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Adaptations of insects at high altitudes of Chimborazo, Ecuador

Abstract:

Carabid beetles (Coleoptera: Carabidae) were collected from an altitudinal gradient at Chimborazo, Ecuador, in March 1994. Bembidion andinum Bates was the dominant species at 4,800 m. Pelmatellus andium Bates at 4,500 m and Agraphoderus integer Bates at 4,250 m. During daytime, the beetles were sheltering under rocks, but were caught in pitfall traps on open ground during the night. At 0.5 cm depth, soil temperatures from -4 to 41°C were recorded at 4,800 m and from -3 to 52°C at 4,500m, but fluctuations were greatly buffered at 2 and 5 cm depths. All three species had mean supercooling points of -5 to -6°C. Rates of water loss at 18°C and 5% RH were 4,4, 1.2 and 1.1% of fresh weight per hour, respectively. Apparently, the carabid beetles are poorly adapted to low temperatures and aridity. To survive the harsh climatic conditions at high altitudes on Chimorazo, they depend on sheltered microhabitats under rocks or below vegetation. Surface activity is restricted to certain periods during the night when conditions are more favorable. In comparison, lower rates of water loss were found in an unidentified species of Dermaptera and a curculioind beetle.