In press. Reducing green sea turtle bycatch in small-scale fisheries using illuminated gillnets: the cost of saving a sea turtle. Marine Ecology Progress Series.

The population genetic structure of Oligoryzomys longicaudatus colilargo was examined at two geographical scales: (a) regional, including five populations of the Argentinean Patagonia separated by 60–315 km and (b) landscape scale, using five populations from different valleys of the locality of Cholila in the subantarctic forest separated by 6–27 km, and a nearby locality of the Patagonian steppe, with an average distance from Cholila of 33 km. Eight microsatellite loci specific for O. longicaudatus were used as genetic markers. At the regional scale, four genetic clusters were detected by the Geneland software. The genetic structure was found to follow a latitudinal pattern. This result was supported by the FST statistic, indicating low levels of current gene flow within the region. At the landscape level, genetic differentiation among the five populations was also found. Estimated migration rates were, in general, low and asymmetrical between nearby populations. Using a causal modeling approach, we detected that the combination of landscape features such as lakes, rivers, urban settlements and roads appear to constrain the dispersal of O. longicaudatus at this scale. This result would explain why nearby populations were so different in their genetic composition. The information about geographic features limiting rodent dispersal provided here could help to design more accurate prevention measures against the expansion of hantavirus pulmonary syndrome.

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.

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