Harnessing Natural History Collections to Track Mammalian Responses to Global Change in the Anthropocene

Abstract

In the current era of rapid global change—the Anthropocene—understanding and predicting the varied responses among wild animal populations hinges on identifying the drivers underlying these complex patterns. Morphological trends, particularly in body size, are a key facet of these patterns; size is linked to many aspects of physiology (maintaining body temperature, energy requirements, etc.), ecology (dietary niche, inter- and intraspecific interactions, etc.), and life history (litter size, growth and development, etc.) and can thus both mediate and signal the nature and pace of global-change responses. Moreover, morphological change can be readily assessed over broad spatial and temporal scales thanks to the wealth of biodiversity data stored in natural history collections. My dissertation leverages these robust datasets to evaluate mammalian responses to global change over space and time, with a focus on the effects of shifting population age structure, reduced diet quality, and urbanization. My first chapter shows that population age distribution—despite often being overlooked in mammal research due to the traditional assumption of constant adult size—is a key factor that can help us refine models of morphological variation and unlock insights into demographic responses to climate change. My second chapter demonstrates how multiple forms of specimen-derived data can be used to understand climate-driven reductions in diet quality, or nutrient dilution. Results suggest that small mammalian herbivores, such as cottontail rabbits, may have some ability to buffer against widespread nutrient dilution through diet or habitat selection, but this may be a limited stopgap, as museum data spanning over seventy years indicate range-wide declines in mean body length. Finally, my third chapter evaluates the potential for domestication syndrome—the suite of physical characteristics thought to coincide with close association with humans—among four common, urban-dwelling mammals. Findings indicate that there are no shared, domestication-like trends among these ecologically and taxonomically disparate species, emphasizing the importance of other aspects of responses to urbanization, like local environmental context and population age structure. This research provides further support for the multifaceted nature of body size and shape, targeting key contributors to variation that have not yet been extensively studied in mammals, and underscores the value of natural history collections in unraveling these nuanced trends to construct a more holistic understanding of global-change responses.