Seed polyphenols in a diverse tropical plant community

1.Polyphenols are one of the most common groups of secondary metabolites in plants and thought to play a key role in enhancing plant fitness by protecting plants against enemies. Although enemy‐inflicted mortality at the seed stage can be an important regulator of plant populations and a key determinant of community structure, few studies have assessed community‐level patterns of polyphenol content in seeds. 2.We describe the distribution of the main seed polyphenol groups across 196 tree and liana species on Barro Colorado Island (Panama) and community‐level patterns in two aspects of their biological activity (protein precipitation and oxidative capacity). Taking advantage of substantial variation in morphological and ecological traits in the studied plant community, we test for correlations and trade‐offs between seed polyphenols and nonchemical plant traits hypothesised to make plant species more or less likely to invest in polyphenol production. 3.The majority of species have polyphenols in their seeds. The incidence and concentrations of polyphenols were related to a set of nonchemical plant traits. Polyphenols were most likely to be present (and where present, to be expressed in high concentrations) in species with large seeds, short seed dormancy times, low investment in mechanical seed defences, high wood density, high leaf mass per area, tough leaves and slow growth rates. 4.Synthesis. Our study reveals a potential trade‐off between chemical and mechanical seed defences and shows that plant species that invest in physical defences at later life stages (high wood density and tough leaves) tend not to invest in physical defences of seeds but instead produce secondary metabolites likely to act as seed defences. Overall, our results conform to predictions from the resource availability hypothesis, which states that species in resource‐limited environments (such as slow‐growing shade‐tolerant tree species) will invest more in defences than fast‐growing pioneer species. </p

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

Minimal information for studies of extracellular vesicles 2018 (MISEV2018):a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points

Seed toughness data and code

This zip file contains the dataset as a .csv files and an R script for statistical analyses

Estimación de biomasa de Cedrelinga cateniformis Ducke (tornillo) y Simarouba amara Aublet (marupá) en plantaciones forestales del centro de investigaciones Jenaro Herrera.

TesisEl presente trabajo se realizó en el Centro de Investigaciones de Jenaro Herrera (CIJH) del Instituto de Investigaciones de la Amazonia Peruana (IIAP), ubicado en el distrito de Jenaro Herrera; Loreto, Perú. El objetivo fue estimar la biomasa en las plantaciones de tornillo (Cedrelinga cateniformis Ducke) y marupa (Simaruba amara Aublet) de aproximadamente treinta y cinco años; para tal fin se midió la biomasa del árbol (raíz, fuste, ramas, copa), del sotobosque, de la necromasa y del suelo por calidad de sitio. Además se determinó el modelo matemático que mejor se ajustó a la estimación de la biomasa de los árboles. Para la estimación de biomasa de los componentes de la plantación, se tomaron 3 muestras en parcelas circulares de 500 m2 , por combinación de especies y calidad de sitio. Para desarrollar los modelos matemáticos se midieron 11 árboles por cada combinación de especie y calidad de sitio. Se calculó la biomasa de los componentes fuste, ramas, copa y raíz. La ecuación de regresión consideró la biomasa estimada como variable dependiente y a los parámetros altura y DAP como las variables independientes. Se probaron 15 modelos de regresión escogiendo el de mayor R2 , menor SEE, mejor distribución de residuos y menor dificultad y menor costo en las mediciones de campo. La biomasa estimada para la plantación de tornillo es 365,06 t/ha en calidad de sitio alta y 31 O, 15 tlha en calidad de sitio media; y para la plantación de marupa se reportó 263,47 t/ha y 242,89 t/ha en calidad de sitio alta y calidad de sitio media, respectivamente. No se encontraron diferencias debido a calidad de sitio influenciadas por la biomasa de los árboles. El mejor modelo matemático para tornillo es el logarítmico de la forma Ln B = -1,1288087 + 0,69429302 Ln D + 0,67670054 Ln H con un R2 0,838422; y para marupa el modelo logarítmico Ln B = -0,382076 + 0,723284 Ln D + 0,472940 Ln H con un R2 de 0,861863. Se concluye que existen diferencias significativas entre la biomasa estimada y la biomasa observada

Data from: Functional outcomes of mutualistic network interactions: a community-scale study of frugivore gut passage on germination

1. Current understanding of mutualistic networks is grounded largely in data on interaction frequency, yet mutualistic network dynamics are also shaped by interaction quality—the functional outcomes of individual interactions on reproduction and survival. The difficulty of obtaining data on functional outcomes has resulted in limited understanding of functional variation among a network’s pairwise species interactions, of the study designs that are necessary to capture major sources of functional variation, and of predictors of functional variation that may allow generalization across networks. 2. In this community-scale study, we targeted a key functional outcome in plant-frugivore networks: the impact of frugivore gut passage on seed germination. We used captive frugivore feeding trials and germination experiments in an island ecosystem, attaining species-level coverage across all extant native frugivores and the plants they consume to 1) assess sources of functional variation, 2) separate effects of pulp removal from those of scarification via gut passage, and 3) test trait-based correlates of gut passage effect sizes. 3. We found antagonistic seed predation effects of a frugivore previously assumed to be a seed disperser, highlighting the need to consider functional outcomes rather than interaction frequency alone. The other frugivores each exhibited similar impacts for individual plant species, with benefits primarily caused by pulp removal rather than scarification, supporting the use of animal functional groups in this context. In contrast, plant species varied widely in impacts of gut passage on germination. Species with smaller seeds and more frugivore partners had larger benefits of gut passage, showing promise for network metrics and functional traits to predict functional variation among plants. 4. Synthesis. Combining network and demographic approaches, we assessed the degree and sources of variation in a key functional outcome of plant-frugivore interactions across an entire network. Using a detailed study design, our work shows how simpler study designs can capture primary sources of functional variation and that functional traits and network metrics may allow generalization across networks. Efficiently measuring and generalizing sources of functional variation within mutualistic networks will strengthen our ability to model network dynamics and predict mutualist responses to global change

Data from: Multiple natural enemies cause distance-dependent mortality at the seed-to-seedling transition

Specialised natural enemies maintain forest diversity by reducing tree survival in a density- or distance-dependent manner. Fungal pathogens, insects and mammals are the enemy types most commonly hypothesised to cause this phenomenon. Still, their relative importance remains largely unknown, as robust manipulative experiments have generally targeted a single enemy type and life history stage. Here, we use fungicide, insecticide and physical exclosure treatments to isolate the impacts of each enemy type on two life history stages (germination and early seedling survival) in three tropical tree species. Distance dependence was evident for five of six species-stage combinations, with each enemy type causing distance dependence for at least one species stage and their importance varying widely between species and stages. Rather than implicating one enemy type as the primary agent of this phenomenon, our field experiments suggest that multiple agents acting at different life stages collectively contribute to this diversity-promoting mechanism

Data from: Multiple natural enemies cause distance-dependent mortality at the seed-to-seedling transition

Specialised natural enemies maintain forest diversity by reducing tree survival in a density- or distance-dependent manner. Fungal pathogens, insects and mammals are the enemy types most commonly hypothesised to cause this phenomenon. Still, their relative importance remains largely unknown, as robust manipulative experiments have generally targeted a single enemy type and life history stage. Here, we use fungicide, insecticide and physical exclosure treatments to isolate the impacts of each enemy type on two life history stages (germination and early seedling survival) in three tropical tree species. Distance dependence was evident for five of six species-stage combinations, with each enemy type causing distance dependence for at least one species stage and their importance varying widely between species and stages. Rather than implicating one enemy type as the primary agent of this phenomenon, our field experiments suggest that multiple agents acting at different life stages collectively contribute to this diversity-promoting mechanism

Data from: Linking intra-specific trait variation and plant function: seed size mediates performance trade-offs within species

Substantial intra-specific trait variation exists within plant communities, and in theory this variation could influence community dynamics. Although recent research has focused on intra-specific variation in traits themselves, it is the influence of this variation on plant performance that makes intra-specific trait variation relevant to ecological dynamics within or among species. Understanding the links between trait and performance variation, and the role of traits in mediating relationships among multiple components of performance, is critical for assessing the importance of intra-specific trait variation for community dynamics. Seed size is thought to affect aspects of plant performance including fecundity, seedling growth, dispersal, and tolerance of natural enemies. For two tropical tree species, we assessed how seed size was related to performance variation within each species and determined whether intra-specific trait variation mediates intra-specific performance trade-offs. We used field seed rain collection to characterize size-dependent outcomes of dispersal, sowed seeds of known size in soil collected near or far from conspecifics to characterize susceptibility to soil pathogens, and monitored growth of seedlings from seeds of known size. We found that intra-specific seed size variation caused intra-specific performance variation. The degree of trait-based performance variation was consistently smaller than the degree of trait variation, and seed size influenced different components of performance for each species. One species exhibited a trade-off in which small seeds had a fecundity advantage (more seedlings per unit reproductive mass) but produced smaller seedlings, whereas the other species exhibited a trade-off in which small seeds dispersed to areas of low conspecific density but were less tolerant of density-responsive natural enemies. Our results indicate that a single trait can influence multiple components of performance and can mediate different trade-offs in co-occurring species. Complex and heterogeneous effects of a single trait in multidimensional niche space may favour inter-specific niche differentiation and coexistence

Data and code

Zipped folder containing data from field experiments on seeds and seedlings under fungicide, insecticide, and mammal exclusion treatments and R scripts for analysis