Adaptive thermoregulatory patterns in speciating mole rats.

The thermoregulatory response to cold (6+ or -1oC) and warm (33.5+ or -0.5oC) environments was studied in adult mole rats, belonging to four chromosomal species (2n=52, 54, 58 and 60), of the Spalax ehrenbergi species complex in Israel. Results indicate that 2n=60 is significantly the best thermoregulator both in warm and cold environments. In the warm environment, a physiological cline in thermoregulation was apparent along the following order: 2n=60 > 58 > 52, 54; in the cold environment the order was 2n=60 > 54 > 52 and 58. Differences in thermoregulatory ability within a species were discovered only in 2n=54 when exposed to 33.5+ or -0.5oC. Results support the idea that in the speciation of the Spalax ehrenbergi complex in Israel, physiological correlates are moulded by natural selection as an adaptation to climatic conditions.-from Authors