The legacy of the extinct Neotropical megafauna on plants and biomes.

Large mammal herbivores are important drivers of plant evolution and vegetation patterns, but the extent to which plant trait and ecosystem geography currently reflect the historical distribution of extinct megafauna is unknown. We address this question for South and Central America (Neotropical biogeographic realm) by compiling data on plant defence traits, climate, soil, and fire, as well as on the historical distribution of extinct megafauna and extant mammal herbivores. We show that historical mammal herbivory, especially by extinct megafauna, and soil fertility explain substantial variability in wood density, leaf size, spines and latex. We also identified three distinct regions (''antiherbiomes''), differing in plant defences, environmental conditions, and megafauna history. These patterns largely matched those observed in African ecosystems, where abundant megafauna still roams, and suggest that some ecoregions experienced savanna-to-forest shifts following megafauna extinctions. Here, we show that extinct megafauna left a significant imprint on current ecosystem biogeography.

Species richness both impedes and promotes alien plant invasions in the Brazilian Cerrado.

Worldwide, alien plant invasions have been intensively studied in the past decades, but mechanisms controlling the invasibility of native communities are not fully understood yet. The stochastic niche hypothesis predicts that species-rich plant communities are less prone to alien plant invasions than species-poor communities, which is supported by some but not all field studies, with some very species-rich communities such as the Brazilian Cerrado becoming heavily invaded. However, species-rich communities potentially contain a greater variety of facilitative interactions in resource exploitation than species-poor communities, from which invasive plants might benefit. This alternative hypothetical mechanism might explain why nutrient-poor, species-rich ecosystems are prone to invasion. Here we show that a high species richness both impedes and promotes invasive plants in the Brazilian Cerrado, using structural equation modelling and data from 38 field sites. We found support for the stochastic niche hypothesis through an observed direct negative influence of species richness on abundance of alien invasive species, but an indirect positive effect of species richness on invasive alien plants through soil phosphatase activity that enhances P availability was also found. These field observations were supported with results from a mesocosm experiment. Root phosphatase activity of plants increased with species richness in the mesocosms, which was associated with greater community P and N uptake. The most prominent alien grass species of the region, Melinis minutiflora, benefited most from the higher N and P availability in the species mixtures. Hence, this study provides a novel explanation of why species-richness may sometimes promote rather than impede invasion, and highlights the need to perform facilitation experiments in multi-species communities.

High heat tolerance in plants from the Andean highlands: Implications for paramos in a warmer world.

Tropical plant species are expected to have high heat tolerance reflecting phenotypic adjustments to warm regions or their evolutionary adaptation history. However, tropical highland specialists adapted to the colder temperatures found in the highlands, where short and prostrated vegetation decouples plants from ambient conditions, could exhibit different upper thermal limits than those of their lowland counterparts. Here we evaluated leaf heat tolerance of 21 tropical alpine paramo species to determine: 1) whether species with restricted distribution (i.e., highland specialists) have lower heat tolerance and are more vulnerable to warming than species with widespread distribution; 2) whether different growth forms have different heat tolerance; and 3) whether species height (i.e., microhabitat) influences its heat tolerance. We quantified heat tolerance by evaluating T50, which is the temperature that causes a reduction in 50% of initial Fv/Fm values and reflects an irreversible damage to the photosynthetic apparatus. Additionally, we estimated the thermal safety margins as the difference between T50 and the maximum leaf temperature registered for the species. All species presented high T50 values ranging between 45.4°C and 53.9°C, similar to those found for tropical lowland species. Heat tolerance was not correlated with species distributions or plant height, but showed a strong relationship with growth form, with rosettes having the highest heat tolerance. Thermal safety margins ranged from 12.1 to 31.0°C. High heat tolerance and broad thermal safety margins suggest low vulnerability of paramo species to warming as long as plants are capable of regulating the leaf temperature within this threshold. Whether paramo plants would be able to regulate leaf temperature if drought episodes become more frequent and transpirational cooling is compromised is the next question that needs to be answered.

Spatial distribution analysis of Dicksonia sellowiana Hook. in Araucaria forest fragments with different sizes / Análise da distribuição espacial de Dicksonia sellowiana Hook. em fragmentos de Floresta com Araucária com diferentes tamanhos

Abstract Dicksonia sellowiana Hook. (Dicksoniaceae) is target of extractive exploitation and is threatened with extinction. We analyzed the population structure, the spatial distribution pattern of D. sellowiana and its relationship with environmental parameters within three fragments of Araucaria Forest in Rio Grande do Sul, Brazil. The fragments are of different sizes, namely, large (H1LF) with 246 ha, medium (H2MF) with 57 ha and small (H3SF) with 5.2 ha. Within each site, 1 ha was delimited, divided into 100 subplots (100 m2), of which 20 were selected with a draw. In each subplot, counting of the individuals, the registration of the caudice height and the coverage of leaves (SC) (m2), measurements of photosynthetically active radiation (PAR), canopy opening degree (CO), soil moisture (SM) and litter thickness (LT). The temperature (T) was measured inside each site. A total of 792 plants were sampled, of which 551 were concentrated in H1LF, 108 in H2MF and 133 in H3SF. An average of 1320 ha-1 individuals were estimated. Of the total including the three fragments, 96.9% of the individuals are in the first class of height (up to 0.8 m), indicating a great potential of population development. The spatial distribution pattern (AI) was aggregated in the three populations and the plants presented a heterogeneous total coverage, between 4.73 m2 (H2MF) and 2,223.47 m2 (H1LF). The highest values ​​of SC and SM were more related to the distribution of individuals in H1LF whereas the opposite was recorded in H2MF. The highest values ​​of PAR, LT and CO correlated with the distribution of D. sellowiana in H3SF. In addition to revealing that the H1LF population is among the most dense in southern Brazil, the results demonstrated a significant structural distinction between the interior populations of the fragments, in spite of them being located near to one another and being part of the same natural field matrix.

Resumo Dicksonia sellowiana Hook. (Dicksoniaceae) é alvo de exploração extrativista e encontra-se ameaçada de extinção. Analisamos a estrutura populacional, o padrão de distribuição espacial de D. sellowiana e sua relação com parâmetros ambientais no interior de três fragmentos de Floresta com Araucária, no Rio Grande do Sul (RS), Brasil. Os fragmentos possuem diferentes tamanhos sendo denominados de grande (H1LF) com 246 ha, médio (H2MF) com 57 ha e de pequeno (H3SF) com 5,2 ha. No interior de cada sítio, foi demarcado 1 ha, fracionado em 100 subparcelas (100m2), das quais 20 foram sorteadas. Em cada subparcela foi feita a contagem dos indivíduos, o registro da altura do cáudice e da cobertura (SC) (m2) das folhas, as medições da radiação fotossinteticamente ativa (PAR), grau de abertura do dossel (CO), umidade do solo (SM) e espessura da serapilheira (LT). A temperatura (T) foi medida no interior de cada sítio. Foram amostradas 792 plantas, das quais 551 concentradas no H1LF, 108 no H2MF e 133 no H3SF e em média foram estimados 1320 indivíduos ha-1. Do total dos três fragmentos, 96,9% dos indivíduos estão na primeira classe de altura (até 0,8 m), indicando grande potencial de desenvolvimento das populações. O padrão de distribuição espacial (AI) foi agregado nas três populações e as plantas apresentaram uma cobertura total heterogênea, entre 4,73m2 (H2MF) e 2.223,47m 2 (H1LF). Os maiores valores de SC e de SM foram mais relacionadas com a distribuição dos indivíduos no H1LF enquanto que o contrário foi registrado no H2MF. Os maiores valores de PAR, LT e de CO relacionaram-se com a distribuição de D. sellowiana no H3SF. Além de revelar que a população do H1LF está entre as mais densas já descritas no sul do Brasil, os resultados demonstraram uma significativa distinção estrutural entre as populações dos interiores dos fragmentos com diferentes tamanhos, embora muito próximos geograficamente e inseridos em uma mesma matriz de campo natural.

Vagrant birds as a dispersal vector in transoceanic range expansion of vascular plants.

Birds are thought to be important vectors underlying the disjunct distribution patterns of some terrestrial biota. Here, we investigate the role of birds in the colonisation by Ochetophila trinervis (Rhamnaceae), a vascular plant from the southern Andes, of sub-Antarctic Marion Island. The location of O. trinervis on the island far from human activities, in combination with a reconstruction of island visitors' travel history, precludes an anthropogenic introduction. Notably, three bird species occurring in the southern Andes inland have been observed as vagrants on Marion Island, with the barn swallow Hirundo rustica as the most common one. This vagrant displays long-distance migratory behaviour, eats seeds when insects are in short supply, and has started breeding in South America since the 1980s. Since naturalised O. trinervis has never been found outside the southern Andes and its diaspores are incapable of surviving in seawater or dispersing by wind, a natural avian dispersal event from the Andes to Marion Island, a distance of >7500 km, remains the only probable explanation. Although one self-incompatible shrub seems doomed to remain solitary, its mere establishment on a Southern Ocean island demonstrates the potential of vagrancy as a driver of extreme long-distance dispersal of terrestrial biota.

Spatial distribution analysis of Dicksonia sellowiana Hook. in Araucaria forest fragments with different sizes.

Dicksonia sellowiana Hook. (Dicksoniaceae) is target of extractive exploitation and is threatened with extinction. We analyzed the population structure, the spatial distribution pattern of D. sellowiana and its relationship with environmental parameters within three fragments of Araucaria Forest in Rio Grande do Sul, Brazil. The fragments are of different sizes, namely, large (H1LF) with 246 ha, medium (H2MF) with 57 ha and small (H3SF) with 5.2 ha. Within each site, 1 ha was delimited, divided into 100 subplots (100 m2), of which 20 were selected with a draw. In each subplot, counting of the individuals, the registration of the caudice height and the coverage of leaves (SC) (m2), measurements of photosynthetically active radiation (PAR), canopy opening degree (CO), soil moisture (SM) and litter thickness (LT). The temperature (T) was measured inside each site. A total of 792 plants were sampled, of which 551 were concentrated in H1LF, 108 in H2MF and 133 in H3SF. An average of 1320 ha-1 individuals were estimated. Of the total including the three fragments, 96.9% of the individuals are in the first class of height (up to 0.8 m), indicating a great potential of population development. The spatial distribution pattern (AI) was aggregated in the three populations and the plants presented a heterogeneous total coverage, between 4.73 m2 (H2MF) and 2,223.47 m2 (H1LF). The highest values ​​of SC and SM were more related to the distribution of individuals in H1LF whereas the opposite was recorded in H2MF. The highest values ​​of PAR, LT and CO correlated with the distribution of D. sellowiana in H3SF. In addition to revealing that the H1LF population is among the most dense in southern Brazil, the results demonstrated a significant structural distinction between the interior populations of the fragments, in spite of them being located near to one another and being part of the same natural field matrix.

Epidemics on plants: Modeling long-range dispersal on spatially embedded networks.

Here we develop an epidemic model that accounts for long-range dispersal of pathogens between plants. This model generalizes the classical compartmental models-Susceptible-Infected-Susceptible (SIS) and Susceptible-Infected-Recovered (SIR)-to take into account those factors that are key to understand epidemics in real plant populations. These ingredients are the spatial characteristics of the plots and fields in which plants are embedded and the effect of long-range dispersal of pathogens. The spatial characteristics are included through the use of random rectangular graphs which allow to consider the effects of the elongation of plots and fields, while the long-range dispersal is implemented by considering transformations, such as the Mellin and Laplace transforms, of a generalization of the adjacency matrix of the geometric graph. Our results point out that long-range dispersal favors the propagation of pathogens while the elongation of plant plots increases the epidemic threshold and decreases dramatically the number of affected plants. Interestingly, our model is able of reproducing the existence of patchy regions of infected plants and the absence of a clear propagation front centered in the initial infected plants, as it is observed in real plant epidemics.

Plant species diversity in a Neotropical wetland: patterns of similarity, effects of distance, and altitude

ABSTRACT The Brazilian Pantanal is an extensive wetland with heterogeneous habitats, primarily due to the river-floodplain system and plants with differential adaptations and reproductive strategies. Factors such as altitude, distance among plant formations, and flood pulse must be considered to better understand its diversity. Aiming to assess the influence of biogeographic patterns in this system, we analyzed the floristic composition of six areas along the Paraguay River, including residual relieves, verifying the pattern of similarity, and effects of distance and altitude. We recorded 356 species in 87 families, mostly perennial (75%), and some annuals (15%) and pluriannuals (5%). Herbaceous plants were the most represented (48%), followed by arboreal (23%), shrubby (15%) and epiphytic (14%) habits, only 12% being endemic to Brazil. The studied areas showed low floristic similarity, but higher resemblance of species between neighboring areas, and no relation with altitude. The upper Paraguay River is diverse, with high spatial variability of species, predominantly perennial. The river-floodplain connectivity may be a determinant factor in species richness and occurrence of endemic species.

Species Distribution Modelling: Contrasting presence-only models with plot abundance data.

Species distribution models (SDMs) are widely used in ecology and conservation. Presence-only SDMs such as MaxEnt frequently use natural history collections (NHCs) as occurrence data, given their huge numbers and accessibility. NHCs are often spatially biased which may generate inaccuracies in SDMs. Here, we test how the distribution of NHCs and MaxEnt predictions relates to a spatial abundance model, based on a large plot dataset for Amazonian tree species, using inverse distance weighting (IDW). We also propose a new pipeline to deal with inconsistencies in NHCs and to limit the area of occupancy of the species. We found a significant but weak positive relationship between the distribution of NHCs and IDW for 66% of the species. The relationship between SDMs and IDW was also significant but weakly positive for 95% of the species, and sensitivity for both analyses was high. Furthermore, the pipeline removed half of the NHCs records. Presence-only SDM applications should consider this limitation, especially for large biodiversity assessments projects, when they are automatically generated without subsequent checking. Our pipeline provides a conservative estimate of a species' area of occupancy, within an area slightly larger than its extent of occurrence, compatible to e.g. IUCN red list assessments.

Plant species diversity in a Neotropical wetland: patterns of similarity, effects of distance, and altitude.

The Brazilian Pantanal is an extensive wetland with heterogeneous habitats, primarily due to the river-floodplain system and plants with differential adaptations and reproductive strategies. Factors such as altitude, distance among plant formations, and flood pulse must be considered to better understand its diversity. Aiming to assess the influence of biogeographic patterns in this system, we analyzed the floristic composition of six areas along the Paraguay River, including residual relieves, verifying the pattern of similarity, and effects of distance and altitude. We recorded 356 species in 87 families, mostly perennial (75%), and some annuals (15%) and pluriannuals (5%). Herbaceous plants were the most represented (48%), followed by arboreal (23%), shrubby (15%) and epiphytic (14%) habits, only 12% being endemic to Brazil. The studied areas showed low floristic similarity, but higher resemblance of species between neighboring areas, and no relation with altitude. The upper Paraguay River is diverse, with high spatial variability of species, predominantly perennial. The river-floodplain connectivity may be a determinant factor in species richness and occurrence of endemic species.

Adding landscape genetics and individual traits to the ecosystem function paradigm reveals the importance of species functional breadth.

Animal pollination mediates both reproduction and gene flow for the majority of plant species across the globe. However, past functional studies have focused largely on seed production; although useful, this focus on seed set does not provide information regarding species-specific contributions to pollen-mediated gene flow. Here we quantify pollen dispersal for individual pollinator species across more than 690 ha of tropical forest. Specifically, we examine visitation, seed production, and pollen-dispersal ability for the entire pollinator community of a common tropical tree using a series of individual-based pollinator-exclusion experiments followed by molecular-based fractional paternity analyses. We investigate the effects of pollinator body size, plant size (as a proxy of floral display), local plant density, and local plant kinship on seed production and pollen-dispersal distance. Our results show that while large-bodied pollinators set more seeds per visit, small-bodied bees visited flowers more frequently and were responsible for more than 49% of all long-distance (beyond 1 km) pollen-dispersal events. Thus, despite their size, small-bodied bees play a critical role in facilitating long-distance pollen-mediated gene flow. We also found that both plant size and local plant kinship negatively impact pollen dispersal and seed production. By incorporating genetic and trait-based data into the quantification of pollination services, we highlight the diversity in ecological function mediated by pollinators, the influential role that plant and population attributes play in driving service provision, and the unexpected importance of small-bodied pollinators in the recruitment of plant genetic diversity.

Diameter distribution in a Brazilian tropical dry forest domain: predictions for the stand and species.

Currently, there is a lack of studies on the correct utilization of continuous distributions for dry tropical forests. Therefore, this work aims to investigate the diameter structure of a brazilian tropical dry forest and to select suitable continuous distributions by means of statistic tools for the stand and the main species. Two subsets were randomly selected from 40 plots. Diameter at base height was obtained. The following functions were tested: log-normal; gamma; Weibull 2P and Burr. The best fits were selected by Akaike's information validation criterion. Overall, the diameter distribution of the dry tropical forest was better described by negative exponential curves and positive skewness. The forest studied showed diameter distributions with decreasing probability for larger trees. This behavior was observed for both the main species and the stand. The generalization of the function fitted for the main species show that the development of individual models is needed. The Burr function showed good flexibility to describe the diameter structure of the stand and the behavior of Mimosa ophthalmocentra and Bauhinia cheilantha species. For Poincianella bracteosa, Aspidosperma pyrifolium and Myracrodum urundeuva better fitting was obtained with the log-normal function.

Travelling to the south: Phylogeographic spatial diffusion model in Monttea aphylla (Plantaginaceae), an endemic plant of the Monte Desert.

Effects of Pleistocene climatic oscillations on plant phylogeographic patterns are relatively well studied in forest, savanna and grassland biomes, but such impacts remain less explored on desert regions of the world, especially in South America. Here, we performed a phylogeographical study of Monttea aphylla, an endemic species of the Monte Desert, to understand the evolutionary history of vegetation communities inhabiting the South American Arid Diagonal. We obtained sequences of three chloroplast (trnS-trnfM, trnH-psbA and trnQ-rps16) and one nuclear (ITS) intergenic spacers from 272 individuals of 34 localities throughout the range of the species. Population genetic and Bayesian coalescent analyses were performed to infer genealogical relationships among haplotypes, population genetic structure, and demographic history of the study species. Timing of demographic events was inferred using Bayesian Skyline Plot and the spatio-temporal patterns of lineage diversification was reconstructed using Bayesian relaxed diffusion models. Palaeo-distribution models (PDM) were performed through three different timescales to validate phylogeographical patterns. Twenty-five and 22 haplotypes were identified in the cpDNA and nDNA data, respectively. that clustered into two main genealogical lineages following a latitudinal pattern, the northern and the southern Monte (south of 35° S). The northern Monte showed two lineages of high genetic structure, and more relative stable demography than the southern Monte that retrieved three groups with little phylogenetic structure and a strong signal of demographic expansion that would have started during the Last Interglacial period (ca. 120 Ka). The PDM and diffusion models analyses agreed in the southeast direction of the range expansion. Differential effect of climatic oscillations across the Monte phytogeographic province was observed in Monttea aphylla lineages. In northern Monte, greater genetic structure and more relative stable demography resulted from a more stable climate than in the southern Monte. Pleistocene glaciations drastically decreased the species area in the southern Monte, which expanded in a southeastern direction to the new available areas during the interglacial periods.

Diameter distribution in a Brazilian tropical dry forest domain: predictions for the stand and species

ABSTRACT Currently, there is a lack of studies on the correct utilization of continuous distributions for dry tropical forests. Therefore, this work aims to investigate the diameter structure of a brazilian tropical dry forest and to select suitable continuous distributions by means of statistic tools for the stand and the main species. Two subsets were randomly selected from 40 plots. Diameter at base height was obtained. The following functions were tested: log-normal; gamma; Weibull 2P and Burr. The best fits were selected by Akaike's information validation criterion. Overall, the diameter distribution of the dry tropical forest was better described by negative exponential curves and positive skewness. The forest studied showed diameter distributions with decreasing probability for larger trees. This behavior was observed for both the main species and the stand. The generalization of the function fitted for the main species show that the development of individual models is needed. The Burr function showed good flexibility to describe the diameter structure of the stand and the behavior of Mimosa ophthalmocentra and Bauhinia cheilantha species. For Poincianella bracteosa, Aspidosperma pyrifolium and Myracrodum urundeuva better fitting was obtained with the log-normal function.

Caryocar coriaceum (Caryocaraceae) diaspore removal and dispersal distance on the margin and in the interior of a Cerrado area in Northeastern Brazil / Remoción y distancia de dispersión de las diásporas de Caryocar coriaceum (Caryocaraceae) en el margen e interior de un área de Cerrado, Noreste de Brasil

Abstract:The seed dispersal process is a crucial stage in plant regeneration and maintenance of forest biological diversity. While the number of removed seeds is quantitative, the distance to which a seed is removed from its origin is qualitative, because it affects the probability that a seed will germinate and recruit to the next life stage. However, the creation of forest margins can negatively affect the seed dispersal process, especially for largediaspore plant species. In this study, the diaspore removal and dispersal distance of Caryocar coriaceum, a tree with large diaspores that is in danger of extinction, were analyzed. The study was conducted for two consecutive years in a protected forest in Northeastern Brazil. Each year, 1 200 diaspores with a nylon wire and a satin tape yellow were used and equally distributed in 120 experimental stations established on the forest margin and in the interior. During the first year of the study, no differences in diaspore removal and dispersal distance were found among the investigated environments. However, for the second year of the study, the number of removed diaspores differed significantly; nevertheless, the dispersal distance was not different between the forest margin and the interior. The low diaspore removal percentages suggest that species recruitment may be compromised because the diaspore accumulation close to the relatives enables higher fungi and insect attack. In addition, most of the few removed diaspores were found at short distances from their sources (up to 5 m), which can lead to low genetic variability. Virtually no diaspore was found buried by hoarding rodents, and no diaspore was found preyed upon by these animals. Evidence found in this study suggests the local loss of species dispersers, which can compromise the maintenance of forest biological diversity. Rev. Biol. Trop. 64 (3): 1117-1127. Epub 2016 September 01.

ResumenEl proceso de dispersión de semillas es una etapa crucial en la regeneración de las plantas y el mantenimiento de la diversidad biológica de los bosques. Mientras que el número de semillas removidas es cuantitativo, la distancia a la que se elimina una semilla desde su origen es cualitativa, porque afecta la probabilidad de que una semilla germine y sea reclutada para la próxima etapa del ciclo de vida. Sin embargo, la creación de márgenes de los bosques puede afectar negativamente el proceso de dispersión, especialmente para especies de plantas con diásporas grandes. En este estudio, analizamos la remoción diásporas y la distancia de dispersión de C. coriaceum, un árbol de diásporas grandes que está en peligro de extinción. El estudio se llevó a cabo durante dos años consecutivos en un bosque protegido en el Noreste de Brasil. Cada año, un total de 1 200 diásporas fueron igualmente distribuidas, con un hilo de nylon y una cinta amarilla de satén, en 120 estaciones experimentales establecidas en el margen y en el interior del bosque. En el primer año del estudio, no se encontraron diferencias en la remocíon de las diásporas y la distancia de dispersión entre los ambientes estudiados. Sin embargo, en el segundo año el número de diásporas retiradas difería significativamente, pero la distancia de dispersión no fue diferente entre el margen de bosques y el interior. El bajo porcentaje de remoción encontrado sugiere que el reclutamiento de especies puede estar comprometido, ya que la acumulación de diásporas próximas unas de otras es propicio para un mayor ataque de hongos e insectos. Además, la mayoría de las pocas diásporas removidas fueron encontradas a pequeñas distancias de su origen (hasta 5 m), lo que puede generar una baja variabilidad genética. Prácticamente ninguna diáspora fue encontrada enterrada por los roedores recolectores y ninguna estaba depredada por estos animales. La evidencia encontrada en este estudio indica la pérdida local de dispersores de las especies, lo que puede poner en peligro el mantenimiento de la diversidad biológica de los bosques.

Estimating Tropical Forest Structure Using a Terrestrial Lidar.

Forest structure comprises numerous quantifiable biometric components and characteristics, which include tree geometry and stand architecture. These structural components are important in the understanding of the past and future trajectories of these biomes. Tropical forests are often considered the most structurally complex and yet least understood of forested ecosystems. New technologies have provided novel avenues for quantifying biometric properties of forested ecosystems, one of which is LIght Detection And Ranging (lidar). This sensor can be deployed on satellite, aircraft, unmanned aerial vehicles, and terrestrial platforms. In this study we examined the efficacy of a terrestrial lidar scanner (TLS) system in a tropical forest to estimate forest structure. Our study was conducted in January 2012 at La Selva, Costa Rica at twenty locations in a predominantly undisturbed forest. At these locations we collected field measured biometric attributes using a variable plot design. We also collected TLS data from the center of each plot. Using this data we developed relative vegetation profiles (RVPs) and calculated a series of parameters including entropy, Fast Fourier Transform (FFT), number of layers and plant area index to develop statistical relationships with field data. We developed statistical models using a series of multiple linear regressions, all of which converged on significant relationships with the strongest relationship being for mean crown depth (r2 = 0.88, p < 0.001, RMSE = 1.04 m). Tree density was found to have the poorest significant relationship (r2 = 0.50, p < 0.01, RMSE = 153.28 n ha-1). We found a significant relationship between basal area and lidar metrics (r2 = 0.75, p < 0.001, RMSE = 3.76 number ha-1). Parameters selected in our models varied, thus indicating the potential relevance of multiple features in canopy profiles and geometry that are related to field-measured structure. Models for biomass estimation included structural canopy variables in addition to height metrics. Our work indicates that vegetation profiles from TLS data can provide useful information on forest structure.

Effects of Fragment and Vegetation Structure on the Population Abundance of Ateles hybridus, Alouatta seniculus and Cebus albifrons in Magdalena Valley, Colombia.

Many primate species currently subsist in fragmented and anthropogenically disturbed habitats. Different threats arise depending on the species' life history strategy, dietary requirements and habitat preference. Additionally, anthropogenic disturbance is far from uniform and may affect individual forest fragments in a single landscape in differing ways. We studied the effects of fragmentation on three species of diurnal primate, Cebus albifrons, Alouatta seniculus and Ateles hybridus, in Magdalena Valley, Colombia. We tested the assumption that generalist species are more resilient than specialist species to habitat degradation by examining the fragments' vegetation and spatial structure and how these affected primate presence and abundance patterns. We found C. albifrons, a generalist, to be the most abundant species in 9 of 10 forest fragments, regardless of the level of habitat disturbance. A. hybridus, a large-bodied primate with a specialist diet, was either absent or low in abundance in fragments that had experienced recent disturbances and was found only in higher-quality fragments, regardless of the fragment size. A. seniculus, a species considered to have a highly flexible diet and the ability to survive in degraded habitat, was found in intermediate abundances between those of Cebus spp. and Ateles spp., and was more frequently found in high-quality fragments.

Caryocar coriaceum (Caryocaraceae) diaspore removal and dispersal distance on the margin and in the interior of a Cerrado area in Northeastern Brazil.

The seed dispersal process is a crucial stage in plant regeneration and maintenance of forest biological diversity. While the number of removed seeds is quantitative, the distance to which a seed is removed from its origin is qualitative, because it affects the probability that a seed will germinate and recruit to the next life stage. However, the creation of forest margins can negatively affect the seed dispersal process, especially for large-diaspore plant species. In this study, the diaspore removal and dispersal distance of Caryocar coriaceum, a tree with large diaspores that is in danger of extinction, were analyzed. The study was conducted for two consecutive years in a protected forest in Northeastern Brazil. Each year, 1 200 diaspores with a nylon wire and a satin tape yellow were used and equally distributed in 120 experimental stations established on the forest margin and in the interior. During the first year of the study, no differences in diaspore removal and dispersal distance were found among the investigated environments. However, for the second year of the study, the number of removed diaspores differed significantly; nevertheless, the dispersal distance was not different between the forest margin and the interior. The low diaspore removal percentages suggest that species recruitment may be compromised because the diaspore accumulation close to the relatives enables higher fungi and insect attack. In addition, most of the few removed diaspores were found at short distances from their sources (up to 5 m), which can lead to low genetic variability. Virtually no diaspore was found buried by hoarding rodents, and no diaspore was found preyed upon by these animals. Evidence found in this study suggests the local loss of species dispersers, which can compromise the maintenance of forest biological diversity.

Nature and Age of Neighbours Matter: Interspecific Associations among Tree Species Exist and Vary across Life Stages in Tropical Forests.

Detailed information about interspecific spatial associations among tropical tree species is scarce, and hence the ecological importance of those associations may have been underestimated. However, they can play a role in community assembly and species diversity maintenance. This study investigated the spatial dependence between pairs of species. First, the spatial associations (spatial attraction and spatial repulsion) that arose between species were examined. Second, different sizes of trees were considered in order to evaluate whether the spatial relationships between species are constant or vary during the lifetime of individuals. Third, the consistency of those spatial associations with the species-habitat associations found in previous studies was assessed. Two different tropical ecosystems were investigated: a montane cloud forest and a lowland moist forest. The results showed that spatial associations among species exist, and these vary among life stages and species. The rarity of negative spatial interactions suggested that exclusive competition was not common in the studied forests. On the other hand, positive interactions were common, and the results of this study strongly suggested that habitat associations were not the only cause of spatial attraction among species. If this is true, habitat associations and density dependence are not the only mechanisms that explain species distribution and diversity; other ecological interactions, such as facilitation among species, may also play a role. These spatial associations could be important in the assembly of tropical tree communities and forest succession, and should be taken into account in future studies.

Bird-flower visitation networks in the Galápagos unveil a widespread interaction release.

Owing to food scarcity and to the high densities that vertebrates often reach on islands, typical insect- and seed-eaters widen their feeding niche and interact with a greater fraction of species than their mainland counterparts. This phenomenon, coined here 'interaction release', has been previously reported for single species but never for an entire community. During 4 years, we gathered data on bird-flower visitation on 12 Galápagos islands. We show that all sampled land birds exploit floral resources and act as potential pollinators across the entire archipelago, in all major habitats and all year round. Although species and link composition varies among islands, strong interaction release takes place on all islands, making their bird-flower network highly generalized. Interaction release is crucial to the survival of native birds but simultaneously threatens the unique biodiversity of this archipelago, as the birds also visit invading plants, likely facilitating their integration into pristine native communities.