Paper No. 12
Presentation Time: 11:00 AM
DO WARM CLIMATES ALWAYS HAVE HIGH LEAF HERBIVORY? A STUDY OF INSECT DAMAGE ON LEAVES OF WESTERN OAKS
LECKEY, Erin H., Geological Sciences, University of Colorado, Boulder, CO 80309 and SMITH, Dena, CU Museum of Natural History, Univ of Colorado, Campus Box 265, Boulder, CO 80309, Erin.Leckey@colorado.edu
Insects inflict more damage on leaves in warmer climates. This pattern has been found in both fossil and modern communities. Although warm temperatures have a strong correlation with increased herbivory at the community level, the effects of climate on herbivory in individual taxa is not always clear. Individual host-herbivore pairs represent an evolutionary relationship that may not respond to shifting climate in the same ways as broader communities of hosts and herbivores. Oaks (
Quercus) are host to a diverse group of herbivores, some with relationships lasting for millions of years. Their occurrence across broad climatic zones makes them ideal for examining whether variations in local climate have a significant effect on feeding patterns through time. In this study we examined leaves of oaks from western North America with ages ranging from Oligocene to Pliocene (25 to 5 MA) with a range of mean annual temperature (2 to 13°C) and precipitation (6 to 19 cm) levels.
Fifteen floras were examined from the following paleofloral regions: Great Basin, Columbia Plateau, Northwest Coast and Southern Central California. For these floras, 2,351 oak leaves were examined, of which approximately 50% had insect damage. The amount of leaf tissue removed was 4% on average, with most leaves displaying damage from only one functional feeding guild. Neither mean annual temperature nor mean annual precipitation was a significant determinant of either the percentage of leaves with damage (F=0.93, P=0.352, temperature; F=2.22 P=0.160, precipitation), or the amount of leaf tissue removed per flora. The lack of a climatic influence was found both for overall levels of herbivory and for those types of damage made by herbivores that specialized on oaks. These data suggest that the interactions between oaks and their insect herbivores are driven more strongly by their long-term evolutionary history than by short-term ecological perturbations caused by shifting climates.
