Thermal habitat and life history of two congeneric species of darkling beetles (Coleoptera: Tenebrionidae) on Tenerife (Canary Islands)

Relationships among minimum temperature, activity density, and life history were examined in two species of the genus Pimelia (Coleoptera: Tenebrionadae) oil two extreme sites along an elevation range oil Tenerife. On highest site, P. ascendens presented a 2-year life cycle with larvae and adults overwintering, spring breeding, and emergence of adults in summer. Changes in adult activity density were directly proportional to the minimum temperature. On lower site, P. canariensis was characterized by a 1-year life cycle, without larval or adult overwintering, winter breeding, and emergence of adults throughout the year. In this species, changes in adult activity density were inversely proportional to the minimum temperature, However, both species were eurythermic, displaying considerable overlap in adult preferred temperatures, which were 12-13 degrees C. In addition, the activity density patterns were different when analysed at broad scale and fine scales. Our results suggest conservatism of thermal optima over broad-scale environmental changes that occur with elevation. The stabilization in a constant thermal environment is achieved by behavioral, physiological, and developmental adjustments in the two species of Pimelia. (c) 2005 Elsevier Ltd. All rights reserved.