Treefrogs of the genus Pithecopus Cope, 1866 exhibit expressive chromosomal homogeneity which contrasts with a high variation frequency of the nucleolus organizer region (NOR) related to the group. Currently, the genus contains eleven species and no chromosomal data are available on P. palliatus Peters, 1873, P. ayeaye Lutz, 1966 and P. megacephalus Miranda-Ribeiro, 1926. Here, we describe the karyotypes of these three species based on Giemsa staining, C-banding, silver impregnation and in situ hybridization (FISH). We were also analyze the evolutionary dynamic of the NOR-bearing chromosome in species of genus under a phylogenetic view. The results indicate that P. palliatus, P. ayeaye, and P. megacephalus have similar karyotypes, which are typical of the genus Pithecopus. In P. palliatus the NOR was detected in the pericentromeric region of pair 9p whereas in P. ayeaye and P. megacephalus we report cases of the multiple NOR sites in karyotypes. In P. ayeaye the NOR was detected in the pericentromeric region of pair 9p in both homologues and additional sites was detected in pairs 3q, 4p, and 8q, all confirmed by FISH experiments. Already in P. megacephalus the NOR sites were detected in pericentromeric region homologues of pair 8q and additionally in one chromosome of pair 13q. A comparative overview of all the Pithecopus karyotypes analyzed up to now indicates the recurrence of the NOR-bearing chromosome pairs and the position of the NORs sites on these chromosomes. We hypothesized that this feature is a result of a polymorphic condition present in the common ancestor of Pithecopus. In such case, the lineages derived from polymorphic ancestor have reached fixation independently after divergence of lineages, resulting in a high level of homoplasy observed in this marker. Our findings help to fill the gaps in the understanding of the karyotype of the genus Pithecopus and reinforce the role of the evolutionary dynamics of the rDNA genes in karyotype diversification in this group.

中文翻译：

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Pithecopus Cope 属猴蛙的活性 NOR 位点的反复变异，1866（Phyllomedusidae，Anura）。

Pithecopus Cope, 1866 属的树蛙表现出表达性染色体同质性，这与该群体相关的核仁组织区 (NOR) 的高变异频率形成鲜明对比。目前，该属包含 11 个物种，并且没有 P. palliatus Peters, 1873、P. ayeaye Lutz, 1966 和 P. megacephalus Miranda-Ribeiro, 1926 的染色体数据。这里，我们基于 Giemsa 描述这三个物种的核型。染色、C 显带、银浸渍和原位杂交 (FISH)。我们还从系统发育的角度分析了属物种中NOR染色体的进化动态。结果表明，P. palliatus、P. ayeaye 和 P. megacephalus 具有相似的核型，是猿属的典型核型。在 P. palliatus 中，在 9p 对的着丝粒周围区域检测到 NOR，而在 P. ayeaye 和 P. megacephalus 中，我们报告了核型中存在多个 NOR 位点的病例。在 P. ayeaye 中，在两个同源物的 9p 对的着丝粒周围区域中检测到 NOR，并且在 3q、4p 和 8q 对中检测到其他位点，所有这些均通过 FISH 实验证实。在P. megacephalus 中，已经在第8q 对的着丝粒周围区域同源物以及第13q 对的一条染色体中检测到了NOR 位点。对迄今为止分析的所有 Pithecopus 核型的比较概述表明，带有 NOR 的染色体对的重复出现以及 NOR 位点在这些染色体上的位置。我们假设这一特征是古猿共同祖先中存在的多态性条件的结果。在这种情况下，源自多态祖先的谱系在谱系分歧后已独立地达到固定，导致在该标记中观察到高水平的同质性。我们的研究结果有助于填补对古猿属核型理解的空白，并加强 rDNA 基因的进化动力学在该类群核型多样化中的作用。