HABITAT SELECTION IN EVOLVING MOLE RATS

The actively speciating four chromosomal species of fossorial mole rats of the Spalax ehrenbergi complex in Israel (2 n=52, 58, 54 and 60) which inhabit an increasingly arid environment in this order were tested to determine their habitat preference. The testing apparatus simulated four climatic regimes based on temperature and humidity combinations corresponding to the climatic origins of the four chromosomal species: coolhumid, cool-dry, warm-humid and warm-dry, respectively. The tests involved 175 adults comprising all four chromosome species and representing 10 populations. Out of the 139 analyzed animals 88% selected the warm cages and only 12% selected the cool cages. The four karyotype progressively preferred the warm-dry cage in the following order: 53, 59, 60 and 72% for 2 n=58, 52, 54 and 60 respectively, largely in accord with their increasingly arid climatic origins. Even larger differences were found in populations within karyotypes in accord with the local climatic variation within a karyotype range. The results of our analysis indicate that the chromosomal species and populations select their climatic habitat in accord with the climatic conditions of their geographic localities. The humidity index appears to be the prime differentiator of habitat selection and may have been a substantial ecological factor in species differentiation and distribution of the Spalax ehrenbergi complex in Israel. © 1979 Springer-Verlag.