Consumptive and non-consumptive effect of predators and food quality on arthropod herbivores

Mgr. Jan KOLLROSS

Doctoral thesis

Abstract:

Top-down and bottom-up controls are crucial mechanisms that shape ecosystems and biodiversity. In this thesis, I investigate both bottom-up and top-down forces, their interplay and specific effects on arthropod communities, herbivores, and their behaviour across vertical forest gradients. The thesis consists of four chapters. The first chapter explores the top-down regulation of arthropods and the resulting herbivore damage across a vertical forest gradient in a Japanese temperate forest, focusing on the effect of three groups of insectivorous predators. In my second chapter, I attempt to compare the relative impact of bottom-up and top-down control. I studied their relative effects on arthropods and herbivore damage by manipulating nutrient availability and access of predators to trees in a temperate forest in the Czech Republic. In my third chapter, I focused on one of the most important insect orders, the Coleoptera. I investigated the Coleoptera communities and the influence of predators on them along the vertical forest gradient in two different temperate sites: in Japan and Germany. Finally, I examined the nonlethal effect of predators on herbivore prey, testing the effect of bird presence on locust behavior and their stress hormone levels. Overall, my thesis examines the complexity of tri-trophic interactions between plants, herbivorous arthropods, and their insectivorous predators. It highlights the importance of nutrient availability, and the access of insectivorous predators to plants, for the functioning and result of multi-trophic interactions. It also discusses lethal as well as nonlethal effects separately.

Abstract:

Top-down and bottom-up controls are crucial mechanisms that shape ecosystems and biodiversity. In this thesis, I investigate both bottom-up and top-down forces, their interplay and specific effects on arthropod communities, herbivores, and their behaviour across vertical forest gradients. The thesis consists of four chapters. The first chapter explores the top-down regulation of arthropods and the resulting herbivore damage across a vertical forest gradient in a Japanese temperate forest, focusing on the effect of three groups of insectivorous predators. In my second chapter, I attempt to compare the relative impact of bottom-up and top-down control. I studied their relative effects on arthropods and herbivore damage by manipulating nutrient availability and access of predators to trees in a temperate forest in the Czech Republic. In my third chapter, I focused on one of the most important insect orders, the Coleoptera. I investigated the Coleoptera communities and the influence of predators on them along the vertical forest gradient in two different temperate sites: in Japan and Germany. Finally, I examined the nonlethal effect of predators on herbivore prey, testing the effect of bird presence on locust behavior and their stress hormone levels. Overall, my thesis examines the complexity of tri-trophic interactions between plants, herbivorous arthropods, and their insectivorous predators. It highlights the importance of nutrient availability, and the access of insectivorous predators to plants, for the functioning and result of multi-trophic interactions. It also discusses lethal as well as nonlethal effects separately.

Keywords

Bottom-up control, top-down control, arthropod communities, herbivory, vertical forest gradient, nutrient availability, predator presence, trophic cascades, ecosystem dynamics, nonlethal predator effects, Coleoptera, temperate forests

Language used: English

Date on which the thesis was submitted / produced: 12. 7. 2024

Thesis defence

• Supervisor: Mgr. Kateřina Sam, Ph.D.

UNIVERSITY OF SOUTH BOHEMIA IN ČESKÉ BUDĚJOVICE

Faculty of Science

Doctoral programme / field:
Biology / Entomology