How plant traits respond to and affect vertebrate and invertebrate herbivores---are measurements comparable across herbivore types?

Abstract

Examining how plant traits respond to and affect herbivory is a common approach to exploring plant-herbivore interactions and their impact on ecosystem processes and functioning. Despite plants being potentially exposed to both vertebrate and invertebrate herbivores simultaneously, fundamental differences in the ecology and evolution of these two herbivore guilds results in them often being studied separately. A synthesis of the literature is needed to understand the types of plant traits examined and their response to, and effect on (in terms of forage selection) vertebrate and invertebrate herbivory, and to identify associated knowledge gaps. Focusing on grassland systems and species, we found 139 articles that met our criteria: 40 invertebrate, 97 vertebrate and 2 focussed on both vertebrate and invertebrate herbivores. Invertebrate focussed research, research conducted in the Southern Hemisphere and research on non-domesticated herbivores was significantly underrepresented based on our search. Differences in study focus (trait response or trait affect), along with considerable differences in the types of traits examined, led to limited capacity for comparison between the two herbivore guilds. For both invertebrates and vertebrates however, plant traits related to growth, such as leaf nitrogen and photosynthetic capacity, were often positively associated with herbivory. Future research should prioritise understanding how invertebrates, and the combined impact of both invertebrates and vertebrates’ respond to and affect plant traits. This review can be used as a guide for future research to select plant traits which are commonly measured either within one, or across both guild/s, as to help improve comparability and the broader significance of results, while also extending research breadth and knowledge.

Integrating functional traits into trophic rewilding science

“…Interestingly, more ‘intact’ herbivore communities with large and megaherbivores, which are the target of trophic rewilding, are characterised by lower selectivity (Schowanek et al., 2021). Despite these wide‐ranging relationships from positive to negative (or no effect at all; Lebbink et al., 2023), we see incorporating herbivore traits, densities and site conditions as an important way of resolving these idiosyncrasies.…”