Abstract
Karyotype (2 n) and allozyme diversity at 37 gene loci were determined in 69 subterranean mole rats in Turkey belonging to the two superspecies: the ancestor Spalax leucodon ( n = 55; 20 populations) and the descendant S. ehrenbergi ( n = 14: four populations. We identified remarkable variation of diploid chromosome numbers in the S. leucodon superspecies: 2 n = 38, 40, 50, 54, 60 and 62; and in the S. ehrenbergi superspecies: 2 n = 52, 56 and 58. Genetic diversity indices were low on average in both S. leucodon and S. ehrenbergi superspecies: Allele diversity, A = 1.081 and 1.074; polymorphism, P-5 0 0 = 0.077 and 0.068; heterozygosity, H = 0.038 and 0.027; and gene diversity, H = 0.038 and 0.034, respectively. H ranged from 0 in mesic or semimesic regions to 0.088 in arid Anatolia. We consider the populations with different diploid chromosome numbers, 2 n, as good biological species. Karyotypic diversity may mark extensive ecological speciation. Nee's genetic distances, D average 0.174, range 0.002 0.422) and ecogeographical criteria suggest that almost each population may represent a different biological species, but critical future testing is necessary to support this claim. Karyotypes and allozymes are nonrandomly distributed across Turkey, displaying remarkable correlations with climatic and biotic factors. Both 2 n and H are significantly correlated with aridity stress (2 n/rainfall. r = −0.74; P < 0.001), and in our region also with climatic unpredictability. These results support the niche-width genetic variation hypothesis in space and time. Climatic selection in Turkey appears to be a major architect of karyotype and genetic (allozyme) diversity and divergence in mole rat evolution, in both speciation and adaptation.
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