▪ Abstract In this review, we discuss the ecological and evolutionary consequences of plant-herbivore interactions in tropical forests. We note first that herbivory rates are higher in tropical forests than in temperate ones and that, in contrast to leaves in temperate forests, most of the damage to tropical leaves occurs when they are young and expanding. Leaves in dry tropical forests also suffer higher rates of damage than in wet forests, and damage is greater in the understory than in the canopy. Insect herbivores, which typically have a narrow host range in the tropics, cause most of the damage to leaves and have selected for a wide variety of chemical, developmental, and phenological defenses in plants. Pathogens are less studied but cause considerable damage and, along with insect herbivores, may contribute to the maintenance of tree diversity. Folivorous mammals do less damage than insects or pathogens but have evolved to cope with the high levels of plant defenses. Leaves in tropical forests are ...

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Herbivory and plant defenses in tropical forests

Characteristics of higher plant terpenoids that result in mediation of numerous kinds of ecological interactions are discussed as a framework for this Symposium on Chemical Ecology of Terpenoids. However, the role of terpenoid mixtures, either constitutive or induced, their intraspecific qualitative and quantitative compositional variation, and their dosage-dependent effects are emphasized in subsequent discussions. It is suggested that little previous attention to these characteristics may have contributed to terpenoids having been misrepresented in some chemical defense theories. Selected phytocentric examples of terpenoid interactions are presented: (1) defense against generalist and specialist insect and mammalian herbivores, (2) defense against insect-vectored fungi and potentially pathogenic endophytic fungi, (3) attraction of entomophages and pollinators, (4) allelopathic effects that inhibit seed germination and soil bacteria, and (5) interaction with reactive troposphere gases. The results are integrated by discussing how these terpenoids may be contributing factors in determining some properties of terrestrial plant communities and ecosystems. A terrestrial phytocentric approach is necessitated due to the magnitude and scope of terpenoid interactions. This presentation has a more broadly based ecological perspective than the several excellent recent reviews of the ecological chemistry of terpenoids.

Higher plant terpenoids:a phytocentric overview of their ecological roles

An Improved Grading System For Measuring Plant Diseases Vol-36

Defense against herbivores often changes dramatically as plants develop. Hypotheses based on allocation theory and herbivore selection patterns predict that defense should increase or decrease, respectively, across ontogeny, and previous research partly supports both predictions. Thus, it remains unclear which pattern is more common and what factors contribute to variability among studies. We conducted a meta-analysis of 116 published studies reporting ontogenetic patterns in plant defense traits and herbivory. Patterns varied depending on plant life form (woody, herbaceous, grass), type of herbivore (insect, mollusk, mammal), and type of defense trait (secondary chemistry, physical defense, tolerance). In woody plants, chemical defense increased during the seedling stage, followed by an increase in physical defenses during the vegetative juvenile stage. Mammalian herbivores showed a strong preference for mature compared to juvenile tissues in woody plants. Herbs experienced a significant increase in secondary chemistry across the entire ontogenetic trajectory, although the magnitude of increase was greatest during the seedling stage. Correspondingly, mollusks preferred young compared to older herbs. Future research investigating growth/defense trade-offs, allometry, herbivore selection patterns, and ecological costs would shed light on the mechanisms driving the ontogenetic patterns observed.

https://www.jstor.org/stable/info/10.1086/650722

The Ontogeny of Plant Defense and Herbivory: Characterizing General Patterns Using Meta‐Analysis

Ehrlich and Raven's postulate that rapid diversification follows innovation in plant defense has often been invoked a posteriori for plant lineages of unusual diversity and chemical distinctiveness. The postulate can be more rigorously tested by defining a novel class of defense using chemical and/or anatomical criteria, independent of taxonomic lineage. If multiple plant lineages have evolved the new defense type, then according to the postulate they should be consistently more diverse than their sister groups (of equal age, by definition) when the latter retain the primitive defensive repertoire. Secretory canals are an independently defined, repeat- edly evolved feature that functions to protect plants from herbivores and pathogens. The canals might therefore be expected to allow plant radiation in an adaptive zone of reduced herbivory and disease. We have quantified the evidence for this hypothesis by comparing the diversities of lineages that have independently evolved canal systems with their sister groups for as many plant lineages as current taxonomic evidence allows. A sign test showed that canal-bearing lineages have consistently higher diversities than their sister groups (P = .0021). Explanations for this result, other than selective advantage conferred by secretory canals, are examined and provisionally rejected.

W.H. Stubblebine

Papers

Hymenaea and Copaifera leaf sesquiterpenes in relation to lepidopteran herbivory in southeastern Brazil

Leaf development in the tropical leguminous tree Copaifera in relation to microlepidopteran herbivory