Elevational and Seasonal Variation in the Foliar Quality and Arthropod Community ofAcer pensylvanicum

Abstract

Elevational gradients provide natural experiments for examining how variation in abiotic forces such as nutrient mineralization rates, risk of photodamge, temperature, and precipitation influence plant-insect interactions. At the Coweeta LTER site in the Southern Appalachian Mountains, we examined spatial and temporal variation in striped maple, Acer pensylvanicum, foliar quality and associated patterns in the arthropod community. Variation in herbivore densities was associated more strongly with seasonal variation in plant quality than with spatial variation in quality among three sampling sites. Leaf chewer, but not phloem feeder or arthropod predator, densities increased with elevation. Foliar quality, by our measures, decreased throughout the growing season, with decreases in nitrogen concentrations and increases in lignin concentrations. Foliar quality varied among the three sites but not systematically along the elevational gradient. We conclude that, in this system, temporal heterogeneity in plant quality is likely to be more important to insect herbivores than is spatial heterogeneity and that other factors, such as the abiotic environment and natural enemies, likely have substantial effects on herbivore density.

Elevational gradients in plant defences and insect herbivory: recent advances in the field and prospects for future research

“…low diurnal range and moderate seasonality) climatic conditions promote larger population sizes and higher species richness of consumers (Rasmann et al 2014a). Accordingly, current evidence suggests that increased insect herbivore pressure at low elevations favours greater investment in plant defences (Scheidel and Bruelheide 2001, Zehnder et al 2009, Rodríguez-Castañeda et al 2010, Garibaldi et al 2011, Pellissier et al 2012, Rasmann et al 2014a ( Fig. 1A-B, Supplementary material Appendix 1 Table A1).…”

Reading the Leaves’ Palm: Leaf Traits and Herbivory along the Microclimatic Gradient of Forest Layers

“…Carbon content is negatively correlated to leaf palatability [24] because mechanical or chemical defenses are often carbon-based [25,26]. Also leaf toughness negatively influences palatability for herbivore insects [27,28]. Negative changes of leaf traits for herbivore insects can suppress expected high rates of herbivory in warm environments [29].…”

Comparison of the severity of selection among beech leaves prior to egg-laying between a leaf-mining and two gall-inducing insects

“…Indeed, such extensive surveys, involving many different samples from different locations are now considered of fundamental importance to ensure a comprehensive grasp of plant-animal relationships. This is because contextual variability may substantially influence and appreciably modulate more deterministic ecological relationships (Trager et al, 2009;Zehnder et al, 2009). As quoted by Gripenberg & Roslin (2007), "the mere spatial location of a site will have major impact on local insect populations", and thus, "descriptive studies of individual habitats or sites will fall short of generality".…”

“…The notion that insects select from among the host-units available, quantified in terms of the acceptance ratio, makes sense because the host-units, for example, the leaves of a given plant or tree, are generally of unequal "quality" regarding future larval development (resources, protection, etc.). Thus, the geometrical, physical, chemical and other characteristics of the same type of host-unit may often vary in space and time (Morrison & Quiring, 2009;Sarfraz et al, 2009;Zehnder et al, 2009), for example, leaves may vary in quite an unsuspected manner in many traits within the canopy of an individual tree or even within the same branch (Faeth, 1991;Kozlov & Koricheva, 1991;. At least, some of these characteristics may affect the development of the larvae growing upon or within a host-unit.…”