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Katrin Bohninggaese - One of the best experts on this subject based on the ideXlab platform.
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frugivore diversity increases Frugivory rates along a large elevational gradient
Oikos, 2016Co-Authors: Stefan W Ferger, Hamadi I Dulle, Matthias Schleuning, Katrin BohninggaeseAbstract:The effect of biodiversity on ecosystem functioning is increasingly well understood, but it has mainly been studied in small-scale experiments of plant-based ecosystem functions. In contrast, the relevance of biodiversity for animal-mediated ecosystem functions like seed dispersal still poses an important gap in ecological knowledge. In particular, it is little understood how avian diversity affects Frugivory rates, one of the most important parameters of seed dispersal rates, along large environmental gradients. Even less is known about the environmental context dependence of the frugivore–Frugivory relationship. We used artificial fruits to analyze experimentally how the abundance and richness of three avian frugivore guilds (with incrementally more stringent classifications of Frugivory) contributed to Frugivory rates across 13 different habitat types along an elevational gradient from 870 to 4550 m a.s.l. at Mt Kilimanjaro, Tanzania. We further investigated how environmental context, in terms of local vegetation structure and natural fruit availability, modified the relationship between frugivores and Frugivory rates. Our results demonstrate that the positive effect of avian diversity on Frugivory rates holds along a large elevational gradient. We found marked differences in Frugivory rates among the 13 habitat types, which were strongly related to the abundance and richness of obligate frugivorous birds. Vegetation structure had no significant effect on Frugivory rates. An intermediate abundance of natural fruits enhanced Frugivory rates, but this effect did not alter the positive frugivore–Frugivory relationship. These results emphasize the fundamental importance of obligate frugivore diversity for Frugivory rates and suggest that the positive effect of biodiversity on ecosystem functioning holds along large environmental gradients.
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frugivore diversity increases Frugivory rates along a large elevational gradient
Oikos, 2016Co-Authors: Stefan W Ferger, Hamadi I Dulle, Matthias Schleuning, Katrin BohninggaeseAbstract:The effect of biodiversity on ecosystem functioning is increasingly well understood, but it has mainly been studied in small-scale experiments of plant-based ecosystem functions. In contrast, the relevance of biodiversity for animal-mediated ecosystem functions like seed dispersal still poses an important gap in ecological knowledge. In particular, it is little understood how avian diversity affects Frugivory rates, one of the most important parameters of seed dispersal rates, along large environmental gradients. Even less is known about the environmental context dependence of the frugivore–Frugivory relationship. We used artificial fruits to analyze experimentally how the abundance and richness of three avian frugivore guilds (with incrementally more stringent classifications of Frugivory) contributed to Frugivory rates across 13 different habitat types along an elevational gradient from 870 to 4550 m a.s.l. at Mt Kilimanjaro, Tanzania. We further investigated how environmental context, in terms of local vegetation structure and natural fruit availability, modified the relationship between frugivores and Frugivory rates. Our results demonstrate that the positive effect of avian diversity on Frugivory rates holds along a large elevational gradient. We found marked differences in Frugivory rates among the 13 habitat types, which were strongly related to the abundance and richness of obligate frugivorous birds. Vegetation structure had no significant effect on Frugivory rates. An intermediate abundance of natural fruits enhanced Frugivory rates, but this effect did not alter the positive frugivore–Frugivory relationship. These results emphasize the fundamental importance of obligate frugivore diversity for Frugivory rates and suggest that the positive effect of biodiversity on ecosystem functioning holds along large environmental gradients.
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constant properties of plant frugivore networks despite fluctuations in fruit and bird communities in space and time
Ecology, 2013Co-Authors: Michaela Plein, Laura Langsfeld, Eike Lena Neuschulz, Christina Schultheis, Lili Ingmann, Till Topfer, Katrin Bohninggaese, Matthias SchleuningAbstract:Human-induced changes in anthropogenic landscapes are a predominant threat to biodiversity and have been documented to affect mutualistic interactions between plants and animals, such as avian seed dispersal. Interactions between fleshy-fruited plants and frugivorous birds are highly seasonal in temperate ecosystems. Nevertheless, combined effects of landscape modification and seasonal variation on plant-frugivore interactions have never been assessed from a network perspective. Here, we present the first study that simultaneously investigates effects of landscape modification and seasonal variation on plant-frugivore interactions and on functional and interaction diversity of plant-frugivore networks. We recorded visitation rates of 39 frugivorous bird species to 28 fruiting-plant species in Central Germany from early summer to late autumn in hedgerows within three landscape types arranged along a gradient of decreasing anthropogenic modification and increasing structural diversity (i.e., farmland, orchard, forest edge). We analyzed how species richness, abundance, and community composition, as well as functional and interaction diversity of fruiting plants and frugivorous birds changed with landscape type, fruit availability, and season. We found that visitation rates of frugivorous birds were lower in farmland, but only in summer. In autumn, visitation rates were similar in all landscape types and strongly increased with increasing local fruit availability. The functional diversity of fruits and frugivorous birds and their interaction diversity remained surprisingly constant in all landscape types. Due to seasonal changes in communities of fruiting plants and frugivorous birds, functional dispersion of fruiting plants was lower in autumn than in summer, whereas functional richness and dispersion of frugivorous birds was higher in autumn than in summer. Our results indicate that seasonal changes in fruit availability influence the abundance of frugivorous birds along gradients of structural diversity at the landscape scale. Although seasonal fluctuations influenced the functional diversity of avian frugivore communities, we found constant interaction diversity of plant-frugivore networks in space and time, probably due to the functional redundancy of frugivorous birds. These findings indicate a high robustness of avian Frugivory to moderate levels of human-induced landscape modification in temperate ecosystems and call for studies testing the generality of these findings for ultimate avian seed dispersal functions.
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plant frugivore networks are less specialized and more robust at forest farmland edges than in the interior of a tropical forest
Oikos, 2012Co-Authors: Sebastian Menke, Katrin Bohninggaese, Matthias SchleuningAbstract:Forest fragmentation and local disturbance are prevailing threats to tropical forest ecosystems and affect frugivore communities and animal seed dispersal in different ways. However, very little is known about the effects of anthropogenic forest edges and of local disturbance on the structure and robustness of plant–frugivore networks. We carried out focal tree observations to record the frugivore species feeding on eight canopy tree species in the forest interior and at forest–farmland edges in a little and a highly disturbed part of a Kenyan rain forest. For each frugivore species, we recorded its body mass and its forest dependence. We examined how forest edge and local disturbance affected the abundance, the richness and the composition of the frugivore community and tested whether forest edge and local disturbance affected plant–frugivore networks. Abundance and species richness of frugivores were higher at edges than in the forest interior. Forest visitors and small-bodied frugivores increased, while forest specialists decreased in abundance at forest edges. The changes in frugivore community composition resulted in plant–frugivore networks that were more connected, more nested and more robust against species extinctions at forest–farmland edges than in the forest interior. Network specialization was lower at forest edges than in the forest interior because at the edges plant specialization on frugivores was very low in small-fruited species. In contrast, small-fruited plants were more specialized than large-fruited plants in the forest interior. Our findings suggest that forest-visiting birds may stabilize seed-dispersal services for small-fruited plant species at rain forest margins, while seed-dispersal services for large-fruited plant species may be disrupted at forest edges due to the decrease of large-bodied frugviores. To assess the ultimate consequences of bird movements from farmland to forest edges for ecosystem functioning, future studies are required to investigate the seed-dispersal qualities provided by forest-visiting bird species in the tropics.
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frugivores and seed dispersal mechanisms and consequences for biodiversity of a key ecological interaction
Biology Letters, 2011Co-Authors: Pedro Jordano, Katrin Bohninggaese, Anna Traveset, Joanna E Lambert, Pierremichel Forget, Joseph S WrightAbstract:The 5th Symposium on Frugivores and Seed Dispersal, held in Montpellier (France), 13–18 June 2010, brought together more than 220 researchers exemplifying a wide diversity of approaches to the study of Frugivory and dispersal of seeds. Following Ted Fleming and Alejandro Estrada's initiative in 1985, this event was a celebration of the 25th anniversary of the first meeting in Veracruz, Mexico. Frugivory and seed dispersal are active research areas that have diversified in multiple directions since 1985 to include evolution (e.g. phylogenetic diversity and dispersal adaptations), physiology (e.g. sensory cues and digestion), landscape ecology (movement patterns), molecular ecology (e.g. gene flow, genetic diversity and structure), community ecology (e.g. mutualistic interaction networks) and conservation biology (effects of hunting, fragmentation, invasion and extinction), among others. This meeting provided an opportunity to assess conceptual and methodological progress, to present ever more sophisticated insights into Frugivory in animals and dispersal patterns in plants, and to report the advances made in examining the mechanisms and consequences of seed dispersal for plants and frugivores.
Nina Farwig - One of the best experts on this subject based on the ideXlab platform.
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moving from Frugivory to seed dispersal incorporating the functional outcomes of interactions in plant frugivore networks
Journal of Animal Ecology, 2018Co-Authors: Benno I Simmons, Jorg Albrecht, Nina Farwig, Pedro Jordano, Daniel Garcia, William J Sutherland, Lynn V Dicks, Juan P GonzalezvaroAbstract:1. There is growing interest in understanding the functional outcomes of species interactions in ecological networks. For many mutualistic networks, including pollination and seed dispersal networks, interactions are generally sampled by recording animal foraging visits to plants. However, these visits may not reflect actual pollination or seed dispersal events, despite these typically being the ecological processes of interest. 2. Frugivorous animals can act as seed dispersers, by swallowing entire fruits and dispersing their seeds, or as pulp peckers or seed predators, by pecking fruits to consume pieces of pulp or seeds. These processes have opposing consequences for plant reproductive success. Therefore, equating visitation with seed dispersal could lead to biased inferences about the ecology, evolution and conservation of seed dispersal mutualisms. 3. Here, we use natural history information on the functional outcomes of pairwise bird–plant interactions to examine changes in the structure of seven European plant–frugivore visitation networks after non‐mutualistic interactions (pulp pecking and seed predation) have been removed. Following existing knowledge of the contrasting structures of mutualistic and antagonistic networks, we hypothesized a number of changes following interaction removal, such as increased nestedness and lower specialization. 4. Non‐mutualistic interactions with pulp peckers and seed predators occurred in all seven networks, accounting for 21%–48% of all interactions and 6%–24% of total interaction frequency. When non‐mutualistic interactions were removed, there were significant increases in network‐level metrics such as connectance and nestedness, while robustness decreased. These changes were generally small, homogenous and driven by decreases in network size. Conversely, changes in species‐level metrics were more variable and sometimes large, with significant decreases in plant degree, interaction frequency, specialization and resilience to animal extinctions and significant increases in frugivore species strength. 5. Visitation data can overestimate the actual frequency of seed dispersal services in plant–frugivore networks. We show here that incorporating natural history information on the functions of species interactions can bring us closer to understanding the processes and functions operating in ecological communities. Our categorical approach lays the foundation for future work quantifying functional interaction outcomes along a mutualism–antagonism continuum, as documented in other frugivore faunas.
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trait associated loss of frugivores in fragmented forest does not affect seed removal rates
Journal of Ecology, 2017Co-Authors: Nina Farwig, Dana G. Schabo, Jorg AlbrechtAbstract:Summary Seed dispersal by frugivorous animals forms the basis for regeneration of numerous plant species. Habitat fragmentation has been found to be one major factor perturbing frugivore communities and dependent plant species. Yet, community-wide consequences of fragmentation for both frugivore and plant communities are still hardly understood. Here, we studied the effects of habitat fragmentation on the seed removal by frugivorous birds and mammals from nine fleshy-fruited plant species in Bialowieza Forest (Eastern Poland). This last relict of old-growth lowland forest in Europe poses an exceptional reference site for studying the impact of habitat fragmentation on seed dispersal processes in temperate forest ecosystems. In particular, (i) we tested for associations between forest fragmentation and response traits of frugivores, that is forest specialization and body mass; (ii) we studied the relationship between frugivore response and effect traits, that is centrality (number of consumed plant species) and interaction type (mutualistic vs. antagonistic); and (iii) we assessed the feedback of fragmentation-induced changes on plant–frugivore interactions and seed removal rates. We found that fragmentation led to shifts in the frugivore community, associated with the response traits forest specialization and body mass, with fewer forest specialists and large-bodied frugivores in fragmented than in continuous forests. However, forest generalists and small-bodied frugivores were more central in the plant–frugivore associations than forest specialists and large-bodied frugivores. Therefore, the loss of vulnerable species did not result in reduced seed removal rates in fragmented compared with continuous forest. Synthesis. These results indicate that seed removal may be relatively robust in spite of shifts in the frugivore community in forest fragments. The correlation between response and effect traits of frugivores highlights the importance of forest generalists and small-bodied frugivores for maintaining dispersal processes in fragmented forests in temperate regions. Yet, future studies should aim at quantifying the consequences of seed disperser loss on other aspects of dispersal, such as long-distance dispersal, spatial patterns of seed deposition, seed germination and plant regeneration.
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high conservation value of forest fragments for plant and frugivore communities in a fragmented forest landscape in south africa
Biotropica, 2014Co-Authors: Dana G Berens, Lackson Chama, Jorg Albrecht, Nina FarwigAbstract:Fragmentation is a major threat factor for plant–frugivore communities in tropical and subtropical forests. Resulting changes in the distribution of traits within these communities, e.g., a loss in large-bodied frugivores, may lead to strong changes in plant–frugivore interactions in fragmented forests. Yet, we still lack a thorough understanding of the interplay between forest fragmentation, the trait-composition of communities and resulting plant–frugivore interactions on a community-scale. In a fragmented South African landscape comprising different forest categories—i.e., continuous natural forest, forest fragments surrounded by natural grassland, and forest fragments surrounded by sugarcane—we investigated the relationship between communities of fruiting plants and their frugivore visitors in response to forest fragmentation, as well as the interactive effects of forest fragmentation and fruit size of the plants on the number of frugivore visitors and their body size. Neither the fruit size of plant nor the body mass of frugivore communities differed between natural forest sites and forest fragments. Moreover, in-depth analyses of frugivore assemblages visiting plant species revealed no effect of forest category on the number of frugivore visits or their mean body mass. The number of visits and body mass of frugivores were merely determined by the crop and fruit size of the focal plant species. Overall, our results suggest that Frugivory of plant species with differently sized fruits was not reduced in forest fragments. Thus, fragments with high fruit availability may be key elements maintaining the functional connectivity of a heterogeneous forest landscape.
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Guild-specific shifts in visitation rates of frugivores with habitat loss and plant invasion
Oikos, 2013Co-Authors: Ingo Grass, Dana G Berens, Nina FarwigAbstract:Habitat loss and plant invasions are two major drivers of global change in subtropical and tropical ecosystems. Both lead to a loss of biodiversity and alter species interactions, which may imperil vital ecosystem processes such as seed dispersal by frugivores. Reponses of frugivores to disturbance are often linked to their specialization on certain habitats or resources. Yet, it is poorly understood how habitat loss and plant invasion structure interactions between plants and different habitat or feeding guilds. Here we investigated whether visitation rates of frugivores change guild-specifically with increasing habitat loss and invasion level in a heterogeneous subtropical landscape. In 756 h of observations, we recorded 1446 plant–frugivore interactions among 18 plant species and 42 avian frugivore species. Visitation rates of forest specialists decreased with increasing habitat loss, but not with changes in invasion level. In contrast forest generalists and forest visitors were unaffected by either driver. Similarly, obligate frugivores that overall showed a generalized fruit choice were unaffected by habitat loss and changes in invasion level. Contrary, visitation rates of specialized partial and opportunistic frugivores decreased with higher invasion level. Importantly, the negative effect of plant invasion on partial frugivores was more pronounced as habitat loss in the same study site increased, indicating a synergistic effect of the two drivers. The implications of our study are twofold: first, frugivores respond guild-specifically to habitat loss and plant invasion. Thereby forest dependency is mainly related to habitat loss, and degree of Frugivory mainly related to plant invasion. Forest generalists and obligate frugivores in turn may play a key-role for forest regeneration in disturbed forest landscapes. Second, particularly frugivores with a specialized fruit choice may be threatened by synergistic effects between habitat loss and plant invasion.
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habitat characteristics of forest fragments determine specialisation of plant frugivore networks in a mosaic forest landscape
PLOS ONE, 2013Co-Authors: Lackson Chama, Dana G Berens, Colleen T. Downs, Nina FarwigAbstract:Plant-frugivore networks play a key role in the regeneration of sub-tropical forest ecosystems. However, information about the impact of habitat characteristics on plant-frugivore networks in fragmented forests is scarce. We investigated the importance of fruit abundance, fruiting plant species richness and canopy cover within habitat fragments for the structure and robustness of plant-frugivore networks in a mosaic forest landscape of South Africa. In total, 53 avian species were involved in fruit removal of 31 fleshy-fruiting plant species. Species specialisation was always higher for plants than for frugivores. Both species and network-level specialisation increased with increasing fruit abundance and decreased with increasing fruiting plant species richness and canopy cover within fragments. Interaction diversity was unaffected by fruit abundance and canopy cover, but increased slightly with increasing fruiting plant species richness. These findings suggest that especially the availability of resources is an important determinant of the structure of plant-frugivore networks in a fragmented forest landscape.
Matthias Schleuning - One of the best experts on this subject based on the ideXlab platform.
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frugivore diversity increases Frugivory rates along a large elevational gradient
Oikos, 2016Co-Authors: Stefan W Ferger, Hamadi I Dulle, Matthias Schleuning, Katrin BohninggaeseAbstract:The effect of biodiversity on ecosystem functioning is increasingly well understood, but it has mainly been studied in small-scale experiments of plant-based ecosystem functions. In contrast, the relevance of biodiversity for animal-mediated ecosystem functions like seed dispersal still poses an important gap in ecological knowledge. In particular, it is little understood how avian diversity affects Frugivory rates, one of the most important parameters of seed dispersal rates, along large environmental gradients. Even less is known about the environmental context dependence of the frugivore–Frugivory relationship. We used artificial fruits to analyze experimentally how the abundance and richness of three avian frugivore guilds (with incrementally more stringent classifications of Frugivory) contributed to Frugivory rates across 13 different habitat types along an elevational gradient from 870 to 4550 m a.s.l. at Mt Kilimanjaro, Tanzania. We further investigated how environmental context, in terms of local vegetation structure and natural fruit availability, modified the relationship between frugivores and Frugivory rates. Our results demonstrate that the positive effect of avian diversity on Frugivory rates holds along a large elevational gradient. We found marked differences in Frugivory rates among the 13 habitat types, which were strongly related to the abundance and richness of obligate frugivorous birds. Vegetation structure had no significant effect on Frugivory rates. An intermediate abundance of natural fruits enhanced Frugivory rates, but this effect did not alter the positive frugivore–Frugivory relationship. These results emphasize the fundamental importance of obligate frugivore diversity for Frugivory rates and suggest that the positive effect of biodiversity on ecosystem functioning holds along large environmental gradients.
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frugivore diversity increases Frugivory rates along a large elevational gradient
Oikos, 2016Co-Authors: Stefan W Ferger, Hamadi I Dulle, Matthias Schleuning, Katrin BohninggaeseAbstract:The effect of biodiversity on ecosystem functioning is increasingly well understood, but it has mainly been studied in small-scale experiments of plant-based ecosystem functions. In contrast, the relevance of biodiversity for animal-mediated ecosystem functions like seed dispersal still poses an important gap in ecological knowledge. In particular, it is little understood how avian diversity affects Frugivory rates, one of the most important parameters of seed dispersal rates, along large environmental gradients. Even less is known about the environmental context dependence of the frugivore–Frugivory relationship. We used artificial fruits to analyze experimentally how the abundance and richness of three avian frugivore guilds (with incrementally more stringent classifications of Frugivory) contributed to Frugivory rates across 13 different habitat types along an elevational gradient from 870 to 4550 m a.s.l. at Mt Kilimanjaro, Tanzania. We further investigated how environmental context, in terms of local vegetation structure and natural fruit availability, modified the relationship between frugivores and Frugivory rates. Our results demonstrate that the positive effect of avian diversity on Frugivory rates holds along a large elevational gradient. We found marked differences in Frugivory rates among the 13 habitat types, which were strongly related to the abundance and richness of obligate frugivorous birds. Vegetation structure had no significant effect on Frugivory rates. An intermediate abundance of natural fruits enhanced Frugivory rates, but this effect did not alter the positive frugivore–Frugivory relationship. These results emphasize the fundamental importance of obligate frugivore diversity for Frugivory rates and suggest that the positive effect of biodiversity on ecosystem functioning holds along large environmental gradients.
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constant properties of plant frugivore networks despite fluctuations in fruit and bird communities in space and time
Ecology, 2013Co-Authors: Michaela Plein, Laura Langsfeld, Eike Lena Neuschulz, Christina Schultheis, Lili Ingmann, Till Topfer, Katrin Bohninggaese, Matthias SchleuningAbstract:Human-induced changes in anthropogenic landscapes are a predominant threat to biodiversity and have been documented to affect mutualistic interactions between plants and animals, such as avian seed dispersal. Interactions between fleshy-fruited plants and frugivorous birds are highly seasonal in temperate ecosystems. Nevertheless, combined effects of landscape modification and seasonal variation on plant-frugivore interactions have never been assessed from a network perspective. Here, we present the first study that simultaneously investigates effects of landscape modification and seasonal variation on plant-frugivore interactions and on functional and interaction diversity of plant-frugivore networks. We recorded visitation rates of 39 frugivorous bird species to 28 fruiting-plant species in Central Germany from early summer to late autumn in hedgerows within three landscape types arranged along a gradient of decreasing anthropogenic modification and increasing structural diversity (i.e., farmland, orchard, forest edge). We analyzed how species richness, abundance, and community composition, as well as functional and interaction diversity of fruiting plants and frugivorous birds changed with landscape type, fruit availability, and season. We found that visitation rates of frugivorous birds were lower in farmland, but only in summer. In autumn, visitation rates were similar in all landscape types and strongly increased with increasing local fruit availability. The functional diversity of fruits and frugivorous birds and their interaction diversity remained surprisingly constant in all landscape types. Due to seasonal changes in communities of fruiting plants and frugivorous birds, functional dispersion of fruiting plants was lower in autumn than in summer, whereas functional richness and dispersion of frugivorous birds was higher in autumn than in summer. Our results indicate that seasonal changes in fruit availability influence the abundance of frugivorous birds along gradients of structural diversity at the landscape scale. Although seasonal fluctuations influenced the functional diversity of avian frugivore communities, we found constant interaction diversity of plant-frugivore networks in space and time, probably due to the functional redundancy of frugivorous birds. These findings indicate a high robustness of avian Frugivory to moderate levels of human-induced landscape modification in temperate ecosystems and call for studies testing the generality of these findings for ultimate avian seed dispersal functions.
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plant frugivore networks are less specialized and more robust at forest farmland edges than in the interior of a tropical forest
Oikos, 2012Co-Authors: Sebastian Menke, Katrin Bohninggaese, Matthias SchleuningAbstract:Forest fragmentation and local disturbance are prevailing threats to tropical forest ecosystems and affect frugivore communities and animal seed dispersal in different ways. However, very little is known about the effects of anthropogenic forest edges and of local disturbance on the structure and robustness of plant–frugivore networks. We carried out focal tree observations to record the frugivore species feeding on eight canopy tree species in the forest interior and at forest–farmland edges in a little and a highly disturbed part of a Kenyan rain forest. For each frugivore species, we recorded its body mass and its forest dependence. We examined how forest edge and local disturbance affected the abundance, the richness and the composition of the frugivore community and tested whether forest edge and local disturbance affected plant–frugivore networks. Abundance and species richness of frugivores were higher at edges than in the forest interior. Forest visitors and small-bodied frugivores increased, while forest specialists decreased in abundance at forest edges. The changes in frugivore community composition resulted in plant–frugivore networks that were more connected, more nested and more robust against species extinctions at forest–farmland edges than in the forest interior. Network specialization was lower at forest edges than in the forest interior because at the edges plant specialization on frugivores was very low in small-fruited species. In contrast, small-fruited plants were more specialized than large-fruited plants in the forest interior. Our findings suggest that forest-visiting birds may stabilize seed-dispersal services for small-fruited plant species at rain forest margins, while seed-dispersal services for large-fruited plant species may be disrupted at forest edges due to the decrease of large-bodied frugviores. To assess the ultimate consequences of bird movements from farmland to forest edges for ecosystem functioning, future studies are required to investigate the seed-dispersal qualities provided by forest-visiting bird species in the tropics.
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Specialization and interaction strength in a tropical plant-frugivore network differ among forest strata.
Ecology, 2011Co-Authors: Matthias Schleuning, Martina Florchinger, Julius Braun, Nico Bluthgen, H. Martin Schaefer, Katrin Böhning-gaeseAbstract:The degree of interdependence and potential for shared coevolutionary history of frugivorous animals and fleshy-fruited plants are contentious topics. Recently, network analyses revealed that mutualistic relationships between fleshy-fruited plants and frugivores are mostly built upon generalized associations. However, little is known about the determinants of network structure, especially from tropical forests where plants' dependence on animal seed dispersal is particularly high. Here, we present an in-depth analysis of specialization and interaction strength in a plant-frugivore network from a Kenyan rain forest. We recorded fruit removal from 33 plant species in different forest strata (canopy, midstory, understory) and habitats (primary and secondary forest) with a standardized sampling design (3447 interactions in 924 observation hours). We classified the 88 frugivore species into guilds according to dietary specialization (14 obligate, 28 partial, 46 opportunistic frugivores) and forest dependence (50 forest species, 38 visitors). Overall, complementary specialization was similar to that in other plant-frugivore networks. However, the plant-frugivore interactions in the canopy stratum were less specialized than in the mid- and understory, whereas primary and secondary forest did not differ. Plant specialization on frugivores decreased with plant height, and obligate and partial frugivores were less specialized than opportunistic frugivores. The overall impact of a frugivore increased with the number of visits and the specialization on specific plants. Moreover, interaction strength of frugivores differed among forest strata. Obligate frugivores foraged in the canopy where fruit resources were abundant, whereas partial and opportunistic frugivores were more common on mid- and understory plants, respectively. We conclude that the vertical stratification of the frugivore community into obligate and opportunistic feeding guilds structures this plant-frugivore network. The canopy stratum comprises stronger links and generalized associations, whereas the lower strata are composed of weaker links and more specialized interactions. Our results suggest that seed-dispersal relationships of plants in lower forest strata are more prone to disruption than those of canopy trees.
Daniel Garcia - One of the best experts on this subject based on the ideXlab platform.
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from structure to function in mutualistic interaction networks topologically important frugivores have greater potential as seed dispersers
Journal of Animal Ecology, 2020Co-Authors: Juan Fernando Acevedoquintero, Joan Gaston Zamoraabrego, Daniel GarciaAbstract:Networks of mutualistic interactions between animals and plants are considered a pivotal part of ecological communities. However, mutualistic networks are rarely studied from the perspective of species-specific roles, and it remains to be established whether those animal species more relevant for network structure also contribute more to the ecological functions derived from interactions. Here, we relate the contribution to seed dispersal of vertebrate species with their topological role in frugivore-plant interaction networks. For one year in two localities with remnant patches of Colombian tropical dry forest, we sampled abundance, morphology, behaviour and fruit consumption from fleshy-fruited plants of various frugivore species. We assessed the network topological role of each frugivore species by integrating their degree of generalization in interactions with plants with their contributions to network nestedness and modularity. We estimated the potential contribution of each frugivore species to community-wide seed dispersal, on the basis of a set of frugivore ecological, morphological and behavioural characteristics important for seed dispersal, together with frugivore abundance and Frugivory degree. The various frugivore species showed strong differences in their network structural roles, with generalist species contributing the most to network modularity and nestedness. Frugivores also showed strong variability in terms of potential contribution to seed dispersal, depending on the specific combinations of frugivore abundance, Frugivory degree and the different traits and behaviours. For both localities, the seed dispersal potential of a frugivore species responded positively to its contribution to network structure, evidencing that the most important frugivore species in the network topology were also those making the strongest contribution as seed dispersers. Contribution to network structure was correlated with frugivore abundance, diet and behavioural characteristics. This suggests that the species-level link between structure and function is due to the fact that the occurrence of frugivore-plant interactions depends largely on the characteristics of the frugivore involved, which also condition its ultimate role in seed dispersal.
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moving from Frugivory to seed dispersal incorporating the functional outcomes of interactions in plant frugivore networks
Journal of Animal Ecology, 2018Co-Authors: Benno I Simmons, Jorg Albrecht, Nina Farwig, Pedro Jordano, Daniel Garcia, William J Sutherland, Lynn V Dicks, Juan P GonzalezvaroAbstract:1. There is growing interest in understanding the functional outcomes of species interactions in ecological networks. For many mutualistic networks, including pollination and seed dispersal networks, interactions are generally sampled by recording animal foraging visits to plants. However, these visits may not reflect actual pollination or seed dispersal events, despite these typically being the ecological processes of interest. 2. Frugivorous animals can act as seed dispersers, by swallowing entire fruits and dispersing their seeds, or as pulp peckers or seed predators, by pecking fruits to consume pieces of pulp or seeds. These processes have opposing consequences for plant reproductive success. Therefore, equating visitation with seed dispersal could lead to biased inferences about the ecology, evolution and conservation of seed dispersal mutualisms. 3. Here, we use natural history information on the functional outcomes of pairwise bird–plant interactions to examine changes in the structure of seven European plant–frugivore visitation networks after non‐mutualistic interactions (pulp pecking and seed predation) have been removed. Following existing knowledge of the contrasting structures of mutualistic and antagonistic networks, we hypothesized a number of changes following interaction removal, such as increased nestedness and lower specialization. 4. Non‐mutualistic interactions with pulp peckers and seed predators occurred in all seven networks, accounting for 21%–48% of all interactions and 6%–24% of total interaction frequency. When non‐mutualistic interactions were removed, there were significant increases in network‐level metrics such as connectance and nestedness, while robustness decreased. These changes were generally small, homogenous and driven by decreases in network size. Conversely, changes in species‐level metrics were more variable and sometimes large, with significant decreases in plant degree, interaction frequency, specialization and resilience to animal extinctions and significant increases in frugivore species strength. 5. Visitation data can overestimate the actual frequency of seed dispersal services in plant–frugivore networks. We show here that incorporating natural history information on the functions of species interactions can bring us closer to understanding the processes and functions operating in ecological communities. Our categorical approach lays the foundation for future work quantifying functional interaction outcomes along a mutualism–antagonism continuum, as documented in other frugivore faunas.
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exotic birds increase generalization and compensate for native bird decline in plant frugivore assemblages
Journal of Animal Ecology, 2014Co-Authors: Daniel Garcia, Daniel B. Stouffer, Jason M. Tylianakis, Daniel MartinezAbstract:Summary 1. Exotic species are thought to alter the structure of natural communities and disrupt ecosystem functioning through invasion. Nevertheless, exotic species may also provide ecological insurance when they contribute to maintain ecosystem functions after the decline of native species following anthropogenic disturbance. 2. Here, this hypothesis is tested with the assemblage of frugivorous birds and fleshy-fruited plants of New Zealand, which has suffered strong historical declines in native birds while simultaneously gaining new frugivores introduced by European settlers. 3. We studied the plant–frugivore assemblage from measures of fruit and bird abundances and fruit consumption in nine forest patches, and tested how this changed across a gradient of relative abundance of exotic birds. We then examined how each bird species’ role in the assemblage (the proportion of fruits and the number of plant species consumed) varied with their relative abundance, body size and native/exotic status. 4. The more abundant and, to a lesser extent, larger birds species consumed a higher proportion of fruits from more plant species. Exotic birds consumed fruits less selectively and more proportionate to the local availability than did native species. Interaction networks in which exotic birds had a stronger role as frugivores had higher generalization, higher nestedness and higher redundancy of plants. 5. Exotic birds maintained Frugivory when native birds became rarer, and diversified the local spectrum of frugivores for co-occurring native plants. These effects seemed related to the fact that species abundances, rather than trait-matching constraints, ultimately determined the patterns of interactions between birds and plants. By altering the structure of plant–frugivore assemblages, exotic birds likely enhance the stability of the community-wide seed dispersal in the face of continued anthropogenic impact.
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the spatial scale of plant animal interactions effects of resource availability and habitat structure
Ecological Monographs, 2011Co-Authors: Daniel Garcia, Regino Zamora, Guillermo C AmicoAbstract:Plant–animal interactions are crucial nodes in the structure of communities and pivotal drivers of ecosystem functioning. Much of this relevance may depend on how animals cope with plant resources at different spatial scales. However, little is known about how and why different interactions perform at different scales in the same environmental setting. In this study we assess the spatial scales at which two plant–animal interactions operate and disentangle the environmental factors (plant resource availability vs. habitat structure) underpinning these operational scales. We studied two interactions with opposite (mutualistic vs. antagonistic) ecological effects on fleshy-fruited trees, Frugivory and seed dispersal by birds, and the later predation by rodents on bird-dispersed seeds. Employing a standardized sampling, we covered three temperate ecosystems hosting structurally similar plant–frugivore–seed predator systems: Cantabrian forest, Mediterranean shrubland, and Patagonian forest. We sampled habitat...
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patterns of resource tracking by avian frugivores at multiple spatial scales two case studies on discordance among scales
Ecography, 2004Co-Authors: Daniel Garcia, Raul OrtizpulidoAbstract:Scaling is relevant for the analysis of plant-frugivore interaction, since the ecological and evolutionary outcomes of seed dispersal depend on the spatial and temporal scale at which Frugivory patterns emerge. We analyse the relationship between fruit abundance and frugivore activity at local and landscape spatial scales in two different systems composed, respectively, by the bird-dispersed woody plants Juniperus communis and Bursera fagaroides, and their frugivore assemblages. We use a hierarchical approach of nested patchiness of fruit-resource, where patches are defined by individual plants within site, at the local scale, and by sites within region, at the landscape scale. The structure of patches is also described in terms of contrast (differences in fruit availability among patches) and aggregation (spatial distribution of patches). For J. communis, frugivore activity was positively related to fruit availability at the landscape scale, this pattern seldom emerging at the local scale; conversely, B. fagaroides showed a general trend of positive local pattern that disappeared at the landscape scale. These particular trends might be partially explained by differences in contrast and aggregation. The strong contrast among plants within site together with a high aggregation among sites would promote the B. fagaroides pattern to be only local, whereas in J. communis, low aggregation among sites within region would favour a sharp landscape-scale pattern. Both systems showed discordant patterns of fruitresource tracking among consecutive spatial scales, but the sense of discordance differed among systems. These results, and the available multi-scale Frugivory data, suggest that discordance among successive scales allows to link directly Frugivory patterns to resource-tracking mechanisms acting at particular scales, resulting, thus, more informative than concordance observational data, in which landscape patterns might result from accumulated effect of local mechanisms. In this context, we propose new methodological approaches for a better understanding of the hierarchical behavioural mechanisms underpinning the multi-scale resource tracking by frugivores.
Stefan W Ferger - One of the best experts on this subject based on the ideXlab platform.
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frugivore diversity increases Frugivory rates along a large elevational gradient
Oikos, 2016Co-Authors: Stefan W Ferger, Hamadi I Dulle, Matthias Schleuning, Katrin BohninggaeseAbstract:The effect of biodiversity on ecosystem functioning is increasingly well understood, but it has mainly been studied in small-scale experiments of plant-based ecosystem functions. In contrast, the relevance of biodiversity for animal-mediated ecosystem functions like seed dispersal still poses an important gap in ecological knowledge. In particular, it is little understood how avian diversity affects Frugivory rates, one of the most important parameters of seed dispersal rates, along large environmental gradients. Even less is known about the environmental context dependence of the frugivore–Frugivory relationship. We used artificial fruits to analyze experimentally how the abundance and richness of three avian frugivore guilds (with incrementally more stringent classifications of Frugivory) contributed to Frugivory rates across 13 different habitat types along an elevational gradient from 870 to 4550 m a.s.l. at Mt Kilimanjaro, Tanzania. We further investigated how environmental context, in terms of local vegetation structure and natural fruit availability, modified the relationship between frugivores and Frugivory rates. Our results demonstrate that the positive effect of avian diversity on Frugivory rates holds along a large elevational gradient. We found marked differences in Frugivory rates among the 13 habitat types, which were strongly related to the abundance and richness of obligate frugivorous birds. Vegetation structure had no significant effect on Frugivory rates. An intermediate abundance of natural fruits enhanced Frugivory rates, but this effect did not alter the positive frugivore–Frugivory relationship. These results emphasize the fundamental importance of obligate frugivore diversity for Frugivory rates and suggest that the positive effect of biodiversity on ecosystem functioning holds along large environmental gradients.
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frugivore diversity increases Frugivory rates along a large elevational gradient
Oikos, 2016Co-Authors: Stefan W Ferger, Hamadi I Dulle, Matthias Schleuning, Katrin BohninggaeseAbstract:The effect of biodiversity on ecosystem functioning is increasingly well understood, but it has mainly been studied in small-scale experiments of plant-based ecosystem functions. In contrast, the relevance of biodiversity for animal-mediated ecosystem functions like seed dispersal still poses an important gap in ecological knowledge. In particular, it is little understood how avian diversity affects Frugivory rates, one of the most important parameters of seed dispersal rates, along large environmental gradients. Even less is known about the environmental context dependence of the frugivore–Frugivory relationship. We used artificial fruits to analyze experimentally how the abundance and richness of three avian frugivore guilds (with incrementally more stringent classifications of Frugivory) contributed to Frugivory rates across 13 different habitat types along an elevational gradient from 870 to 4550 m a.s.l. at Mt Kilimanjaro, Tanzania. We further investigated how environmental context, in terms of local vegetation structure and natural fruit availability, modified the relationship between frugivores and Frugivory rates. Our results demonstrate that the positive effect of avian diversity on Frugivory rates holds along a large elevational gradient. We found marked differences in Frugivory rates among the 13 habitat types, which were strongly related to the abundance and richness of obligate frugivorous birds. Vegetation structure had no significant effect on Frugivory rates. An intermediate abundance of natural fruits enhanced Frugivory rates, but this effect did not alter the positive frugivore–Frugivory relationship. These results emphasize the fundamental importance of obligate frugivore diversity for Frugivory rates and suggest that the positive effect of biodiversity on ecosystem functioning holds along large environmental gradients.
