Meiotic differentiation in two allopatric population groups of the tetraploid frog Odontophrynus americanus from Argentina

The Odontophrynus americanus species complex is widely distributed in South America and is formed of diploid and tetraploid cryptic species. We studied the meiotic prophase stages of two allopatric tetraploid population groups from southeastern and northwestern Argentina. These two allopatric population groups showed a bouquet polarization in zigotene and pachytene, and in the latter stage a complete synapsis of quadrivalents and bivalents. In diakinesis, the frequencies of the different elements per cell were recorded and compared with two theoretical distributions for an autotetraploid organism. Both model tests showed the same overall results. The frequency of quadrivalents did not depart significantly from the models in southeastern populations, and must be considered autotetraploid of recent origin. However, northwestern populations have a significantly reduced number of multivalents, which can be explained by diploidization or allotetraploidy. The reduction of quadrivalents is relatively low when compared with one of the models. Additionally, different chiasmatic frequencies were observed between bivalents and quadrivalents in both population groups. The presence of extra chromosomes detected in southeastern populations and the mitotic and meiotic irregularities reported from other populations, not observed in the present study, account for a high cytological variability between populations of the tetraploid frog Odontophrynus americanus, which can be ascribed to polyploidy.

Fil: Lanzone, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina

Fil: Baldo, Juan Diego. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Fil: Rosset, Sergio Daniel. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina