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Keywords:

  • rodent;
  • evolution;
  • species concepts;
  • Saccostomus campestris;
  • systematics

Abstract

A large degree of karyotypic diversity in the pouched mouse Saccostomus campestris, ranging from 2n=28 to 2n=46, is mostly due to centric fusions. The taxon comprises a complex of cryptic species, of which the 2n=32 and 2n=46 karyotypes represent two different species. Crossbreeding pure 2n=32 and pure 2n=46 karyotypes up to the F3 hybrid generation yielded F1 hybrids with 39 chromosomes, seven of which were unpaired. Unpaired chromosomes ranged in size from very long to short. We measured the growth rate, testis structure and litter size of these crosses and did not find any indication that the F1, F2 or F3 generations exhibit any degree of hybrid disadvantage or hybrid breakdown. The interpretation of these results is strongly affected by the species concept used, but weakens the conclusions of several other authors that S. campestris in southern Africa comprises a complex of cryptic species.