Predicting the distribution of a novel bark beetle and its pine hosts under future climate conditions

U nderstanding the distribution of key biotic elements of forest ecosystems is essential in contemporary forest management and in planning to meet future management needs. Habitat distribution (niche) models based on known occurrences provide geographical structure for such management as the environmental factors change. 2B ark beetles play critical roles in coniferous forest dynamics in western North America. Among these insects, Dendroctonus rhizophagus Thomas and Bright, which occurs in the Sierra Madre Occidental in Mexico, is unique in that it attacks only immature trees (Pinus spp.) and therefore represents a threat to forest regeneration. We developed current habitat distribution models for D. rhizophagus and its Pinus hosts and projected these to future climate scenarios. 3P redicted suitable habitat ofD. rhizophagus currently covers approximately 119 000 km 2 of which approximately 11% is occupied, and overlap with suitable habitat for all Pinus hosts exceeds 99.5%. Some suitable habitat occurs isolated from known D. rhizophagus occurrences in Mexico and the south-western U.S.A. 4H abitat distribution models were projected to four potential climate scenarios for the period 2040-2060 and this predicted the gains and losses of suitable D. rhizophagus habitat throughout the region. Areas of north-western Mexico maintain large areas of suitable D. rhizophagus and Pinus host habitat in all scenarios. Dispersal to isolated areas of D. rhizophagus habitat appears unlikely. 5T he results of the present study can be used to targetD. rhizophagus monitoring and management activities and may serve as a model for the management of other invasive species.