Light environments affect herbivory patterns but not reproductive performance of a multivoltine specialist moth, Pareuchaetes pseudoinsulata

Osariyekemwen O Uyi

doi:10.1038/s41598-020-74079-9

Abstract

Unravelling the responses of insect herbivores to light-environment-mediated variation in the traits of their host plants is central to our understanding of the nutritional ecology of, and factors driving the population dynamics in, these species. This study examined the effect of light environment (shaded vs full-sun habitat) on leaf toughness and leaf nutritional quality in Chromolaena odorata (an invasive species in West Africa) and related these attributes to the abundance, herbivory patterns and reproductive performance of a multivoltine specialist moth, Pareuchaetes pseudoinsulata (a biological control agent). In this system, plants growing in shaded areas in the field experienced more herbivory and had higher herbivore abundance than those growing in full-sun. In the laboratory, P. pseudoinsulata larvae consumed significantly greater amounts of shaded foliage relative to full-sun foliage. However, reproductive performance metrics such as mating success, pre-oviposition period, number of eggs laid, duration of egg laying, egg hatchability, and adult longevity in P. pseudoinsulata did not differ according to foliage types. Reduced leaf toughness, increased water and nitrogen contents in shaded leaves coincided with increased leaf consumption by the larvae of P. pseudoinsulata. In summary, this study showed for the first time that light environments affect herbivory patterns but not reproductive performance of P. pseudoinsulata and hypothesized that high foliar nitrogen and water contents in shaded leaves resulted in feedback and necessity consumption patterns.

Highlights

Conspecific plant species vary their leaf chemistry and phenotypic characteristics when grown in different habitats[1,2,3,4]
Plants growing in full-sun habitats develop some morphological, physiological, and/or biochemical adaptations resulting in plants with tough leaves and low water content, high defense compounds, and low foliar nitrogen relative to shaded p lants[1,3,11,15]
These sunlight-induced adaptations in the leaves of full-sun plants may influence plant and herbivore water balance and/or alter nutrient intake by herbivorous insects[7,8]. This alteration over time may lead to varying coevolutionary dynamics that can later influence the ability of herbivores to utilize foliage of plants, in different light environments or with different photosynthetic pathways (e.g. C3 vs C4 plants; C3: soft leaves, lower carbon content and higher foliar nitrogen; C4: tougher leaves, higher carbon content, lower foliar nitrogen)[16,17,18,19]

Summary

Introduction

Conspecific plant species vary their leaf chemistry and phenotypic characteristics when grown in different habitats[1,2,3,4]. Plants growing in full-sun habitats develop some morphological, physiological, and/or biochemical adaptations resulting in plants with tough leaves and low water content (an adaptation for desiccation resistance), high defense compounds (e.g. tannins and phenolics: an adaptation to prevent or limit herbivory), and low foliar nitrogen relative to shaded p lants[1,3,11,15] These sunlight-induced adaptations in the leaves of full-sun plants may influence plant and herbivore water balance and/or alter nutrient intake by herbivorous insects[7,8]. The earlier s tudy[9] relied on laboratory data to show preference and performance of P. pseudoinsulata and did not document the effects of light-mediated changes in the leaf characteristics of C. odorata plants on leaf consumption and key herbivore reproductive performance metrics This current study conducted both field and laboratory studies to address these knowledge gaps by asking the following questions: (1) do larvae of P. pseudoinsulata prefer to feed on shaded or full-sun foliage in the field?

Methods

Results

Conclusion