Re-examining the fundamentals of grazing: freshwater, marine and terrestrial similarities and contrasts (commentary on Burkepile 2013).

摘要

Burkepile (2013) provides an insightful comparison of herbivory in aquatic and terrestrial grazing-based ecosystems. These comparisons suggest a number of similarities: the disproportionate importance of megaherbivores, the facilitation of primary production and nutrient cycling by herbivores, the important role of grazing specificity on ecosystem resilience, and the nuanced impacts of predator size, behavior, and prey preference on herbivory dynamics and primary production. However, Burkepile restricts his review to ‘grazing ecosystems’; systems where comparatively large grazers determine plant community dynamics and ecosystem processes. We feel that there are additional insights to be gleaned from a fundamental re-examination of the assumptions underlying plant–herbivore interactions across a broader array of systems including freshwater macrophytes and insects, marine kelps and invertebrate herbivores, and terrestrial insect–plant systems. For all systems, a critical examination of the fundamental underpinnings is essential. We specifically ask: a) what is a grazer b) what is a plant c) how accessible is each ‘plant’ to each grazer d) does herbivory vary by scale and e) are all herbivores taxonomically and functionally equal System-specific answers will highlight where apt similarities and contrasts are appropriate, and may elucidate some surprises (as we will consider below).