Evolutionary theory and processes of active speciation and adaptive radiation in subterranean mole rats, Spalax ehrenbergi superspecies in Israel

The inter and multi-disciplinary evolutionary model of active ecological speciation and climatic adaptive radiation of blind subterranean mole rats of the Spalax ehrenbergi superspecies (Spalacidae, Rodentia) in Israel, is overviewed in the light of the synthetic theory of Darwinian evolution, and its current challenges. The S. ehrenbergi superspecies in Israel comprise four chromosomal species (2n=52, 54, 58 and 60) displaying progressive stages of late chromosomal speciation. Their adaptive radiation in Israel from Early Pleistocene to Recent times is closely associated with the mediterranean and steppic climates, subterraneity, and an environmental gradient of increasing aridity stress, hence with distinct climatic diversity: 2n=52 (cool-humid); 2n=54 (cool-semidry); 2n=58 (warm-humid) and 2n=60 (warm-dry). The ecological speciational trend of S. ehrenbergi into increasingly arid environments initiated apparently peripatrically in small peripheral isolates by rapid random fixation of Robertsonian chromosomal mutations. This emergence was followed by gradual genic accumulation of positive assortative mating based on premating ethological species-specific isolating mechanisms involving olfaction, vocalization, seismic (vibrational), aggression and mating (via bacular variation) cues. The speciational trend budded off a sequence of daughter species with increasingly higher diploid chromosome numbers (2n) towards the desert, each species displaying a syndrome of adaptations at all organizational levels. These integrate genotypic-molecular (DNA, nuclear and mitochondrial, as well as proteins), and phenotypic organismal (morphological, physiological and behavioural) levels as multiple adaptive strategies to the following major challenges: (i) Temporal (seasonal annual division into dry summer and wet winter); (ii) Local (subterranean ecotope with its stresses of low productivity, energetics, hypoxic-hypercapnic burrow atmosphere, and total darkness), and (iii) Regional (gradient of increasing aridity and predictability southwards; 2n=52->58->60; and eastwards: 2n=52->54). S. ehrenbergi represents a pluralistic example where chromosomal and genic mutations, genetic drift, migration, isolation, and natural selection all interact in producing new adaptive species to environmental diverse challenges. The evolution of S. ehrenbergi is explicable by the Synthetic Theory of Evolution, and defies many of its current challenges.