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The emergence of a new sex-system (XX/XY1Y2) suggests a species complex in the "monotypic" rodent Oecomys auyantepui (Rodentia, Sigmodontinae).

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Oliveira da Silva, Willam  ORCID logo
Rosa, Celina Coelho 
Ferguson-Smith, Malcolm Andrew  ORCID logo
O'Brien, Patricia Caroline Mary 


X-autosome translocation (XY1Y2) has been reported in distinct groups of vertebrates suggesting that the rise of a multiple sex system within a species may act as a reproductive barrier and lead to speciation. The viability of this system has been linked with repetitive sequences located between sex and autosomal portions of the translocation. Herein, we investigate Oecomys auyantepui, using chromosome banding and Fluorescence In Situ Hybridization with telomeric and Hylaeamys megacephalus whole-chromosome probes, and phylogenetic reconstruction using mtDNA and nuDNA sequences. We describe an amended karyotype for O. auyantepui (2n = 64♀65♂/FNa = 84) and report for the first time a multiple sex system (XX/XY1Y2) in Oryzomyini rodents. Molecular data recovered O. auyantepui as a monophyletic taxon with high support and cytogenetic data indicate that O. auyantepui may exist in two lineages recognized by distinct sex systems. The Neo-X exhibits repetitive sequences located between sex and autosomal portions, which would act as a boundary between these two segments. The G-banding comparisons of the Neo-X chromosomes of other Sigmodontinae taxa revealed a similar banding pattern, suggesting that the autosomal segment in the Neo-X can be shared among the Sigmodontinae lineages with a XY1Y2 sex system.



Animals, Chromosome Painting, In Situ Hybridization, Fluorescence, Phylogeny, Rodentia, Sex Chromosomes, Sigmodontinae

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Springer Science and Business Media LLC
Conselho Nacional de Desenvolvimento Científico e Tecnológico (305876/2017-1, 552032/2010-7)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (047/2012, 88882.315778/2019-01)
Fundação Amazônia Paraense de Amparo à Pesquisa (2010/110447, ICAAF 007/2011)
Banco Nacional de Desenvolvimento Econômico e Social (2.318.697.0001)
PAPQ/PROPESP, Universidade Federal do Pará, Brazil (06/2021)