Supplementary Material for: Tracking Chromosome Evolution in Southern African Gerbils Using Flow-Sorted Chromosome Paints

<i>Desmodillus</i> and <i>Gerbilliscus</i> (formerly <i>Tatera</i>) comprise a monophyletic group of gerbils (subfamily Gerbillinae) which last shared an ancestor approximately 8 million years ago; diploid chromosome number variation among the species ranges from 2n = 36 to 2n = 50. In an attempt to shed more light on chromosome evolution and speciation in these rodents, we compared the karyotypes of 7 species, representing 3 genera, based on homology data revealed by chromosome painting with probes derived from flow-sorted chromosomes of the hairy footed gerbil, <i>Gerbillurus paeba</i> (2n = 36). The fluorescent in situ hybridization data revealed remarkable genome conservation: these species share a high proportion of conserved chromosomes, and differences are due to 10 Robertsonian (Rb) rearrangements (3 autapomorphies, 3 synapomorphies and 4 hemiplasies/homoplasies). Our data suggest that chromosome evolution in <i>Desmodillus </i>occurred at a rate of ∼1.25 rearrangements per million years (Myr), and that the rate among <i>Gerbilliscus</i> over a time period spanning 8 Myr is also ∼1.25 rearrangements/Myr. The recently diverged <i>Gerbillurus (G. tytonis </i>and<i> G. paeba)</i> share an identical karyotype, while <i>Gerbilliscus kempi, G. afra</i> and <i>G. leucogaster</i> differ by 6 Rb rearrangements (a rate of ∼1 rearrangement/Myr). Thus, our data suggests a very slow rate of chromosomal evolution in Southern African gerbils.