Date Published: April 4, 2019
Publisher: Public Library of Science
Author(s): Jamie R. Wood, Janet M. Wilmshurst, Ignasi Torre.
Large herbivores facilitate a range of important ecological processes yet globally have experienced high rates of decline and extinction over the past 50,000 years. To some extent this lost function may be replaced through the introduction of ecological surrogate taxa, either by active management or via historic introductions. However, comparing the ecological effects of herbivores that existed in the same location, but at different times, can be a challenging proposition. Here we provide an example from New Zealand that demonstrates an approach for making such comparisons. In New Zealand it has been suggested that post-19th Century mammal introductions (e.g. deer and hare) may have filled ecological niches left vacant after the 15th Century AD extinction of large avian herbivores (moa). We quantified pollen assemblages from fecal samples deposited by these two asynchronous herbivore communities to see whether they were comparable. The fecal samples were collected at the same location, and in a native-dominated vegetation community that has experience little anthropogenic disturbance and their contents reflect both the local habitat and diet preferences of the depositing herbivore. The results reveal that the current forest understory is relatively sparse and species depauperate compared to the prehistoric state, indicating that deer and moa had quite different impacts on the local vegetation community. The study provides an example of how combining coprolite and fecal analyses of prehistoric and modern herbivores may clarify the degree of ecological overlap between asynchronous herbivore communities and provide insights into the extent of ecological surrogacy provided by introduced taxa.
Large herbivores facilitate a range of important ecological processes and are commonly keystone species within terrestrial ecosystems [1,2]. However, large herbivore communities around the world have experienced high rates of extinction because of severe climate change and human hunting during the late Quaternary period [3–5]. The extinction of large herbivores over the past 50,000 years has affected the structure, functioning and composition of vegetation communities globally, through the disruption of dispersal, disturbance and nutrient cycling processes [6–10]. This process is ongoing. With around 60% of the world’s large herbivore species currently under threat of extinction  the complete consequences for terrestrial ecosystems have yet to be fully realized.