Foliar herbivory and its effects on plant growth in native and exotic species in the Patagonian steppe

Abstract

Studies of herbivory and its consequences on the growth of native and exotic plants could help elucidate some processes involved in plant invasions. Introduced species are likely to experience reduced herbivory in their new range due to the absence of specialist enemies and, thus, may have higher benefits if they reduce the investment in resistance and increase their compensatory capacity. In order to evaluate the role of herbivory in disturbed areas within the Patagonian steppe, we quantified and compared the leaf levels of herbivory of four native and five exotic species and recorded the associated insect fauna. We also performed greenhouse experiments in which we simulated herbivory in order to evaluate the compensatory capacity of native and exotic species under different herbivory levels that resembled naturally occurring damage. Natural herbivory levels in the field were similar between the studied exotic and native plants. Field observations confirmed that they both shared some herbivore insects, most of which are generalists. In the greenhouse experiments, both exotic and native plants fully compensated for herbivory. Our results suggest that the studied exotic plants are not released from herbivory in the Patagonian steppe but are able to fully compensate for it. The capacity to recover from herbivory coupled with other potential adaptations, such as a better performance under disturbance and greater competitive ability than that of the native species, may represent some of the mechanisms responsible for the success of plant invasion in the Patagonian steppe.

Can the nutrient-rich soil patches created by leaf-cutting ants favor plant compensation for foliar damage? A test of the compensatory continuum hypothesis

“…We simulated leaf damage by clipping twothirds of 50 % of the leaves (i.e., 33 % leaf loss) in assigned individuals. We applied this type of damage because complete tissue loss is the most common type of foliar damage in these species and in general, fewer than 50 % of the leaves suffered herbivory (see Pirk and Farji-Brener 2012). As for the amount of tissue loss, we wanted to represent high levels of herbivory, yet realistic ones (*33 % is the maximum value observed in the field; Pirk and Farji-Brener 2012).…”

Vertical profiles of leaf photosynthesis and leaf traits and soil nutrients in two tropical rainforests in French Guiana before and after a 3-year nitrogen and phosphorus addition experiment

“…For saplings, total phenolic concentration of the leaves was measured using an improved Folin-Ciocalteu assay (Singleton and Rossi, 1965;Marigo, 1973), and total leaf tannin concentration of the leaves was determined with the butanol-HCl method (Porter et al, 1985) modified as in Makkar and Goodchild (1996). The extracts for both phenol and tannin concentrations were determined using a Helios Alpha spectrophotometer (Thermo Spectronic, Cambridge, UK) at 760 and 550 nm, respectively.…”

“…Herbivory rates, i.e., foliar damage by herbivores, of the saplings was estimated as punctual herbivory (%) according to Pirk and Farji-Brener (2012). We visually assessed the missing area of the leaf and assigned each leaf to the following categories: 0 %, 0.1 %-5 %, 5.1 %-25 %, 25.1 %-50 %, and 50.1 %-100 % area consumed.…”

Vertical profiles of leaf photosynthesis and leaf traits, and soil nutrients in two tropical rainforests in French Guiana before and after a three-year nitrogen and phosphorus addition experiment

“…Herbivory rates, i.e. foliar damage by herbivores, of the saplings was estimated as punctual herbivory (%) according to Pirk and Farji-Brener (2012). We visually assessed the missing area of the leaf and assigned each leaf to the following categories: 0, 0.1-5, 5.1-25, 25.1-50, 50.1-100 % area consumed.…”