CHANGES IN INSECT HERBIVORY ACROSS THE PALEOCENE-EOCENE BOUNDARY IN THE BIGHORN BASIN, WYOMING

The late Paleocene and early Eocene is a period of marked temperature fluctuations, significant mammalian turnover events, and moderate floral turnover. However, changes in plant-insect interactions during this interval are little known. The primary objective of this study is to track changes in insect damage on angiosperm leaves in the Bighorn Basin of Wyoming and to test whether these changes correlate with temperature, precipitation, leaf nutrient levels, and time since the Cretaceous-Tertiary (K-T) extinction. The late Paleocene through early Eocene can be divided into six intervals of climate change: the late Paleocene warming, Initial Eocene Thermal Maximum (IETM), post-IETM early Eocene, early Eocene cool period, warming to the early Eocene climatic optimum (EECO), and EECO. Insect damage censuses are being conducted at leaf localities from each interval. One thousand dicot leaves are censused for each interval, and insect damage on each leaf is defined using the damage morphotypes of Labandeira et al (2004). Quantitative correlations between insect herbivory and temperature, precipitation, floral diversity, leaf nutrient levels, and time since the K-T extinction can be made using time series analysis and other statistical methods. Because food webs incorporating plants and phytophagous insects account for up to 75% of global biodiversity, it is essential to examine how factors like global warming and cooling affect insect herbivory.