SINCLAIR, B.J.; CHOWN, S.L.; Univ. Nevada, Las Vegas; Univ. Stellenbosch, South Africa: Climatic variability and hemispheric differences in insect cold tolerance: Support from southern Africa

Insects generally survive sub-zero temperatures by utilising either freeze tolerance or freeze avoidance. Meta-analyses from a limited dataset have indicated that freeze tolerance may be predominant among species at temperate latitudes in the southern hemisphere, while freeze avoidance dominates in the north. We investigate the cold tolerance strategies of cockroaches and beetles from cold regions in southern Africa, and find that eight of eleven species (73%) are freeze tolerant and that at least one freeze intolerant species displays a rapid cold-hardening response. Overall, 77% of species investigated in the southern hemisphere (n = 27) are freeze tolerant which is significantly different from the 29% (n = 258) in the north (p<0.001). We propose that these differences arise as a consequence of climatic variability around the freezing point of water resulting from the oceanic nature of southern hemisphere, and that these hemispheric differences may be generally applicable to ecology.