Species delimitation in the Acomys cahirinus - dimidiatus complex (Rodentia, Muridae) inferred from chromosomal and morphological analyses

Our earlier chromosome banding studies of Acomys cahirinus and A. dimidiatus (the latter long considered to be a subspecies of the former) revealed that despite very close diploid numbers (36 vs. 38), these taxa possess sharply different karyotypes and undoubtedly belong to different species. In this context, the taxonomic status and the relationship between the two chromosomal forms in Sinai (2n=36) and Israel (2n=38), chromosomally homozygous across a vast range except for a very narrow hybrid zone, remain poorly documented. Neither of these forms have previously been studied by chromosome banding, thus the exact nature of chromosomal differences as well as the species to which these forms should be assigned remain unknown. Here we present the data on comparative G-banding analysis and morphometrics of Acomys from Israel, from Sinai, from Saudi Arabia and a hybrid obtained in laboratory crosses between latter two. The analysis revealed that karyotype of Acomys from Israel is identical to that of Acomys from Saudi Arabia and both are different from that of Acomys from Sinai by one Robertsonian fusion. Therefore karyotypically all three are very different from A. c.. It follows from the study that Sinai and probably Arabian peninsula and Minor Asia must be excluded from geographical distribution of A. c., which is limited from West Sahara to Egypt along Nile river (except Sinai). Further, the synthesis of chromosomal and recent molecular data suggests a phylogeographic scenario explaining the modern distribution of Acomys in the Sinai and Arabian peninsulas and permits the update of the taxonomic status of these populations