Causes of vertical stratification in the density of Cameraria hamadryadella

Abstract

Abstract. 1. The density of Cameraria hamadryadella, a leaf-mining moth, is vertically stratified within the crown of oak trees. It occurs at higher densities on foliage in the lower crown.2. Oviposition preference tests indicate that females display no preference to oviposit on foliage from the lower tree crown over foliage from the upper tree crown.3. Experiments in which potted trees were placed at various heights indicate that foliage nearest ground level receives more oviposition, and that the higher rates of oviposition on foliage near the ground is not caused by differences in quality between foliage from low or high in the tree crown.4. Host-plant-and natural-enemy-mediated juvenile mortality and the abundance of parasitoids did not differ between the upper and lower crown.5. Vertical differences in the timing of leaf production within the tree crown are unlikely to account for the observed gradient in the abundance of C. hamadryadella. Furthermore, the mean date of leaf fall does not differ among heights within the tree crown.6. It is argued that microclimatic gradients and interspecific competition are also unlikely to account for the observed gradients in the density of C. hamadryadella within the tree crown.7. Because of the absence of effects of other potentially causal factors, the most likely explanation for the gradient in density of C. hamadryadella is a lack of movement by females into the upper tree crown from overwintering, emergence, or resting sites located in the lower tree crown, combined with egg depletion by females as they move from the lower to the upper tree crown.8. It is suggested that the lack of movement and egg depletion hypothesis should serve as the null hypothesis in studies of vertical stratification of tree-feeding insects.In the absence of evidence of an effect of foliage quality, natural enemies, plant phenology, interspecific competition, or microclimate, the movement and egg depletion hypothesis is the most reasonable.

Impact of the leaf miner Cameraria ohridella on whole-plant photosynthetic productivity of Aesculus hippocastanum: insights from a model

“…In fact, similar to other leaf miners (Brown et al 1997), the density of C. ohridella mines is vertically stratified within the crown of horse chestnut trees, showing highest density in the lower part of the crown. Leaves were sampled at 2, 6, 10 and 14 m above the ground with the help of a professional tree-climber.…”

“…This might intuitively suggest that infested trees suffered heavy damage in terms of photosynthetic productivity because of the consistent reduction of foliage lifespan. It has to be noted, however, that damage to A. hippocastanum crown develops gradually over the season because of the vertical stratification of the moth attacks (Brown et al 1997). In our case, starting from the earliest attack recorded in 2003 (early May, Fig.…”

Persistence of labile organic matter and microbial biomass in Antarctic shelf sediments: evidence of a sediment ‘food bank’

“…Because 9 discrete sediment depths were sampled with each sediment core, seasonal differences in profiles of chl a, EHAA, and ATP concentrations (mass g -1 sediment dry wt) were analyzed using 2-factor repeatedmeasures ANOVA (cf. Brown et al 1997). In all tests, each sediment core was treated as a separate subject, with depth as the repeated measures factor and season as the between-subjects factor (Sokal & Rohlf 1995).…”

Arthropod vertical stratification in temperate deciduous forests: Implications for conservation-oriented management

“…In many cases, as discussed elsewhere, the abundance or quality of host resources appear to be less important than other factors (e.g., proximity to overwintering sites (Section 8), sun exposure (Section 5), etc.) in determining these patterns (e.g., Nielsen and Ejlersen, 1977;Rowe and Potter, 1996;Brown et al, 1997;Thomas et al, 2010). Finally, it should be mentioned that the outer layer of foliage often extends uninterrupted from the upper canopy to the ground at forest edges, bringing species normally restricted largely to the tree tops in close proximity to the forest floor (Toda, 1987(Toda, , 1992Wermelinger et al, 2007).…”