Abstract
We investigated the NOR distribution in ten populations of Physalaemus cuvieri from different regions of Brazil and Argentina. A high variability in NOR pattern was observed and provided a useful tool in grouping several populations. The specimens from the state of Tocantins, northern Brazil, could easily be distinguished from all the other analyzed populations, since its karyotype presented NORs in the chromosome pairs 1,3,4 and 10 (and sometimes also in chromosome 5), and several pericentromeric C-bands. A NOR-site in chromosome 9 characterized three populations from the northeastern region of Brazil. Interestingly, the P. cuvieri populations located in opposite extremes of the geographic distribution had, as a fixed condition, the presence of NORs in 8q int and llp. Besides interpopulational divergences, intrapopulational variability was observed in the number of NORs, except for populations from the states of Bahia and Minas Gerais, which are boundary states respectively in the northeastern and southeastern regions of Brazil. In relation to NOR size, interindividual variations occurred in all Brazilian and Argentinean populations. Additionally, intraindividual variability in NOR size was detected in specimens from Minas Gerais. The data presented herein revealed substantial geographic polytypic variation in P. cuvieri and indicated that a taxonomic reexamination of this species is necessary.
Highlights
The frog genus Physalaemus in South America belongs to the family Leiuperidae, together with Edalorhina, Engystomops, Eupemphix, Pleurodema, Pseudopaludicola and Somuncuria (Grant et al, 2006)
Since the size and morphology of pairs 8 and 9 were very similar in these three populations, the C-banding technique was essential in distinguishing between them; pair 8 had heterochromatic bands adjacent to the secondary constriction, probably containing the NOR (Fig. 2b), whereas dark C-bands coincided with the NORs in pair 9 (Fig 3)
NORs have been described in several cytogenetic studies (Sumner, 1990; Sánchez et al, 1995; Dobigny et al, 2002) and in some papers such findings have been attributed to the heterochromatic nature of these sites (Nardi et al 1978, De Lucchini et al, 1997). These data were in accordance with our present interpretation of the results found in P. cuvieri TO karyotypes
Summary
The frog genus Physalaemus in South America belongs to the family Leiuperidae, together with Edalorhina, Engystomops, Eupemphix, Pleurodema, Pseudopaludicola and Somuncuria (Grant et al, 2006). The Physalaemus comprises 41 species that are distributed east of the Andes (Frost, 2007). These species were classified in seven phenetic groups: “albifrons”, “cuvieri”,. No phylogenetic intrageneric relationships have been proposed for Physalaemus. The species Physalaemus cuvieri is widely distributed throughout South America, occurring in the northeastern, central, and southern regions of Brazil, Misiones and Corrientes in Argentina, eastern Paraguay, Department of Santa Cruz in Bolivia and possibly lowlands of Received: July 18, 2008.
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