Phytochemical variation in treetops: causes and consequences for tree-insect herbivore interactions

Abstract

The interaction of plants and their herbivorous opponents has shaped the evolution of an intricate network of defences and counter-defences for millions of years. The result is an astounding diversity of phytochemicals and plant strategies to fight and survive. Trees are specifically challenged to resist the plethora of abiotic and biotic stresses due to their dimension and longevity. Here, we review the recent literature on the consequences of phytochemical variation in trees on insect–tree–herbivore interactions. We discuss the importance of genotypic and phenotypic variation in tree defence against insects and suggest some molecular mechanisms that might bring about phytochemical diversity in crowns of individual trees.

Independent and interactive effects of plant genotype and environment on plant traits and insect herbivore performance: A meta‐analysis with Salicaceae

“…This finding corresponds well with previous work (Barbour et al., , ; Johnson, Agrawal, Maron, & Salminen, ) and a meta‐analysis of heritability estimates for plant functional traits (Geber & Griffen, ), which found that plant secondary chemistry was more heritable than plant growth and size metrics ( h 2 = 0.43 and 0.16, respectively). Secondary metabolites mediate plant interactions with the environment and thus often undergo variable selection pressures across space and time, resulting in highly variable expression across plant genets (Lämke & Unsicker, ; Moore, Andrew, Külheim, & Foley, ). This broad pattern is seen in levels of salicinoids and condensed tannins in Salicaceae species, which can vary up to 10‐fold across genets grown in a common location (Boeckler et al., ; Förster, Ulrichs, Zander, Kätzel, & Mewis, ; Lindroth & St. Clair, ).…”

From plants to herbivores: novel insights into the ecological and evolutionary consequences of plant variation

“…In various temperate trees, temperature, water availability and herbivory are major factors causing changes in concentrations of volatile organic compounds and phenolics, as reviewed by Lämke and Unsicker (2018). In contrast to temperate trees, induction by herbivores seems to be of less relevance in expanding leaves of neotropical trees, where only phenolics slightly increase after herbivore damage (Coley et al 2018).…”

“…Lämke and Unsicker (2018) indicate that genome duplication, followed by functional diversification as well as hybridization are major drivers of variation. Coley et al (2018) review and integrate their years of research on Inga, a speciose genus of tropical trees.…”

“…Intrinsic mechanisms underlying withinand among-plant variation Two reviews (Coley et al 2018;Lämke and Unsicker 2018) examine the underlying molecular mechanisms and consequences of variation in plant defenses to long-lived trees, which are often understudied. Lämke and Unsicker (2018) indicate that genome duplication, followed by functional diversification as well as hybridization are major drivers of variation.…”

“…The studies of this special topic cover a broad range of plant life forms, from marine algae in an aquatic system (Ledet et al 2018) to terrestrial herbs (Calf et al 2018;Chiriboga et al 2018;Cuny et al 2018;Howard et al 2018;Humphrey et al 2018;Kergunteuil et al 2018;Quintero and Bowers 2018), to shrubs (Nell et al 2018;Ochoa-López et al 2018), to long-lived trees (Albrectsen et al 2018;Bagchi et al 2018;Cipollini and Peterson 2018;Coley et al 2018;Falk et al 2018;Lämke and Unsicker 2018). In twelve case studies and four review papers, selected aspects of the huge variation in phenomena and underlying mechanisms are highlighted and new research questions opened, which may inspire further research in this exciting field.…”