Three questions in paleobotany: fossil bias, plant development, and herbivory interactions, in the fossil record

Abstract

The study of fossil plants informs our understanding of habitats and climate conditions through time. Thus, an accurate picture of how plant communities lived and preserved in the fossil record is important in reconstructing the past. This study seeks to answer three questions in analyzing the plant fossil record: how organisms are preserved as the fossils we see, how these organisms grew and developed in life, and how they would have interacted with other organisms in their environment. To answer these questions, three studies were conducted on plant fossils. (1) I analyzed pyritized remains of a fossil gymnosperm pollen cone from the Miocene Lake deposits near Clarkia, Idaho, using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) to understand how fossils mineralize and what biases there are in this mode of plant preservation. Pyritization is localized to quickly decaying structures and was likely constrained by time after decay, a bias that should be taken into consideration when evaluating similar floras. (2) I analyzed specialized plant-insect interactions from fossil leaf material from the German Geiseltal deposits to explain how leaf development can be ascertained from bud-feeding trace fossils on plants using digital modeling, physical models, and experimental damaging of living leaves. Analysis of these leaves provides geometric and biological criteria for evaluating bud feeding traces in fossil leaves. (3) I characterized insect damage from the Mazon Creek fossil deposits from Illinois using qualitative and quantitative methods to understand how terrestrial food webs developed during the Paleozoic. Observed damage types are noted in other Pennsylvanian sites, such as the Williamson Drive in Texas. The site also hosts a low level of herbivory diversity and intensity, mostly localized on seed ferns, indicating that a seed fern preference may have been important to the proliferation of terrestrial insect herbivory. The results from these three studies allow us to more accurately interpret the fossil record and the potential ecological interactions they preserve.