Abstract
The sedimentary succession near the village of Villafeliche in the Calatayud-Montalbán Basin (Spain) is well known for its very rich, densely sampled and well dated fossil mammal record of Miocene age and roughly spans the time interval between 17 and 10 million years ago. The exceptional quality of this fossil
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record provides ideal conditions for studying the biostratigraphy, evolution and changes in the community structure of small mammals. Extensive research on Neogene mammal paleontology has been carried out in this area for decades and has previously been focused primarily on the rodent families present. Their fossil record has yielded new insights in small-mammal community dynamics. The role of the pikas (Ochotonidae, Lagomorpha) in this context has so far remained unexplored and is the subject of the present thesis. Pikas represent a family of small-sized herbivores that is closely related to the family of rabbits and hares. Although they are currently extinct in Europe, pikas are a common component in small-mammal fossil assemblages of Miocene age in which they are often abundantly present. The time interval covered by the mammal succession is characterized by major shifts and distinctive episodes in global climate, such as the Miocene Climate Optimum, which represents the warmest phase of the Neogene, and the Middle Miocene Climate Transition, which encompasses one of the major cooling phases in the Cenozoic. These characteristic climate intervals significantly influenced the local environment of the research area, in particular with respect to precipitation patterns and humidity, which in turn influenced the evolution and local diversity of mammals. The present study is focused on the evolutionary history of pikas in Spain during the Miocene and their role in small-mammal communities in relation to the influence of major changes in global climate. Analysis of the several thousands of fossil teeth from the succession has resulted in the identification of two new species within the four evolutionary lineages present in the region and has led to new insight in their phylogenetic affinity. Secondly, it is shown that the timing of evolutionary changes and of immigrations in the small-mammal communities, including those of the pikas, and changes in the fauna composition due to (local) extinction, appear to be strongly related to changes in global climate and its associated shifts in local humidity. Thirdly, the analysis of the intra- and interspecific variability of tooth morphology suggests that beside climate, interspecific competition appears to have played a significant role in the evolutionary and coexistence patterns of Spanish pikas in the Miocene. Analysis of the changes in the composition of the small-mammal primary consumer community confirms the patterns of disassembly, assembly and succession of small-mammal communities on a geological time scale previously established on the basis of rodents. Three out of the four pika lineages present are identified as belonging to the group of species with long residence times that defines local temporal communities in geological time. Pikas were therefore likely an important component of Spanish ecological communities in the Miocene
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