Acquiring nutrients from tree leaves: effects of leaf maturity and development type on a generalist caterpillar

Abstract

The rapid growth and prolific reproduction of many insect herbivores depend on the efficiencies and rates with which they acquire nutrients from their host plants. However, little is known about how nutrient assimilation efficiencies are affected by leaf maturation or how they vary between plant species. Recent work showed that leaf maturation can greatly decrease the protein assimilation efficiency (PAE) of Lymantria dispar caterpillars on some tree species, but not on species in the willow family (Salicaceae). One trait of many species in the Salicaceae that potentially affects PAE is the continuous (or "indeterminate") development of leaves throughout the growing season. To improve our understanding of the temporal and developmental patterns of nutrient availability for tree-feeding insects, this study tested two hypotheses: nutrients (protein and carbohydrate) are more efficiently assimilated from immature than mature leaves, and, following leaf maturation, nutrients are more efficiently assimilated from indeterminate than determinate tree species. The nutritional physiology and growth of a generalist caterpillar (L. dispar) were measured on five determinate and five indeterminate tree species while their leaves were immature and again after they were mature. In support of the first hypothesis, caterpillars that fed on immature leaves had significantly higher PAE and carbohydrate assimilation efficiency (CAE), as well as higher protein assimilation rates and growth rates, than larvae that fed on mature leaves. Contrary to the second hypothesis, caterpillars that fed on mature indeterminate tree leaves did not have higher PAE than those that fed on mature determinate leaves, while CAE differed by only 3% between tree development types. Instead, "high-PAE" and "low-PAE" tree species were found across taxonomic and development categories. The results of this study emphasize the importance of physiological mechanisms, such as nutrient assimilation efficiency, to explain the large variation in host plant quality for insect herbivores.

Physiological responses of Pedunculate oak (Quercus robur L.) to Corythucha arcuata (Say, 1832) attack

“…Previous studies reported on variations of macroelement concentrations (N, P, K, Ca, Na) in leaves of different pedunculate oak genotypes as a result of the interaction of a certain genotype and environmental factors [55]. Furthermore, foliar nutritional quality changes greatly during leaf maturation, as well as insect assimilation efficiency of compounds such as carbohydrates and proteins [56]. Along with these differences, the variability in nutrient amounts between plant species and even within a single plant (leaf maturity, for example) suggests that most insect herbivores facing heterogeneous nutritional sources regulate their nutrient intake [23].…”

Herbivory in a changing climate—Effects of plant genotype and experimentally induced variation in plant phenology on two summer‐active lepidopteran herbivores and one fungal pathogen

“…Leaf age and traits associated with plant genotype are regarded as important determinants for the performance of plant attackers (Barbehenn et al, 2017 ; Barker et al, 2019 ; Dodd et al, 2008 ; Edwards & Ayres, 1982 ; Ekholm et al, 2017 ; Falk et al, 2018 ; Tikkanen & Julkunen‐Tiitto, 2003 ). Therefore, predicting how plant phenology responds to elevated temperatures, and how this affects resource quality for higher trophic levels, requires an understanding of how climate warming influences plant phenology throughout the year.…”

“…Fresh leaves are usually dominated by high levels of nitrogen and defensive compounds, while old leaves have a tougher surface than fresh leaves (Barton et al, 2019 ; Falk et al, 2018 ; Feeny, 1970 ; Salminen et al, 2004 ). Studies have demonstrated that leaf age can have an effect on both survival and growth rate of insect herbivores and infection by pathogens, where young leaves are usually favored (Barbehenn et al, 2017 ; Dantec et al, 2015 ; Dodd et al, 2008 ; Edwards & Ayres, 1982 ; Falk et al, 2018 ; Tikkanen & Julkunen‐Tiitto, 2003 ). From the perspective of a plant attacker, rapid changes in leaf properties can define a “window of opportunity” in spring, where leaves of a certain age are of particularly high quality to the attacker.…”

Oviposition preference maximizes larval survival in the grass-feeding butterfly Melanitis leda (Lepidoptera: Nymphalidae)

“…That eggs were typically laid on the penultimate leaves of creeping grasses may be explained by nutrition and by avoidance of natural enemies. Eggs laid on second leaves will hatch on a tender young leaf, which is probably more nutritious than both the youngest leaf and older leaves (Barbehenn et al, 2017). Furthermore, walking predators may be less likely to fi nd prey at the shoot tips of complex plants since there are many such tips, compared to other plant parts (Casas & Djemai, 2002).…”