Document: OWE-3-51-6

Influence of cold weather on the abundance of pinyon pine sawflies.

SHOLES, O.D.V.*

Assumption College, Worcester, MA 01609 USA ¹

Abstract:
Larvae of the sawfly Neodiprion edulicolus feed on needles of Pinus edulis (pinyon pine) during April in northern Arizona, USA. I censused the abundance of sawflies at two elevations (1740 m and 1830 m) between 19941999. Even though competition and predation can cause significant sawfly mortality, severe weather can overwhelm these biotic effects and cause abrupt population declines. Abundance in 1999 fell to 3% of the previous low, and throughout the sixyear census period there was a significant effect of cold April weather on sawfly abundance. Change in abundance (ln N _t+1 ln N _t) was significantly correlated (df = 3) with maximum consecutive days of snow (r = .953 at 1740 m; r = .944 at 1830 m; P < .02), with amount of snowfall (r = .994 at 1740 m; P < .01), and with lowest temperature (r = .964 at 1830 m; P < .02). If climate change increases the amount of severe weather and/or the variance of temperature and precipitation, abiotic effects may become more significant in population fluctuation, especially for insects and other poikilotherms.

Keywords: Pinus edulis, Neodiprion edulicolus, temperature, population fluctuation

This abstract is being presented at: 4:00 PM in session:
Oral Session #53: Terrestrial Invertebrate Ecology.