Journal articles: 'Seed dispersal network'

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Rehm, E., E. Fricke, J. Bender, J. Savidge, and H. Rogers. "Animal movement drives variation in seed dispersal distance in a plant–animal network." Proceedings of the Royal Society B: Biological Sciences 286, no. 1894 (January 16, 2019): 20182007. http://dx.doi.org/10.1098/rspb.2018.2007.

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Frugivores play differing roles in shaping dispersal patterns yet seed dispersal distance is rarely quantified across entire communities. We model seed dispersal distance using gut passage times and bird movement for the majority (39 interactions) of known bird–tree interactions on the island of Saipan to highlight differences in seed dispersal distances provided by the five avian frugivores. One bird species was found to be a seed predator rather than a disperser. The remaining four avian species dispersed seeds but differences in seed dispersal distance were largely driven by interspecific variation in bird movement rather than intraspecific variation in gut passage times. The median dispersal distance was at least 56 m for all species-specific combinations, indicating all species play a role in reducing high seed mortality under the parent tree. However, one species—the Micronesian Starling—performed 94% of dispersal events greater than 500 m, suggesting this species could be a key driver of long-distance dispersal services (e.g. linking populations, colonizing new areas). Assessing variation in dispersal patterns across this network highlights key sources of variation in seed dispersal distances and suggests which empirical approaches are sufficient for modelling how seed dispersal mutualisms affect populations and communities.

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Lavabre, Jessica E., Luis J. Gilarranz, Miguel A. Fortuna, and Jordi Bascompte. "How does the functional diversity of frugivorous birds shape the spatial pattern of seed dispersal? A case study in a relict plant species." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1694 (May 19, 2016): 20150280. http://dx.doi.org/10.1098/rstb.2015.0280.

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Genetic markers used in combination with network analysis can characterize the fine spatial pattern of seed dispersal and assess the differential contribution of dispersers. As a case study, we focus on the seed dispersal service provided by a small guild of frugivorous birds to the common yew, Taxus baccata L., in southern Spain. We build the spatial networks of seed dispersal events between trees and seed-plots within the studied population—local network—and the spatial network that includes all dispersal events—regional network. Such networks are structured in well-defined modules, i.e. groups of tightly connected mother trees and seed-plots. Neither geographical distance, nor microhabitat type explained this modular structure, but when long-distance dispersal events are incorporated in the network it shows a relative increase in overall modularity. Independent field observations suggested the co-occurrence of two complementary groups, short- and long-distance dispersers, mostly contributing to the local and regional seed rain, respectively. The main long-distance disperser at our site, Turdus viscivorus , preferentially visits the most productive trees, thus shaping the seed rain at the landscape scale and affecting the local modular organization. We end by discussing how DNA barcoding could serve to better quantify the role of functional diversity.

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Heleno, Ruben H., Jens M. Olesen, Manuel Nogales, Pablo Vargas, and Anna Traveset. "Seed dispersal networks in the Galápagos and the consequences of alien plant invasions." Proceedings of the Royal Society B: Biological Sciences 280, no. 1750 (January 7, 2013): 20122112. http://dx.doi.org/10.1098/rspb.2012.2112.

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Alien plants are a growing threat to the Galápagos unique biota. We evaluated the impact of alien plants on eight seed dispersal networks from two islands of the archipelago. Nearly 10 000 intact seeds from 58 species were recovered from the droppings of 18 bird and reptile dispersers. The most dispersed invaders were Lantana camara , Rubus niveus and Psidium guajava , the latter two likely benefiting from an asynchronous fruit production with most native plants, which facilitate their consumption and spread. Lava lizards dispersed the seeds of 27 species, being the most important dispersers, followed by small ground finch, two mockingbirds, the giant tortoise and two insectivorous birds. Most animals dispersed alien seeds, but these formed a relatively small proportion of the interactions. Nevertheless, the integration of aliens was higher in the island that has been invaded for longest, suggesting a time-lag between alien plant introductions and their impacts on seed dispersal networks. Alien plants become more specialized with advancing invasion, favouring more simplified plant and disperser communities. However, only habitat type significantly affected the overall network structure. Alien plants were dispersed via two pathways: dry-fruited plants were preferentially dispersed by finches, while fleshy fruited species were mostly dispersed by other birds and reptiles.

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Heleno, Ruben H., Jaime A. Ramos, and Jane Memmott. "Integration of exotic seeds into an Azorean seed dispersal network." Biological Invasions 15, no. 5 (November 27, 2012): 1143–54. http://dx.doi.org/10.1007/s10530-012-0357-z.

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Wang, Biao, Hai Bin Zheng, Ying Jue Fang, and Jun Jie Wei. "Overlapping Community Detection Algorithm Based on Seed Diffusion." Applied Mechanics and Materials 556-562 (May 2014): 3300–3304. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.3300.

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Thinking applied to the seed dispersal weighted network using node strength to find seed node, and through seed nodes for each node fitness Looking node's home societies, and update the node in the iterative process of fitness makes societies divided stabilized. The experimental results show that the network based on the weighted overlap Societies seed dispersal algorithm can be found in weighted social networks effectively divided and divided more tends to be refined.

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Acosta-Rojas, Diana Carolina, María Victoria Jiménez-Franco, Víctor Manuel Zapata-Pérez, Pilar De la Rúa, and Vicente Martínez-López. "An integrative approach to discern the seed dispersal role of frugivorous guilds in a Mediterranean semiarid priority habitat." PeerJ 7 (October 11, 2019): e7609. http://dx.doi.org/10.7717/peerj.7609.

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Seed dispersal is an essential process to maintain the viability of plant populations, and understanding this ecological process allows management strategies to be developed to conserve ecosystems. European Union priority habitat 5220* is defined as “Mediterranean arborescent shrubland with Ziziphus lotus” and it represents a favorable microclimate within the severe climatic conditions typical of the semiarid south-eastern region of the Iberian Peninsula. Therefore, the study of seed dispersal in this priority habitat by different frugivorous guilds, is a challenge for its conservation. In this study, we have characterized a mutualistic network of seed dispersal that is mediated by vertebrates (mammals and birds) in the protected habitat 5220*. The aims of this study were to: (i) identify the seed disperser community; (ii) analyze the relative role of key species in the dispersal process; and (iii) compare the functional ecology of the seed dispersal process between mammals and birds. As such, we collected animal faeces to determine seed dispersers taxonomy, identifying the mammals through the visual aspect of the faeces and the birds by DNA barcoding. In the case of birds, we also collected regurgitated seeds in which the disperser species was also identified through molecular techniques. This allowed us to build-up a mutualistic network and to identify the relative role of these animals in seed dispersal. Our results showed that mammals and birds fulfilled complementary roles in seed dispersal, with birds representing the main dispersers of key plants within the 5220* habitat, and mammals the main dispersers of human-cultivated plants. Herein, we provide a useful approach with relevant information that can be used to propose management policies that focus on restoring the threatened 5220* habitat, promoting the role of birds to disperse key species that structure plant communities of this priority habitat.

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Correia, Marta, Susana Rodríguez-Echeverría, Sérgio Timóteo, Helena Freitas, and Ruben Heleno. "Integrating plant species contribution to mycorrhizal and seed dispersal mutualistic networks." Biology Letters 15, no. 5 (May 2019): 20180770. http://dx.doi.org/10.1098/rsbl.2018.0770.

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Mutualistic interactions like those established between plants and mycorrhizal fungi or seed dispersers are key drivers of plant population dynamics and ecosystem functioning; however, these interactions have rarely been explored together. We assembled a tripartite fungi–plant–disperser network in the Gorongosa National Park—Mozambique, to test (1) if diversity and importance of plant mutualists above- and belowground are correlated, and (2) whether biotically and abiotically dispersed plants are associated with distinct arbuscular mycorrhizal fungi (AMF). We quantified seed dispersal by animals for 1 year and characterized the AMF of 26 common plant species. Sixteen plant species were dispersed by 15 animals and colonized by 48 AMF virtual taxa (VT), while the remaining 10 plant species were not dispersed by animals and associated with 34 AMF VT. We found no evidence for a correlation between the number of plant partners above- and belowground or on plant specialization on both types of partners. We also found no evidence for differentiation of AMF communities between biotically and abiotically dispersed plants. Our results suggest that the establishment of plant interactions with seed dispersers and mycorrhizal fungi is largely independent and that both biotically and abiotically dispersed plants seem to associate with similar communities of AMF.

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Burin, Gustavo, Paulo R. Guimarães, and Tiago B. Quental. "Macroevolutionary stability predicts interaction patterns of species in seed dispersal networks." Science 372, no. 6543 (May 13, 2021): 733–37. http://dx.doi.org/10.1126/science.abf0556.

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Assessing deep-time mechanisms affecting the assembly of ecological networks is key to understanding biodiversity changes on broader time scales. We combined analyses of diversification rates with interaction network descriptors from 468 bird species belonging to 29 seed dispersal networks to show that bird species that contribute most to the network structure of plant–frugivore interactions belong to lineages that show higher macroevolutionary stability. This association is stronger in warmer, wetter, less seasonal environments. We infer that the macroevolutionary sorting mechanism acts through the regional pool of species by sorting species on the basis of the available relative differences in diversification rates, rather than absolute rates. Our results illustrate how the interplay between interaction patterns and diversification dynamics may shape the organization and long-term dynamics of ecological networks.

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Vizentin-Bugoni, Jeferson, Jinelle H. Sperry, J. Patrick Kelley, Jason M. Gleditsch, Jeffrey T. Foster, Donald R. Drake, Amy M. Hruska, Rebecca C. Wilcox, Samuel B. Case, and Corey E. Tarwater. "Ecological correlates of species’ roles in highly invaded seed dispersal networks." Proceedings of the National Academy of Sciences 118, no. 4 (January 11, 2021): e2009532118. http://dx.doi.org/10.1073/pnas.2009532118.

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Ecosystems with a mix of native and introduced species are increasing globally as extinction and introduction rates rise, resulting in novel species interactions. While species interactions are highly vulnerable to disturbance, little is known about the roles that introduced species play in novel interaction networks and what processes underlie such roles. Studying one of the most extreme cases of human-modified ecosystems, the island of Oʻahu, Hawaii, we show that introduced species there shape the structure of seed dispersal networks to a greater extent than native species. Although both neutral and niche-based processes influenced network structure, niche-based processes played a larger role, despite theory predicting neutral processes to be predominantly important for islands. In fact, ecological correlates of species’ roles (morphology, behavior, abundance) were largely similar to those in native-dominated networks. However, the most important ecological correlates varied with spatial scale and trophic level, highlighting the importance of examining these factors separately to unravel processes determining species contributions to network structure. Although introduced species integrate into interaction networks more deeply than previously thought, by examining the mechanistic basis of species’ roles we can use traits to identify species that can be removed from (or added to) a system to improve crucial ecosystem functions, such as seed dispersal.

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Neumann, Ulla, and Angela Hay. "Seed coat development in explosively dispersed seeds of Cardamine hirsuta." Annals of Botany 126, no. 1 (December 4, 2019): 39–59. http://dx.doi.org/10.1093/aob/mcz190.

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Abstract Background and Aims Seeds are dispersed by explosive coiling of the fruit valves in Cardamine hirsuta. This rapid coiling launches the small seeds on ballistic trajectories to spread over a 2 m radius around the parent plant. The seed surface interacts with both the coiling fruit valve during launch and subsequently with the air during flight. We aim to identify features of the seed surface that may contribute to these interactions by characterizing seed coat differentiation. Methods Differentiation of the outermost seed coat layers from the outer integuments of the ovule involves dramatic cellular changes that we characterize in detail at the light and electron microscopical level including immunofluorescence and immunogold labelling. Key Results We found that the two outer integument (oi) layers of the seed coat contributed differently to the topography of the seed surface in the explosively dispersed seeds of C. hirsuta vs. the related species Arabidopsis thaliana where seed dispersal is non-explosive. The surface of A. thaliana seeds is shaped by the columella and the anticlinal cell walls of the epidermal oi2 layer. In contrast, the surface of C. hirsuta seeds is shaped by a network of prominent ridges formed by the anticlinal walls of asymmetrically thickened cells of the sub-epidermal oi1 layer, especially at the seed margin. Both the oi2 and oi1 cell layers in C. hirsuta seeds are characterized by specialized, pectin-rich cell walls that are deposited asymmetrically in the cell. Conclusions The two outermost seed coat layers in C. hirsuta have distinct properties: the sub-epidermal oi1 layer determines the topography of the seed surface, while the epidermal oi2 layer accumulates mucilage. These properties are influenced by polar deposition of distinct pectin polysaccharides in the cell wall. Although the ridged seed surface formed by oi1 cell walls is associated with ballistic dispersal in C. hirsuta, it is not restricted to explosively dispersed seeds in the Brassicaceae.

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Costa, José M., Jaime A. Ramos, Luís P. da Silva, Sérgio Timóteo, Pedro Andrade, Pedro M. Araújo, Camilo Carneiro, et al. "Rewiring of experimentally disturbed seed dispersal networks might lead to unexpected network configurations." Basic and Applied Ecology 30 (August 2018): 11–22. http://dx.doi.org/10.1016/j.baae.2018.05.011.

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Carlo, Tomás A., and Suann Yang. "Network models of frugivory and seed dispersal: Challenges and opportunities." Acta Oecologica 37, no. 6 (November 2011): 619–24. http://dx.doi.org/10.1016/j.actao.2011.08.001.

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Naniwadekar, Rohit, Saniya Chaplod, Aparajita Datta, Akanksha Rathore, and Hari Sridhar. "Large frugivores matter: Insights from network and seed dispersal effectiveness approaches." Journal of Animal Ecology 88, no. 8 (May 24, 2019): 1250–62. http://dx.doi.org/10.1111/1365-2656.13005.

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Correa, Sandra Bibiana, Joisiane K. Arujo, Jerry Penha, Catia Nunes da Cunha, Karen E. Bobier, and Jill T. Anderson. "Stability and generalization in seed dispersal networks: a case study of frugivorous fish in Neotropical wetlands." Proceedings of the Royal Society B: Biological Sciences 283, no. 1837 (August 31, 2016): 20161267. http://dx.doi.org/10.1098/rspb.2016.1267.

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When species within guilds perform similar ecological roles, functional redundancy can buffer ecosystems against species loss. Using data on the frequency of interactions between fish and fruit, we assessed whether co-occurring frugivores provide redundant seed dispersal services in three species-rich Neotropical wetlands. Our study revealed that frugivorous fishes have generalized diets; however, large-bodied fishes had greater seed dispersal breadth than small species, in some cases, providing seed dispersal services not achieved by smaller fish species. As overfishing disproportionately affects big fishes, the extirpation of these species could cause larger secondary extinctions of plant species than the loss of small specialist frugivores. To evaluate the consequences of frugivore specialization for network stability, we extracted data from 39 published seed dispersal networks of frugivorous birds, mammals and fish (our networks) across ecosystems. Our analysis of interaction frequencies revealed low frugivore specialization and lower nestedness than analyses based on binary data (presence–absence of interactions). In that case, ecosystems may be resilient to loss of any given frugivore. However, robustness to frugivore extinction declines with specialization, such that networks composed primarily of specialist frugivores are highly susceptible to the loss of generalists. In contrast with analyses of binary data, recently developed algorithms capable of modelling interaction strengths provide opportunities to enhance our understanding of complex ecological networks by accounting for heterogeneity of frugivore–fruit interactions.

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Donoso, Isabel, Matthias Schleuning, Daniel García, and Jochen Fründ. "Defaunation effects on plant recruitment depend on size matching and size trade-offs in seed-dispersal networks." Proceedings of the Royal Society B: Biological Sciences 284, no. 1855 (May 31, 2017): 20162664. http://dx.doi.org/10.1098/rspb.2016.2664.

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Defaunation by humans causes a loss of large animals in many ecosystems globally. Recent work has emphasized the consequences of downsizing in animal communities for ecosystem functioning. However, no study so far has integrated network theory and life-history trade-offs to mechanistically evaluate the functional consequences of defaunation in plant–animal networks. Here, we simulated an avian seed-dispersal network and its derived ecosystem function seedling recruitment to assess the relative importance of different size-related mechanisms. Specifically, we considered size matching (between bird size and seed size) and size trade-offs, which are driven by differences in plant or animal species abundance (negative size–quantity relationship) as well as in recruitment probability and disperser quality (positive size–quality relationship). Defaunation led to impoverished seedling communities in terms of diversity and seed size, but only if models accounted for size matching. In addition, size trade-off in plants, in concert with size matching, provoked rapid decays in seedling abundance in response to defaunation. These results underscore a disproportional importance of large animals for ecosystem functions. Downsizing in ecological networks will have severe consequences for ecosystem functioning, especially in interaction networks that are structured by size matching between plants and animals.

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Vizentin-Bugoni, Jeferson, Corey E. Tarwater, Jeffrey T. Foster, Donald R. Drake, Jason M. Gleditsch, Amy M. Hruska, J. Patrick Kelley, and Jinelle H. Sperry. "Structure, spatial dynamics, and stability of novel seed dispersal mutualistic networks in Hawaiʻi." Science 364, no. 6435 (April 4, 2019): 78–82. http://dx.doi.org/10.1126/science.aau8751.

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Increasing rates of human-caused species invasions and extinctions may reshape communities and modify the structure, dynamics, and stability of species interactions. To investigate how such changes affect communities, we performed multiscale analyses of seed dispersal networks on Oʻahu, Hawaiʻi. Networks consisted exclusively of novel interactions, were largely dominated by introduced species, and exhibited specialized and modular structure at local and regional scales, despite high interaction dissimilarity across communities. Furthermore, the structure and stability of the novel networks were similar to native-dominated communities worldwide. Our findings suggest that shared evolutionary history is not a necessary process for the emergence of complex network structure, and interaction patterns may be highly conserved, regardless of species identity and environment. Introduced species can quickly become well integrated into novel networks, making restoration of native ecosystems more challenging than previously thought.

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Sakai, Shoko, Soeren Metelmann, Yukihiko Toquenaga, and Arndt Telschow. "Geographical variation in the heterogeneity of mutualistic networks." Royal Society Open Science 3, no. 6 (June 2016): 150630. http://dx.doi.org/10.1098/rsos.150630.

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Plant–animal mutualistic networks are characterized by highly heterogeneous degree distributions. The majority of species interact with few partner species, while a small number are highly connected to form network hubs that are proposed to play an important role in community stability. It has not been investigated, however, if or how the degree distributions vary among types of mutualisms or communities, or between plants and animals in the same network. Here, we evaluate the degree distributions of pollination and seed-dispersal networks, which are two major types of mutualistic networks that have often been discussed in parallel, using an index based on Pielou's evenness. Among 56 pollination networks we found strong negative correlation of the heterogeneity between plants and animals, and geographical shifts of network hubs from plants in temperate regions to animals in the tropics. For 28 seed-dispersal networks, by contrast, the correlation was positive, and there is no comparable geographical pattern. These results may be explained by evolution towards specialization in the presence of context-dependent costs that occur if plants share the animal species as interaction partner. How the identity of network hubs affects the stability and resilience of the community is an important question for future studies.

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Donatti, Camila I., Paulo R. Guimarães, Mauro Galetti, Marco Aurélio Pizo, Flávia M. D. Marquitti, and Rodolfo Dirzo. "Analysis of a hyper-diverse seed dispersal network: modularity and underlying mechanisms." Ecology Letters 14, no. 8 (June 23, 2011): 773–81. http://dx.doi.org/10.1111/j.1461-0248.2011.01639.x.

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Machado-de-Souza, Tiago, Ricardo Pamplona Campos, Mariano Devoto, and Isabela Galarda Varassin. "Local drivers of the structure of a tropical bird-seed dispersal network." Oecologia 189, no. 2 (January 5, 2019): 421–33. http://dx.doi.org/10.1007/s00442-018-4322-0.

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Andersen, K. F., C. E. Buddenhagen, P. Rachkara, R. Gibson, S. Kalule, D. Phillips, and K. A. Garrett. "Modeling Epidemics in Seed Systems and Landscapes To Guide Management Strategies: The Case of Sweet Potato in Northern Uganda." Phytopathology® 109, no. 9 (September 2019): 1519–32. http://dx.doi.org/10.1094/phyto-03-18-0072-r.

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Seed systems are critical for deployment of improved varieties but also can serve as major conduits for the spread of seedborne pathogens. As in many other epidemic systems, epidemic risk in seed systems often depends on the structure of networks of trade, social interactions, and landscape connectivity. In a case study, we evaluated the structure of an informal sweet potato seed system in the Gulu region of northern Uganda for its vulnerability to the spread of emerging epidemics and its utility for disseminating improved varieties. Seed transaction data were collected by surveying vine sellers weekly during the 2014 growing season. We combined data from these observed seed transactions with estimated dispersal risk based on village-to-village proximity to create a multilayer network or “supranetwork.” Both the inverse power law function and negative exponential function, common models for dispersal kernels, were evaluated in a sensitivity analysis/uncertainty quantification across a range of parameters chosen to represent spread based on proximity in the landscape. In a set of simulation experiments, we modeled the introduction of a novel pathogen and evaluated the influence of spread parameters on the selection of villages for surveillance and management. We found that the starting position in the network was critical for epidemic progress and final epidemic outcomes, largely driven by node out-degree. The efficacy of node centrality measures was evaluated for utility in identifying villages in the network to manage and limit disease spread. Node degree often performed as well as other, more complicated centrality measures for the networks where village-to-village spread was modeled by the inverse power law, whereas betweenness centrality was often more effective for negative exponential dispersal. This analysis framework can be applied to provide recommendations for a wide variety of seed systems.[Formula: see text] Copyright © 2019 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

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Sebastián-González, Esther, Mathias M. Pires, Camila I. Donatti, Paulo R. Guimarães, and Rodolfo Dirzo. "Species traits and interaction rules shape a species-rich seed-dispersal interaction network." Ecology and Evolution 7, no. 12 (May 17, 2017): 4496–506. http://dx.doi.org/10.1002/ece3.2865.

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Bastazini, Vinicius AG, Vanderlei J. Debastiani, Bethânia O. Azambuja, Paulo R. Guimarães, and Valério D. Pillar. "Loss of Generalist Plant Species and Functional Diversity Decreases the Robustness of a Seed Dispersal Network." Environmental Conservation 46, no. 1 (November 9, 2018): 52–58. http://dx.doi.org/10.1017/s0376892918000334.

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SummaryUnderstanding cascading effects of species loss is a major challenge for ecologists. Traditionally, the robustness of ecological networks has been evaluated based on simulation studies where primary extinctions occur at random or as a function of species specialization, ignoring other important biological factors. Here, we estimate the robustness of a seed dispersal network from a grassland–forest mosaic in southern Brazil, simulating distinct scenarios of woody plant species extinction, including scenarios where species are eliminated based on their evolutionary and functional distinctiveness. Our results suggest that the network is more robust when species are eliminated based on their evolutionary uniqueness, followed by random extinctions, the extinction of the most specialist species, functional distinctiveness and, at last, when the most generalist species are sequentially eliminated. Our results provide important information for grassland–forest mosaic management, as they indicate that loss of generalist species and functional diversity makes the system more likely to collapse.

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Alencar, Luana, and Edson Guilherme. "Bird-plant interactions on the edge of a forest fragment in southwestern Brazilian Amazonia." Acta Scientiarum. Biological Sciences 42 (August 27, 2020): e51485. http://dx.doi.org/10.4025/actascibiolsci.v42i1.51485.

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Seed dispersal is one of the principal ecological processes that determine the richness and distribution of plants in tropical forests. Birds play an important role in the zoochoric dispersal of seeds in these forests. The present study investigated the bird-plant interactions involving the ingestion and dispersal of seeds by the birds found in the edge habitat of an isolated forest fragment on the Catuaba Experimental Farm in eastern Acre, in southwestern Brazilian Amazonia. The birds were captured using mist nets, and the seeds were collected from fecal samples obtained during the handling of the animals. These seeds were sorted and identified. The bird and the plant species identified during the study were used to calculate the connectivity and nestedness of the bird-plant interactions. We captured 82 species of birds, with a total sampling effort of 203,180 h.m². Fecal samples obtained from 19 of the bird species contained a total of 2,086 seeds, representing 23 plant species. The interaction network had an intermediate connectance, and significant nestedness. Ramphocelus carbo had the highest importance index and was the bird with the largest number of plant interactions, while Cecropia latiloba was the plant with the highest importance index, followed by Schefflera morototoni. Most of the seed-dispersing birds identified in the present study are generalists found in both the forest core and its edge. The results of the study indicated that the community of generalist-frugivore birds interacts extensively with the plant community of the fragment, providing seed dispersal services that include the deforested areas adjacent to the fragment.

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Fricke, Evan C., Joshua J. Tewksbury, and Haldre S. Rogers. "Defaunation leads to interaction deficits, not interaction compensation, in an island seed dispersal network." Global Change Biology 24, no. 1 (August 17, 2017): e190-e200. http://dx.doi.org/10.1111/gcb.13832.

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Peredo, Andrés, Daniel Martínez, Javier Rodríguez-Pérez, and Daniel García. "Mammalian seed dispersal in Cantabrian woodland pastures: Network structure and response to forest loss." Basic and Applied Ecology 14, no. 5 (August 2013): 378–86. http://dx.doi.org/10.1016/j.baae.2013.05.003.

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Machado-de-Souza, Tiago, Ricardo Pamplona Campos, Mariano Devoto, and Isabela Galarda Varassin. "Correction to: Local drivers of the structure of a tropical bird‑seed dispersal network." Oecologia 190, no. 1 (April 29, 2019): 273. http://dx.doi.org/10.1007/s00442-019-04392-2.

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Fricke, Evan C., Joshua J. Tewksbury, Elizabeth M. Wandrag, and Haldre S. Rogers. "Mutualistic strategies minimize coextinction in plant–disperser networks." Proceedings of the Royal Society B: Biological Sciences 284, no. 1854 (May 10, 2017): 20162302. http://dx.doi.org/10.1098/rspb.2016.2302.

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The global decline of mutualists such as pollinators and seed dispersers may cause negative direct and indirect impacts on biodiversity. Mutualistic network models used to understand the stability of mutualistic systems indicate that species with low partner diversity are most vulnerable to coextinction following mutualism disruption. However, existing models have not considered how species vary in their dependence on mutualistic interactions for reproduction or survival, overlooking the potential influence of this variation on species' coextinction vulnerability and on network stability. Using global databases and field experiments focused on the seed dispersal mutualism, we found that plants and animals that depend heavily on mutualistic interactions have higher partner diversity. Under simulated network disruption, this empirical relationship strongly reduced coextinction because the species most likely to lose mutualists depend least on their mutualists. The pattern also reduced the importance of network structure for stability; nested network structure had little effect on coextinction after simulations incorporated the empirically derived relationship between partner diversity and mutualistic dependence. Our results highlight a previously unknown source of stability in mutualistic networks and suggest that differences among species in their mutualistic strategy, rather than network structure, primarily accounts for stability in mutualistic communities.

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Rodier, Christophe, and Paul Struik. "Nodal Farmers’ Motivations for Exchanging Sorghum Seeds in Northwestern Ethiopia." Sustainability 10, no. 10 (October 16, 2018): 3708. http://dx.doi.org/10.3390/su10103708.

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One of the main challenges of Ethiopian agriculture is the shortage of certified seeds of improved varieties, which results in uneven dispersal of quality seed amongst farmers. In a context where 80% to 90% of the seed requirement is covered by the informal seed sector, understanding how and why seeds are exchanged through informal channels is crucial. This study aims to describe why nodal farmers disseminate seeds at a higher rate than other farmers in their network. Following a social network analysis, in-depth surveys were conducted with identified nodal and connector sorghum farmers in order to determine the main social characteristics that differentiate them from other farmers in a western lowlands community of the Tigray Region of Ethiopia. We examined empirically the main factors that motivate them, the main drawbacks they experience, and the behavioral decisions that could potentially speed up or slow down the adoption of newly released improved varieties of sorghum. The study showed that, in this district, few significant socio-demographic differences exist between nodal and non-nodal farmers. The seed exchange network was hyper localized, as the majority of exchanges took place within village boundaries. Focus group discussions showed that a nodal position should not be taken for granted, as the network is dynamic and in constant evolution. In-depth interviews revealed that it was unlikely for accessing farmers to be consistently denied seeds due to a deeply rooted social norm insisting that one should not, under any circumstances, be turned down when asking for seeds. However, in practice, chronic seed insecure farmers suffering from poor performances may find themselves unable to access quality seeds, as automatic support should not be assumed. In terms of motivation, nodal farmers ranked maintaining friendships and relationships as the two most important. Thus, beyond the risk-sharing mechanism underlying much of the seed exchange, it is a mix of personal and community interests that motivates nodal farmers to have more exchange partners and thus disseminate more seeds on average than other farmers in the seed networks. This indicates that their social capital is the major driver to exchange seeds.

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Zhang, Hongmao, Zhenzhen Wang, Qinghuan Zeng, Gang Chang, Zhenyu Wang, and Zhibin Zhang. "Mutualistic and predatory interactions are driven by rodent body size and seed traits in a rodent–seed system in warm-temperate forest in northern China." Wildlife Research 42, no. 2 (2015): 149. http://dx.doi.org/10.1071/wr14211.

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Context Mutualistic interactions between animals and plants shape the structure of plant–animal systems and, subsequently, affect plant-community structure and regeneration. Aims To assess the effects of plant and rodent functional traits on the formation of mutualistic and predatory interactions regarding seed dispersal and predation in a warm-temperate forest. Methods Seed scatter-hoarding and predation by six sympatric rodent species on seeds belonging to five sympatric tree species were tested under enclosure conditions. Key results Functional traits (i.e. rodent body size and seed traits) are important to mutualism/predation in this seed–rodent system. The rodent–seed network is highly nested: large-sized rodents have mutualistic or predatory interactions with both large- and small-sized seed species, but small-sized rodents interacted with small-sized seed species only. Large seeds or seeds with hard coats enhanced mutualism and reduced predation. Conclusion Body size of rodents and seed traits such as handling time and nutritional value are key factors in the formation of mutualistic and predatory interactions within seed–rodent systems. Implications To promote seedling establishment in degenerated forests, introducing or protecting large-sized scatter hoarders and reducing the density of pure seed eaters are needed.

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Yan, Yujing, and Zhiyao Tang. "Protecting endemic seed plants on the Tibetan Plateau under future climate change: migration matters." Journal of Plant Ecology 12, no. 6 (July 15, 2019): 962–71. http://dx.doi.org/10.1093/jpe/rtz032.

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Abstract Aims Climate change in the near future may become a major threat to high-altitude endemics by greatly altering their distribution. Our aims are to (i) assess the potential impacts of future climate change on the diversity and distribution of seed plants endemic to the Tibetan Plateau and (ii) evaluate the conservation effectiveness of the current National Nature Reserves (NNRs) in protecting the endemic plants in the face of climate change. Methods We projected range shifts of 993 endemic species to the years 2050 and 2070 under two representative concentration pathway scenarios using an ensemble species distribution modeling framework and evaluated range loss, species-richness change and coverage of the current conservation network considering two dispersal scenarios. Important Findings In a full-dispersal scenario, 72–81% of the species would expand their distribution by 2070, but 6–20% of the species would experience >30% range loss. Most species would shift to the west. The projected species net richness would increase across the region on average. In a no-dispersal scenario, 15–59% of the species would lose >30% of their current habitat by 2070. Severe species loss may occur in the southeastern and the eastern peripheral plateau. Seventeen percent of species ranges are covered by the NNRs on average and may increase in the future if species disperse freely. We found a significant difference of species redistribution patterns between different dispersal scenarios and highlighted the importance of migration in this region.

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García-Zubia, Luis C., Javier Hernández-Velasco, José C. Hernández-Díaz, Sergio L. Simental-Rodríguez, Carlos A. López-Sánchez, Carmen Z. Quiñones-Pérez, Artemio Carrillo-Parra, and Christian Wehenkel. "Spatial genetic structure in Pinus cembroides Zucc. at population and landscape levels in central and northern Mexico." PeerJ 7 (November 6, 2019): e8002. http://dx.doi.org/10.7717/peerj.8002.

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Background Spatial genetic structure (SGS) analysis is a powerful approach to quantifying gene flow between trees, thus clarifying the functional connectivity of trees at population and landscape scales. The findings of SGS analysis may be useful for conservation and management of natural populations and plantations. Pinus cembroides is a widely distributed tree species, covering an area of about 2.5 million hectares in Mexico. The aim of this study was to examine five natural seed stands of P. cembroides in the Sierra Madre Occidental to determine the SGS at population (within the seed stand) and landscape (among seed stands) levels in order to establish guidelines for the conservation and management of the species. We hypothesized that P. cembroides, in which the seeds are dispersed by birds and mammals, creates weaker SGS than species with wind-dispersed seeds. Methods DNA fingerprinting was performed using the amplified fragment length polymorphism (AFLP) technique. In order to estimate the SGS at population and landscape levels, we measured the geographical (spatial) distance as the Euclidean distance. We also estimated the genetic distances between individuals using the pairwise kinship coefficient. Results The results showed non-significant autocorrelation in four out of five seed stands studied (i.e., a mainly random distribution in the space of the genetic variants of P. cembroides at population level). Discussion SGS was detected at the landscape scale, supporting the theory of isolation by distance as a consequence of restricted pollen and seed dispersal. However, the SGS may also have been generated by our sampling strategy. We recommended establishing a close network of seed stands of P. cembroides to prevent greater loss of local genetic variants and alteration of SGS. We recommend seed stands of P. cembroides of a minimum width of 225 m.

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Lalleroni, Aurélie, Pierre-Yves Quenette, Tanguy Daufresne, Maryline Pellerin, and Christophe Baltzinger. "Exploring the potential of brown bear (Ursus arctos arctos) as a long-distance seed disperser: a pilot study in South-Western Europe." Mammalia 81, no. 1 (January 1, 2017): 1–9. http://dx.doi.org/10.1515/mammalia-2015-0092.

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AbstractPlant dispersal is crucial to maintaining plant community dynamics, especially in the current context of rapid environmental changes such as global warming and landscape fragmentation. We seized the opportunity to carry out a pilot study on endozoochorous dispersal by the endangered Pyrenean brown bear. We based our study on faeces collected by the Brown Bear Network and location data from three bears fitted with GPS collars and translocated from Slovenia to the Pyrenees in 2006. We studied 39 faecal samples, 25 of which contained seeds from two to three different taxa. We identified a total of 47 plant taxa, 30 to the genus level and 21 to the species level. The seeds from plants bearing fleshy fruits:

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Sechet, Julien, Annie Marion-Poll, and Helen North. "Emerging Functions for Cell Wall Polysaccharides Accumulated during Eudicot Seed Development." Plants 7, no. 4 (September 29, 2018): 81. http://dx.doi.org/10.3390/plants7040081.

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The formation of seeds is a reproductive strategy in higher plants that enables the dispersal of offspring through time and space. Eudicot seeds comprise three main components, the embryo, the endosperm and the seed coat, where the coordinated development of each is important for the correct formation of the mature seed. In addition, the seed coat protects the quiescent progeny and can provide transport mechanisms. A key underlying process in the production of seed tissues is the formation of an extracellular matrix termed the cell wall, which is well known for its essential function in cytokinesis, directional growth and morphogenesis. The cell wall is composed of a macromolecular network of polymers where the major component is polysaccharides. The attributes of polysaccharides differ with their composition and charge, which enables dynamic remodeling of the mechanical and physical properties of the matrix by adjusting their production, modification or turnover. Accordingly, the importance of specific polysaccharides or modifications is increasingly being associated with specialized functions within seed tissues, often through the spatio-temporal accumulation or remodeling of particular polymers. Here, we review the evolution and accumulation of polysaccharides during eudicot seed development, what is known of their impact on wall architecture and the diverse roles associated with these in different seed tissues.

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Dáttilo, Wesley, Nubia Lara-Rodríguez, Pedro Jordano, Paulo R. Guimarães, John N. Thompson, Robert J. Marquis, Lucas P. Medeiros, Raul Ortiz-Pulido, Maria A. Marcos-García, and Victor Rico-Gray. "Unravelling Darwin's entangled bank: architecture and robustness of mutualistic networks with multiple interaction types." Proceedings of the Royal Society B: Biological Sciences 283, no. 1843 (November 30, 2016): 20161564. http://dx.doi.org/10.1098/rspb.2016.1564.

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Trying to unravel Darwin's entangled bank further, we describe the architecture of a network involving multiple forms of mutualism (pollination by animals, seed dispersal by birds and plant protection by ants) and evaluate whether this multi-network shows evidence of a structure that promotes robustness. We found that species differed strongly in their contributions to the organization of the multi-interaction network, and that only a few species contributed to the structuring of these patterns. Moreover, we observed that the multi-interaction networks did not enhance community robustness compared with each of the three independent mutualistic networks when analysed across a range of simulated scenarios of species extinction. By simulating the removal of highly interacting species, we observed that, overall, these species enhance network nestedness and robustness, but decrease modularity. We discuss how the organization of interlinked mutualistic networks may be essential for the maintenance of ecological communities, and therefore the long-term ecological and evolutionary dynamics of interactive, species-rich communities. We suggest that conserving these keystone mutualists and their interactions is crucial to the persistence of species-rich mutualistic assemblages, mainly because they support other species and shape the network organization.

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Hervías-Parejo, S., C. Tur, R. Heleno, M. Nogales, S. Timóteo, and A. Traveset. "Species functional traits and abundance as drivers of multiplex ecological networks: first empirical quantification of inter-layer edge weights." Proceedings of the Royal Society B: Biological Sciences 287, no. 1939 (November 25, 2020): 20202127. http://dx.doi.org/10.1098/rspb.2020.2127.

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Many vertebrate species act as both plant pollinators and seed-dispersers, thus interconnecting these processes, particularly on islands. Ecological multilayer networks are a powerful tool to explore interdependencies between processes; however, quantifying the links between species engaging in different types of interactions (i.e. inter-layer edges) remains a great challenge. Here, we empirically measured inter-layer edge weights by quantifying the role of individually marked birds as both pollinators and seed-dispersers of Galápagos plant species over an entire year. Although most species (80%) engaged in both functions, we show that only a small proportion of individuals actually linked the two processes, highlighting the need to further consider intra-specific variability in individuals' functional roles. Furthermore, we found a high variation among species in linking both processes, i.e. some species contribute more than others to the modular organization of the multilayer network. Small and abundant species are particularly important for the cohesion of pollinator seed-dispersal networks, demonstrating the interplay between species traits and neutral processes structuring natural communities.

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Nagaishi, Ellie, and Kazuhiro Takemoto. "Network resilience of mutualistic ecosystems and environmental changes: an empirical study." Royal Society Open Science 5, no. 9 (September 2018): 180706. http://dx.doi.org/10.1098/rsos.180706.

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It is theorized that a mutualistic ecosystem's resilience against perturbations (e.g. species extinction) is determined by a single macroscopic parameter (network resilience), calculable from the network. Given that such perturbations occur owing to environmental changes (e.g. climate change and human impact), it has been predicted that mutualistic ecosystems that exist despite extensive environmental changes exhibit higher network resilience; however, such a prediction has not been confirmed using real-world data. Thus, in this study, the effects of climate change velocity and human activities on mutualistic network resilience were investigated. A global dataset of plant–animal mutualistic networks was used, and spatial analysis was performed to examine the effects. Moreover, the potential confounding effects of network size, current climate and altitude were statistically controlled. It was demonstrated that mutualistic network resilience was globally influenced by warming velocity and human impact, in addition to current climate. Specifically, pollination network resilience increased in response to human impact, and seed-dispersal network resilience increased with warming velocity. The effect of environmental changes on network resilience for plants was remarkable. The results confirmed the prediction obtained based on the theory and imply that real-world mutualistic networks have a structure that increases ecosystem resilience against environmental changes. These findings will enhance the understanding of ecosystem resilience.

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Pigot, Alexander L., Tom Bregman, Catherine Sheard, Benjamin Daly, Rampal S. Etienne, and Joseph A. Tobias. "Quantifying species contributions to ecosystem processes: a global assessment of functional trait and phylogenetic metrics across avian seed-dispersal networks." Proceedings of the Royal Society B: Biological Sciences 283, no. 1844 (December 14, 2016): 20161597. http://dx.doi.org/10.1098/rspb.2016.1597.

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Quantifying the role of biodiversity in ecosystems not only requires understanding the links between species and the ecological functions and services they provide, but also how these factors relate to measurable indices, such as functional traits and phylogenetic diversity. However, these relationships remain poorly understood, especially for heterotrophic organisms within complex ecological networks. Here, we assemble data on avian traits across a global sample of mutualistic plant–frugivore networks to critically assess how the functional roles of frugivores are associated with their intrinsic traits, as well as their evolutionary and functional distinctiveness. We find strong evidence for niche complementarity, with phenotypically and phylogenetically distinct birds interacting with more unique sets of plants. However, interaction strengths—the number of plant species dependent on a frugivore—were unrelated to evolutionary or functional distinctiveness, largely because distinct frugivores tend to be locally rare, and thus have fewer connections across the network. Instead, interaction strengths were better predicted by intrinsic traits, including body size, gape width and dietary specialization. Our analysis provides general support for the use of traits in quantifying species ecological functions, but also highlights the need to go beyond simple metrics of functional or phylogenetic diversity to consider the multiple pathways through which traits may determine ecological processes.

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Lemke, Andreas, Sascha Buchholz, Ingo Kowarik, Uwe Starfinger, and Moritz von der Lippe. "Interaction of traffic intensity and habitat features shape invasion dynamics of an invasive alien species (Ambrosia artemisiifolia) in a regional road network." NeoBiota 64 (March 24, 2021): 155–75. http://dx.doi.org/10.3897/neobiota.64.58775.

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Road corridors are important conduits for plant invasions, and an understanding of the underlying mechanisms is necessary for efficient management of invasive alien species in road networks. Previous studies identified road type with different traffic volumes as a key driver of seed dispersal and abundance of alien plants along roads. However, how the intensity of traffic interacts with the habitat features of roadsides in shaping invasion processes is not sufficiently understood. To elucidate these interactions, we analyzed the population dynamics of common ragweed (Ambrosia artemisiifolia L.), a common non-indigenous annual species in Europe and other continents, in a regional road network in Germany. Over a period of five years, we recorded plant densities at roadsides along four types of road corridors, subject to different intensities of traffic, and with a total length of about 300 km. We also classified roadsides in regard to habitat features (disturbance, shade). This allowed us to determine corridor- and habitat-specific mean population growth rates and spatial-temporal shifts in roadside plant abundances at the regional scale. Our results show that both traffic intensity and roadside habitat features significantly affect the population dynamics of ragweed. The combination of high traffic intensity and high disturbance intensity led to the highest mean population growth whereas population growth in less suitable habitats (e.g. shaded roadsides) declined with decreasing traffic intensity. We conclude that high traffic facilitates ragweed invasion along roads, likely due to continued seed dispersal, and can compensate partly for less suitable habitat features (i.e. shade) that decrease population growth along less trafficked roads. As a practical implication, management efforts to decline ragweed invasions within road networks (e.g. by repeated mowing) should be prioritized along high trafficked roads, and roadside with disturbed, open habitats should be reduced as far as possible, e.g. by establishing grassland from the regional species pool.

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Hernández-Velasco, Javier, José Ciro Hernández-Díaz, Matthias Fladung, Álvaro Cañadas-López, José Ángel Prieto-Ruíz, and Christian Wehenkel. "Spatial genetic structure in four Pinus species in the Sierra Madre Occidental, Durango, Mexico." Canadian Journal of Forest Research 47, no. 1 (January 2017): 73–80. http://dx.doi.org/10.1139/cjfr-2016-0154.

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In this study, we examined the spatial genetic structure (SGS) in extensively managed, but naturally regenerated forest stands of Pinus cembroides Zucc., Pinus discolor Bailey et Hawksworth, Pinus durangensis Martínez, and Pinus teocote Schiede ex Schltdl. & Cham. at local (within the stands) and large (among the stands) scales using amplified fragment length polymorphisms (AFLP), with respect to conservation and sustainable management of genetic resources of these species. Because these four pine species grow in different landscape structures, we expected to find differences in their SGS, although all of them are widely spread, wind pollinated, and often occur at high population densities. At the local scale, there was no evidence of significant SGS in the four species under study (except in 1 out of 18 seed stands), suggesting that the genetic variants of these species are almost always randomly distributed in space, probably due to high wind pollination and seed dispersal. At a larger scale, the significant SGS found may be the result of isolation by distance among populations. We recommend (i) establishing a tight network of seed stands, with a maximum distance of 3–11 km between seed stands, to prevent greater loss of local genetic structure, and (ii) using these seeds to establish reforestations within a maximal radius of 3–5 km from seed provenances.

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Bregman, Tom P., Alexander C. Lees, Hannah E. A. MacGregor, Bianca Darski, Nárgila G. de Moura, Alexandre Aleixo, Jos Barlow, and Joseph A. Tobias. "Using avian functional traits to assess the impact of land-cover change on ecosystem processes linked to resilience in tropical forests." Proceedings of the Royal Society B: Biological Sciences 283, no. 1844 (December 14, 2016): 20161289. http://dx.doi.org/10.1098/rspb.2016.1289.

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Vertebrates perform key roles in ecosystem processes via trophic interactions with plants and insects, but the response of these interactions to environmental change is difficult to quantify in complex systems, such as tropical forests. Here, we use the functional trait structure of Amazonian forest bird assemblages to explore the impacts of land-cover change on two ecosystem processes: seed dispersal and insect predation. We show that trait structure in assemblages of frugivorous and insectivorous birds remained stable after primary forests were subjected to logging and fire events, but that further intensification of human land use substantially reduced the functional diversity and dispersion of traits, and resulted in communities that occupied a different region of trait space. These effects were only partially reversed in regenerating secondary forests. Our findings suggest that local extinctions caused by the loss and degradation of tropical forest are non-random with respect to functional traits, thus disrupting the network of trophic interactions regulating seed dispersal by forest birds and herbivory by insects, with important implications for the structure and resilience of human-modified tropical forests. Furthermore, our results illustrate how quantitative functional traits for specific guilds can provide a range of metrics for estimating the contribution of biodiversity to ecosystem processes, and the response of such processes to land-cover change.

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Farris, Emmanuele, Martino Orrù, Mariano Ucchesu, Arianna Amadori, Marco Porceddu, and Gianluigi Bacchetta. "Morpho-Colorimetric Characterization of the Sardinian Endemic Taxa of the Genus Anchusa L. by Seed Image Analysis." Plants 9, no. 10 (October 6, 2020): 1321. http://dx.doi.org/10.3390/plants9101321.

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In this work, the seed morpho-colorimetric differentiation of the Sardinian endemic species of Anchusa (Boraginaceae) was evaluated. In Sardinia, the Anchusa genus includes the following seven taxa: A. capellii, A. crispa ssp. crispa, A. crispa ssp. maritima, A. formosa, A. littorea, A. montelinasana, and A. sardoa. Seed images were acquired using a flatbed scanner and analyzed using the free software package ImageJ. A total of 74 seed morpho-colorimetric features of 2692 seed lots of seven taxa of Anchusa belonging to 17 populations were extrapolated and used to build a database of seed size, shape, and color features. The data were statistically elaborated by the stepwise linear discriminant analysis (LDA) to compare and discriminate each accession and taxon. In addition, the seed morpho-colorimetric differences among coastal and mountainous taxa were evaluated. Considering the ecological conditions, the LDA was able to discriminate among the Anchusa taxa with a correct identification of 87.4% and 90.8% of specimens for mountainous and coastal plants, respectively. Moreover, the LDA of the 17 populations of Anchusa showed a low separation among species and populations within the coastal group, highlighting how the long-distance dispersal by flotation on the sea water surface and the pollination network may influence the similarity patterns observed. In addition, a misattribution was observed for A. crispa ssp. crispa, which was misclassified as A. crispa ssp. maritima in 14.1% of cases, while A. crispa ssp. maritima was misidentified as A. crispa ssp. crispa in 21.1% of cases, highlighting a close phenotypic relationship between these two taxa. The statistical results obtained through the seed image analysis showed that the morpho-colorimetric features of the seeds provide important information about the adaptation and evolution of Anchusa taxa in Sardinia.

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Salazar-Rivera, Gabriela I., Lázaro R. Sánchez-Velásquez, and Ernesto Ruelas Inzunza. "Passage Through a Bird’s Gut Confers a Germination Head Start to the Seeds of the Nightshade Witheringia stramoniifolia." Tropical Conservation Science 13 (January 2020): 194008292093109. http://dx.doi.org/10.1177/1940082920931093.

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In frugivory networks, birds offer plants the advantage of dispersing their seeds away from the parent plants in exchange for macronutrients, primarily sugars, and water. The benefits for birds are clear, as they obtain food and water from fruits, and highly variable for plants, as birds may act in ways that vary from effective dispersers to seed predators. We studied two common species that interact frequently in the frugivory network of a Neotropical, periurban park: The clay-colored thrush ( Turdus grayi) and a nightshade ( Witheringia stramoniifolia), in order to evaluate the advantage of passing its seeds through a bird’s gut. We set up an investigation using captive thrushes that we fed with fruits of W. stramoniifolia. We had four experimental treatments: in two of them, seeds that had passed through the digestive tract of thrushes were germinated under greenhouse and controlled conditions; in the remaining two treatments, we germinated seeds that were not consumed by thrushes and were likewise germinated under greenhouse and controlled conditions. W. stramoniifolia seeds consumed by birds had a germination onset that was 1 to 2 weeks earlier than nonconsumed seeds. Mean germination rate and final germinability, however, did not differ significantly among treatments. In our study, passage through a bird’s gut accelerates the germination onset of seeds, an advantage that possibly enhances seedling establishment, but is not indispensable, for the dispersal of W. stramoniifolia. This bird–plant relationship ultimately accounts to a true mutualism.

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Jacobsen, Rannveig M., Anne Sverdrup-Thygeson, Håvard Kauserud, and Tone Birkemoe. "Revealing hidden insect–fungus interactions; moderately specialized, modular and anti-nested detritivore networks." Proceedings of the Royal Society B: Biological Sciences 285, no. 1876 (April 4, 2018): 20172833. http://dx.doi.org/10.1098/rspb.2017.2833.

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Ecological networks are composed of interacting communities that influence ecosystem structure and function. Fungi are the driving force for ecosystem processes such as decomposition and carbon sequestration in terrestrial habitats, and are strongly influenced by interactions with invertebrates. Yet, interactions in detritivore communities have rarely been considered from a network perspective. In the present study, we analyse the interaction networks between three functional guilds of fungi and insects sampled from dead wood. Using DNA metabarcoding to identify fungi, we reveal a diversity of interactions differing in specificity in the detritivore networks, involving three guilds of fungi. Plant pathogenic fungi were relatively unspecialized in their interactions with insects inhabiting dead wood, while interactions between the insects and wood-decay fungi exhibited the highest degree of specialization, which was similar to estimates for animal-mediated seed dispersal networks in previous studies. The low degree of specialization for insect symbiont fungi was unexpected. In general, the pooled insect–fungus networks were significantly more specialized, more modular and less nested than randomized networks. Thus, the detritivore networks had an unusual anti-nested structure. Future studies might corroborate whether this is a common aspect of networks based on interactions with fungi, possibly owing to their often intense competition for substrate.

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Medeiros, Lucas P., Guilherme Garcia, John N. Thompson, and Paulo R. Guimarães. "The geographic mosaic of coevolution in mutualistic networks." Proceedings of the National Academy of Sciences 115, no. 47 (November 7, 2018): 12017–22. http://dx.doi.org/10.1073/pnas.1809088115.

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Ecological interactions shape adaptations through coevolution not only between pairs of species but also through entire multispecies assemblages. Local coevolution can then be further altered through spatial processes that have been formally partitioned in the geographic mosaic theory of coevolution. A major current challenge is to understand the spatial patterns of coadaptation that emerge across ecosystems through the interplay between gene flow and selection in networks of interacting species. Here, we combine a coevolutionary model, network theory, and empirical information on species interactions to investigate how gene flow and geographical variation in selection affect trait patterns in mutualistic networks. We show that gene flow has the surprising effect of favoring trait matching, especially among generalist species in species-rich networks typical of pollination and seed dispersal interactions. Using an analytical approximation of our model, we demonstrate that gene flow promotes trait matching by making the adaptive landscapes of different species more similar to each other. We use this result to show that the progressive loss of gene flow associated with habitat fragmentation may undermine coadaptation in mutualisms. Our results therefore provide predictions of how spatial processes shape the evolution of species-rich interactions and how the widespread fragmentation of natural landscapes may modify the coevolutionary process.

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Amaro-Blanco, Ignacio, María D. Osuna, Yolanda Romano, Rafael Roldán-Gómez, Candelario Palma-Bautista, João Portugal, and Rafael De Prado. "Selection for glyphosate resistance in Conyza spp. occurring in the railway network of southern Spain." Canadian Journal of Plant Science 99, no. 4 (August 1, 2019): 413–19. http://dx.doi.org/10.1139/cjps-2018-0254.

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Conyza spp. are broadleaf weeds that occur in many crops but are also common in non-crop systems such as roadsides and railways. Conyza have selected for glyphosate resistance along railway tracks in southern Spain due to the misuse of this herbicide and the high seed dispersal rate of these species. Twenty-three samples of the genus Conyza (11 Conyza canadensis and 12 Conyza bonariensis) were collected from the margins of railways in different routes of the Andalusia railway network running adjacent to nearby crop fields. The glyphosate resistance level of Conyza populations was evaluated through GR50 (herbicide rate causing 50% growth reduction) and resistance factor (RF) values in every population collected. The highest GR50 were 1851.2 g a.e. ha−1 (RF = 52.53) in C. canadensis (Malaga–Cordoba route) and 1972.4 g a.e. ha−1 (RF = 35.20) in C. bonariensis (Seville–Cordoba route), and the lowest were 46.9 g a.e. ha−1 (RF = 1.33) in C. canadensis (Seville–Cordoba route) and 23.2 g a.e. ha−1 (RF = 0.41) in C. bonariensis (Seville–Cordoba route). The results showed that, among all the C. canadensis populations collected, 18.2% were glyphosate-resistant (RF > 10), 45.5% showed a tendency to develop resistance (RF = 2.5–5), and 36.4% were susceptible (RF < 2.5). Of the 25% of C. bonariensis populations that had resistance to glyphosate, 16.7% had moderate resistance (RF = 5–10) and 58.3% were susceptible. This study found that there are already glyphosate-resistant Conyza spp. along the railway network in southern Spain. This could lead to possible seed exchange between the railway and adjacent places. Therefore, it is vital to consider the railway network when planning control measures against resistance.

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Fedriani, José M., and Thorsten Wiegand. "Hierarchical mechanisms of spatially contagious seed dispersal in complex seed-disperser networks." Ecology 95, no. 2 (February 2014): 514–26. http://dx.doi.org/10.1890/13-0718.1.

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Silva, Adriano M., Pietro K. Maruyama, Luís Pedro M. Paniago, and Celine Melo. "Modularity in ecological networks between frugivorous birds and congeneric plant species." Journal of Tropical Ecology 32, no. 6 (August 31, 2016): 526–35. http://dx.doi.org/10.1017/s0266467416000444.

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Abstract:Ecological and evolutionary factors influence the presence of modules in species interaction networks, and these modules usually cluster functional similar species. But whether closely related species form modules is still unknown. We tested whether the interaction networks formed by frugivorous birds and Miconia plants are modular and evaluated how modules were divided. To do so, we gathered from the literature data concerning four networks of Miconia and their frugivorous birds (three from Brazilian savanna and one from a rain forest in Panama). We quantified modularity using binary and weighted algorithms and also tested the relationship between bird traits (body mass, dietary specialization, migratory behaviour and phylogeny) in relation to within- and among-module connectivity indices (c and z values). If considering only binary information, networks did not present distinct modular structure. Nevertheless, by including interaction strength, modules can be detected in all four Miconia-bird networks. None of the bird traits, however, was related with the connectivity indices. The possible fluctuation of frugivorous bird abundance coupled with the asynchronic fruiting period of Miconia might favour the formation of temporal modules comprising birds and plant species with phenological overlap, ensuring seed dispersal and facilitating the coexistence in sympatry. Bird traits had little effect on the role that each species plays within the modular network, probably because the frugivorous assemblages were dominated by small-bodied and opportunistic species.

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Andreazzi, Cecilia S., Alexandra S. Pires, Clarissa S. Pimenta, and Fernando A. S. Fernandez. "Increased female reproduction favours the large-seeded palm Attalea humilis in small Atlantic Forest fragments." Journal of Tropical Ecology 28, no. 3 (April 12, 2012): 321–25. http://dx.doi.org/10.1017/s0266467412000089.

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Palms are important components of tropical forest plant communities, due both to their abundance (Henderson et al. 2000) and to the network of interactions with their pollinators and dispersers (Henderson 2002, Zona & Henderson 1989). Forest fragmentation alters the biotic and abiotic conditions of habitats (Ewers & Didham 2006, Fahrig 2003) and it has been observed that Attalea palms increase their densities in disturbed sites (Aguiar & Tabarelli 2009, Andreazzi et al. 2012, Lorenzi et al. 2004). Increased light availability (Salm 2005, Souza & Martins 2004), changes in seed dispersal and predation patterns (Andreazzi et al. 2012, Pimentel & Tabarelli 2004, Wright et al. 2000), and ability to recover after disturbance (Souza & Martins 2004) are among the main mechanisms that have been proposed to explain enhanced palm densities. However, how altered conditions following disturbances influence the dynamics of flower and fruit production is still little understood.

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Olesen, Jens M., Jordi Bascompte, Yoko L. Dupont, Heidi Elberling, Claus Rasmussen, and Pedro Jordano. "Missing and forbidden links in mutualistic networks." Proceedings of the Royal Society B: Biological Sciences 278, no. 1706 (September 15, 2010): 725–32. http://dx.doi.org/10.1098/rspb.2010.1371.

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Ecological networks are complexes of interacting species, but not all potential links among species are realized. Unobserved links are either missing or forbidden. Missing links exist, but require more sampling or alternative ways of detection to be verified. Forbidden links remain unobservable, irrespective of sampling effort. They are caused by linkage constraints. We studied one Arctic pollination network and two Mediterranean seed-dispersal networks. In the first, for example, we recorded flower-visit links for one full season, arranged data in an interaction matrix and got a connectance C of 15 per cent. Interaction accumulation curves documented our sampling of interactions through observation of visits to be robust. Then, we included data on pollen from the body surface of flower visitors as an additional link ‘currency’. This resulted in 98 new links, missing from the visitation data. Thus, the combined visit–pollen matrix got an increased C of 20 per cent. For the three networks, C ranged from 20 to 52 per cent, and thus the percentage of unobserved links (100 − C ) was 48 to 80 per cent; these were assumed forbidden because of linkage constraints and not missing because of under-sampling. Phenological uncoupling (i.e. non-overlapping phenophases between interacting mutualists) is one kind of constraint, and it explained 22 to 28 per cent of all possible, but unobserved links. Increasing phenophase overlap between species increased link probability, but extensive overlaps were required to achieve a high probability. Other kinds of constraint, such as size mismatch and accessibility limitations, are briefly addressed.

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Lu, Sheng-You, Ching-I. Peng, Yu-Ping Cheng, Kuo-Hsiang Hong, and Tzen-Yuh Chiang. "Chloroplast DNA phylogeography of Cunninghamia konishii (Cupressaceae), an endemic conifer of Taiwan." Genome 44, no. 5 (October 1, 2001): 797–807. http://dx.doi.org/10.1139/g01-074.

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Abstract:

In this study, we investigated the genetic structure and phylogeographic pattern of the genus Cunninghamia, a member of the Cupressaceae restricted to mainland China and Taiwan, based on sequences of the trnDtrnT noncoding spacer of the chloroplast DNA. Maternal inheritance of chloroplasts was determined experimentally. No paternal leakage was detected. Both parsimony and neighbor-joining analyses revealed the polyphyly of Cunninghamia konishii, populations of which were nested in clades of C. lanceolata from mainland China. The nucleotide diversity of chloroplast DNA sequences within C. konishii (0.0118) was higher than that between species (0.0104), which agrees with a previous allozyme investigation. Based on mutational differences between sequences, a minimum spanning network consisting of five clades was constructed. Significant genetic differentiation (ΦST = 0.130, P < 0.001) was detected between the clades based on AMOVA analyses. We infer several possible refugia in the Yunnan, Zhejiang, and Guangdong provinces of south China, all located in the minimum network as interior nodes. We also infer possible migration routes of Cunninghamia populations. The phylogeographic pattern shown in the reconstructed network suggests that the present-day Cunninghamia populations in Taiwan were derived from six different sources in continental Asia via long-distance seed dispersal. A migrant-pool model explains the heterogeneous composition of the organelle DNA in Taiwan's populations and the low differentiation between populations of Taiwan and China (ΦCT = 0.012, P = 0.454). In contrast with the genetic heterogeneity within geographic populations, many local populations have attained coalescence at the trnDtrnT alleles, which has led to significant differentiation at the population level.Key words: AMOVA, coalescence, cpDNA, Cunninghamia konishii, Cunninghamia lanceolata, minimum spanning network, phylogeography.

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Journal articles on the topic 'Seed dispersal network'

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