Análisis de factores demográficos y genéticos para la conservación de poblaciones de plantas en un hábitat fragmentado

Muchos son los factores que determinan la dinámica de poblaciones de plantas entre los cuales hay demográficos (variabilidad ambiental, densidad poblacional, etc.) y genéticos (variabilidad genética de los individuos, deriva genética y/o depresión por consanguinidad). Entender los efectos de esos factores sobre la tasa de cambio poblacional es básico para diseñar planes de conservación efectivos que reduzcan la probabilidad de extinción. Esto es especialmente importante en casos de especies de plantas afectadas por la fragmentación del hábitat dado que la fragmentación reduce el número de individuos por población y aumenta el grado de aislamiento entre poblaciones. Tradicionalmente los planes de conservación de especies en hábitats fragmentados se basan en el conocimiento demográfico de las poblaciones a pesar de que existe unanimidad en el hecho de que factores genéticos (como la depresión por consanguinidad) tienen un papel muy importante en el proceso de extinción. En cambio, son muy pocos los planes de conservación que consideran los efectos demográficos de factores genéticos. El objetivo de este artículo es el de resaltar la importancia de la genética para la conservación de plantas así como el de exponer algunas aproximaciones para cuantificar las implicaciones demográficas de factores genéticos.Several ecological (e.g., environmental variability, density dependence) and genetic (e.g., genetic variability, genetic drift, inbreeding depression) factors determine the dynamics of plant populations. Understanding the effect of such factors on population growth rate becomes crucial to design effective conservation plans to reduce extinction probability. This is especially relevant in a context of habitat fragmentation since fragmentation leads to decreasing population size and increasing isolation between extant populations. Traditionally conservation plans of fragmented plant species are purely based on demographic knowledge although it is accepted that genetic factors (such as inbreeding depression) play a significant role in determining extinction risks. In contrast, only a handful of conservation plans take into account the demographic effects of genetic factors. The goal of this paper is to highlight the importance of genetics for plant conservation as well as to explain approaches to quantify the demographic implications of genetic processes

Genetic change following fire in populations of a seed-banking perennial plant

Disturbances such as fire have the potential to remove genetic variation, but seed banks may counter this loss by restoring alleles through a reservoir effect. We used allozyme analysis to characterize genetic change in two populations of the perennial Hypericum cumulicola, an endemic of the fire-prone Florida scrub. We assessed genetic variation before and 1, 2, and 3 years after fire that killed nearly all aboveground plants. Populations increased in size following fire, with most seedlings likely recruited from a persistent seed bank. Four of five loci were variable. Most alleles were present in low frequencies, but our large sample sizes allowed detection of significant trends. Expected heterozygosity increased, and allele presence and allele frequencies showed marked shifts following fire. The post-fire seedling cohort contained new alleles to the study and one new allele to the species. Population differentiation between the two study sites did not change. Our study is the first to directly documents genetic changes following fire, a dominant ecological disturbance worldwide, and is also one of the few to consider shifts in a naturally recruiting post-disturbance seedling cohort. We demonstrate the potential of seed banks to restore genetic variation lost between disturbances. Our study demonstrates that rapid genetic change can occur with disturbance and that fire can have positive effects on the genetics of rare species

Competencias Digitales: Realidad de ingreso de los estudiantes a la vida universitària

El presente estudio pretende revelar las condiciones de entrada con las cuales ingresan los estudiantes a la vida universitaria respecto a la adquisición de las competencias digitales, declaradas como una competencia clave para insertarse en sociedad por varias instituciones gubernamentales y académicas, dada la globalización y dinamización de la sociedad facilitada por la red global de internet, la cual ha modificado todas las formas de comunicación, socialización y operación de los servicios más básicos de la cotidianeidad. Por ello no debe faltar en el desarrollo de saberes, habilidades y actitudes de todo ser humano, siendo entendida como una herramienta imprescindible para toda la ciudadanía. La Universidad de Magallanes en Chile, ha instaurado desde el año 2010 para todos los estudiantes que ingresan a primer año, en cualquiera de sus carreras profesionales, la aplicación de una Prueba de Suficiencia en Computación, la cual tiene como objetivo validar las habilidades y saberes relativos a las Tecnologías de Información y la Comunicación (TIC) de los estudiantes, basándose básicamente en la propuesta que el sistema educativo Chileno promueve en este orden para la enseñanza básica y media, diseñada por el Centro de Educación y Tecnologías - Red Enlaces del Ministerio de Educación (2009), para así reconocer cuáles son las competencias adquiridas durante ese proceso, y otorgando la posibilidad de valorar saberes previos, y eximirse de cursar una asignatura, en caso de aprobación. El objetivo principal de la prueba, en el contexto de ésta investigación, es saber si realmente los estudiantes ingresan a la vida universitaria con competencias digitales instaladas, si se encuentran formados o preparados en este ámbito, y por otra parte tiene que ver con conocer los ámbitos con áreas de oportunidad que se detecten a partir de la evaluación y que tengan relación primeramente con la Matriz de Habilidades TIC para el aprendizaje y las consideradas de experiencias de otras universidades e instituciones del mundo, que permita gestar comentarios y sugerencias para potenciarlas en el proceso formativo universitario

Lluvia de semillas y establecimiento en comunidades sucesionales en Chiapas, México

Antecedentes y Objetivos: La agricultura en los trópicos reduce, fragmenta y altera los bosques y los paisajes forestales. Evaluamos la riqueza de especies y la dominancia de formas de vida en la lluvia de semillas, y la abundancia y supervivencia anual de nuevos reclutas en bosques maduros, medianamente maduros, bosques tempranos, potreros y campos de cultivo en ambientes naturales y humanizados. Pronosticamos diferencias en composición y número de semillas y de reclutas en función de los diferentes hábitats y de las matrices de vegetación que los circundan. Métodos: Durante un año se colectaron muestras de semillas y plantas en Lacanjá-Chansayab y Bonampak-Bethel, ambas dentro de la zona de amortiguamiento de la Reserva de la Biosfera de Montes Azules, Selva Lacandona, Chiapas, México. Para la lluvia de semillas, instalamos 14 trampas en sitios que representan el gradiente de sucesión en la vegetación local (2 sitios × 6 hábitats × 14 trampas; n = 168). Independientemente, para evaluar los cambios en reclutamiento y supervivencia tempranas se establecieron 15 cuadros (0.5 × 2.0 m) en cada comunidad arbolada (2 sitios × 3 comunidades × 15 cuadros; n = 90). Resultados clave: Colectamos ~13,600 semillas de 144 especies pertenecientes a 48 familias botánicas. Los bosques maduros presentaron la mayor riqueza (60-61) y los potreros la menor (14-11). Observamos una reducción en la riqueza de especies y un cambio en la dominancia de las formas de vida a través del gradiente sucesional. Los bosques incluyeron principalmente semillas de árboles, mientras los potreros estuvieron dominados por unas pocas especies de gramíneas. La lluvia de semillas en las áreas agrícolas se caracterizó por un reducido número de especies generalistas. Para los reclutas de especies leñosas, se registraron ~3416 individuos (<0.5 m de altura) de 238 morfoespecies, de las cuales 129 fueron identificadas a nivel de especie en 42 familias. El mayor número de reclutas ocurrió en bosques maduros comparados con bosques tempranos y su supervivencia fue mayor en los bosques maduros. Conclusiones: Documentamos la progresiva simplificación y homogenización en la composición florística y el efecto generalizado de los humanos en las regiones tropicales.Background and Aims: Agriculture in the tropics is decreasing, fragmenting and altering forests and forest landscapes. We hypothesized differences in species richness and dominance of life forms in the seed rain and in richness and survival in the recruit assemblages among mature forests, mid-successional forests, early successional forests, pastures and milpa fields (arable lands with maize) surrounded by natural and human disturbed habitats. Methods: Samples of seeds and plants were collected during a year in Lacanjá-Chansayab and Bonampak-Bethel, in the buffer zone of the Montes Azules Biosphere Reserve, Selva Lacandona, Chiapas, Mexico. We deployed 14 seed traps in 12 sites representing a gradient of vegetation succession (2 sites × 6 habitats × 14 traps; n = 168 traps). Independently, to assess changes in recruitment and early survival, we established 15 quadrats (0.5 × 2.0 m) in each of the studied forests (2 sites × 3 habitats × 15 quadrats; n = 90 quadrats). Key results: We collected ~13,600 seeds of 144 species from 48 botanical families. Mature forests had the highest seed rain species richness (60-61) and pastures (14-11) the lowest. We observed a decline in species richness and a change in dominance of life forms in the seed rain from less disturbed to most perturbed habitats. Mature forests included seeds of diverse tree species while the assemblage in pastures was dominated by seeds of few grass species. Intensive traditional milpa fields showed homogeneous seed assemblages. For the new recruits, we recorded ~3,416 individuals (<0.5 m height) of 238 morphospecies in 42 families, 129 were identified to species level. The largest number of species occurred in mature and mid-successional stands compared to early forests. Annual survival of recruits was higher in mid- and late successional forests than in early ones.Conclusions: We document species loss and widespread simplification and homogenization in community composition due to pervasive effect of humans on remnant tropical lowland forests

The implications of seasonal climatic effects for managing disturbance dependent populations under a changing climate

The frequency of ecological disturbances, such as fires, is changing due to changing land use and climatic conditions. Disturbance-adapted species may thus require the manipulation of disturbance regimes to persist. However, the effects of changes in other abiotic factors, such as climatic conditions, are frequently disregarded in studies of such systems. Where climatic effects are included, relatively simple approaches that disregard seasonal variation in the effects are typically used. We compare predictions of population persistence using different fire return intervals (FRIs) under recent and predicted future climatic conditions for the rare fire-dependent herb Eryngium cuneifolium. We used functional linear models (FLMs) to estimate the cumulative effect of climatic variables across the annual cycle, allowing the strength and direction of the climatic impacts to differ over the year. We then estimated extinction probabilities and minimum population sizes under past and forecasted future climatic conditions and a range of FRIs. Under forecasted climate change, E. cuneifolium is predicted to persist under a much broader range of FRIs, because increasing temperatures are associated with faster individual growth. Climatic impacts on fecundity do not result in a temporal trend in this vital rate due to antagonistic seasonal effects operating through winter and summer temperatures. These antagonistic seasonal climatic effects highlight the importance of capturing the seasonal dependence of climatic effects when forecasting their future fate. Synthesis. Awareness of the potential effects of climate change on disturbance-adapted species is necessary for developing suitable management strategies for future environmental conditions. However, our results suggest that widely used simple methods for modelling climate impacts, that disregard seasonality in such effects, may produce misleading inferences

Exploring population responses to environmental change when there is never enough data: a factor analytic approach

© 2018 The Authors. Methods in Ecology and Evolution published by John Wiley & Sons Ltd on behalf of British Ecological Society Temporal variability in the environment drives variation in vital rates, with consequences for population dynamics and life-history evolution. Integral projection models (IPMs) are data-driven structured population models widely used to study population dynamics and life-history evolution in temporally variable environments. However, many datasets have insufficient temporal replication for the environmental drivers of vital rates to be identified with confidence, limiting their use for evaluating population level responses to environmental change. Parameter selection, where the kernel is constructed at each time step by randomly selecting the time-varying parameters from their joint probability distribution, is one approach to including stochasticity in IPMs. We consider a factor analytic (FA) approach for modelling the covariance matrix of time-varying parameters, whereby latent variable(s) describe the covariance among vital rate parameters. This decreases the number of parameters to estimate and, where the covariance is positive, the latent variable can be interpreted as a measure of environmental quality. We demonstrate this using simulation studies and two case studies. The simulation studies suggest the FA approach provides similarly accurate estimates of stochastic population growth rate to estimating an unstructured covariance matrix. We demonstrate how the latent parameter can be perturbed to show how selection on reproductive delays in the monocarp Carduus nutans changes under different environmental conditions. We develop a demographic model of the fire dependent herb Eryngium cuneifolium to show how a putative driver of the variation in environmental quality can be incorporated with the addition of a single parameter. Using perturbation analyses we determine optimal management strategies for this species. This approach estimates fewer parameters than previous approaches and allows novel eco-evolutionary insights. Predictions on population dynamics and life-history evolution under different environmental conditions can be made without necessarily identifying causal factors. Putative environmental drivers can be incorporated with relatively few parameters, allowing for predictions on how populations will respond to changes in the environment

The implications of seasonal climatic effects for managing disturbance dependent populations under a changing climate

The frequency of ecological disturbances, such as fires, is changing due to changing land use and climatic conditions. Disturbance-adapted species may thus require the manipulation of disturbance regimes to persist. However, the effects of changes in other abiotic factors, such as climatic conditions, are frequently disregarded in studies of such systems. Where climatic effects are included, relatively simple approaches that disregard seasonal variation in the effects are typically used. We compare predictions of population persistence using different fire return intervals (FRIs) under recent and predicted future climatic conditions for the rare fire-dependent herb Eryngium cuneifolium. We used functional linear models (FLMs) to estimate the cumulative effect of climatic variables across the annual cycle, allowing the strength and direction of the climatic impacts to differ over the year. We then estimated extinction probabilities and minimum population sizes under past and forecasted future climatic conditions and a range of FRIs. Under forecasted climate change, E. cuneifolium is predicted to persist under a much broader range of FRIs, because increasing temperatures are associated with faster individual growth. Climatic impacts on fecundity do not result in a temporal trend in this vital rate due to antagonistic seasonal effects operating through winter and summer temperatures. These antagonistic seasonal climatic effects highlight the importance of capturing the seasonal dependence of climatic effects when forecasting their future fate. Synthesis. Awareness of the potential effects of climate change on disturbance-adapted species is necessary for developing suitable management strategies for future environmental conditions. However, our results suggest that widely used simple methods for modelling climate impacts, that disregard seasonality in such effects, may produce misleading inferences

Fine-scale spatial variation in fitness is comparable to disturbance-induced fluctuations in a fire-adapted species

The spatial scale at which demographic performance (e.g., net reproductive output) varies can profoundly influence landscape-level population growth and persistence, and many demographically pertinent processes such as species interactions and resource acquisition vary at fine scales. We compared the magnitude of demographic variation associated with fine-scale heterogeneity (1 ha) fluctuations associated with fire disturbance. We used a spatially explicit model within an IPM modeling framework to evaluate the demographic importance of fine-scale variation. We used a measure of expected lifetime fruit production, EF, that is assumed to be proportional to lifetime fitness. Demographic differences and their effects on EF were assessed in a population of the herbaceous perennial Hypericum cumulicola (~2,600 individuals), within a patch of Florida rosemary scrub (400 × 80 m). We compared demographic variation over fine spatial scales to demographic variation between years across 6 yr after a fire. Values of EF changed by orders of magnitude over <10 m. This variation in fitness over fine spatial scales (<10 m) is commensurate to postfire changes in fitness for this fire-adapted perennial. A life table response experiment indicated that fine-scale spatial variation in vital rates, especially survival, explains as much change in EF as demographic changes caused by time-since-fire, a key driver in this system. Our findings show that environmental changes over a few tens of meters can have ecologically meaningful implications for population growth and extinction

Temporal migration rates affect the genetic structure of populations in the biennial Erysimum mediohispanicum with reproductive asynchrony

Funding was provided by projects CGL2009-07487/BOS and CGL2016-77720-P (AEI/FEDER, UE) to F.X.P., by the Impact Fellow programme from the University of Stirling to M.A. and by the Portuguese Foundation for Science and Technology (SFRH/BPD/111015/2015) to A.J.M.-P.We are grateful to Armando Caballero, Juan Pedro Martínez Camacho, Mario Vallejo-Marin, Mohammed Bakkali, Robin S. Waples, Xavier Thibert-Plante and Antonio Castilla for their comments and discussions on a previous draft of the manuscript. Esperanza Manzano, Leticia Ayllón and Rocío Gómez assisted in the laboratory. The EVOFLOR discussion group stimulated the development of this study. We thank the Sierra Nevada National Park headquarters for the permits and the support during our samplings in the field. We thank Bioportal at the University of Oslo and Residencia de Estudiantes de la Universidad de Zaragoza in Jaca for logistic support. We also thank the staff of the laboratory of molecular ecology (LEM) of the EBD-CSIC for assistance.Migration is a process with important implications for the genetic structure of populations. However, there is an aspect of migration seldom investigated in plants: migration between temporally isolated groups of individuals within the same geographic population. The genetic implications of temporal migration can be particularly relevant for semelparous organisms, which are those that reproduce only once in a lifetime after a certain period of growth. In this case, reproductive asynchrony in individuals of the same population generates demes of individuals differing in their developmental stage (non-reproductive and reproductive). These demes are connected by temporal migrants, that is, individuals that become annually asynchronous with respect to the rest of individuals of their same deme. Here, we investigated the extent of temporal migration and its effects on temporal genetic structure in the biennial plant Erysimum mediohispanicum. To this end, we conducted two independent complementary approaches. First, we empirically estimated temporal migration rates and temporal genetic structure in four populations of E. mediohispanicum during three consecutive years using nuclear microsatellites markers. Second, we developed a demographic genetic simulation model to assess genetic structure for different migration scenarios differing in temporal migration rates and their occurrence probabilities. We hypothesized that genetic structure decreased with increasing temporal migration rates due to the homogenizing effect of migration. Empirical and modelling results were consistent and indicated a U-shape relationship between genetic structure and temporal migration rates. Overall, they indicated the existence of temporal genetic structure and that such genetic structure indeed decreased with increasing temporal migration rates. However, genetic structure increased again at high temporal migration rates. The results shed light into the effects of reproductive asynchrony on important population genetic parameters. Our study contributes to unravel the complexity of some processes that may account for genetic diversity and genetic structure of natural populations.AEI/FEDER, UE CGL2009-07487/BOS CGL2016-77720-PImpact Fellow programme from the University of StirlingPortuguese Foundation for Science and Technology SFRH/BPD/111015/201