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The nominal species Oligoryzomys flavescens (yellow pygmy rice rat) appears in different phylogenetic reconstructions as paraphyletic, forming a complex together with Oligoryzomys fornesi (Fornes' pygmy rice rat) or Oligoryzomys sp. B. To test if O. flavescens includes cryptic species, we used a phylogenetic and a phylogeographic approach to analyze the evolutionary relationships among the lineages of this complex and estimated their geographical distributions using niche modeling analysis. We analyzed a portion of the mitochondrial cytochrome b (Cytb), exon 1 of the Interphotoreceptor Retinoid Binding Protein (Rhp3), and intron 7 of the beta fibrinogen (Fgb) genes and estimated divergence times among lineages using a fossil-calibrated molecular clock. The Cytb phylogenetic tree shows 2 main clades: 1 clustering individuals distributed predominantly in the east of the study area and the other grouping individuals from the west, which would correspond to the subspecies O. f. occidentalis. The eastern clade includes 5 lineages: Oligoryzomys sp. B, O. fornesi, and 3 clades named O. flavescens (O. flavescens Uruguay and southeastern Brazil, O. flavescens eastern Brazil, and O. f. flavescens). The phylogenetic break between these 2 main clades occurred about 0.89 million years ago. These clades were not recovered when nuclear markers were evaluated, revealing incomplete lineage sorting and retention of ancestral polymorphisms. The spatial distributions of the ecological niche of the clades obtained in the Cytb phylogenetic reconstructions were predominantly parapatric; narrow overlapping zones between some of them were detected. Phylogeographic analyses in O. f. flavescens revealed a population expansion about 100,000 years ago, and conformed to an isolation by distance pattern. Our results, together with morphological differences previously described between populations belonging to the east and the samples referable to O. f. occidentalis, suggest that the latter should be recognized as a full species. Fil: Rivera, Paula Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina Fil: González Ittig, Raúl Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina Fil: Robainas Barcia, Aymée. Pierre Fabre Iberica; España Fil: Trimarchi, Laura Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina Fil: Levis, Silvana. Instituto Nacional de Enfermedades Virales Humanas Dr Julio I. Maiztegui; Argentina Fil: Calderon, Gladys. Instituto Nacional de Enfermedades Virales Humanas Dr Julio I. Maiztegui; Argentina Fil: Gardenal, Cristina Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina

The long-tailed pygmy rice rat Oligoryzomys longicaudatus (Rodentia, Cricetidae) experiences marked population density fluctuations. This species is the major reservoir of the Andes orthohantavirus associated with the hantavirus pulmonary syndrome in southern Argentina, and information on dispersal patterns at different population densities, or differences in dispersal between the sexes during those periods, could contribute to understanding risk of viral transmission among individuals. We examined the spatial genetic structure of O. longicaudatus at a local scale to elucidate how variation in population density influences dispersal patterns. Effective dispersal levels were estimated through spatial genetic autocorrelation (SGA) analyses in periods of different density, and for females and males separately, within an area of 510 × 180 m, using seven microsatellite loci. In autumn (high-intermediate and intermediate densities), SGA was primarily determined by females, which show philopatric behavior in defense of their nests and newborns. In summer (low density), neither sex showed SGA, which could be due to spacing behavior combined with high recruitment rates among adjacent environments. At high-intermediate densities, females remained close to each other, contracting their home ranges. These established individuals would “fence” the area, preventing the immigration of individuals from proximate areas, until population density declines again. We detected differential patterns of effective dispersal for both sexes in different stages of the annual and inter-annual population phases of O. longicaudatus. Since high levels of gene flow were reported for both sexes in summer and for males in all analyzed seasons, the transmission risk of diseases such as hantavirus pulmonary syndrome would be high at a local scale.La densidad poblacional del ratón “colilargo” Oligoryzomys longicaudatus (Rodentia, Cricetidae) experimenta marcadas fluctuaciones. Esta especie es el principal reservorio del ortohantavirus Andes, asociado con el síndrome pulmonar por hantavirus en el sur de Argentina. El conocimiento sobre los patrones de dispersión a diferentes densidades poblacionales y entre los sexos durante esos períodos, podría contribuir a evaluar el riesgo de transmisión viral entre individuos. Examinamos la estructura genética espacial de O. longicaudatus a escala local para determinar de qué manera las variaciones en la densidad poblacional influyen sobre los patrones de dispersión del roedor. Los niveles de dispersión efectiva se estimaron mediante análisis de autocorrelación genética espacial (AGE) utilizando siete loci de microsatélites, dentro de un área de 510 × 180 m. Los análisis se hicieron en distintos períodos de densidad para la población general y para hembras y machos por separado. En otoño (densidad alta-intermedia e intermedia), la AGE estuvo determinada principalmente por las hembras, lo que podría explicarse por su comportamiento filopátrico en relación a la defensa de sus nidos y crías. En verano (baja densidad), ninguno de los sexos mostró AGE, debido a un comportamiento de espaciamiento combinado con altas tasas de reclutamiento entre ambientes adyacentes con diferentes recursos. A densidades altas-intermedias, las hembras permanecieron cerca una de la otra, contrayendo su área de acción. Estos individuos cercarían el área, evitando la inmigración de individuos de áreas cercanas, hasta que la densidad poblacional disminuya nuevamente. Detectamos patrones diferenciales de dispersión efectiva para ambos sexos en cada una de las fases de densidad poblacional (anual e interanual) de O. longicaudatus. El riesgo de transmisión del síndrome pulmonar por hantavirus sería elevado a escala local, dado que se detectaron altos niveles de flujo génico para ambos sexos en verano y para los machos en todas las estaciones analizadas.

In the present study, we analysed the genetic structure of Triatoma infestans populations with a phylogeographical approach using sequences of the mitochondrial NADH dehydrogenase subunit 5 (ND5) and the nuclear elongation factor-1 alpha (EF-1α) genes of bugs obtained from Argentina and Bolivia. Spatially circumscribed haplogroups were distinguished from the ND5 gene sequences, one distributed exclusively to the south of the studied area and, in agreement with the results from the EF-1α gene, one haplogroup limited to Bolivia and another to Morajú located in the Chaco region of Argentina. In both the ND5 and EF-1α networks, the most widespread haplogroup or allele group showed a star-like topology, which is compatible with a recent demographic expansion. The asymmetric historical gene flow detected from a population of the Chaco region towards Bolivia and the spatiotemporal phylogeographical reconstruction of lineage dispersal would support the hypothesis that postulates the Chaco biogeographical region as the area of origin for the species. However, additional studies with a broader sampling in the Andean region are needed to define with certainty whether the origin of T. infestans is Chacoan or Andean.

The rodent Calomys musculinus is the reservoir of the Junin virus, which causes Argentine hemorrhagic fever. A phylogeographic approach was used for the analysis of 6 populations from central Argentina based on cytochrome-b sequences from 27 individuals. Thirteen haplotypes were detected, each closely linked in the phylogenetic network; 2 of the most frequent haplotypes were internal, whereas the majority were unique to single populations and presented distal positions in the network. Most of the variance was explained by withinpopulation genetic diversity. Results of a mismatch distribution analysis and the deviation from neutrality confirmed that C. musculinus has experienced a recent range expansion; genetic drift has apparently been the main force acting at present, with low to moderate current gene flow. These results are in agreement with previous studies based on polymerase chain reaction–restriction fragment length polymorphism data of the mitochondrial D-loop region, and they support the reliability of both types of techniques.