An increase in biotic interactions towards lower latitudes is one of the most consistent patterns in ecology. Higher temperatures and more stable climatic conditions at low latitudes are thought to enhance biotic interactions, accelerating biological evolution and leading to stronger anti-herbivore defences in plants. However, some studies report contradictory findings, highlighting the need for further investigation into the underlying mechanisms. We used a combination of field observations and feeding trials in controlled environments to investigate the effect of climate on chemical defences and insect herbivory in pedunculate oak (Quercus robur L.) throughout most of its geographic range in Europe, while controlling for physical defences. The concentration of lignin, flavonoids, and total phenolics increased significantly with temperature, whereas both field herbivory and weight of spongy moth (Lymantria dispar L.) larvae were negatively influenced by temperature. Lignin concentration positively influenced the weight of spongy moth larvae whereas it had no effect on field herbivory. We found no evidence of strong positive relationships between insect herbivory and larvae growth with leaf defences. Our study underscores the complexity of plant-herbivore interactions along climatic gradients and highlights the need for further research to disentangle these intricate relationships.

• Klíčová slova
• Lymantria dispar, Larvae biomass, Leaf chemical defences, Plant–insect interactions,
• MeSH
• býložravci * MeSH
• dub (rod) * chemie   fyziologie   metabolismus   MeSH
• fenoly * metabolismus   MeSH
• flavonoidy metabolismus   MeSH
• larva fyziologie   růst a vývoj   MeSH
• lignin metabolismus   MeSH
• listy rostlin * chemie   metabolismus   MeSH
• můry * fyziologie   růst a vývoj   MeSH
• podnebí * MeSH
• teplota MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Evropa MeSH
• Názvy látek
• fenoly * MeSH
• flavonoidy MeSH
• lignin MeSH

To what extent particular plant defences against herbivorous insects are constitutive or inducible will depend on the costs and benefits in their neighbourhood. Some defensive chemicals in leaves are thought to be costly and hard to produce rapidly, while others, including volatile organic compounds that attract natural enemies, might be cheaper and can be released rapidly. When surrounding tree species are more closely related, trees can face an increased abundance of both specialist herbivores and their parasitoids, potentially increasing the benefits of constitutive and inducible defences. To test if oaks (Quercus robur) respond more to herbivore attacks with volatile emission than with changes in leaf phenolic chemistry and carbon to nitrogen ratio (C: N), and whether oaks respond to the neighbouring tree species, we performed an experiment in a forest in Poland. Oak saplings were placed in neighbourhoods dominated by oak, beech, or pine trees, and half of them were treated with the phytohormone methyl jasmonate (elicitor of anti-herbivore responses). Oaks responded to the treatment by emitting a different volatile blend within 24 h, while leaf phenolic chemistry and C: N remained largely unaffected after 16 days and multiple treatments. Leaf phenolics were subtly affected by the neighbouring trees with elevated flavan-3-ols concentrations in pine-dominated plots. Our results suggest that these oaks rely on phenols as a constitutive defence and when attacked emit volatiles to attract natural enemies. Further studies might determine if the small effect of the neighbourhood on leaf phenolics is a response to different levels of shading, or if oaks use volatile cues to assess the composition of their neighbourhood.

• Klíčová slova
• Intra-specific Variation, Methyl Jasmonate, Polyphenols, Tritrophic Interactions, VOCs,
• MeSH
• acetáty MeSH
• býložravci * MeSH
• cyklopentany metabolismus   chemie   MeSH
• dub (rod) * chemie   metabolismus   MeSH
• dusík metabolismus   MeSH
• flavonoidy * metabolismus   analýza   chemie   MeSH
• listy rostlin * chemie   metabolismus   MeSH
• oxylipiny metabolismus   chemie   MeSH
• těkavé organické sloučeniny * metabolismus   chemie   analýza   MeSH
• uhlík metabolismus   chemie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• acetáty MeSH
• cyklopentany MeSH
• dusík MeSH
• flavan-3-ol MeSH Prohlížeč
• flavonoidy * MeSH
• methyl jasmonate MeSH Prohlížeč
• oxylipiny MeSH
• těkavé organické sloučeniny * MeSH
• uhlík MeSH