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Although interwetland dispersal is thought to play an important role in regional persistence of pond-breeding amphibians, few researchers have modeled amphibian metapopulation or source-sink dynamics. Results of recent modeling studies suggest anthropogenic stressors, such as pollution, can negatively affect density and population viability of amphibians breeding in isolated wetlands. Presumably population declines also result in reduced dispersal to surrounding (often uncontaminated) habitats, potentially affecting dynamics of nearby populations. We used our data on the effects of mercury (Hg) on the American toad (Bufo americanus) as a case study in modeling the effects of anthropogenic stressors on landscape-scale amphibian dynamics. We created a structured metapopulation model to investigate regional dynamics of American toads and to evaluate the degree to which detrimental effects of Hg contamination on individual populations can disrupt interpopulation dynamics. Dispersal from typical American toad populations supported nearby populations that would otherwise have been extirpated over long time scales. Through support of such sink populations, dispersal between wetland-associated subpopulations substantially increased overall productivity of wetland networks, but this effect declined with increasing interwetland distance and decreasing wetland size. Contamination with Hg substantially reduced productivity of wetland-associated subpopulations and impaired the ability of populations to support nearby sinks within relevant spatial scales. Our results add to the understanding of regional dynamics of pond-breeding amphibians, the wide-reaching negative effects of environmental contaminants, and the potential for restoration or remediation of degraded habitats. Aunque se piensa que la dispersión entre humedales juega un papel importante en la persistencia regional anfibios que se reproducen en charcas, pocos investigadores han modelado la dinámica de metapoblaciones o fuente-vertedero de anfibios. Resultados de estudios recientes sugieren que los estresantes antropogénicos como la contaminación pueden afectar negativamente a la densidad y viabilidad poblacional de anfibios que se reproducen en humedales aislados. Las declinaciones poblacionales presumiblemente también resultan en la reducción de la dispersión hacia hábitats circunvecinos (a menudo no contaminados), afectando potencialmente la dinámica de poblaciones cercanas. Utilizamos nuestros datos sobre los efectos de mercurio (Hg) sobre el sapo (Bufo americanus) como un estudio de caso para modelar los efectos de estresantes antropogénicos sobre la dinámica de anfibios a nivel de paisaje. Creamos un modelo de metapoblación estructurada para investigar la dinámica regional de sapos y para evaluar el grado en que los efectos perjudiciales de la contaminación por mercurio sobre poblaciones individuales puede alterar la dinámica interpoblacional. La dispersión desde poblaciones típicas de sapos soportó a poblaciones cercanas que de otra manera hubieran sido extirpadas en el largo plazo. Mediante soporte a tales poblaciones vertedero, la dispersión entre subpoblaciones asociadas a humedales incrementó sustancialmente la productividad total de las redes de humedales, pero este efecto declinó con el incremento de la distancia entre humedales y el decremento del tamaño del humedal. La contaminación por mercurio redujo sustancialmente la productividad de subpoblaciones asociadas con humedales y limitó la capacidad de las poblaciones para soportar a vertederos cercanos en escalas espaciales relevantes. Nuestros resultados contribuyen al entendimiento de la dinámica regional de anfibios que se reproducen en charcas, de los efectos negativos de gran alcance de los contaminantes ambientales y del potencial de restauración o remediación de hábitats degradados.

The conservation of species with declining populations requires information on population demography and identification of factors that limit population growth. For landbird species, an understanding of large-scale population declines often requires assessment of local population processes, including the production of offspring, the survival of those offspring, and adult survival. Population growth has been modeled for several species of landbirds to date, and these studies have provided important information on relationships between population status and population-limiting factors. Several recent studies have illuminated field methods and analytical techniques that can aid in increasing the accuracy of productivity and survival estimates for population models. We reviewed these methods and recommend their implementation, including quantification of the season-long productivity of individuals, collection of empirical data on juvenile survival during the postfledging and overwintering periods, and incorporation of adult breeding dispersal into annual adult survival estimates. Such methods will allow for more accurate assessment of population status and provide a better understanding of the factors on which to focus our conservation efforts.

Effective population size (N e ) determines the strength of genetic drift and can influence the level of genetic diversity a population can maintain. Assessing how changes in demographic rates associated with environmental variables and management actions affect N e thus can be crucial to the conservation of endangered species. Calculation of N e through demographic models makes it possible to use elasticity analyses to study this issue. The elasticity of N e to a given vital rate is the proportional change in N e associated with a proportional increase in that vital rate. In addition, demographic models can be used to study N e and population growth rate (λ) simultaneously. Simultaneous examination is important because some vital rates differ diametrically in their associations with λ and N e . For example, in some cases increasing these vital rates increases λ and decreases N e . We used elasticity analysis to study the effect of stage-specific survival and flowering rates on N e , annual effective population size (N a ), and λ in seven populations of the endangered plant Austrian dragonhead (Oracocephalum austriacum). In populations with λ > 1, the elasticities of N e and N a were similar to those of λ. Survival rates of adults were associated with greater elasticities than survival rates of juveniles, flowering rates, or fecundity. In populations with λ < 1, N e and N a exhibited greater elasticities to juvenile than to adult vital rates. These patterns are similar to those observed in other species with similar life histories. We did not observe contrasting effects of any vital rate on λ and N e ; thus, management actions that increase the λ of populations of Austrian dragonhead will not increase genetic drift. Our results show that elasticity analyses of N e and N a can complement elasticity analysis of λ. Moreover, such analyses do not require more data than standard matrix models of population dynamics. El tamaño poblacional efectivo (N e ) determina la fuerza de la deriva gènica y puede influir en el nivel de diversidad genética que mantiene una población. Por lo tanto, la evaluación del efecto de los cambios en tasas demográficas asociadas con variables ambientales y de las acciones de manejo sobre N e puede ser crucial para la conservación de una especie en peligro. La estimación de N e mediante modelos demográficos posibilita el uso de análisis de elasticidad para estudiar este tópico. La elasticidad de N e a una tasa vital determinada es el cambio proporcional en N e asociado con un incremento proporcional en esa tasa vital.Adicionalmente, los modelos demográficos pueden ser utilizados para estudiar N e y la tasa de crecimiento poblacional (λ) simultáneamente. Esto es importante porque algunas tasas vitales difieren diametralmente en sus asociaciones con λ y N e . Por ejemplo, en algunos casos el incremento de estas tasas vitales incrementa λ y disminuye N e . Utilizamos análisis de elasticidad para estudiar el efectos de tasas de floración y supervivencia específicas de estadios sobre N e , el tamaño efectivo anual (N a ), y λ en siete poblaciones de la planta en peligro Dracocephalum austriacum. Las elasticidades de N e y N a en poblaciones con λ > 1 fueron similares a las de 1.Las tasas de supervivencia de adultos se asociaron con elasticidades mayores que las tasas de supervivencia de juveniles, las tasas de floración o la fecundidad. En poblaciones con λ < 1, N e y N a presentaron mayor elasticidad en las tas vitales juveniles que en las adultas. Estos patrones fueron similares a los observados en otras especies con historias de vida similares. No observamos efectos contrastantes de ninguna tasa vital sobre λ y N e ; por lo tanto, las acciones de manejo que incrementan la λ de las poblaciones de D. austriacum no incrementarán la deriva gènica. Nuestros resultados muestran que los análisis de elasticidad de N e y N a pueden complementar el análisis de elasticidad de λ. Más aun, tales análisis no requieren más datos que los modelos matriciales de dinámica poblacional estándar.

Although land preservation and promotion of successful regeneration are important conservation actions, their ability to increase population growth rates of slow-growing, long-lived trees is limited. We investigated the demography of Taxus floridana Nutt., a rare understory conifer, in three populations in different ravine forests spanning its entire geographic range along the Apalachicola River Bluffs in northern Florida (U.S.A.). We examined spatial and temporal patterns in demographic parameters and projected population growth rates by using four years of data on the recruitment and survival of seedlings and established stems, and on diameter growth from cross-sections of dead stems. All populations experienced a roughly 10-fold increase in seedling recruitment in 1996 compared with other years. The fates of seedlings and stems between 8 and 16 mm differed among populations. The fates of stems in two other size classes (the 2- to 4-mm class and the 4- to 8-mm class) differed among both populations and years. Individual stems in all populations exhibited similarly slow growth rates. Stochastic matrix models projected declines in all populations. Stochastic matrix analysis revealed the high elasticity of a measure of stochastic population growth rate to perturbations in the stasis of large reproductive stems for all populations. Additional analyses also indicated that occasional episodes of high recruitment do not greatly affect population growth rates. Conservation efforts directed at long-lived, slow-growing rare plants like Taxus floridana should both protect established reproductive individuals and further enhance survival of individuals in other life-history stages, such as juveniles, that often do not appear to contribute greatly to population growth rates.

Although there has been a call for the integration of behavioral ecology and conservation biology, there are few tools currently available to achieve this integration. Explicitly including information about behavioral strategies in population viability analyses may enhance the ability of conservation biologists to understand and estimate patterns of extinction risk. Nevertheless, most behavioral-based PVA approaches require detailed individual-based data that are rarely available for imperiled species. We present a mechanistic approach that incorporates spatial and demographic consequences of behavioral strategies into population models used for conservation. We developed a stage-structured matrix model that includes the costs and benefits of movement associated with 2 habitat-selection strategies (philopatry and direct assessment). Using a life table for California sea lions ( Zalophus californianus), we explored the sensitivity of model predictions to the inclusion of these behavioral parameters. Including behavioral information dramatically changed predicted population sizes, model dynamics, and the expected distribution of individuals among sites. Estimated population sizes projected in 100 years diverged up to 1 order of magnitude among scenarios that assumed different movement behavior. Scenarios also exhibited different model dynamics that ranged from stable equilibria to cycles or extinction. These results suggest that inclusion of behavioral data in viability models may improve estimates of extinction risk for imperiled species. Our approach provides a simple method for incorporating spatial and demographic consequences of behavioral strategies into population models and may be easily extended to other species and behaviors to understand the mechanisms of population dynamics for imperiled populations.

A joint demographic and population genetics stage-based model for a subdivided population was applied to Gentiana pneumonanthe, an early successional perennial herb, at a regional (metapopulation) scale. We used numerical simulations to determine the optimal frequency of habitat disturbance (sod cutting) and the intensity of gene flow among populations of G. pneumonanthe to manage both population viability and genetic diversity in this species. The simulations showed that even small populations that initially had near-equal allele frequencies could, if managed properly through sod cutting every 6 to 7 years, sustain their high genetic variation over the long run without gene flow. The more the allele frequencies in the small populations are skewed, however, the higher the probability that in the absence of gene flow, some alleles will be lost and within-population genetic variation will decrease even under proper management. This implies that although local population dynamics should be the major target for management, regional dynamics become important when habitat fragmentation and decreased population size lead to the loss of local genetic diversity. The recommended strategy to improve genetic composition of small populations is the introduction of seeds or seedlings of nonlocal origin.

Marine protected areas (MPAs) that allow some degree of artisanal fishing have been proposed to control the overexploitation of marine resources while allowing extraction by local communities. Nevertheless, the management of MPAs is often impaired by the absence of data on the status of their resources. We devised a method to estimate population growth rates with the type of data that are usually available for reef fishes. We used 7 years of spatially explicit abundance data on the leopard grouper ( Mycteroperca rosacea) in an MPA in the Gulf of California, Mexico, to construct a matrix population model that incorporated the effects of El Niño/La Niña Southern Oscillation on population dynamics. An environmental model that estimated different demographic estimates for El Niño and La Niña periods performed better than a single-environment model, and a single-habitat model performed better than a model that considered different depths as different habitats. Our results suggest that the population of the leopard grouper off the main island of the MPA is not viable under present conditions. Although the impact of fishing on leopard grouper populations in the MPA has not yet been established, fishing should be closed as a precautionary measure at this island if a priority of the MPA is to ensure the sustainability of its fish populations.

The population movement and the decentralization of urban areas and their outskirts are shaping, in the last thirty years, a different process of spatial distribution and the definition of a new population establishment model. Traditionally, displacements were rural-urban and the major reason was the economic one. Nevertheless, recently this process is more complex and triangular: rural-rural displacements and intern urban migrations in which the population moves from small cores (outskirts) to the capital (urban centre). The economic angle is not able anymore to explain most of the displacements: the biggest rural cores are concentrating the migration flows of outskirt areas, shaping, instead of a traditional marshallian industrial district, a social district that we have named Rural District, which becomes a new concept for territorial development. El movimiento demográfico y la desconcentración en las áreas urbanas y sus áreas periféricas, conforman, en los últimos treinta años, un proceso distinto de distribución espacial y la definición de un nuevo modelo de asentamiento de la población. Tradicionalmente, eran desplazamientos rural-urbano y la principal razón era la económica. Sin embargo, el proceso más reciente es más complejo y más triangular: movimientos rural-rural y corredores urbanos, el movimiento de la población se realiza de los núcleos más pequeños (periferia) a la cabecera comarcal (centro), la dimensión económica no logra explicar la mayor parte de los desplazamientos, sino que aparecen los núcleos rurales más grandes como concentradores de la población absorbida de los núcleos periféricos, conformando un distrito social frente al tradicional distrito industrial de tradición marshalliana, y que nosotros denominamos como Distrito Rural que se convierte, así, en un nuevo concepto para el desarrollo territorial.

Recovering small populations of threatened species is an important global conservation strategy. Monitoring the anticipated recovery, however, often relies on uncertain abundance indices rather than on rigorous demographic estimates. To counter the severe threat from poaching of wild tigers (Panthera tigris), the Government of Thailand established an intensive patrolling system in 2005 to protect and recover its largest source population in Huai Kha Khaeng Wildlife Sanctuary. Concurrently, we assessed the dynamics of this tiger population over the next 8 years with rigorous photographic capture-recapture methods. From 2006 to 2012, we sampled across 624-1026 km² with 137-200 camera traps. Cameras deployed for 21,359 trap days yielded photographic records of 90 distinct individuals. We used closed model Bayesian spatial capture-recapture methods to estimate tiger abundances annually. Abundance estimates were integrated with likelihood-based open model analyses to estimate rates of annual and overall rates of survival, recruitment, and changes in abundance. Estimates of demographic parameters fluctuated widely: annual density ranged from 1.25 to 2.01 tigers/100 km², abundance from 35 to 58 tigers, survival from 79.6% to 95.5%, and annual recruitment from 0 to 25 tigers. The number of distinct individuals photographed demonstrates the value of photographic capture-recapture methods for assessments of population dynamics in rare and elusive species that are identifiable from natural markings. Possibly because of poaching pressure, overall tiger densities at Huai Kha Khaeng were 82-90% lower than in ecologically comparable sites in India. However, intensified patrolling after 2006 appeared to reduce poaching and was correlated with marginal improvement in tiger survival and recruitment. Our results suggest that population recovery of low-density tiger populations may be slower than anticipated by current global strategies aimed at doubling the number of wild tigers in a decade. Recuperar las poblaciones pequeñas de las especies amenazadas es una importante estrategia global de conservación. Sin embargo, monitorear la recuperación esperada generalmente depende de índices inciertos de abundancia en lugar de estimados demográficos rigurosos. Para contrarrestar la gran amenaza causada por la cacería furtiva de tigres (Panthera tigris), el Gobierno de Tailandia estableció un sistema intensivo de patrullaje en 2005 para proteger y recuperar la población fuente más grande en el Santuario Huai Kha Khaeng. Simultáneamente, evaluamos las dinámicas de esta población de tigres durante los siguientes ocho años con rigurosos métodos fotográficos de captura-recaptura. De 2006 a 2012 muestreamos a lo largo de 624-1026 km² con 137-200 trampas cámara. Las cámaras desplegadas durante 21,359 días de trampa produjeron registros fotográficos de 90 individuos distinguibles. Usamos métodos espaciales de capturarecaptura y modelo bayesiano cerrado para estimar anualmente la abundancia de los tigres. Los estimados de abundancia estuvieron integrados por análisis de modelo abierto basados en la probabilidad para estimar la tasa anual y las tasas generales de supervivencia, reclutamiento y cambios en la abundancia. Los estimados de los parámetros demográficos fluctuaron ampliamente: la densidad anual varió entre 1.25 y 2.01 tigres/100 km², la abundancia entre 35 a 58 tigres, la supervivencia entre 79-6 y 95.5% y el reclutamiento anual de 0 a 25 tigres. El número de individuos distinguibles que fue fotografiado demuestra el valor de los métodos de captura-recaptura para la evaluación de las dinámicas poblacionales de especies raras y elusivas que son identificables gracias a marcas naturales. Posiblemente por causa de la presión ejercida por la caza furtiva, la densidad general de los tigres en Huai Kha Khaeng fue 82-90% más baja que en sitios ecológicamente comparables de India. Sin embargo, el patrullaje intensivo después de 2006 pareció reducir la caza furtiva y estuvo correlacionado con el mejoramiento marginal de la supervivencia y reclutamiento de los tigres. Nuestros resultados sugieren que la recuperación de las poblaciones de tigres con baja densidad puede ser más lenta de lo esperado por las estrategias globales actuales enfocadas en la duplicación del número de tigres en una década.

Evidence for severe declines in large predatory fishes is increasing around the world. Because of its long history of intense fishing, the Mediterranean Sea offers a unique perspective on fish population declines over historical timescales. We used a diverse set of records dating back to the early 19th and mid 20th century to reconstruct long-term population trends of large predatory sharks in the northwestern Mediterranean Sea. We compiled 9 time series of abundance indices from commercial and recreational fishery landings, scientific surveys, and sighting records. Generalized linear models were used to extract instantaneous rates of change from each data set, and a meta-analysis was conducted to compare population trends. Only 5 of the 20 species we considered had sufficient records for analysis. Hammerhead (Sphyrna spp.), blue (Prionace glauca), mackerel (Isurus oxyrinchus and Lamna nasus), and thresher sharks (Alopias vulpinus) declined between 96 and 99.99% relative to their former abundance. According to World Conservation Union (IUCN) criteria, these species would be considered critically endangered. So far, the lack of quantitative population assessments has impeded shark conservation in the Mediterranean Sea. Our study fills this critical information gap, suggesting that current levels of exploitation put large sharks at risk of extinction in the Mediterranean Sea. Possible ecosystem effects of these losses involve a disruption of top-down control and a release of midlevel consumers.