. By contrast, they were more similar to Q. faginea in leaf size and shape. Despite their intermediate leaf traits, hybrids always showed lower losses by consumption than both parental species, which suggests that they possess inherent higher resistance to herbivores, which cannot be explained by their dissimilarities in leaf traits. Within each genetic group, differences in leaf size were the most important determinant of differences in herbivory losses, which increased with leaf size. In turn, leaf size increased significantly with the increase in mean annual temperatures across the climatic gradient, in parallel with herbivory losses. In conclusion, contrary to our expectations, hybrids maintained lower levels of herbivory than their parent species. Given the potential negative effect of leaf herbivory on carbon fixation, this advantage of the hybrids would imply a threat to the persistence of both pure species. More research is needed to elucidate possible alternative mechanisms that allow for maintaining species integrity in the absence of reproductive barriers.
昆虫食草行为因其对植物适合度的影响而吸引了研究人员的极大关注。然而，仍存在一些问题，例如决定啃食水平的最重要叶片性状是什么，食草动物压力是否存在纬度梯度，或者杂种与其亲本物种之间的易感性是否存在差异。在这项研究中，我们针对两种地中海栎属植物（法氏栎亚种法氏栎Lam.和比利牛斯栎Wild.）及其杂种解决了所有这些问题。在两年多的时间里，我们分析了叶片的出现情况以及11个叶片性状（生物力学、化学和形态学），以及沿着气候梯度分布的不同地点的三个遗传群体叶片上昆虫的食草水平。杂种在叶片出现、化学性状和结构强化方面表现出介于两个物种之间的中间值。相比之下，它们在叶片大小和形状上更类似于法氏栎。尽管杂种具有中间叶片性状，但它们的被啃食损失总是低于两个亲本物种，这表明它们对食草动物具有内在的更高抗性，而这无法用它们在叶片性状上的差异来解释。在每个遗传群体中，叶片大小的差异是食草损失差异的最重要决定因素，食草损失随叶片大小增加而增加。反过来，叶片大小随着气候梯度上年平均温度的升高而显著增加，与食草损失同步。总之，与我们的预期相反，杂种的食草水平低于其亲本物种。鉴于叶片食草行为对碳固定的潜在负面影响，杂种的这一优势可能对两个纯合物种的存续构成威胁。需要更多研究来阐明在没有生殖隔离的情况下允许维持物种完整性的可能替代机制。
