Supplementary Material for: Diversity and Karyotypic Evolution in the Genus <b><i>Neacomys </i></b>(Rodentia, Sigmodontinae)

<i>Neacomys</i> (Sigmodontinae) comprises 8 species mainly found in the Amazonian region. We describe 5 new karyotypes from Brazilian Amazonia: 2 cytotypes for <i>N. paracou</i> (2n = 56/FNa = 62-66), 1 for <i>N. dubosti </i>(2n = 64/FNa = 68), and 2 for <i>Neacomys</i> sp. (2n = 58/FNa = 64-70), with differences in the 18S rDNA. Telomeric probes did not show ITS. We provide a phylogeny using <i>Cyt</i>b, and the analysis suggests that 2n = 56 with a high FNa is ancestral for the genus, as found in <i>N. paracou</i>, being retained by the ancestral forms of the other species, with an increase in 2n occurring independently in <i>N. spinosus</i> and <i>N. dubosti</i>. Alternatively, an increase in 2n may have occurred in the ancestral taxon of the other species, followed by independent 2n-reduction events in <i>Neacomys</i> sp. and in the ancestral species of <i>N. tenuipes</i>, <i>N. guianae</i>, <i>N. musseri</i>, and <i>N. minutus</i>. Finally, a drastic reduction event in the diploid number occurred in the ancestral species of <i>N. musseri</i> and <i>N. minutus </i>which exhibit the lowest 2n of the genus. The karyotypic variations found in both intra- and interspecific samples, associated with the molecular phylogeny, suggest a chromosomal evolution with amplification/deletion of constitutive heterochromatin and rearrangements including fusions, fissions, and pericentric inversions.