Reevaluation of Firasian Mammal Faunas from Argentina, Bolivia and Chile
Darin Croft, Case Western Reserve University
Roughly 80% of South America is in the tropics, the low-latitude area on either side of the Equator that includes rain forests, deserts, and a variety of other habitats. This vast area the Neotropics harbors most of South Americas biodiversity, as well as a significant part of the earths biodiversity as a whole. The increasing encroachment of humans into the Neotropics and other factors such as climate change have made this an area of highest conservation priority. But what is the best strategy to preserve this biodiversity not only the present biodiversity, but that of the future? One way to answer this question is to study patterns of ancient biodiversity to better understand factors that affect numbers and types of species in particular places at particular times. Our project will take just such an approach by investigating the evolutionary and biogeographic histories of some of the most important and conspicuous members of Neotropical communities: mammals. In particular, we will address three hypotheses about how the modern mammal communities of South America developed over the past 20 million years: (1) mammal species tend to originate in the tropics and then disperse to higher latitudes; (2) the tropics act as a museum for mammal species by preserving species that have gone extinct elsewhere on the continent; and (3) global cooling was the main driver of habitat change and mammal evolution in South America between about 20 and 10 million years ago. Evaluating these hypotheses will allow us to better predict how biodiversity might change in the future, permitting conservationists to make more educated decisions about the best strategies for preserving biodiversity. Most of our project will be devoted to collecting the primary data that will allow us to evaluate the hypotheses described above. Although South America has a good fossil record of mammals overall, most localities are from outside the Neotropics, and the time slice from about 15-10 million years ago is not well represented. We will address both of these issues through fieldwork at two relatively new fossil localities in Neotropical Bolivia that pertain this time interval: Cerdas and Quebrada Honda. Fossils collected from these sites will be taken to PotosÃ, Bolivia, where they will be cleaned and curated. The specimens will then be compared with those from similarly-aged but generally unstudied faunas from southern Chile and Argentina. We will revise the mammals from all of these localities through detailed comparisons, phylogenetic analyses, by assessments of individual dental variation based on new studies of modern and fossil populations. The results of our proposed research will be broadly disseminated through a variety of media including public lectures, museum exhibits, our local science café, and the internet. Bolivian and US students will gets hands-on paleontological experience through participation in laboratory and field aspects of this research, and the project will support the career development of a US-based Ph.D. student.
