Presentation Information
[C01-04]Understanding the Balance Between Specialist and Generalist Herbivores in Plant-Insect Communities
*Toshiyuki Namba1 (1. Osaka Metropolitan University (Japan))
Keywords:
herbivorous insect,specialist,generalist,plant,diversity
Insects constitute more than 50% of all species on Earth, while higher plants comprise approximately 20%. Among insects, herbivores represent around half of all species, making them a significant component of global biodiversity together with higher plants. Therefore, understanding the mechanisms that sustain biodiversity requires investigating the interactions between herbivorous insects and plants using large-scale mathematical models that capture the key characteristics of these interactions.To enhance reproductive success, plants develop defenses against herbivory, while herbivorous insects evolve strategies to overcome these defenses. Plant defenses are generally classified as qualitative or quantitative. Qualitative defenses involve secondary metabolites that disrupt insect metabolism even in small amounts, leading to the evolution of specialist herbivores that adapt to a narrow range of plant species. In contrast, quantitative defenses involve structural compounds such as lignins and tannins that are difficult for insects to digest. Generalist herbivores, unable to overcome qualitative defenses, feed on a wide variety of plant species to mitigate the effects of quantitative defenses.Specialists reduce competition by exploiting plant species that are inedible to most other insects, but they face a heightened risk of extinction if their preferred host plants decline. Conversely, generalists can adapt to the loss of specific plant species by switching to alternative hosts, yet they experience greater competition with other generalists for shared resources.
What factors determine the balance between the species richness and population sizes of specialists and generalists? In this talk, I will present a mathematical model composed of a system of coupled difference equations to describe the discrete-time population dynamics of plant-herbivore interactions. By examining key parameters, including the strength of interspecific plant competition, the proportion of auxiliary host plants utilized by specialists, and the diversity of plant species consumed by generalists, we aim to elucidate the mechanisms regulating the balance between specialist and generalist herbivores in plant-insect communities.
What factors determine the balance between the species richness and population sizes of specialists and generalists? In this talk, I will present a mathematical model composed of a system of coupled difference equations to describe the discrete-time population dynamics of plant-herbivore interactions. By examining key parameters, including the strength of interspecific plant competition, the proportion of auxiliary host plants utilized by specialists, and the diversity of plant species consumed by generalists, we aim to elucidate the mechanisms regulating the balance between specialist and generalist herbivores in plant-insect communities.