Body size and diet quality: the interplay between plant and animal traits

Abstract

This dissertation investigates the interaction between herbivore body size and plant traits. The five chapters explore this topic from diverse perspectives.Chapter One is a synthesis and review of the Jarman-Bell Principle, an influential idea in herbivore ecology. This chapter synthesizes existing knowledge, organizes and evaluates existing hypotheses, and highlights several promising future directions. Chapter Two is a simple mathematical model of the diverse tradeoffs present when herbivores foraging on plants. The model solution illustrates a mechanism by which large and small herbivores should prefer to eat different plant species. Chapter Three is a comparative study of the diets of 14 large mammalian herbivores in Gorongosa National Park, in central Mozambique, using plant functional traits to investigate patterns of niche partitioning. Among the findings, we provide evidence that herbivore body size constitutes the second major axis of niche partitioning (after the grazer-browser spectrum) and identify multiple plant traits associated with this axis. Chapter Four tests the effects of nutrient addition and biomass removal on vegetation in a seasonally flooded grassland in Gorongosa National Park. The results challenge the importance of the grazing lawn paradigm in this system and identify key processes supporting the very large herbivore biomass in the floodplain ecosystem. In Chapter Five investigates the importance of large mammalian herbivores in maintaining vegetation composition in Alas Purwo National Park, in Java, Indonesia. Results from short-term exclusion show that herbivores strongly constrain plant species composition.