Leaf trait variation onErythroxylum tortuosum(Erythroxylaceae) and its relationship with oviposition preference and stress by a host‐specific leaf miner

Abstract

It has been suggested that plant physical and chemical traits vary considerably in space and time. Hence, leaf-mining insects may adjust their oviposition in response to leaf attributes representing high quality. Moreover, herbivorous insects can modify leaf morphology by acting as stressors, increasing, for example, fluctuating asymmetry (FA) levels. Here, we investigate oviposition preference in Agnippe sp.2, a leaf-mining moth of Erythroxylum tortuosum, in relation to differences in leaf nutritional quality (i.e. levels of water, nitrogen and tannin content), leaf area (i.e. quantity of resource hypothesis) and FA. We also verify whether temporal variation in plant nutritional quality emerges as an alternative hypothesis to explain oviposition distribution in time, and whether this leaf miner is a stress-causing agent, increasing FA during larval development. Mined leaves and leaves with and without eggs were periodically collected from plants located in a Cerrado fragment in Brazil. In the laboratory, leaf traits were assessed (using image analysis software) and quantified (biochemical analysis) according to the aims previously determined. Oviposition probability did not change in relation to variations in nitrogen, tannins and FA of leaves. However, leaf-miner females preferred to oviposit on leaves having large areas and low water contents. It was also verified that new leaves of E. tortuosum, which carried most leaf-miner eggs, presented significantly lower tannins and greater levels of nitrogen and water than old leaves.The oviposition choice exhibited by leaf miners was found to be non-random because they appear to use resource quantity and water content as cues as where to lay their eggs.The temporal variation of plant nutritional quality is likely to influence the time of leaf-miner oviposition; and leaf FA was not increased during larval feeding, suggesting that these herbivores do not cause variations in FA levels.

Edge effect and phenology in Erythroxylum tortuosum (Erythroxylaceae), a typical plant of the Brazilian Cerrado

“…It is unclear why these differences were not observed in older foliage (Table 1). One possible explanation is a temporal shift in concentrations of chemical compounds (Salminen et al, 2004;Schoonhoven et al, 2005); at the beginning of the season, young leaves of E. tortuosum have higher levels of water and nitrogen and lower levels of tannins than adult leaves (Ishino et al, 2011). Because E. tortuosum leaves become more coriaceous with age, greater water loss is expected to occur when leaves are young.…”

“…In such cases, neither DA nor AS are treated as estimates of developmental instability. Nevertheless, studying FA on E. tortuosum leaves, Ishino et al (2011) verified that the RW-LW values were normally distributed, characterising true FA (Palmer and Strobeck, 1986;Graham et al, 1998), and DA was not observed. Because asymmetry may be size-dependent, some studies use correction indices in FA estimations (Hódar, 2002;Freeman et al, 2004;Cornelissen and Stiling, 2005).…”

“…Erythroxylum tortuosum Mart. is a deciduous shrub-arboreal species typical of the cerrado community (Ishino et al, 2011). There is currently little information on the biology or ecology of this species.…”

“…Because asymmetry may be size-dependent, some studies use correction indices in FA estimations (Hódar, 2002;Freeman et al, 2004;Cornelissen and Stiling, 2005). However, evidence of size-dependence has not been observed for E. tortuosum leaves (Ishino et al, 2011).…”

“…To determine whether physical and chemical leaf traits differed between interior and edge plants, linear mixed effects models were used (Crawley, 2007) with plants and location (interior and edge) as random and fixed effects, respectively. As water, tannins, and nitrogen concentrations in E. tortuosum leaves change throughout development (Ishino et al, 2011), mixed models were computed separately for young and adult leaves. Linear mixed effects models were run in the R System for Windows, version 2.11.0 (R Development Core Team, 2010).…”