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.