Cytogenetics of Four Species of the Green Clade <b><i>Aplastodiscus</i></b> Lutz, 1950 (Anura: Cophomantinae): New Insights into the Chromosomal Evolution of the Genus

Abstract

The tree frog &lt;i&gt;Aplastodiscus&lt;/i&gt; 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 (&lt;i&gt;Aplastodiscus perviridis&lt;/i&gt; group), 2n = 22 (&lt;i&gt;Aplastodiscus albofrenatus&lt;/i&gt; group), 2n = 20, and 2n = 18 (both within &lt;i&gt;Aplastodiscus albosignatus&lt;/i&gt; 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. &lt;i&gt;Aplastodiscus weygoldti&lt;/i&gt; showed 2n = 22; Ag-NOR and FISH 18S rDNA signals were located in the interstitial region of the short arms of chromosome pair 6. &lt;i&gt;Aplastodiscus cavicola, Aplastodiscus&lt;/i&gt; sp. 4, and &lt;i&gt;Aplastodiscus&lt;/i&gt; 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 &lt;i&gt;Aplastodiscus&lt;/i&gt;, including a new chromosome fission event&lt;i&gt;.&lt;/i&gt; 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.

Repetitive DNA Mapping in Five Genera of Tree Frogs (Amphibia: Anura) from the Atlantic Forest: New Highlights on Genomic Organization in Hylidae

“…Most of the karyotyped species belonging to the family Hylidae had a diploid number equal to 24 chromosomes, which allowed some authors to propose an ancestral diploid number for hylids [2, 23, 37]. It is worth noticing that the chromosomes of the genus Dendropsophus are smaller than in the other species analyzed here and are associated with higher diploid numbers within this genus.…”

“…Cytogenetic studies have contributed to the understanding of the diversity of Anuran species, especially those characteristic of the Brazilian Atlantic Rainforest [22,23]. Chromosomal information is increasingly playing an important role in the integrative approach; thus, it can be integrated with bioacoustics, morphological, and molecular data, for stronger taxonomic hypotheses, as a basic step for establishing conservation strategies [29][30][31][32].…”

“…This distinct karyotypic formula among Bokermannohyla species indicates a high level of chromosomal differentiation [13]. In particular, this increase in chromosome arms in B. ibitipoca could be caused by multiple fission-fusion events, centromeric shifts, or heterochromatin expansion [23, 37].…”

“…Peixoto et al [22] showed that the conserved distribution pattern of CAT (10) and CA (15) probes in species of the genus Scinax has some functional relevance for evolutionary studies, but studies using these microsatellites are still experimental and largely inconclusive in hylids. Comparative studies using classical and molecular cytogenetic techniques have been instrumental for understanding processes of karyotypic evolution in certain groups or even tribes of Anura [14,19,23].…”