Collaborators from four institutions will address the ecological and evolutionary responses of mammals from the Miocene fossil record of Pakistan to changes in global climate, sea level, tectonic barriers, and immigrant species. The Siwalik record consists of highly fossiliferous Neogene sediments deposited in the Himalayan foreland basin from Pakistan to Myanmar. In the Potwar Plateau of Pakistan, this record provides an unparalleled history of faunal and environmental change in a continuous sequence of strata spanning the last 18 million years. During this time period, mammalian paleocommunities exhibited a changing mixture of cosmopolitan groups, endemic lineages, and relict taxa. Environmental processes that may have driven these faunal changes are known from deep-sea cores and other geological evidence. These processes occurred at different biogeographic scales, ranging from those of the global climate system and sea level to regional (South Asian) tectonism to the local floodbasin and its vegetation and local climate. The proposed analyses will test the relationship between environmental processes and biological responses by (1) evaluating mammalian faunal change under different geodynamic and climatic conditions over the interval between 18.0 and 5.5 million years ago, and (2) integrating multiple indicators of changing paleoclimate from the Siwalik record, including a new geochemical method for estimating soil moisture using iron oxides, information from snail opercula about seasonality of precipitation, stable isotopes from tooth enamel and soil carbonate, and measures of diet and body size for extinct mammals using functional morphology.
We evaluated ecological and evolutionary responses of mammals from the Miocene fossil record of Pakistan to changes in global climate, sea level, tectonic barriers, and immigrant species. Our approach is to use the mineralogical and isotope record in the sediments to provide ecological information that can be used to test hypothesis concerning mammalian evolution and how it is related to tectonics and climate change. We use the Siwalik sequence in southeast Asia because of the long, semi-continuous record of mammalian evolution present over the past 20 million years. In this proposal, we focus on the middle Miocene interval. Key finding include that the paleosols record difference in the iron oxide minerals, especially in regard to position in the landscape; Pila fossils record seasonal variations on an annual basis; microwear analysis of bovid and equids suggest that a grass component to their diets prior to the C4 biomass expansion, implying that C3 grass may have been important; stable isotopes of proboscideans show no seasonal change in carbon isotopes, and limited seasonality in oxygen isotopes through time; stable isotopes in rodents show a similar change in carbon isotopes as do larger mammals; in situ speciation of rodents shows changes associated with diets over the long time interval of this sequnce.
