From Plant Press, Vol. 18, No. 3, July 2015.
Herbivores can coexist even in the face of limited resources by consuming different plants than their neighbors. This dietary niche partitioning eases competition between large herbivores that share a geographical space. Previous hypotheses for dietary niche partitioning proposed a “grazer-browser continuum,” suggesting a separation of plant types consumed. Additional hypotheses pointed to body size, morphology, digestive strategy (whether a species is ruminant or non-ruminant), or spatiotemporal partitioning to explain the coexistence. In a recent publication for Proceedings of the National Academy of Sciences, David Erickson, W. John Kress, and Maria Kuzmina with colleagues from Princeton University and the Mpala Research Center in Kenya used DNA metabarcoding to explore the breadth, composition, and overlap of large mammalian herbivore (LMH) diet at the plant species level.
The group analyzed fecal samples from seven African species ranging from grazers to browsers, including a range of body sizes and digestion types. They found that dietary overlap was greatest in herbivores of similar body size and position on the grazer-browser spectrum, but that actual diet composition differed between all species—grazers were eating similar total amounts of grass but different grass species. These results support previous explanations, but also suggest a greater link between plant diversity and LMH diversity than has been recognized. DNA metabarcoding had not previously been applied to this type of study. Even so, it proved to be more effective than traditional methods of direct observation or microhistology (identifying plant parts visually from feces samples), offering a non-invasive but comprehensive technique to identify and quantify diet.