Herbivore resistance in congeneric and sympatric Nothofagus species is not related to leaf habit

Abstract

Premise Two fundamental hypotheses on herbivore resistance and leaf habit are the resource availability hypothesis (RAH) and the carbon–nutrient balance hypothesis (CNBH). The RAH predicts higher constitutive resistance by evergreens, and the CNBH predicts higher induced resistance by deciduous species. Although support for these hypotheses is mixed, they have rarely been examined in congeneric species. Methods We compared leaf constitutive and induced resistance (as leaf polyphenol and tannin concentrations, and as damage level in non‐choice experiments) and leaf traits associated with herbivory of coexisting Nothofagus species using (1) a defoliation experiment and (2) natural defoliation caused by an outbreak of a common defoliator of Nothofagus species. Results In the defoliation experiment, polyphenol and tannin concentrations were similar between deciduous and evergreen species; regardless of leaf habit, polyphenols increased in response to defoliation. In the natural defoliation survey, N. pumilio (deciduous) had significantly higher herbivory, lower carbon/nitrogen ratio and leaf mass per area, and higher nitrogen and phosphorus concentrations than N. betuloides (evergreen); N. antarctica (deciduous) had intermediate values. Polyphenol concentrations and herbivore resistance indicated by the non‐choice experiment were lower in N. pumilio than in N. antarctica and N. betuloides, which had similar values. Conclusions Higher herbivory in N. pumilio was associated with a higher nutritional value and a lower level of leaf carbon‐based defenses compared to both the evergreen and the other deciduous species, indicating that herbivore resistance in Nothofagus species cannot be attributed to only leaf habit as predicted by the RAH or CNBH.

Intermediate harvesting intensities enhance native tree performance of contrasting species while conserving herbivore diversity in a Patagonian woodland

“…In this study, evergreen species resulted in resource conservative species, being their leaves less palatable to herbivores due to low nutrient content and high proportion of support tissue (Chabot & Hicks, 1982). Similar findings were reported by Piper et al (2019), where N. betuloides (similar evergreen species) was less consumed than N. pumilio. In turn, deciduous species in this study are identified as a resource acquisitive species, since they have higher specific leaf area and higher nitrogen concentrations than evergreen species, as Diehl et al, (2008) measured.…”

The Role of Nonstructural Carbohydrates Storage in Forest Resilience under Climate Change

“…For example a defoliation experiment on juveniles of N. pumilio showed an extremely high regrowth capacity and survival; however, recurrent defoliations by the caterpillar could have different effects. In fact, the outbreaks of O. amphimone occur much more frequently in some stands than in others [75,76], and a previous study found that leaf resistance to O. amphimone was similar between trees from a stand without outbreak history and counterparts from a recurrently outbreak-affected stand [79]. However, it remains unknown if N. pumilio populations without outbreak history are as tolerant to defoliation as populations recurrently affected by outbreaks.…”

Relationships between population traits, nonstructural carbohydrates, and elevation in alpine stands of Vaccinium myrtillus

“…Carbohydrate reserves enable plants to uncouple growth from C assimilation throughout the year, allowing survival under seasonal stressful conditions. Instead, soluble sugars serve as important regulators of both physiological adjustment of plants to drought and freezing stress (Larcher and Thomaser‐Thin, ; Meletiou‐Christou et al., ; Lloret et al., ; Yamada and Osakabe, ) and pathogen or herbivore attack (Tauzin and Giardina, ; Piper et al., ). Nonstructural carbohydrates are involved in frost resistance (Palacio et al., ; Sperling et al., ) by protecting plants from intracellular desiccation (Sung et al., ).…”