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Sökning: WFRF:(Menges Eric S.)

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1.
  • Crone, Elizabeth E., et al. (författare)
  • Ability of Matrix Models to Explain the Past and Predict the Future of Plant Populations
  • 2013
  • Ingår i: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 27:5, s. 968-978
  • Tidskriftsartikel (refereegranskat)abstract
    • Uncertainty associated with ecological forecasts has long been recognized, but forecast accuracy is rarely quantified. We evaluated how well data on 82 populations of 20 species of plants spanning 3 continents explained and predicted plant population dynamics. We parameterized stage-based matrix models with demographic data from individually marked plants and determined how well these models forecast population sizes observed at least 5 years into the future. Simple demographic models forecasted population dynamics poorly; only 40% of observed population sizes fell within our forecasts' 95% confidence limits. However, these models explained population dynamics during the years in which data were collected; observed changes in population size during the data-collection period were strongly positively correlated with population growth rate. Thus, these models are at least a sound way to quantify population status. Poor forecasts were not associated with the number of individual plants or years of data. We tested whether vital rates were density dependent and found both positive and negative density dependence. However, density dependence was not associated with forecast error. Forecast error was significantly associated with environmental differences between the data collection and forecast periods. To forecast population fates, more detailed models, such as those that project how environments are likely to change and how these changes will affect population dynamics, may be needed. Such detailed models are not always feasible. Thus, it may be wiser to make risk-averse decisions than to expect precise forecasts from models. Habilidad de los Modelos Matriciales para Explicar el Pasado y Predecir el Futuro de las Poblaciones de Plantas Resumen La incertidumbre asociada con el pronostico ecologico ha sido reconocida durante un largo tiempo pero rara vez se cuantifica su seguridad. Evaluamos que tan bien la informacion de 82 poblaciones de 20 especies de plantas a lo largo de 3 continentes explica y predice la dinamica de poblacion de las plantas. Realizamos parametros con modelos matriciales con base en estadios con datos demograficos a partir de plantas marcadas individualmente y determinamos que tan bien estos modelos pronostican el tamano de las poblaciones al menos 5 anos en el futuro. Los modelos demograficos simples pronosticaron pobremente las dinamicas de poblacion; solamente el 40% de las poblaciones observadas cayo dentro de los limites de confianza de 85% de nuestros pronosticos. Estos modelos sin embargo explicaron la dinamica de poblacion a lo largo de los anos en los que se colectaron datos; los cambios observados en el tamano de la poblacion durante el periodo de colecta de datos estuvieron positivamente correlacionados con la tasa de crecimiento de la poblacion. Asi, estos modelos son por lo menos una manera segura de cuantificar el estado de la poblacion. Los pronosticos debiles no estuvieron asociados con el numero de plantas individuales o con los anos de datos. Probamos si las tasas vitales dependian de la densidad y encontramos que existe dependencia hacia la densidad tanto positiva como negativa, sin embargo la dependencia de densidad no se asocio con el error de pronostico. El error de pronostico estuvo significativamente asociado con diferencias ambientales entre la recoleccion de datos y los periodos de pronostico. Para predecir el destino de las poblaciones se necesitan modelos mas detallados, como aquellos que proyectan los cambios probables en el ambiente y como estos cambios afectaran a la dinamica de las poblaciones. Tales modelos tan detallados no siempre son factibles. Por ello puede ser mejor tomar decisiones aversas a riesgos que esperar pronosticos precisos de los modelos.
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2.
  • Shefferson, Richard P., et al. (författare)
  • Drivers of vegetative dormancy across herbaceous perennial plant species
  • 2018
  • Ingår i: Ecology Letters. - : WILEY. - 1461-023X .- 1461-0248. ; 21:5, s. 724-733
  • Tidskriftsartikel (refereegranskat)abstract
    • Vegetative dormancy, that is the temporary absence of aboveground growth for 1year, is paradoxical, because plants cannot photosynthesise or flower during dormant periods. We test ecological and evolutionary hypotheses for its widespread persistence. We show that dormancy has evolved numerous times. Most species displaying dormancy exhibit life-history costs of sprouting, and of dormancy. Short-lived and mycoheterotrophic species have higher proportions of dormant plants than long-lived species and species with other nutritional modes. Foliage loss is associated with higher future dormancy levels, suggesting that carbon limitation promotes dormancy. Maximum dormancy duration is shorter under higher precipitation and at higher latitudes, the latter suggesting an important role for competition or herbivory. Study length affects estimates of some demographic parameters. Our results identify life historical and environmental drivers of dormancy. We also highlight the evolutionary importance of the little understood costs of sprouting and growth, latitudinal stress gradients and mixed nutritional modes.
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3.
  • Crone, Elizabeth E., et al. (författare)
  • How do plant ecologists use matrix population models?
  • 2011
  • Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 14:1, s. 1-8
  • Tidskriftsartikel (refereegranskat)abstract
    • P>Matrix projection models are among the most widely used tools in plant ecology. However, the way in which plant ecologists use and interpret these models differs from the way in which they are presented in the broader academic literature. In contrast to calls from earlier reviews, most studies of plant populations are based on < 5 matrices and present simple metrics such as deterministic population growth rates. However, plant ecologists also cautioned against literal interpretation of model predictions. Although academic studies have emphasized testing quantitative model predictions, such forecasts are not the way in which plant ecologists find matrix models to be most useful. Improving forecasting ability would necessitate increased model complexity and longer studies. Therefore, in addition to longer term studies with better links to environmental drivers, priorities for research include critically evaluating relative/comparative uses of matrix models and asking how we can use many short-term studies to understand long-term population dynamics.
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4.
  • Jones, Owen R., et al. (författare)
  • Diversity of ageing across the tree of life
  • 2014
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 505:7482, s. 169-
  • Tidskriftsartikel (refereegranskat)abstract
    • Evolution drives, and is driven by, demography. A genotype moulds its phenotype's age patterns of mortality and fertility in an environment; these two patterns in turn determine the genotype's fitness in that environment. Hence, to understand the evolution of ageing, age patterns of mortality and reproduction need to be compared for species across the tree of life. However, few studies have done so and only for a limited range of taxa. Here we contrast standardized patterns over age for 11 mammals, 12 other vertebrates, 10 invertebrates, 12 vascular plants and a green alga. Although it has been predicted that evolution should inevitably lead to increasing mortality and declining fertility with age after maturity, there is great variation among these species, including increasing, constant, decreasing, humped and bowed trajectories for both long-and short-lived species. This diversity challenges theoreticians to develop broader perspectives on the evolution of ageing and empiricists to study the demography of more species.
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5.
  • Tye, Matthew R., et al. (författare)
  • A demographic menage a trois : interactions between disturbances both amplify and dampen population dynamics of an endemic plant
  • 2016
  • Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 104:6, s. 1778-1788
  • Tidskriftsartikel (refereegranskat)abstract
    • Natural and anthropogenic disturbances co-occur in most systems, but how they interact to shape demographic outcomes remains poorly understood. Such interactions may alter dynamics of populations in non-additive ways, making demographic predictions challenging when focusing on only one disturbance. Thus, understanding the interactive effects of such disturbances is critically important to determine the population viability of most species under a diversity of stressors. We used a hierarchical integral projection model (IPM), parameterized with 13years of field data across 20 populations, encompassing 2435 individuals of an endangered herb, Liatris ohlingerae. We examined interactive effects of vertebrate herbivory, fire and anthropogenic activities (sand roads) on vital rates (e.g. survival, growth, reproduction, recruitment) and ultimately on population growth rates (), to test the hypothesis that interactions amplify or dampen differences in depending on environmental contexts. We constructed megamatrices to determine coupled dynamics in individuals damaged vs. not damaged by herbivores in roadsides and in Florida scrub with different times since fire. We identified strong interactive effects of fire with herbivory and habitat with herbivory on vital rates and on population growth rates in the IPM model. We also found different patterns of variation in between habitat and time-since-fire scenarios; population growth rates were higher in roadside populations compared to scrub populations and declined with increasing time since fire. Herbivory had interactive effects with both fire and human disturbances on . Herbivory resulted in decreased differences in due to anthropogenic disturbance and slightly increased differences in due to time since fire.Synthesis. The co-occurrence of various disturbances may both amplify and dampen the effects of other disturbances on population growth rate, thus shaping complex population dynamics that are neither linear nor additive. These realistic nonlinearities represent challenges in understanding and projecting of population dynamics. Here, we examined the effects of various sources of disturbance on the population dynamics of an endangered plant species, finding complex interactions affecting population growth rates. We argue that integration of multiple, interacting stressors in IPMs will allow more accurate estimation of the overall effects of ecological processes on species viability.
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