Genetic differentiation during speciation [11]

SPECIATION theory is still largely descriptive. How many and what kind of genes are implicated in speciation is a central unresolved problem of evolutionary biology^1,2. Does speciation require major genomic changes^3-5 or may minor ones suffice^1,6-9? Similarly, does speciation depend on structural or on regulatory genes¹⁰? We have investigated these questions with reference to the actively speciating fossorial mole rats of the Spalax ehrenbergi complex in Israel, which comprises four morphologically indistinguishable chromosome forms (2n = 52, 54, 58, 60) ¹¹ adapted in that order to increasing aridity¹². Narrow hybrid zones between karyotypes¹³ and mate selection¹⁴ (through olfaction¹⁵, vocalisation¹⁶ and aggression ¹⁷) suggest that the recently¹⁸ formed species represent progressive stages of final speciation¹³. Genic diversity proved low, and genic similarity between karyotypes very high, in the previous test based on 17 gene loci of tissue proteins⁸. The test of eight additional loci of blood proteins, which is reported here, reinforces earlier conclusions and sheds light on the allozyme-environment association and on the amount of genetic differentiation during speciation.