GENETIC POLYMORPHISMS IN SUBTERRANEAN MAMMALS (SPALAX-EHRENBERGI SUPERSPECIES) IN THE NEAR-EAST REVISITED - PATTERNS AND THEORY

Allozyme diversity in the superspecies Spalax ehrenbergi has been revi sited by studying 36 gene loci in 241 subterranean mole rats from 22 p opulations and nine chromosomal species, four from Turkey (2n = 52E (e ast), 52W (west), 56 and 58), four from Israel(2n = 52, 54, 58 and 60) , and one from Egypt (2n = 60). The following results were indicated. (1) Genetic patterns: 11 of the 36 loci analysed (30.5 per cent) were monomorphic across the range, fifteen (41.7 per cent) were weakly poly morphic and the remaining 10 loci (27.8 per cent) were strongly polymo rphic. (2) Heterozygosity: the average H was 0.051, range 0.00-0.098. In Israel, H increased with aridity and climatic unpredictability towa rds the northern Negev Desert, and was remarkably high in small steppi c semi-isolates and desert isolates. (3) Species discrimination: some of the S. ehrenbergi species can be discriminated qualitatively. (4) G enetic distances (D): between species these values averaged 0.077, ran ge 0.001-0.269, with the highest D between the ancestor Turkish and de scendant Israeli and Egyptian species. The phylogenetic tree supports the Turkish origin of the Israeli Spalax ehrenbergi species, and the r ecent speciation of the Egyptian Spalax. (5) Genetic diversity is most ly (58 per cent) within populations. (6) Allozyme correlates: allozyme diversity was significantly correlated with the external physical (bo th climatic and edaphic) and biotic (parasite infection and plant cove r) environment. (7) Spatial autocorrelation of allozyme frequencies su ggests that migration is not influential. (8) Gametic phase disequilib ria were significant in four out of five species tested, and were asso ciated with climatic and edaphic factors. These results support the en vironmental selection hypothesis of genetic diversity including the ni che-width variation hypothesis in space and time. Natural selection ap pears to play a major role in genetic differentiation of proteins in a daptive radiation and speciation.