The tree frog <i>Aplastodiscus</i> is a Neotropical taxon that encompasses 15 species in the Atlantic forest biome, with one isolated species in the Central Brazilian Cerrado. To date, only 8 species have been karyotyped, showing high levels of diploid number variation, which allowed clustering species in chromosome number groups: 2n = 24 (<i>Aplastodiscus perviridis</i> group), 2n = 22 (<i>Aplastodiscus albofrenatus</i> group), 2n = 20, and 2n = 18 (both within <i>Aplastodiscus albosignatus</i> group). This study aims to report karyotypic information on 4 species from the last 2 groups using classical and molecular cytogenetic techniques and hypothesize chromosomal evolutionary trends within the species groups. <i>Aplastodiscus weygoldti</i> showed 2n = 22; Ag-NOR and FISH 18S rDNA signals were located in the interstitial region of the short arms of chromosome pair 6. <i>Aplastodiscus cavicola, Aplastodiscus</i> sp. 4, and <i>Aplastodiscus</i> sp. 6 showed 2n = 18; Ag-NOR and FISH 18S rDNA bands were located in the terminal region of the long arm of chromosome pair 9. Our results support multiple and independent chromosome fusion events within <i>Aplastodiscus</i>, including a new chromosome fission event<i>.</i> Ag-NOR and FISH 18S rDNA patterns were restricted to the small chromosome pairs, similar to the other species within this genus, and confirm overall chromosome morphology conservation among the genera of Cophomantinae.
The genus Enyalius is composed of 10 described species inhabiting forest areas in Amozônia, Cerrado and Atlantic forest biomes. Currently, eight species with high levels of chromosome variation have been karyotyped. The study aims to characterize the karyotype of Enyalius boulengeri, with classical and molecular techniques, and improve knowledge about the karyotype evolution of the lizard genus Enyalius. The species has 2n = 36 chromosomes (8m + 4sm + 24mc), FN = 24; NORs and 18S rDNA were subtelomeric and located on chromosome pair 2. Repetitive DNA probes (CAT)10 accumulated on centromeric and terminal regions of some macrochromosomes. (GA)15 probe showed conspicuous accumulation on the pericentromeric region of chromosome pairs 1 and 6. Repetitive FISH patterns obtained with (GC)15 probe marked the pericentromeric region of the first chromosome pair. All probes showed accumulation in the microchromosomes. The chromosomal formula found on E. boulengeri has been considered the ancestral karyotype for pleurodont Iguania. The genus Enyalius is characterized by two distinctive chromosomal groups; one with highly conserved karyotypes, whereas the other is karyotypically diverse. Our molecular cytogenetics data are promising and will increase knowledge about the genus Enyalius chromosome evolution.
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