Abstract Rodentia has a high species number and chromosomal variability. The South American genus Akodon is one of the most speciose muroids, with more than 40 species included in several species groups. Here, we characterize cytogenetically specimens of Akodon from central-western Argentina. Subsequently, we reviewed and analyzed the cytogenetic data for this genus, build a phylogeny and mapped chromosome changes to interpret its evolution. Specimens of A. dolores from central-western Argentina have 2n=42-44/FNa=44 (46, 48) due to a Robertsonian rearrangement. Our data expand the distribution range known for this polymorphism and confirm its geographic structure. Other specimens had 2n=40/FNa=40, representing populations of A. oenos, A. polopi, and A. spegazzinii. All karyotypes have a low amount of heterochromatin, concentrated in centromeres and sex chromosomes, as in other rodents. The complement with 2n=40/FNa=40 is the most frequent in Akodon and is shared by most species in some groups. Chromosome numbers are very diverse. The FNa shows less variability; FNa=42 was recovered as ancestral, excluding A. mimus, which was connected at the base of the Akodon tree and has FNa=44. This indicates a complex chromosome evolution in Akodon, and suggests that reductions and increases in the 2n and FNa evolved independently in some lineages.

Abstract Glyphonycteris is a poorly known genus of bats that inhabit lowlands and forested mountains of Central and South America. This genus comprises three nominal species, with G. sylvestris being themost widely distributed species in South America. The karyological data previously available for this genusare restricted to those resulting from conventional staining techniques applied to a few specimens from Surinam. Here, we report the first record of G. sylvestris in Argentina extending its southern distribution. Moreover, our new locality represents the seventh record from the Atlantic Forests Biome and the first from Araucaria Moist Forest ecoregions. Our specimen overall exhibits the diagnostic characteristics described for the species except for some differences in the distribution of hairs on the wings and limbs. The fecal sample obtained from our specimen contained only seeds of Piper aduncum. The karyotype was 2n = 22 with a FN = 42; the analysis of fluorochrome banding patterns in the chromosomal pericentromeric regions shows DAPI (4,6-diamidino-2-phenylindole) positive blocks in pairs 5 and 8, whereas pericentromeric regions stained with CMA3. (Chromomicine A3) are positive in pairs 1, 2, 3, 4 and 11. Moreover, the interstitial region of chromosomes shows DAPI and CMA3 positive blocks in pairs 1, 2, 3, 4 and 5. These karyological data are novel to G. sylvestris, contributing to the scarce knowledge of the genus. Thus, filling blanks of information and enabling further comparative chromosome analysis.

We present a synthesis of the current knowledge of the rodents from the province of Misiones, Argentina, with emphasis on taxonomic, chromosomal, biogeographic and conservation issues. In this province, the order is represented by 7 families: Sciuridae (1 genus, 1 species), Cricetidae (17, 24), Caviidae (2, 2), Cuniculidae (1, 1), Dasyproctidae (1, 1), Echymyidae (3, 3) and Erethizontidae (1, 1). From 1 to 5 species -depending on taxonomic authorities- are endemic to Misiones. We briefly discuss some taxonomic problems, highlighting those questions that still persist (e.g., the complex situation of the genus Brucepattersonius). For several species, we provide novel chromosome data and compare it with the information available for Brazil. An analysis of the species richness at the provincial level indicates that the highest values for this parameter occur towards the south-central portion of the territory, in an area of interdigitation between the Interior Atlantic Forest and the ecoregion of Campos y Malezales. We discuss the role of large rivers in the region as barriers to the dispersal of this fauna (e.g., the Paraná between Argentina and eastern Paraguay). At least 9 species of rodents with distribution in the province of Misiones have been classified under some category of threat or near to the threat. In all cases, the survival of these taxa depends on maintaining the integrity and connectivity between forest remnants.

Presentamos una síntesis del conocimiento actual de los roedores de la provincia de Misiones, Argentina, con énfasis en aspectos taxonómicos, cromosómicos, biogeográficos y de conservación. En esta provincia, el orden está representado por 7 familias: Sciuridae (1 género, 1 especie), Cricetidae (17, 24), Caviidae (2, 2), Cuniculidae (1, 1), Dasyproctidae (1, 1), Echymyidae (3, 3) y Erethizontidae (1, 1). De 1 a 5 especies -dependiendo de la autoridad taxonómica usada- son endémicas de Misiones. Discutimos brevemente algunas problemáticas taxonómicas, destacando aquellos interrogantes que aún persisten (e.g., la compleja situación del género Brucepattersonius). Para varias especies aportamos datos cromosómicos novedosos y los comparamos con aquellos disponibles para Brasil. Un análisis de la riqueza a nivel provincial indica que los mayores valores para ese parámetro ocurren hacia el centro-sur del territorio, en un área de interdigitación entre el Bosque Atlántico Interior y la ecorregión de los Campos y Malezales. Discutimos el rol de los grandes ríos de la región como barrera para la dispersión de la fauna (e. g., el Paraná entre Argentina y el este Paraguay). Por lo menos 9 especies de roedores con distribución en la provincia de Misiones han sido referidas bajo alguna categoría de amenaza o cercana a la amenaza. En todos los casos, la supervivencia de esos taxones depende de que se mantenga la integridad y conectividad entre los remanentes boscosos.