Model analysis of mountain pine beetle (Coleoptera : Scolytidae) seasonality

The mountain pine beetle, Dendroctonus ponderosae Hopkins, is a natural dis turbance agent of considerable consequence in western pine forests. This ec onomically and ecologically important insect has a strong requisite for mai ntaining a strict seasonality. Given this ecological requirement, it is som ewhat surprising that no evidence for diapause or other physiological tinti ng mechanism has been found. Seasonality and phenological timing for this s pecies are apparently under direct temperature control. We investigate the consequences of direct temperature control by first constructing a computat ionally efficient phenology model based on previously published temperature dependent developmental data. We explored the dynamic properties of this m odel when subjected to observed microhabitat temperatures representing a ra nge of thermal habitats from one region of the mountain pine beetle distrib ution. We also investigated the consequences of global climate change on ph enology and seasonality. Our results indicate that an adaptive seasonality is a natural consequence of the interaction between developmental parameter s and seasonal temperatures. Although this adaptive phenology appears to be resilient to temperature fluctuations, changes in climate within the magni tude of predicted climate change under a CO2 doubling scenario are capable of shifting a thermally hostile environment to a thermally benign environme nt. Similarly, increasing temperature by the same amount resulted in phenol ogical disruption of a previously favorable thermal habitat. We discuss the implications of these results for restricting the current distribution of mountain pine beetle, and the potential for shifting distribution caused by global climate change.