Tolerance to herbivory and the resource availability hypothesis

Abstract

The resource availability hypothesis (RAH), the most successful theory explaining plant defence patterns, predicts that defence investment is related to the relative growth rate (RGR) of plant species, which is associated with habitat quality. Thus, fast-growing species should show lower resistance than slow-growing species, which would lead fast growers to sustain higher herbivory rates, but the fitness consequences of herbivory would be greater for slow growers. The latter is often assumed but rarely tested. In a temperate rainforest, we tested the expected pattern of tolerance to herbivory derived from the RAH: that fast-growing species should be more tolerant than slow-growing species. We also evaluated whether other plant features covary with RGR (leaf lifespan, shade tolerance and leaf toughness) and thus could also contribute to the patterns of tolerance to herbivory. As expected, seedlings from tree species with higher RGR showed greater tolerance to herbivory. Among the three plant features included, only leaf lifespan showed a significant association with RGR, but RGR was the best predictor of tolerance. We argue that plant tolerance to herbivory must be evaluated to properly verify the assumptions of the RAH.

Macroevolutionary constraints to tolerance: trade‐offs with drought tolerance and phenology, but not resistance

“…Recent calls have been made to more explicitly include tolerance in this framework (Gianoli and Salgado-Luarte 2017). Under RAH, we predict low tolerance in low resource environments, if there is a trade-off between high levels of resistance and tolerance (Fine et al 2006, Gianoli andSalgado-Luarte 2017). For example, plants growing in stressful soils may have reduced ability to replace tissue lost to herbivores, and thus are predicted to have high resistance and low tolerance (Fine et al 2006).…”

“…For example, plants growing in stressful soils may have reduced ability to replace tissue lost to herbivores, and thus are predicted to have high resistance and low tolerance (Fine et al 2006). Indeed, a recent study finds a strong relationship between relative growth rate and resource availability (negative), and relative growth rate and tolerance (positive) in tropical trees (Gianoli and Salgado-Luarte 2017). Another prediction in relation to resources is that species living in limiting resource environments should allocate relatively more resources to roots (Orians et al 2011); in turn, root allocation might help species tolerate damage and result in a positive relationship between tolerance and resource limitation mediated by root storage.…”

“…). Indeed, a recent study finds a strong relationship between relative growth rate and resource availability (negative), and relative growth rate and tolerance (positive) in tropical trees (Gianoli and Salgado‐Luarte ). Another prediction in relation to resources is that species living in limiting resource environments should allocate relatively more resources to roots (Orians et al.…”

“…The Resource Availability Hypothesis (RAH) predicts species living under low resources should have high investment in resistance traits. Recent calls have been made to more explicitly include tolerance in this framework (Gianoli and Salgado‐Luarte ). Under RAH, we predict low tolerance in low resource environments, if there is a trade‐off between high levels of resistance and tolerance (Fine et al.…”

“…The RAH was developed, and has been largely tested, in the context of tropical tree communities with across‐species comparisons (Fine et al. , Endara and Coley , Gianoli and Salgado‐Luarte ). That said, the mechanisms of tolerance in trees is likely to differ greatly from those in herbaceous species (Haukioja and Koricheva , Tiffin , Borowicz , Massad ).…”