Climatic variability and hemispheric differences in insect cold tolerance: support from southern Africa29 March 2007
1. Insects generally survive subzero temperatures by utilizing either freeze tolerance or freeze avoidance. Comparative analyses from a limited data set have indicated that freeze tolerance may be predominant among species at temperate latitudes in the southern hemisphere, while freeze avoidance dominates in the north. 2. We investigated the cold tolerance strategies of cockroaches and beetles from cold regions in southern Africa, including the Cederberg mountains, the Karoo desert and the Drakensberg mountains. 3. We found that 8 of 11 species are freeze tolerant. 4. Overall, 77% of species investigated in the southern hemisphere (n = 27) were freeze tolerant, which is significantly different from the 29% (n = 258) in the north (P < 0·001). 5. There are regular, unpredictable subzero temperature events in the southern African habitats; such variability appears to be a general feature of many cold habitats in the southern hemisphere, which may lead to the observed interhemispheric discrepancies in cold-tolerance strategies.