The Cenozoic Evolution of Morphological and Ecological Diversity in Holarctic Rodents Within the Context of Tectonic and Climatic Change
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Date
2024-08-07
Authors
Peng, Amanda
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Publisher
University of Oregon
Abstract
The evolution of mammalian biodiversity is a complicated process with many complex drivers and mechanisms. It has been a topic of unique interest for several centuries and has been explored from multiple angles. Frequently, biodiversity is measured through some aspect of total species richness, which captures the abundances of some taxonomic unit. But study has been complicated by the fact that biodiversity is comprised not only of taxonomic diversity, but also morphological, ecological, and genetic attributes, with genetic attributes being less relevant in the fossil record. Morphological and ecological diversity are descriptors of functional diversity, which describe the total diversity in the physical characteristics (size, shape, etc.) and ecological role (diet, locomotion, etc.) of a mammal. This work seeks to discover the role that morphological and ecological diversity play in the evolution and distribution of mammals, and how this diversity evolves in response to abiotic drivers, like tectonism and climatic change. I investigate this topic using rodents as a case study. Rodents are uniquely suited to studies of this type for several reasons: they are abundant on the landscape and in the fossil record and respond rapidly to environmental changes. In my first chapter, I examined the relationship between taxonomic diversity and morphological disparity in Neogene rodents of North America. I investigated the role that climate change, tectonic activity, and subsequent landscape heterogeneity play in driving both taxonomic and morphologic diversity, as well as their relationship to one another. I found that taxonomic and morphologic diversity do not respond to tectonism or topographic complexity in a predictable way, and that morphologic diversity in homogeneous landscapes surpasses that of heterogeneous landscapes for much of the Neogene in North America, contrary to what is observed in taxonomic diversity. In my next chapter, I examined the role of morphological diversity in the modern latitudinal diversity gradient. Latitudinal diversity gradients, more aptly described as taxonomic diversity gradients, describe the change in taxonomic diversity with increasing distance from the equator. These gradients are ubiquitous across the tree of life but have rarely been measured in non-taxonomic diversity terms. I explored the relationship between morphological diversity, latitude, and climatic factors, including temperature, precipitation, and solar radiation to deduce the role of these variables in shaping the modern distribution of rodent diversity. I found that latitude does not have strong controls on morphological diversity, rather, latitude appears to correlate with taxonomic diversity more strongly. This suggests that taxonomic and morphologic diversity appear to be driven by separate processes in deep time and in the modern day. In my last chapter, I probed the ecomorphological history of rodents in Asia for parallels with the tectonic and climatic record. I did this by examining ecomorphospace occupation in tandem with significant events in the geologic history of Asia. I find that ecomorphospace occupation in Asian rodents has evolved in a stepwise manner through the Cenozoic. Ecomorphospace tends to contract across aridification events and expand across events of intensified dust transportation, which could be informative for modern predictive efforts in the face of human-mediated climatic and environmental change.
Together, these works progressively narrow in on the role that abiotic factors play in shaping the morphologic and ecologic evolution of rodents. These studies suggest that tectonic, environmental, and climatic drivers have some control on the evolution of ecomorphological diversity in rodents, which has progressed independently to taxonomic diversity for much of the Cenozoic. Future work will continue to examine the drivers of diversity in rodents, and attempt to parse the separate drivers of morphological, ecological, and taxonomic diversity.
This dissertation includes previously published coauthored material. One supplemental file is included with this dissertation, which contains Asian fossil rodent occurrences and ecological data from the New and Old Worlds database, supplemented with morphological and ecological data collected for this dissertation.
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Keywords
Disparity, Diversity, Rodents