PLANT–ARTHROPOD ASSOCIATIONS FROM THE WESTERN INTERIOR OF NORTH AMERICA DURING THE LATE CRETACEOUS

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2020

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Abstract

Insects are unparalleled in species diversity and breadth of ecological associations. The most prominent of these ecological associations is insect herbivory on vascular plants, which has shaped terrestrial ecosystems for hundreds of millions of years. Only recently have scientists begun to understand the diversity and intensity of plant–insect associations in the fossil record. The majority of these studies have documented episodes of rapid change in Earth’s history, such as intervals of global warming. However, there are few studies documenting plant–insect associations around longer time intervals, including the radiation of flowering plants (angiosperms) during the Cretaceous Period from 145 to 66 Ma (Mega-annum), which set the stage for many modern plant–insect associations. Herein, I present the results of specimen-based surveys of Campanian Age (83.6–72.1 Ma) macrofossil floras and their associated insect damage from the Kaiparowits Formation of Utah, USA, a fossiliferous deposit within the Western Interior. First, I describe a new genus of fossil laurel (Lauraceae), and analyze the plant–insect associations found on this taxon. After, I describe the diversity and intensity of plant–insect associations from the a single, well-sampled locality. I then describe a new fossil lyonetiid moth leaf mine, which represents the oldest fossil evidence of a cemiostomine leaf-mining moth, as well as the second oldest record of the Yponomeutoidea–Gracillarioidea clade. Then, I describe acarodomatia (mite houses) on fossil leaves, which constitute the oldest evidence for plant–mite mutualisms in the fossil record. Finally, to understand broad-scale and long-term patterns of insect damage in the fossil record, I analyze all available fossil plant–insect associational datasets spanning the Age of Angiosperms (ca. 76–2 Ma). These results indicate that insect preference for plant hosts may have changed through time as local plant diversity increased, but this may stem from differences in sampling regimes and difficulties in identification of fossil angiosperms. My findings collectively indicate that Late Cretaceous plant–insect associations are often novel, diverse, and may be evolutionarily tied to modern plant–insect associations, as well as the acquired insight into the limitations and future directions for this field of research.

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