Herbivore attack in Casearia nitida influenced by plant ontogenetic variation in foliage quality and plant architecture

Abstract

Traits influencing plant quality as food and/or shelter for herbivores may change during plant ontogeny, and as a consequence, influence the amount of herbivory that plants receive as they develop. In this study, differences in herbivore density and herbivory were evaluated for two ontogenetic stages of the tropical tree Casearia nitida. To assess plant ontogenetic differences in foliage quality as food for herbivores, nutritional and defensive traits were evaluated in saplings and reproductive trees. Predatory arthropods were quantified and the foraging preferences of a parasitoid wasp of the genus Zacremnops were assessed. In addition, survival rates of lepidopteran herbivores (Geometridae) were evaluated experimentally. Herbivore density was three times higher and herbivory was 66% greater in saplings than in reproductive trees. Accordingly, concentrations of total foliar phenolics were higher in reproductive trees than in saplings, whereas leaf toughness, water and nitrogen concentration did not vary between ontogenetic stages. Survival rates of lepidopteran larvae exposed to natural enemies were equivalent in reproductive trees and saplings. Given the greater herbivore density on saplings, equal survival rates implied a greater foraging effort of predators on reproductive trees. Furthermore, observed foraging of parasitoid wasps was restricted to reproductive trees. I propose that herbivore density, and as a consequence, leaf damage were lower in reproductive trees than in saplings due to both traits influencing food quality, and architectural or unmeasured indirect defensive traits influencing foraging preference of natural enemies of herbivores.

Insect herbivores associated with an evergreen tree Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) in a tropical dry forest

“…Younger leaves tend to have higher nutritional quality, resulting in herbivory rates that are 5-25% higher compared to mature leaves (Coley and Barone, 1996). Additionally, plant chemistry is different between young and mature leaves, and carbon-based compounds concentration increase with leaf age (Coley and Barone, 1996;Boege, 2005;Oliveira et al, 2012;Silva et al, 2012). A major line of defense against beetles with chewing mouthparts (e.g.…”

“…temperature, air humidity, insulation), and complex multitrophic interactions (e.g. interspecific competition, predation, mutualism), whereas leaf consumption rates are controlled by plant quality (Coley and Barone, 1996;Boege, 2005;Stiling and Moon, 2005). In this way, insect herbivores also likely use evergreen trees as a habitat during the dry season, in they which provide refuge against harsh microclimatic environmental conditions and natural enemies.…”

Ontogenetic Changes in Azoxyglycoside Levels in the Leaves of Dioon edule Lindl

“…Therefore, there are trade-offs between the metabolic flux into growth or defense, which change throughout plant ontogeny reflecting shifts in developmental and reproductive priorities (Boege and Marquis 2005). Two main processes associated with plant ontogeny influence resource allocation: changes in plant size (i.e., increase in the resource acquisition organs like roots and leaves), and shifts from growth to reproductive priorities (Boege and Depending on the species, specialized metabolites that are part of plant defenses may increase or decrease as plants age (Boege 2005 . One theory that accounts for these apparent differences is that trade-offs between costs and benefits are specific to particular metabolites and reflect the plant's life history traits.…”

Arriving at the right time : a temporal perspective on above-belowground herbivore interactions

“…Although grass species are widely accepted to be tolerant to aboveground herbivory they can also produce a variety of secondary chemicals as defense (Redak 1987). Hence plant compensatory growth and defense activity may compete for plant stored resources when photosynthesis is limited at defoliation (Boege 2005). …”

“…A plant's ability to tolerate herbivore damage can also vary with plant age (Massad 2013) due to developmental changes in plant architecture, storage capacity, and resource allocation (Boege 2005). In general, young plants possess fewer stored reserves and lower capacity of resource acquisition, so that they are less capable of compensating herbivore damage than old plants (Bryant et al 1992).…”