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Ctenomys lami: The highest chromosome variability inCtenomys (Rodentia, Ctenomyidae) due to a centric fusion/fission and pericentric inversion system

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Ctenomys lami Freitas, 2001 is an endemic species of rodent inhabiting the Coastal Plain of southern Brazil, along a narrow line of old dunes formed in the Pleistocene. This species has five different diploid numbers (2n=54, 55a, 55b, 56a, 56b, 57 and 58) and ten different autosomal fundamental numbers (FNa=74, 75, 76, 77, 78, 79, 80, 81, 82, and 84). In a sample of 102 specimens, the combined 2n and FNa formed 26 different karyotypes. The diploid number variation was due to Robertsonian rearrangements that occur in pairs 1 and 2, and the variation of NFas was due to pericentric inversions. The distribution of diploid number variation along the 78 km line of collection sites reveals four population blocks: block A with 2n=54, 55a, and 56a; block B with 2n=57 and 58; block C with 2n=54 and 55a; and block D with 2n=56b and 55b. The inversion system lacks geographic structure with a random distribution of inversions along the population blocks. A very narrow hybrid zone is hypothesized between blocks A and B. Blocks B and C are separated by a geographic barrier, and another hybrid zone is found between blocks C and D. My findings suggest that this species is undergoing a process of speciation due to geographic isolation.

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Correspondence to Thales Renato O. de Freitas.

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Associate editor was Joseph F. Merritt.

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de Freitas, T.R.O. Ctenomys lami: The highest chromosome variability inCtenomys (Rodentia, Ctenomyidae) due to a centric fusion/fission and pericentric inversion system. Acta Theriol 52, 171–180 (2007). https://doi.org/10.1007/BF03194212

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Key words

  • Ctenomys lami
  • Rodentia
  • Ctenomyidae
  • chromosomes
  • G-band
  • C-band
  • NOR band