Representation of chromosomal rearrangements that could have occurred during the chromosomes formation of the six studied species A appearance of a neocentromere (NC) on the ancestral CJA1 and CUN1 B double inversion that could have occurred on chromosome 2 between GGA and CCO/CJA (left). Appearance of a possible terminal fission on ancestral GGA2, which would be at the origin of the formation of CUN2 and microchromosome CUN10 (right) C possible formation of a neocentromere during the evolution of GGAW and CCOW D appearance of several fissions on the ancestral chromosome 4, which would be at the origin of the formation of chromosomes 4, 11, 14 and 19 of the Houbara bustard (left). Appearance of paracentric inversion between GGA4 and ACH4 (right) E formation of a neocentromere between GGA7 and ABA7 (left) or the course of a pericentric inversion between GGA7 and CUN7 (in the middle), deletion of the short arm p of GGA7 and CJA7 could have occurred between during evolution (right) F pericentric inversion could have occurred between GGA8 and (CCO8, CJA8, CUN8) (left), possible formation of a NC between GGA8 and CUN8 as well as the both partridge species (right) G formation of CUNZ following a possible interstitial deletion (fragment corresponding to CUN13) occurring on the ancestral Z chromosome accompanied by a terminal inversion (left). A terminal inversion in Zq2.1 is observed in ABA (right).