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Global losses of oyster populations urgently necessitate evaluating the status of underdocumented populations. The north-Patagonian Ostrea puelchana metapopulation changed in recent decades: certain beds grew and expanded; others became depleted by the Bonamia exitiosa epizootic. We surveyed eight oyster beds from the San Matías and San José gulfs; assessing the extension, demographic structure, and density-distribution pattern of each. We integrated biologic and environmental data on different spatial and temporal scales. Beds from the northestern and southern coasts continued expanding; while the northwestern beds- decimated by B. exitiosa in mid-1990-evidenced signs of recovery. We observed an envelope relationship between adult density and carriage incidence, suggesting a density-dependent compensation. Temporal data revealed decreased mean O. puelchana shell heights during recent decades. We discuss the success of extractive closures for long-term management and stress the effectiveness of a multiscale approach to determine the density-dependent processes structuring and driving marine-bivalve-population development.

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Resumen El conocimiento de la dinámica de poblaciones provee información sobre la historia reciente, el estado actual y la tendencia futura de una población. Physalaemus biligonigerus es un anuro con una amplia distribución en el Neotrópico, presenta una actividad reproductiva elevada y explosiva, pero sus poblaciones parecen estar compuestas por individuos jóvenes. El objetivo de este estudio fue analizar la demografía poblacional de P. biligonigerus en una charca semipermanente en Río Cuarto, Córdoba, Argentina y realizar una proyección poblacional a 30 generaciones. Se determinó la estructura de edad utilizando esqueletocronología, y posteriormente se construyó una tabla de vida estática. Se calculo la fecundidad y las tasas de supervivencia para cada estadío con los que se construyó una Matriz de Leslie y se realizó la proyección poblacional. La proyección muestra oscilaciones en el número de individuos pero a pesar de esto, la tendencia final de la población es a un aumento en su tamaño. La mayor proporción de supervivientes se da en las fases de huevos a larvas, y la fuerza de mortalidad actúa con intensidad sobre la fase de larvas. La tasa neta reproductiva indica que la población de P. biligonigerus de la charca en estudio está en incremento.

Abstract Knowledge of population dynamics provides information on the recent history, current status, and future trends of a population. Physalaemus biligonigerus is widely distributed in the Neotropics, this anuran has a high and explosive reproductive activity, but its populations seem to be composed of young individuals. The objective of this study was to analyze the population demography of P. biligonigerus in a semipermanent pond in Río Cuarto, Córdoba, Argentina and to carry out a population projection through 30 generations. The age structure was determined from the use of skeletochronology, and a static life table was later made. Fertility and survival rates were calculated for each stage, by which a Leslie Matrix was constructed and the population projection was performed. The projection shows oscillations in the number of individuals but in spite of this, the final tendency of the population is an increase in its size. The highest proportion of survivors occurs in the egg-to-larval stages and the mortality force acts intensively on the larval phase. The net reproductive rate indicates that the population of P. biligonigerus of the study pond is increasing. Rev. Biol. Trop. 66(2): 765-775. Epub 2018 June 01.

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The Atlantic Forest (AF) of South America harbors one of the world's highest bird species richness, but to date there is a deficient understanding of the spatial patterns of genetic diversity and the evolutionary history of this biome. Here we estimated the phylogenetic and populational history of the widespread Mouse-colored Tapaculo (Scytalopus speluncae) complex across the Brazilian AF, using data from two mitochondrial genes and 12 microsatellite loci. Both markers uncovered several cryptic, mostly allopatric and well-supported lineages that may represent distinct species-level taxa. We investigated whether diversification in S. speluncae is compatible with the Carnaval-Moritz model of Pleistocene refugia. We found that northern lineages have high levels of genetic diversity, agreeing with predictions of more stable forest refugia in these areas. In contrast, southern lineages have lower levels of mtDNA diversity with a signature of population expansion that occurred earlier (∼0.2Mya) than the last glacial maximum. This result suggests that the AF may be stable enough to maintain endemic taxa through glacial cycles. Moreover, we propose that the "mid-Pleistocene climate transition" between 1.2 and 0.7million years ago, from a warmer to a colder climate, may have played an important but mostly overlooked role in the evolution of AF montane taxa.

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The advancing agricultural frontier has led to an important loss of natural habitats, with significant consequences for biodiversity. The demography for two species of anurans, Physalaemus biligonigerus and Rhinella arenarum, both associated with agricultural systems in the central region of the Córdoba Province, were analyzed and compared in this study. Four sites were sampled: three agroecosystems with different alteration degrees (C1, C2 and SM1) and a fourth site not cultivated (SM2). The sampling was conducted during two reproductive periods, from September 2008 to April 2009 and September 2009 to April 2010. Individuals were captured using live pitfall traps for the metamorphic, juveniles and adults; and visual encounter survey, for the capture of eggs and larvae. With the abundance data, the survival for each age class was estimated using the KNM method (Kiritani Nakasuki Manly). With survival rates and fertility population, Leslie matrices were elaborated to obtain a quantitative projection of the population size. Altered environments showed lower eggs and larvae survival. Population pro-jections were favorable in the site SM2 and were less favorable and a tendency to extinction, in sites dominated by crops. This study showed that the agroecosystems of this region are possibly inhospitable environments for reproduction and survival of the species studied. The aquatic stages in the life cycle of both species would be the more affected, since water bodies deterioration is present or may occur in those areas. We can recognize species-specific effects of agricultural ecosystems; P. biligonigerus was the most affected species, possibly because of their life histories and habitat requirements. We suggested that environmental degradation caused by the cropland in the central region of Argentina would impact on the demographics of the anuran populations in the area.

El crecimiento de la agricultura produce pérdida del hábitat natural, con consecuencias para la biodiversidad de los anfibios. Se analizó la demografía poblacional de dos especies de anfibios en agroecosistemas de la provincia de Córdoba, Rhinella arenarum y Physalaemus biligonigerus. Los muestreos se realizaron en tres agroecosistemas y en un cuarto sitio, no afectado por cultivos. Los individuos se capturaron utilizando trampas de caída viva y relevamientos visuales. Con los datos de abundancia se estimó la supervivencia para cada clase de edad y con las tasas de supervivencia y fertilidad poblacional, se construyeron matrices de Leslie para obtener una proyección cuantitativa del tamaño poblacional. Las proyecciones poblacionales fueron favorables para el sitio SM2 y desfavorables para los sitios cultivados. Los agroecosistemas son ambientes posiblemente inhóspitos para la reproducción y supervivencia de las especies estudiadas. Particularmente se ven afectados aquellos estadios acuáticos del ciclo de vida de estas especies, debido al deterioro de los cuerpos de agua en estas áreas. Se reconocieron efectos especie-específicos de los ecosistemas agrícolas, ya que P. biligonigerus resultó la especie más afectada. Se sugiere un deterioro ambiental producido por cultivos extensivos de soja, lo que impactaría la demografía de las poblaciones de anuros.

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