RESUMO

Introduction: Seed dispersal and seed predation have important impacts on plant diversity and community structure. Rodents participate in both of these types of interactions. Objectives: To evaluate the removal of the seeds of Crescentia alata, Randia capitata, and Zea mays by the squirrel Notocitellus adocetus to determine how it affects these plant species, by dispersing or preying on their seeds. Methods: We studied 14 individuals for C. alata, 24 for R. capitata, and for Z. mays 35 individuals. We observed foraging and used camera traps to determine the part of the fruit (seed and/or pulp) consumed by the squirrels and the amount of fruit or seed consumed. We also placed fine sand traps (FST) to measure the percentage of seed removal. We quantified the fruits produced by the plant species studied and the percentage of damage caused by N. adocetus throughout the plots. Results: Notocitellus adocetus feeds on the seeds and pulp of C. alata and Z. mays. The species with the highest removal rate and the highest percentage of damage was C. alata. Zea mays was the plant species that had the highest percentage of removal from FST, the largest number of fruits, and the lowest percentage of damage. On FST, R. capitata had the lowest seed remotion. Conclusions: Notocitellus adocetus is considered a seed predator; however, due to its behavior and the characteristics of the fruits of C. alata and R. capitata, this rodent could make the seeds available to secondary seed dispersers.

Introducción: La dispersión y depredación de semillas tienen efectos importantes en la diversidad de plantas y estructura de las comunidades. Los roedores participan en estos tipos de interacciones. Objetivos: Evaluar la remoción de semillas de Crescentia alata, Randia capitata y Zea mays por la ardilla Notocitellus adocetus, para determinar su efecto en estas especies de plantas, dispersando o depredando semillas. Métodos: Estudiamos 14 individuos de C. alata, 24 para R. capitata y 35 individuos para Z. mays. Observamos el forrajeo y usamos cámaras trampas para determinar la parte del fruto (semilla y/o pulpa) consumida y la intensidad de consumo por las ardillas. También colocamos trampas de arena fina (FST) para medir el porcentaje de remoción de semillas. Cuantificamos los frutos producidos por las especies estudiadas y el porcentaje de daño ocasionado por N. adocetus, mediante parcelas. Resultados: Notocitellus adocetus se alimenta de las semillas y pulpa de C. alata y Z. mays. La especie que tuvo mayor tasa de remoción y mayor porcentaje de daño fue C. alata. La especie con mayor porcentaje de remoción, mayor número de frutos y menor daño en las FST fue Z. mays. En las trampas de arena fina, R. capitata tuvo la menor remoción de semillas. Conclusiones: Notocitellus adocetus es considerada depredadora de semillas, no obstante, por su comportamiento y las características de los frutos de C. alata y R. capitata, este roedor podría dejar disponibles las semillas a dispersores secundarios de semillas.

RESUMO

Seed dispersal is widely considered an important mechanism for the conservation of plant diversity. In tropical regions, over 80% of woody plant species are dispersed by vertebrates, often through the consumption of fruits. Our understanding of what drives interactions between vertebrates and fruits is limited. Through a systematic literature search, we compiled a database of fruit and seed traits and vertebrate-fruit interactions for tree and vertebrate species occurring in the Guianas, with the aim of facilitating research into seed dispersal and seed predation of tree species in the Guianas. The database was compiled by extracting data from 264 published sources. It consists of 21,082 records, of which 19,039 records contain information about 19 different fruit and seed traits belonging to 1622 different tree species. The other 2043 records contain information on vertebrate-fruit interactions between 161 vertebrate species and 464 tree species. Our analyses showed a taxonomic bias, particularly in the interaction data, toward large-bodied vertebrates, with most interactions recorded for the bearded saki (Chiropotes chiropotes), followed by the lowland tapir (Tapirus terrestris). For plants we found an overrepresentation of the Sapotaceae and Moraceae families and an underrepresentation of the Rubiaceae, Myrtaceae, and Lauraceae families in the interactions. There are no copyright restrictions on the data set; please cite this publication when using these data.

Assuntos

RESUMO

Exotic species are one of the main threats to biodiversity, leading to alterations in the structure and functioning of natural ecosystems. However, they can sometimes also provide ecological services, such as seed dispersal. Therefore, we assessed the ecological impacts of exotic species on native dispersal systems and the mechanisms underlying the disruption of mutualistic plant-disperser interactions. Exotic species negatively affect dispersal mutualisms by (i) altering dispersal behavior and visitation rates of native dispersers, (ii) predating native dispersers, (iii) transmitting forest pathogens, and (iv) predating seeds. Conversely, positive impacts include the dispersal of native plants, forest regeneration, and native habitat restoration via (i) increasing the visitation rates of frugivorous birds, (ii) facilitating the colonization and establishment of native forest trees, (iii) enhancing forest species seedling survival, and (iv) facilitating seed rain and seedling recruitment of early and late successional native plants. The reviewed studies provide similar results in some cases and opposite results in others, even within the same taxa. In almost all cases, exotic species cause negative impacts, although sometimes they are necessary to ensure native species' persistence. Therefore, exotic species management requires a comprehensive understanding of their ecological roles, since the resulting effects rely on the complexity of native-exotic species interactions.

RESUMO

Primates are great fruit consumers and disperse intact seeds from most of the plants they consume, but effective seed dispersal depends, amongst other factors, on handling behavior. Likewise, the treatment in gut and mouth may alter seed fate. Overall, frugivore and folivore-frugivore primates are recognized to provide beneficial gut treatment for Neotropical plant species, but this effect might be overlooked at species-specific levels. In this study, we assessed the role of the southern muriqui (Brachyteles arachnoides), an endangered and endemic primate living in restricted fragments of the Brazilian Atlantic Forest, on potential quality of seed dispersal of native plants. Our main goals were to understand the effect of seed ingestion by this large-bodied atelid on germination of defecated seeds and in seed recovery by offering wild fruits of native species to captive individuals. We found that seven out of nine plant species were defecated intact and were able to germinate. Of those seven, one species showed enhanced and another showed decreased germination potential after defecation, while three species germinated faster after being defecated. The remaining species showed no differences from control seeds. The two non-germinating species were heavily predated, and average seed recovery was lower than expected, suggesting high levels of seed predation. The largest species offered (Inga vulpina) showed the highest dispersal potential. Our data support an overall neutral or potentially positive role of southern muriquis in seed dispersal quality for seven out of nine Atlantic Forest plant species, highlighting these primates' potential to produce an effective seed rain.

Assuntos

RESUMO

The top-down and indirect effects of insects on plant communities depend on patterns of host use, which are often poorly documented, particularly in species-rich tropical forests. At Barro Colorado Island, Panama, we compiled the first food web quantifying trophic interactions between the majority of co-occurring woody plant species and their internally feeding insect seed predators. Our study is based on more than 200 000 fruits representing 478 plant species, associated with 369 insect species. Insect host-specificity was remarkably high: only 20% of seed predator species were associated with more than one plant species, while each tree species experienced seed predation from a median of two insect species. Phylogeny, but not plant traits, explained patterns of seed predator attack. These data suggest that seed predators are unlikely to mediate indirect interactions such as apparent competition between plant species, but are consistent with their proposed contribution to maintaining plant diversity via the Janzen-Connell mechanism.

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RESUMO

BACKGROUND: Consumers should show strong spatial preferences when foraging in environments where food availability is highly heterogeneous and predictable. Postdispersal granivores face this scenario in most arid areas, where soil seed bank abundance and composition associates persistently with vegetation structure at small scales (decimetres to metres). Those environmental features should be exploited as useful pre-harvest information, at least to avoid patches predicted to be poor. However, we did not find the expected spatial association in the algarrobal of the central Monte desert by observing foraging seed-eating birds, a field technique influenced by how much they exploit visited patches. In this work we tested if the first stage of foraging by granivorous birds (patch visit, encounter or exploration) is positively associated with environmental indicators of patch quality by recording the removal of single seeds from 300 scattered experimental devices during seasonal trials. Spatial selectivity was analysed by comparing the structural characteristics of used vs. available microhabitats, and evaluated against bottom-up and top-down hypotheses based on our previous knowledge on local seed bank abundance, composition and dynamics. Their foraging activity was also explored for spatial autocorrelation and environmental correlates at bigger scales. RESULTS: Postdispersal granivorous birds were less selective in their use of foraging space than expected if microhabitat appearance were providing them relevant information to guide their search for profitable foraging patches. No microhabitat type, as defined by their vegetation structure and soil cover, remained safe from bird exploration. Analyses at bigger temporal and spatial scales proved more important to describe heterogeneity in seed removal. CONCLUSIONS: Closeness to tall trees, probably related to bird territoriality and reproduction or to their perception of predation risk, seemed to determine a first level of habitat selection, constraining explorable space. Then, microhabitat openness (rather than seed abundance) exerted some positive influence on which patches were more frequently visited among those accessible. Selective patterns by birds at small scales were closer to our predictions of a top-down spatial effect, with seed consumption creating or strengthening (and not responding to) the spatial pattern and dynamics of the seed bank.

Assuntos

RESUMO

In this study I tested the effect of Syagrus loefgrenii nut size and number on the intensity of removal by rodents across seasons. Trials were performed in which piles of either small or large endocarps (1, 3, 6, 12, and 25) were subjected to removal by rodents in the Cerrado (Brazilian savanna). Despite of variations in the intensity of removal, always this process decrease conform endocarp number. Also, mean proportion of endocarp removal was unrelated to year period, initial number, and size of endocarps. Hence, endocarp removal was consistently negative density-dependent. As, in principle, the observed patterns of nut removal point out similar survival chances for both nut sizes, the pervasive negative density-dependent response emerges as a strategy in S. loefgrenii to swamp rodents all year round irrespective of seed size.(AU)

Avaliei o efeito do tamanho e densidade de endocarpos de Syagrus loefgrenii sobre a intensidade de remoção por roedores conforme a estação do ano. Para tanto, desenvolvi experimentos no Cerrado em que pilhas de endocarpos pequenos ou grandes (1, 3, 6, 12 e 25), foram sujeitos à remoção por roedores. Apesar da intensidade de remoção variar ao longo do ano, sempre esse processo teve relação inversa com o número de endocarpos. Além disso, em qualquer estação do ano, as proporções médias de endocarpos removidos sempre foram menores nas pilhas maiores, independentemente do tamanho dos endocarpos. Portanto, o processo de remoção de endocarpos foi negativamente dependente da densidade. Como, em princípio, os padrões de remoção em S. loefgrenii sugerem chances similares de sobrevivência tanto para endocarpos grandes, quanto pequenos, a preponderância de resposta negativamente dependente da densidade emerge como uma estratégia de S. loefgrenii voltada a saciar roedores em qualquer período do ano independentemente do tamanho de suas sementes.(AU)

Assuntos

RESUMO

Abstract In this study I tested the effect of Syagrus loefgrenii nut size and number on the intensity of removal by rodents across seasons. Trials were performed in which piles of either small or large endocarps (1, 3, 6, 12, and 25) were subjected to removal by rodents in the Cerrado (Brazilian savanna). Despite of variations in the intensity of removal, always this process decrease conform endocarp number. Also, mean proportion of endocarp removal was unrelated to year period, initial number, and size of endocarps. Hence, endocarp removal was consistently negative density-dependent. As, in principle, the observed patterns of nut removal point out similar survival chances for both nut sizes, the pervasive negative density-dependent response emerges as a strategy in S. loefgrenii to swamp rodents all year round irrespective of seed size.

Resumo Avaliei o efeito do tamanho e densidade de endocarpos de Syagrus loefgrenii sobre a intensidade de remoção por roedores conforme a estação do ano. Para tanto, desenvolvi experimentos no Cerrado em que pilhas de endocarpos pequenos ou grandes (1, 3, 6, 12 e 25), foram sujeitos à remoção por roedores. Apesar da intensidade de remoção variar ao longo do ano, sempre esse processo teve relação inversa com o número de endocarpos. Além disso, em qualquer estação do ano, as proporções médias de endocarpos removidos sempre foram menores nas pilhas maiores, independentemente do tamanho dos endocarpos. Portanto, o processo de remoção de endocarpos foi negativamente dependente da densidade. Como, em princípio, os padrões de remoção em S. loefgrenii sugerem chances similares de sobrevivência tanto para endocarpos grandes, quanto pequenos, a preponderância de resposta negativamente dependente da densidade emerge como uma estratégia de S. loefgrenii voltada a saciar roedores em qualquer período do ano independentemente do tamanho de suas sementes.

Assuntos

RESUMO

Poiretia latifolia Vogel (Fabaceae), is a promising plant native of the altitude field ecosystem, inserted in the Atlantic Forest biome in the southern region of Brazil. It is valued for its monoterpene-rich essential oil and exhibits great potential in the pharmaceutical and cosmetic industries. This work aimed at studying the entomofauna associated with P. latifolia, as well as assessing the effects of these insects on this plant's reproductive success. The entomofauna were surveyed between December 2015 and January 2016, in two natural P. latifolia stands found in the Capão Alto and São José do Cerrito municipalities of Santa Catarina State. The entomofauna was monitored for 42 hours in each stand, being marked five plants in each stand that were accompanied hourly, from 9:00 am to 4:00 p.m. The effects of the climatic variables on the insect were analyzed using the Pearson correlation coefficient. To determine the damage due to herbivory, ten P. latifolia plants were marked at each stand, from which the flowers and seeds were collected and the insect damage estimated. The predominant insects in both stands were identified as belonging to the orders Coleoptera, Diptera and Hymenoptera. The Dipteran insects revealed a significant positive correlation with the mean daily temperature (r = 0.84, p = 0.03442) in the Capão Alto stand. Damages caused by insects to the P. latifolia flowers and seeds was higher in São José do Cerrito, corresponding to 54% and 88% of damaged structures, respectively. Environmental changes precipitated by the intense agricultural usage in the vicinity of the P. latifolia stands may have been the reason for these differences.(AU)

Poiretia latifolia Vogel (Fabaceae) é uma promissora planta nativa do ecossistema campos de altitude, inserido no bioma Mata Atlântica na região Sul do Brasil. Seu valor se encontra na composição do seu óleo essencial que é rico em monoterpenos com potencial de uso farmacêutico e cosmético. O objetivo deste trabalho foi estudar a entomofauna associada à P. latifolia, bem como avaliar a influência dos insetos no sucesso reprodutivo da planta. O levantamento da entomofauna foi realizado no período de dezembro de 2015 a janeiro de 2016, em dois povoamentos naturais de P. latifolia localizados nos municípios de Capão Alto e São José do Cerrito, Santa Catarina. A entomofauna foi monitorada por 42 horas em cada local, sendo marcadas cinco plantas em cada área que foram acompanhadas de hora em hora, das 9:00 às 16:00. A influência das variáveis meteorológicas sobre a presença de insetos foi analisada pelo coeficiente de correlação de Pearson. Para determinar os danos por herbivoria, foram marcadas dez plantas de P. latifolia em cada área, das quais foram coletadas flores e sementes para avaliar o dano por insetos. Insetos pertencentes às ordens Coleoptera, Diptera e Hymenoptera foram predominantes em ambos os povoamentos. A presença de insetos da ordem Diptera demonstrou correlação positiva significativa com a temperatura média diária (r = 0,84; p = 0,03442) no povoamento de Capão Alto. Os danos causados por insetos às flores e sementes de P. latifolia foram superiores em São José do Cerrito, correspondendo por 54% e 88% das estruturas danificadas, respectivamente. Alterações ambientais causadas pela intensidade de uso agrícola próximo aos povoamentos de P. latifolia podem ter causado estas diferenças.(AU)

Assuntos

RESUMO

Abstract In this study I tested the effect of Syagrus loefgrenii nut size and number on the intensity of removal by rodents across seasons. Trials were performed in which piles of either small or large endocarps (1, 3, 6, 12, and 25) were subjected to removal by rodents in the Cerrado (Brazilian savanna). Despite of variations in the intensity of removal, always this process decrease conform endocarp number. Also, mean proportion of endocarp removal was unrelated to year period, initial number, and size of endocarps. Hence, endocarp removal was consistently negative density-dependent. As, in principle, the observed patterns of nut removal point out similar survival chances for both nut sizes, the pervasive negative density-dependent response emerges as a strategy in S. loefgrenii to swamp rodents all year round irrespective of seed size.

Resumo Avaliei o efeito do tamanho e densidade de endocarpos de Syagrus loefgrenii sobre a intensidade de remoção por roedores conforme a estação do ano. Para tanto, desenvolvi experimentos no Cerrado em que pilhas de endocarpos pequenos ou grandes (1, 3, 6, 12 e 25), foram sujeitos à remoção por roedores. Apesar da intensidade de remoção variar ao longo do ano, sempre esse processo teve relação inversa com o número de endocarpos. Além disso, em qualquer estação do ano, as proporções médias de endocarpos removidos sempre foram menores nas pilhas maiores, independentemente do tamanho dos endocarpos. Portanto, o processo de remoção de endocarpos foi negativamente dependente da densidade. Como, em princípio, os padrões de remoção em S. loefgrenii sugerem chances similares de sobrevivência tanto para endocarpos grandes, quanto pequenos, a preponderância de resposta negativamente dependente da densidade emerge como uma estratégia de S. loefgrenii voltada a saciar roedores em qualquer período do ano independentemente do tamanho de suas sementes.

RESUMO

Abstract In this study I tested the effect of Syagrus loefgrenii nut size and number on the intensity of removal by rodents across seasons. Trials were performed in which piles of either small or large endocarps (1, 3, 6, 12, and 25) were subjected to removal by rodents in the Cerrado (Brazilian savanna). Despite of variations in the intensity of removal, always this process decrease conform endocarp number. Also, mean proportion of endocarp removal was unrelated to year period, initial number, and size of endocarps. Hence, endocarp removal was consistently negative density-dependent. As, in principle, the observed patterns of nut removal point out similar survival chances for both nut sizes, the pervasive negative density-dependent response emerges as a strategy in S. loefgrenii to swamp rodents all year round irrespective of seed size.

Resumo Avaliei o efeito do tamanho e densidade de endocarpos de Syagrus loefgrenii sobre a intensidade de remoção por roedores conforme a estação do ano. Para tanto, desenvolvi experimentos no Cerrado em que pilhas de endocarpos pequenos ou grandes (1, 3, 6, 12 e 25), foram sujeitos à remoção por roedores. Apesar da intensidade de remoção variar ao longo do ano, sempre esse processo teve relação inversa com o número de endocarpos. Além disso, em qualquer estação do ano, as proporções médias de endocarpos removidos sempre foram menores nas pilhas maiores, independentemente do tamanho dos endocarpos. Portanto, o processo de remoção de endocarpos foi negativamente dependente da densidade. Como, em princípio, os padrões de remoção em S. loefgrenii sugerem chances similares de sobrevivência tanto para endocarpos grandes, quanto pequenos, a preponderância de resposta negativamente dependente da densidade emerge como uma estratégia de S. loefgrenii voltada a saciar roedores em qualquer período do ano independentemente do tamanho de suas sementes.

RESUMO

Poiretia latifolia Vogel (Fabaceae), is a promising plant native of the altitude field ecosystem, inserted in the Atlantic Forest biome in the southern region of Brazil. It is valued for its monoterpene-rich essential oil and exhibits great potential in the pharmaceutical and cosmetic industries. This work aimed at studying the entomofauna associated with P. latifolia, as well as assessing the effects of these insects on this plant's reproductive success. The entomofauna were surveyed between December 2015 and January 2016, in two natural P. latifolia stands found in the Capão Alto and São José do Cerrito municipalities of Santa Catarina State. The entomofauna was monitored for 42 hours in each stand, being marked five plants in each stand that were accompanied hourly, from 9:00 am to 4:00 p.m. The effects of the climatic variables on the insect were analyzed using the Pearson correlation coefficient. To determine the damage due to herbivory, ten P. latifolia plants were marked at each stand, from which the flowers and seeds were collected and the insect damage estimated. The predominant insects in both stands were identified as belonging to the orders Coleoptera, Diptera and Hymenoptera. The Dipteran insects revealed a significant positive correlation with the mean daily temperature (r = 0.84, p = 0.03442) in the Capão Alto stand. Damages caused by insects to the P. latifolia flowers and seeds was higher in São José do Cerrito, corresponding to 54% and 88% of damaged structures, respectively. Environmental changes precipitated by the intense agricultural usage in the vicinity of the P. latifolia stands may have been the reason for these differences.

Poiretia latifolia Vogel (Fabaceae) é uma promissora planta nativa do ecossistema campos de altitude, inserido no bioma Mata Atlântica na região Sul do Brasil. Seu valor se encontra na composição do seu óleo essencial que é rico em monoterpenos com potencial de uso farmacêutico e cosmético. O objetivo deste trabalho foi estudar a entomofauna associada à P. latifolia, bem como avaliar a influência dos insetos no sucesso reprodutivo da planta. O levantamento da entomofauna foi realizado no período de dezembro de 2015 a janeiro de 2016, em dois povoamentos naturais de P. latifolia localizados nos municípios de Capão Alto e São José do Cerrito, Santa Catarina. A entomofauna foi monitorada por 42 horas em cada local, sendo marcadas cinco plantas em cada área que foram acompanhadas de hora em hora, das 9:00 às 16:00. A influência das variáveis meteorológicas sobre a presença de insetos foi analisada pelo coeficiente de correlação de Pearson. Para determinar os danos por herbivoria, foram marcadas dez plantas de P. latifolia em cada área, das quais foram coletadas flores e sementes para avaliar o dano por insetos. Insetos pertencentes às ordens Coleoptera, Diptera e Hymenoptera foram predominantes em ambos os povoamentos. A presença de insetos da ordem Diptera demonstrou correlação positiva significativa com a temperatura média diária (r = 0,84; p = 0,03442) no povoamento de Capão Alto. Os danos causados por insetos às flores e sementes de P. latifolia foram superiores em São José do Cerrito, correspondendo por 54% e 88% das estruturas danificadas, respectivamente. Alterações ambientais causadas pela intensidade de uso agrícola próximo aos povoamentos de P. latifolia podem ter causado estas diferenças.

Assuntos

RESUMO

Harsh environmental conditions in arid ecosystems limit seedling recruitment to microhabitats under nurse structures, such as shrubs or rocks. These structures, however, do not necessarily afford the same benefits to plants because nurse rocks provide only physical nurse effects, whereas nurse plants can provide both physical and biological nurse effects. Nevertheless, if the nurse plant is a conspecific, the benefits it provides may be outweighed by higher mortality due to negative density-dependent processes; consequently, negative density-dependence is expected to limit plants from acting as nurses to their own seedlings. The degree to which an abiotic nurse may be more beneficial than a conspecific one remains largely unexplored. Here, we examine the role and elucidate the mechanisms by which conspecific plants and rocks promote plant establishment in a hyper-arid desert. For 4 years, we examined establishment patterns of Myrcianthes coquimbensis (Myrtaceae), a threatened desert shrub that recruits solely in rock cavities and under conspecific shrubs. Specifically, we characterized these microhabitats, as well as open interspaces for comparison, and conducted germination, seed removal and seedling survival experiments. Our results revealed that conspecific shrubs and nurse rocks modified environmental conditions in similar ways; soil and air temperatures were lower, and water availability was higher than in open interspaces. We found no evidence on negative density-dependent recruitment: seed removal was lowest and seedling emergence highest under conspecific plants, moreover seedling survival probabilities were similar in rock cavities and under conspecific plants. We conclude that the probability of establishment was highest under conspecific plants than in other microhabitats, contrasting what is expected under the Janzen-Connell recruitment model. We suggest that for species living in stressful environments, population regulation may be a function of positive density-dependence and intraspecific facilitation may be a process that promotes the persistence of some plant species within a community.

RESUMO

Post-dispersal seed agents of mortality include pathogens, invertebrates, and vertebrates, which may shape tropical tree populations and communities. In this study I experimentally evaluated Dipteryx alata endocarp removal both in the interior and edge of Cerrado vegetation. Specifically, I simulated primary dispersion of endocarps by bats and evaluated secondary removal intensity according to habitat, season, and endocarp number. This study was developed in the Pombo Natural Municipal Park, a large Cerrado remnant with an area of 9,000 ha, located in the Western Brazil. In each of the two habitat types, I set down 45 points in which D. alata piles of 1, 3, 7, 15, and 40 endocarps were positioned. On average, endocarp removal in the interior was higher than in the edge, so that the intensity of removal varied from positive density-dependent (interior: rains), to negative density-dependent (edge: both seasons). Also, at both habitat types and seasons non removed endocarps were intensely attacked by fungus. Indeed, seed mortality by fungus infestation was positive density-dependent. The results indicate high propensity of endocarps to escape from removal in the edge, in principle, a defaunated area. As Dipteryx species strongly rely on caviomorph rodents for their dispersal, the scarcity of these vectors might reduce recruitment chances of D. alata in remnants of Cerrado. This imply in future changes in the vegetation structure from the edge to the interior towards low tree diversity.(AU)

A mortalidade pós-dispersão de sementes é causada por agentes como patógenos, invertebrados e vertebrados, os quais influenciam a dinâmica de populações e comunidades arbóreas. Nesse estudo, avaliei experimentalmente intensidade de remoção, por roedores, de endocarpos de Dipteryx alata na borda e interior da vegetação do Cerrado. Simulando a dispersão primária por morcegos, posicionei pilhas com diferentes números de endocarpos nos dois hábitats do cerrado e avaliei a remoção secundária, tanto na estação seca quanto na chuvosa. Os experimentos foram desenvolvidos no Parque Natural Municipal do Pombo, um grande remanescente com 9000 ha (Três Lagoas, MS, Brasil). Em cada um dos habitat defini 45 pontos nos quais pilhas com 1, 3, 7, 15 e 40 endocarpos foram posicionadas. A remoção de endocarpos foi significativamente maior no interior em relação à borda, tal que a intensidade de remoção variou de positivamente dependente da densidade (interior: chuvas), a negativamente dependente da densidade (borda: ambas as estações). Além disso, tanto na borda, quanto interior, bem como nas duas estações os endocarpos não removidos foram intensamente infestados por fungos. Consequentemente, a mortalidade causada por esses patógenos foi densidade dependente. Os resultados sugerem que os endocarpos de D. alata teriam maiores chances de escapar à remoção na borda, em princípio, depauperada em termos de roedores dispersores. A escassez desses vetores reduziria as chances de recrutamento de D. alata, favorecendo mudanças futuras na estrutura da vegetação, a partir da borda, em termos de menor diversidade arbórea.(AU)

RESUMO

Abstract Post-dispersal seed agents of mortality include pathogens, invertebrates, and vertebrates, which may shape tropical tree populations and communities. In this study I experimentally evaluated Dipteryx alata endocarp removal both in the interior and edge of Cerrado vegetation. Specifically, I simulated primary dispersion of endocarps by bats and evaluated secondary removal intensity according to habitat, season, and endocarp number. This study was developed in the Pombo Natural Municipal Park, a large Cerrado remnant with an area of 9,000 ha, located in the Western Brazil. In each of the two habitat types, I set down 45 points in which D. alata piles of 1, 3, 7, 15, and 40 endocarps were positioned. On average, endocarp removal in the interior was higher than in the edge, so that the intensity of removal varied from positive density-dependent (interior: rains), to negative density-dependent (edge: both seasons). Also, at both habitat types and seasons non removed endocarps were intensely attacked by fungus. Indeed, seed mortality by fungus infestation was positive density-dependent. The results indicate high propensity of endocarps to escape from removal in the edge, in principle, a defaunated area. As Dipteryx species strongly rely on caviomorph rodents for their dispersal, the scarcity of these vectors might reduce recruitment chances of D. alata in remnants of Cerrado. This imply in future changes in the vegetation structure from the edge to the interior towards low tree diversity.

Resumo A mortalidade pós-dispersão de sementes é causada por agentes como patógenos, invertebrados e vertebrados, os quais influenciam a dinâmica de populações e comunidades arbóreas. Nesse estudo, avaliei experimentalmente intensidade de remoção, por roedores, de endocarpos de Dipteryx alata na borda e interior da vegetação do Cerrado. Simulando a dispersão primária por morcegos, posicionei pilhas com diferentes números de endocarpos nos dois hábitats do cerrado e avaliei a remoção secundária, tanto na estação seca quanto na chuvosa. Os experimentos foram desenvolvidos no Parque Natural Municipal do Pombo, um grande remanescente com 9000 ha (Três Lagoas, MS, Brasil). Em cada um dos habitat defini 45 pontos nos quais pilhas com 1, 3, 7, 15 e 40 endocarpos foram posicionadas. A remoção de endocarpos foi significativamente maior no interior em relação à borda, tal que a intensidade de remoção variou de positivamente dependente da densidade (interior: chuvas), a negativamente dependente da densidade (borda: ambas as estações). Além disso, tanto na borda, quanto interior, bem como nas duas estações os endocarpos não removidos foram intensamente infestados por fungos. Consequentemente, a mortalidade causada por esses patógenos foi densidade dependente. Os resultados sugerem que os endocarpos de D. alata teriam maiores chances de escapar à remoção na borda, em princípio, depauperada em termos de roedores dispersores. A escassez desses vetores reduziria as chances de recrutamento de D. alata, favorecendo mudanças futuras na estrutura da vegetação, a partir da borda, em termos de menor diversidade arbórea.

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Background and Aims: Natural enemies are known to be important in regulating plant populations and contributing to species coexistence (Janzen-Connell effects). The strength of Janzen-Connell effects (both distance- and density-effects) varies across species, but the life history traits that may mediate such a variation are not well understood. This study examined Janzen-Connell effects across the life stages (seed through adult stages) of two sympatric palm species with distinct phenologies and shade tolerances, two traits that may mediate the strength and timing of Janzen-Connell effects. Methods: Populations of two common palm species, Attalea phalerata and Astrocaryum murumuru , were studied in Manu National Park, Peru. Seed predation experiments were conducted to assess Janzen-Connell effects at the seed stage. In the post-seed stages, spatial point pattern analyses of the distributions of individuals and biomass were used to infer the strength of distance- and density-effects. Key Results: Seed predation was both negative distance- and density-dependent consistent with the Janzen-Connell effects. However, only seedling recruitment for asynchronously fruiting Attalea phalerata was depressed near adults while recruitment remained high for synchronously fruiting Astrocaryum murumuru , consistent with weak distance-effects. Negative density-effects were strong in the early stages for shade-intolerant Attalea phalerata but weak or absent in shade-tolerant Astrocaryum murumuru. Conclusions: Distance- and density-effects varied among the life stages of the two palm species in a manner that corresponded to their contrasting phenology and shade tolerance. Generalizing such connections across many species would provide a route to understanding how trait-mediated Janzen-Connell effects scale up to whole communities of species.

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To determine seed removal influence on seed populations, we need to quantify pre- and post-dispersal seed removal. Several studies have quantified seed removal in temperate American deserts, but few studies have been performed in tropical deserts. These studies have only quantified pre- or post-dispersal seed removal, thus underestimating the influence of seed removal. We evaluated pre- and post-dispersal seed removal in the columnar cactus Stenocereus stellatus in a Mexican tropical desert. We performed selective exclosure experiments to estimate percentage of seeds removed by ants, birds and rodents during the pre- and post-dispersal phases. We also conducted field samplings to estimate abundance of the most common seed removers. Birds (10-28%) removed a higher percentage of seeds than ants (2%) and rodents (1-4%) during pre-dispersal seed removal. Melanerpes hypopolius was probably the main bird removing seeds from fruits. Ants (62-64%) removed a higher percentage of seeds than birds (34-38%) and rodents (16-30%) during post-dispersal seed removal. Pogonomyrmex barbatus was probably the main ant removing seeds from soil. Birds and ants are the main pre- and post-dispersal seed removers in S. stellatus, respectively. Further studies in other S. stellatus populations and plants with different life forms and fruit types will contribute to evaluate seed removal in tropical American deserts.

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Abstract In this study I tested the effect of Syagrus loefgrenii nut size and number on the intensity of removal by rodents across seasons. Trials were performed in which piles of either small or large endocarps (1, 3, 6, 12, and 25) were subjected to removal by rodents in the Cerrado (Brazilian savanna). Despite of variations in the intensity of removal, always this process decrease conform endocarp number. Also, mean proportion of endocarp removal was unrelated to year period, initial number, and size of endocarps. Hence, endocarp removal was consistently negative density-dependent. As, in principle, the observed patterns of nut removal point out similar survival chances for both nut sizes, the pervasive negative density-dependent response emerges as a strategy in S. loefgrenii to swamp rodents all year round irrespective of seed size.

Resumo Avaliei o efeito do tamanho e densidade de endocarpos de Syagrus loefgrenii sobre a intensidade de remoção por roedores conforme a estação do ano. Para tanto, desenvolvi experimentos no Cerrado em que pilhas de endocarpos pequenos ou grandes (1, 3, 6, 12 e 25), foram sujeitos à remoção por roedores. Apesar da intensidade de remoção variar ao longo do ano, sempre esse processo teve relação inversa com o número de endocarpos. Além disso, em qualquer estação do ano, as proporções médias de endocarpos removidos sempre foram menores nas pilhas maiores, independentemente do tamanho dos endocarpos. Portanto, o processo de remoção de endocarpos foi negativamente dependente da densidade. Como, em princípio, os padrões de remoção em S. loefgrenii sugerem chances similares de sobrevivência tanto para endocarpos grandes, quanto pequenos, a preponderância de resposta negativamente dependente da densidade emerge como uma estratégia de S. loefgrenii voltada a saciar roedores em qualquer período do ano independentemente do tamanho de suas sementes.

RESUMO

Abstract In this study I tested the effect of Syagrus loefgrenii nut size and number on the intensity of removal by rodents across seasons. Trials were performed in which piles of either small or large endocarps (1, 3, 6, 12, and 25) were subjected to removal by rodents in the Cerrado (Brazilian savanna). Despite of variations in the intensity of removal, always this process decrease conform endocarp number. Also, mean proportion of endocarp removal was unrelated to year period, initial number, and size of endocarps. Hence, endocarp removal was consistently negative density-dependent. As, in principle, the observed patterns of nut removal point out similar survival chances for both nut sizes, the pervasive negative density-dependent response emerges as a strategy in S. loefgrenii to swamp rodents all year round irrespective of seed size.

Resumo Avaliei o efeito do tamanho e densidade de endocarpos de Syagrus loefgrenii sobre a intensidade de remoção por roedores conforme a estação do ano. Para tanto, desenvolvi experimentos no Cerrado em que pilhas de endocarpos pequenos ou grandes (1, 3, 6, 12 e 25), foram sujeitos à remoção por roedores. Apesar da intensidade de remoção variar ao longo do ano, sempre esse processo teve relação inversa com o número de endocarpos. Além disso, em qualquer estação do ano, as proporções médias de endocarpos removidos sempre foram menores nas pilhas maiores, independentemente do tamanho dos endocarpos. Portanto, o processo de remoção de endocarpos foi negativamente dependente da densidade. Como, em princípio, os padrões de remoção em S. loefgrenii sugerem chances similares de sobrevivência tanto para endocarpos grandes, quanto pequenos, a preponderância de resposta negativamente dependente da densidade emerge como uma estratégia de S. loefgrenii voltada a saciar roedores em qualquer período do ano independentemente do tamanho de suas sementes.

RESUMO

In this study, I tested the effect of Syagrus loefgrenii nut number on the removal intensity by rodents across seasons. Also, I assessed both S. loefgrenii fruit production, and dispersion pattern to analyze the relationship between these parameters and nut removal. Trials were performed (autumn, winter, spring, and summer), in which endocarps were placed inside trays (5, 15, and 40 endocarps) in the Cerrado (Brazilian savanna). Syagrus loefgrenii exhibited clumped distribution, although its local density had no correlation with endocarp removal rate. Despite of variations, S. loefgrenii fruit production had no seasonal difference, although, high proportions of endocarps were year round removed. This mostly results from nearly complete endocarp loss in depots of 5 and 15, while the opposite occurred in those of 40. Hence, the intensity of removal consistently decreases with endocarp number, so that endocarp removal conformed to negative distance-dependence. As this palm exhibit clumped distribution and, in principle, fruit asynchronously, if, at least, a group of neighboring stems bore fruits simultaneously, an enhanced number of nuts might be available at a given site. Therefore, seeds within a dense S. loefgrenii fruit patch might experience high survival rates due to satiation of post dispersal seed predators.(AU)

Neste estudo, testei o efeito da densidade de endocarpos de Syagrus loefgrenii sobre a intensidade de remoçمo por roedores conforme a estaçمo do ano. Também, avaliei tanto a produçمo de frutos, quanto o padrمo de dispersمo dessa palmeira em relaçمo à intensidade de remoçمo de endocarpos. Executei experimentos no Cerrado (outono, inverno, primavera e verمo), nos quais acondicionei 5, 15 e 40 endocarpos em pratos plلsticos perfurados (pilhas experimentais). Syagrus loefgrenii exibiu distribuiçمo agrupada. Apesar disso, a densidade local dessa palmeira em nenhuma estaçمo esteve correlacionada com a taxa de remoçمo de endocarpos. Nمo ocorreram diferenças temporais significativas quanto aos nيveis de frutificaçمo, e, simultaneamente, documentei intensa remoçمo de endocarpos. Isso ocorreu, sobretudo, nas pilhas com 5 e 15 endocarpos, as quais, na maioria dos casos, perderam quase todos endocarpos. No entanto, as pilhas com 40 perderam poucos diلsporos. Nesse sentido a intensidade de remoçمo decresceu consistentemente conforme o nْmero de endocarpos, tal que esse processo mostrou ser negativamente dependente da distância. Syagrus loefgrenii exibiu padrمo agrupado de distribuiçمo, além de produzir frutos assincronicamente. Nesse sentido, caso um grupo de palmeiras vizinhas frutifique simultaneamente, uma grande quantidade de diلsporos estarل disponيvel em um dado local. Portanto, sementes em meio a uma densa carga de frutos podem ser favorecidas, uma vez que predadores pَs-dispersمo seriam saciados.(AU)

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