Comparative analysis based on replication banding reveals the mechanism responsible for the difference in the karyotype constitution of treefrogs Ololygon and Scinax (Arboranae, Hylidae, Scinaxinae)

Abstract

According to the recent taxonomic and phylogenetic revision of the family Hylidae, species of the former Scinax catharinae (Boulenger, 1888) clade were included in the resurrected genus Ololygon Fitzinger, 1843, while species of the Scinax ruber (Laurenti, 1768) clade were mostly included in the genus Scinax Wagler, 1830, and two were allocated to the newly created genus Julianus Duellman et al., 2016. Although all the species of the former Scinax genus shared a diploid number of 2n = 24 and the same fundamental number of chromosome arms of FN = 48, two karyotypic constitutions were unequivocally recognized, related mainly to the distinct size and morphology of the first two chromosome pairs. Some possible mechanisms for these differences had been suggested, but without any experimental evidence. In this paper, a comparison was carried out based on replication chromosome banding, obtained after DNA incorporation of 5-bromodeoxiuridine in chromosomes of Ololygon and Scinax. The obtained results revealed that the loss of repetitive segments in chromosome pairs 1 and 2 was the mechanism responsible for karyotype difference. The distinct localization of the nucleolus organizer regions in the species of both genera also differentiates the two karyotypic constitutions.

Chromosome evolution in Lophyohylini (Amphibia, Anura, Hylinae)

“…Within Lophyohylini, most species show a single pair of NORs located on small pairs of chromosomes with similar morphology [18, this study]. This condition is also present in Cophomantini [17], Scinaxini [13,16], and Hylini [18], suggesting a putative homeology between the chromosomes carrying this marker [13,14]. Moreover, the BrdU replication banding pattern information gathered from different neotropical species of hylids strengthens this hypothesis [21,49].…”

“…Several contributions have studied chromosome evolution in different clades of Hylinae (e.g., [12][13][14][15][16][17]). More recently, Schmid et al [18] summarized most cytogenetic information known for Hylidae, further contributing with novel karyotypes for 14 species of Hylinae (2 Cophomantini, 2 Hylini, 2 Scinaxini, and 8 Dendropsophini).…”

Cytogenetics of two hylid frogs from Brazilian Cerrado

“…The nucleolar organizer region (Ag-NOR) was localized herein for the first time for the karyotypes of S. constrictus and O. centralis . It was detected in the long arm of pair 7 in S. constrictus , thus differing from previous data for Scinax and Julianus species (previously, Scinax ruber clade), where they are found in the short arm of pair 11 ( Cardozo et al , 2011 ; Nogueira et al , 2015 ; Peixoto et al , 2016 ; Gruber et al , 2017 ). Notably, the NOR was also found in this same chromosome pair in phylogenetically more distant species, such as those of the genera Xenohyla , Lysapsus , and Pseudis (except for one population).…”

“…Hence, this improved knowledge on the population cytogenetics will contribute with the elucidation of the possible evolutionary differentiation among populations of S. constrictus . Moreover, the chromosome morphology assigned for Scinax (= Scinax rube r clade) and Ololygon (= Scinax catharinae clade) by Bogart (1973) was also now detected for S. constrictus and O. centralis , respectively, as well as in some other previous studies ( Oliveira et al , 2010 ; Cardozo et al , 2011 ; Nogueira et al , 2015 ; Peixoto et al , 2015 , 2016 ; Lourenço et al ., Gruber et al , 2017 ). All these findings demonstrate that chromosomal morphology is a conserved feature in both of these Scinaxinae genera.…”

A review of the elusive bicolored iris Snouted Treefrogs (Anura: Hylidae:Scinax uruguayus group)

“…ruber clades could be attributed to pericentric inversions, addition/loss of repetitive sequences, or still unidentified structural chromosome alterations. Gruber et al [176], based on replication bands, attributed these differences to the loss of repetitive sequences in the chromosomes Pair 1 in two species of the S . catharinae clade ( S .…”