Biogeographic context is related to local scale tree demography, co-occurrence and functional differentiation.

Identifying the drivers of community structure and dynamics is a major pursuit in ecology. Emphasis is typically placed on the importance of local scale interactions when attempting to explain these fundamental ecological patterns. However, regional scale phenomena are also important predictors. The importance of regional scale context should be more evident in assemblages where multiple species are close to their range margins. Here, we test the importance of regional scale context using data from a temperate forest plot that contains two species groups - one near its northern range limit and one near its southern range limit. We show the proximity of species to their southern or northern range margins is linked to local scale co-occurrence, similarity in gene expression responses to a key environmental driver, demographic performance and inter-specific variation in conspecific negative density dependence. In sum, many of the key local scale patterns and processes of interest to community ecologists are linked to biogeographic context that is frequently ignored.

Rodent suppression of seedling establishment in tropical pasture.

Grasses are recognized as a critical regeneration barrier in tropical pastures, yet the effects of rodents and rodent-grass interactions are not well understood. As selective foragers, rodents could shape tree communities, moderating biodiversity in regenerating tropical landscapes. We utilized a fully crossed two-way factorial design to examine the effect that grasses, rodents, and their interaction had on tree seedling establishment in pasture habitat. We followed two separate tree cohorts for 1 year each within the experimental framework. Multiple cohorts were used to better represent successional tree species variation and responses. Trees species were characterized by a gradient of seed masses and as pioneer or persistent successional type. Both cohort seedlings were altered when rodents were present compared to control treatments. In Cohort 1, rodents adversely affected seedlings of persistent tree species only in the absence of grass. In Cohort 2, seedlings of persistent tree species were decimated by rodents in the absence or presence of grass. In both cohorts, seedlings of persistent species established better in grass treatments, while seedlings of pioneer tree species were strongly suppressed. Tree species seed mass positively correlated with seedling establishment across all treatments except no grass-rodent treatments. Strong suppression of tree seedlings by rodents (Sigmodon toltecus) is a novel result in tropical land recently released from agriculture. One implication is that selective foraging by rodents on large-seeded persistent tree species may be facilitated by the removal of grass. Another implication is that temporary rodent control in pastures may permit higher establishment of deep-forest persistent species.

The effects of habitat loss and fragmentation on plant functional traits and functional diversity: what do we know so far?

Habitat loss and fragmentation result in significant landscape changes that ultimately affect plant diversity and add uncertainty to how natural areas will respond to future global change. This uncertainty is important given that the loss of biodiversity often includes losing key ecosystem functions. Few studies have explored the effects of landscape changes on plant functional diversity and evidence so far has shown far more pervasive effects than previously reported by species richness and composition studies. Here we present a review on the impact of habitat loss and fragmentation on (1) individual functional traits-related to persistence, dispersal and establishment-and (2) functional diversity. We also discuss current knowledge gaps and propose ways forward. From the literature review we found that studies have largely focused on dispersal traits, strongly impacted by habitat loss and fragmentation, while traits related to persistence were the least studied. Furthermore, most studies did not distinguish habitat loss from spatial fragmentation and were conducted at the plot or fragment-level, which taken together limits the ability to generalize the scale-dependency of landscape changes on plant functional diversity. For future work, we recommend (1) clearly distinguishing the effects of habitat loss from those of fragmentation, and (2) recognizing the scale-dependency of predicted responses when functional diversity varies in time and space. We conclude that a clear understanding of the effects of habitat loss and fragmentation on functional diversity will improve predictions of the resiliency and resistance of plant communities to varying scales of disturbance.

Local neighbourhood and regional climatic contexts interact to explain tree performance.

Tree neighbourhood modelling has significantly contributed to our understanding of the mechanisms structuring communities. Investigations into the impact of neighbouring crowding on tree performance have generally been conducted at local scales, missing important regional-scale context such as the suitability of the climate for each species. Favourable climates may enhance tree performance, but this may come at the cost of increased neighbourhood crowding and competition negatively impacting survival and growth. Through the synthesis of continental-scale forest inventory and trait datasets from the northeast USA and Puerto Rico we present an analytical approach that elucidates the important interactions between local competitive and regional climatic contexts. Our results show strong asymmetries in competitive interactions and significant niche differences that are dependent on habitat suitability. The strong interaction between local neighbourhood and regional climate highlights the need for models that consider the interaction between these two processes that have been previously ignored.

Analyses of three-dimensional species associations reveal departures from neutrality in a tropical forest.

The study of community spatial structure is central to understanding diversity patterns over space and species co-occurrence at local scales. Although most analytical approaches consider horizontal and vertical dimensions separately, in this study we introduce a three-dimensional spatial analysis that simultaneously includes horizontal and vertical species associations. Using tree census data (2000-2016) and allometries from the Luquillo forest plot in Puerto Rico, we show that spatial organization becomes less random over time as the forest recovered from land-use legacy effects and hurricane disturbance. Tree species vertical segregation is predominant in the forest with almost all species that co-occur in the horizontal plane avoiding each other in the vertical dimension. Horizontal segregation is less common than vertical, whereas three-dimensional aggregation (a proxy for direct tree competition) is the least frequent type of spatial association. Furthermore, dominant species are involved in more non-random spatial associations, implying that species co-occurrence is facilitated by species segregation in space. This novel three-dimensional analysis allowed us to identify and quantify tree species spatial distributions, how interspecific competition was reduced through forest structure, and how it changed over time after disturbance, in ways not detectable from two-dimensional analyses alone.

Tree seedling trait optimization and growth in response to local-scale soil and light variability.

At local scales, it has been suggested that high levels of resources lead to increased tree growth via trait optimization (highly peaked trait distribution). However, this contrasts with (1) theories that suggest that trait optimization and high growth occur in the most common resource level and (2) empirical evidence showing that high trait optimization can be also found at low resource levels. This raises the question of how are traits and growth optimized in highly diverse plant communities. Here, we propose a series of hypotheses about how traits and growth are expected to be maximized under different resource levels (low, the most common, and high) in tree seedling communities from a subtropical forest in Puerto Rico, USA. We studied the variation in the distribution of biomass allocation and leaf traits and seedlings growth rate along four resource gradients: light availability (canopy openness) and soil K, Mg, and N content. Our analyses consisted of comparing trait kurtosis (a measurement of trait optimization), community trait means, and relative growth rates at three resource levels (low, common, and high). Trait optimization varied across the three resource levels depending on the type of resource and trait, with leaf traits being optimized under high N and in the most common K and Mg conditions, but not at any of the light levels. Also, seedling growth increased at high-light conditions and high N and K but was not related to trait kurtosis. Our results indicate that local-scale variability of soil fertility and understory light conditions result in shifts in species ecological strategies that increase growth despite a weak trait optimization, suggesting the existence of alternative phenotypes that achieve similar high performance. Uncovering the links between abiotic factors, functional trait diversity and performance is necessary to better predict tree responses to future changes in abiotic conditions.

Investigating the direct and indirect effects of forest fragmentation on plant functional diversity.

Ongoing habitat loss and fragmentation alter the functional diversity of forests. Generalising the magnitude of change in functional diversity of fragmented landscapes and its drivers is challenging because of the multiple scales at which landscape fragmentation takes place. Here we propose a multi-scale approach to determine whether fragmentation processes at the local and landscape scales are reducing functional diversity of trees in the East Usambara Mountains, Tanzania. We employ a structural equation modelling approach using five key plant traits (seed length, dispersal mode, shade tolerance, maximum tree height, and wood density) to better understand the functional responses of trees to fragmentation at multiple scales. Our results suggest both direct and indirect effects of forest fragmentation on tree functional richness, evenness and divergence. A reduction in fragment area appears to exacerbate the negative effects resulting from an increased amount of edge habitat and loss of shape complexity, further reducing richness and evenness of traits related to resource acquisition and favouring tree species with fast growth. As anthropogenic disturbances affect forests around the world, we advocate to include the direct and indirect effects of forest fragmentation processes to gain a better understanding of shifts in functional diversity that can inform future management efforts.

Alternative designs and tropical tree seedling growth performance landscapes.

The functional trait values that constitute a whole-plant phenotype interact with the environment to determine demographic rates. Current approaches often fail to explicitly consider trait × trait and trait × environment interactions, which may lead to missed information that is valuable for understanding and predicting the drivers of demographic rates and functional diversity. Here, we consider these interactions by modeling growth performance landscapes that span multidimensional trait spaces along environmental gradients. We utilize individual-level leaf, stem, and root trait data combined with growth data from tree seedlings along soil nutrient and light gradients in a hyper-diverse tropical rainforest. We find that multiple trait combinations in phenotypic space (i.e., alternative designs) lead to multiple growth performance peaks that shift along light and soil axes such that no single or set of interacting traits consistently results in peak growth performance. Evidence from these growth performance peaks also generally indicates frequent independence of above- and belowground resource acquisition strategies. These results help explain how functional diversity is maintained in ecological communities and question the practice of utilizing a single trait or environmental variable, in isolation, to predict the growth performance of individual trees.

Advancing an interdisciplinary framework to study seed dispersal ecology.

Although dispersal is generally viewed as a crucial determinant for the fitness of any organism, our understanding of its role in the persistence and spread of plant populations remains incomplete. Generalizing and predicting dispersal processes are challenging due to context dependence of seed dispersal, environmental heterogeneity and interdependent processes occurring over multiple spatial and temporal scales. Current population models often use simple phenomenological descriptions of dispersal processes, limiting their ability to examine the role of population persistence and spread, especially under global change. To move seed dispersal ecology forward, we need to evaluate the impact of any single seed dispersal event within the full spatial and temporal context of a plant's life history and environmental variability that ultimately influences a population's ability to persist and spread. In this perspective, we provide guidance on integrating empirical and theoretical approaches that account for the context dependency of seed dispersal to improve our ability to generalize and predict the consequences of dispersal, and its anthropogenic alteration, across systems. We synthesize suitable theoretical frameworks for this work and discuss concepts, approaches and available data from diverse subdisciplines to help operationalize concepts, highlight recent breakthroughs across research areas and discuss ongoing challenges and open questions. We address knowledge gaps in the movement ecology of seeds and the integration of dispersal and demography that could benefit from such a synthesis. With an interdisciplinary perspective, we will be able to better understand how global change will impact seed dispersal processes, and potential cascading effects on plant population persistence, spread and biodiversity.

The total dispersal kernel: a review and future directions.

The distribution and abundance of plants across the world depends in part on their ability to move, which is commonly characterized by a dispersal kernel. For seeds, the total dispersal kernel (TDK) describes the combined influence of all primary, secondary and higher-order dispersal vectors on the overall dispersal kernel for a plant individual, population, species or community. Understanding the role of each vector within the TDK, and their combined influence on the TDK, is critically important for being able to predict plant responses to a changing biotic or abiotic environment. In addition, fully characterizing the TDK by including all vectors may affect predictions of population spread. Here, we review existing research on the TDK and discuss advances in empirical, conceptual modelling and statistical approaches that will facilitate broader application. The concept is simple, but few examples of well-characterized TDKs exist. We find that significant empirical challenges exist, as many studies do not account for all dispersal vectors (e.g. gravity, higher-order dispersal vectors), inadequately measure or estimate long-distance dispersal resulting from multiple vectors and/or neglect spatial heterogeneity and context dependence. Existing mathematical and conceptual modelling approaches and statistical methods allow fitting individual dispersal kernels and combining them to form a TDK; these will perform best if robust prior information is available. We recommend a modelling cycle to parameterize TDKs, where empirical data inform models, which in turn inform additional data collection. Finally, we recommend that the TDK concept be extended to account for not only where seeds land, but also how that location affects the likelihood of establishing and producing a reproductive adult, i.e. the total effective dispersal kernel.

Employing plant functional groups to advance seed dispersal ecology and conservation.

Seed dispersal enables plants to reach hospitable germination sites and escape natural enemies. Understanding when and how much seed dispersal matters to plant fitness is critical for understanding plant population and community dynamics. At the same time, the complexity of factors that determine if a seed will be successfully dispersed and subsequently develop into a reproductive plant is daunting. Quantifying all factors that may influence seed dispersal effectiveness for any potential seed-vector relationship would require an unrealistically large amount of time, materials and financial resources. On the other hand, being able to make dispersal predictions is critical for predicting whether single species and entire ecosystems will be resilient to global change. Building on current frameworks, we here posit that seed dispersal ecology should adopt plant functional groups as analytical units to reduce this complexity to manageable levels. Functional groups can be used to distinguish, for their constituent species, whether it matters (i) if seeds are dispersed, (ii) into what context they are dispersed and (iii) what vectors disperse them. To avoid overgeneralization, we propose that the utility of these functional groups may be assessed by generating predictions based on the groups and then testing those predictions against species-specific data. We suggest that data collection and analysis can then be guided by robust functional group definitions. Generalizing across similar species in this way could help us to better understand the population and community dynamics of plants and tackle the complexity of seed dispersal as well as its disruption.

Metilación de genes supresores tumorales en pacientes venezolanos con cáncer colorrectal: relación con estadio clínico de la enfermedad / Relationship of Methylation of Tumor Suppressor Genes with Clinical Stage of Colorectal Cancer in Venezuelan Patients

Resumen El cáncer colorrectal es una enfermedad heterogénea, en cuya aparición se involucran factores hereditarios y ambientales. En las formas heredadas existen genes responsables de incrementar el desarrollo tumoral en los portadores, y se consideran a los factores medioambientales como responsables de gran parte de las formas esporádicas. El objetivo de este estudio fue analizar el estado de metilación de 5 genes implicados en la carcinogénesis colorrectal y su relación con los distintos estadios clínicos de estos tumores. Por una parte, nuestro análisis reveló que el estado de metilación de los promotores de los genes HMLH1 (human mut homologue 1), APC (adenomatous poliposis coli), P15, P16 y CDH1, considerados como unas de las alteraciones más tempranas en este proceso; fluctuaron entre 13,3 % para hMLH1 y 56,6 % para APC. También reveló que la inactivación epigenética de los genes APC y P16 podrían ser responsables de la aparición y de la progresión de los tumores ya que se encontraron en pacientes con estadio II. Por otra parte, los genes APC y p15 resultaron estar mutados en todas las etapas de la carcinogénesis, por lo que se involucrarían en todos los procesos tanto de inicio como de invasión y metástasis. Por último, nuestros resultados apoyan la utilización de la identificación de la metilación de los genes supresores ya que se están identificando dianas epigenéticas para el desarrollo de nuevos tratamientos de quimioterapia y está emergiendo como una estrategia con gran potencial dado que, en principio, las alteraciones epigenéticas son potencialmente reversibles.

Abstract Colorectal cancer is a heterogeneous disease which involves hereditary and environmental factors. The inherited forms have genes which are responsible for increasing the tumor development in carriers. Environmental factors are considered responsible for many sporadic forms. The objective of this study was to analyze the methylation status of five genes involved in colorectal carcinogenesis and their relationships with the various clinical stages of these tumors. Our analysis revealed that the methylation status of the promoters of genes HMLH1, APC, P15, P16 and CDH1, considered to be among the earliest alterations in this process, ranged from 13.3% for HMLH1 to 56.6% for APC. In addition, epigenetic inactivation of APC and P16 genes could be responsible for the appearance and progression of tumors since inactivation was found in stage II patients. On the other hand, the APC and p15 gene were mutated in all stages of carcinogenesis, so they could be involved throughout the processes of initiation, invasion and metastasis. Finally, our results support using identification of methylation of suppressor genes since they identify epigenetic targets for development of new chemotherapy treatments. This is emerging as a strategy with great potential since epigenetic alterations are, in principle, potentially reversible.

Aulas asertivas: propuesta fonoaudiología para el abordaje del lenguaje escrito con población adolecente / Assertive classrooms: a speech and language pathology proposal for written language boarding in an adolescent population

“Aulas Asertivas” fue una propuesta de intervención fonoaudiológica aplicada en el colegio Arquidiocesano Juan Pablo II de la comuna 20 de Cali, en la que se pretendía propiciar practicas comunicativas asertivas en los estudiantes de decimo (10º) y undécimo ( 11º), con el fin de disminuir el riesgo de deserción y fracaso escolar, potencializando habilidades como hablar, escuchar, leer y escribir . Se desarrollo bajo el enfoque teórico de análisis del discurso y trabajo colaborativo, y comprendió cuatro fases: 1. Contextualización de aula, 2. Aplicación prueba pre-test, 3. Actividades de intervención, 4. Aplicación prueba post-test. Como resultados de la propuesta se encuentra, principalmente que los estudiantes participantes concibieron la lectura y la escritura como herramientas de comunicación, socialización y participación. Además se evidenciaron cambios significativos en los niveles de comprensión y producción textual antes y después de la intervención.

“Assertive Classrooms " was a phonoaudiological intervention proposal applied in the Juan Pablo II high school located the Cali 20th commune. Its purpose was to promote assertive communication practices in junior (10º) and senior (11º) students in order to reduce the risk of school failure and desertion through the strengthening of speaking, listening, reading and writing skills. Its was developed in four phases under the speech analysis and collaborative work theoretical approach: 1. Classroom contextualizing 2. Pre-test application 3. Intervention activities and 4. Post-test application. As result it was found, mainly, that students perceived reading and writing as communication, socialization and participation tools. Further significant changes in the areas of comprehension and text production were evidenced, as compared before and after the intervention.

Características del desarrollo del lenguaje en un grupo de niños de 0 a 5 años de edad sometidos a tratamientos de cáncer / Characteristics of language development in a group of children 0 to 5 years old subject to cancer treatment

El lenguaje es una herramienta que se adquiere en la primera infancia y de la cual se hace uso durante toda la vida en función del entorno. Cuando por razones como la hospitalización continua y prolongada la dinámica diaria de un niño en la primera infancia se ve alterada, esto se traduce en características especiales en las distintas áreas del desarrollo, incluyendo por supuesto el lenguaje ya que este se encuentra en fase de adquisición y consolidación. El presente estudio caracteriza el desarrollo del lenguaje de 11 niños de 0 a 5 años de edad sometidos a tratamiento para el cáncer. Se realizó un estudio de corte transversal que incluyó la aplicación de la escala de desarrollo del lenguaje, la caracterización de factores contextuales comunicativos (antecedentes clínicos, tipo cáncer, tipo de tratamiento recibido, y contexto comunicativo), también se incluyo la evaluación de los órganos fono articuladores y la evaluación audiológica básica (estado del oído medio y tipo de audición). El 82% de los participantes mostró algún tipo de retraso en los componentes evaluados, observando como característica particular la semifuncionalidad en los contextos comunicativos. Lo anterior muestra que esta condición de salud particular impacta directamente sobre las condiciones contextuales lo que repercute negativamente en el desarrollo del lenguaje y por ende en la comunicación.

Language is a tool that is acquired in early childhood and which they are use throughout life depending on the environment. When, for reasons such as hospitalization and prolonged continuous daily dynamics of a child in early childhood is altered, this translates into special characteristics in different areas of development, including the language course as this is under acquisition and consolidation. This study describes the language development of 11 children between 0 and 5 years of age undergoing treatment for cancer. We performed a crosssectional study that included the application of the scale of language development, the characterization of communication contextual factors (medical history, type of cancer , type of treatment received, and communicative context), also included phone assessment bodies articulators and basic audiological evaluation (middle ear status and type of hearing). 82% of the participants showed some kind of delay in the components evaluated, noting the particular characteristic semifuncionalidad communicative contexts. This shows that this particular health condition directly impacts the contextual conditions that adversely affects the development of language and hence communication.