Pollination networks from natural and anthropogenic-novel communities show high structural similarity (original) (raw)
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The interactions between pairs of native and alien plants via shared use of pollinators have been widely studied. Studies of invasive species effects at the community level on the other hand are still scarce. Few community level studies, however, have considered how differences in the intensity of invasion, and degree of floral trait similarity between native and invasive species, can mediated effects on native plant-pollinator communities. Here, we evaluated the effect of alien species on overall plant-pollinator network structure, and species-level network parameters, across nine coastal communities distributed along 205 km at Yucatán, México that vary in alien species richness and flower abundance. We further assessed the effect of alien plant species on plant-pollinator network structure and robustness via computational simulation of native and invasive plant extinction scenarios. We did not find significant differences between native and alien species in functional floral pheno...
Contrasting effects of invasive plants in plant–pollinator networks
Oecologia, 2008
The structural organization of mutualism networks, typiWed by interspeciWc positive interactions, is important to maintain community diversity. However, there is little information available about the eVect of introduced species on the structure of such networks. We compared uninvaded and invaded ecological communities, to examine how two species of invasive plants with large and showy Xowers (Carpobrotus aYne acinaciformis and Opuntia stricta) aVect the structure of Mediterranean plant-pollinator networks. To attribute diVerences in pollination to the direct presence of the invasive species, areas were surveyed that contained similar native plant species cover, diversity and Xoral composition, with or without the invaders. Both invasive plant species received signiWcantly more pollinator visits than any native species and invaders interacted strongly with pollinators. Overall, the pollinator community richness was similar in invaded and uninvaded plots, and only a few generalist pollinators visited invasive species exclusively. Invasive plants acted as pollination super generalists. The two species studied were visited by 43% and 31% of the total insect taxa in the community, respectively, suggesting they play a central role in the plant-pollinator networks. Carpobrotus and Opuntia had contrasting eVects on pollinator visitation rates to native plants: Carpobrotus facilitated the visit of pollinators to native species, whereas Opuntia competed for pollinators with native species, increasing the nestedness of the plant-pollinator network. These results indicate that the introduction of a new species to a community can have important consequences for the structure of the plant-pollinator network.
Species roles in plant-pollinator communities are conserved across native and alien ranges
Diversity and Distributions, 2016
Aim. Alien species alter interaction networks by disrupting existing interactions, for example between plants and pollinators, and by engaging in new interactions. Predicting the effects of an incoming invader can be difficult, although recent work suggests species roles in interaction networks may be conserved across locations. We test whether species roles in plant-pollinator networks differ between their native and alien ranges, and whether the former can be used to predict the latter. Location: worldwide. Methods. We used 64 plant-pollinator networks to search for species occurring in at least one network in its native range and one network in its alien range. We found 17 species meeting these criteria, distributed in 48 plant-pollinator networks. We characterized each species' role by estimating species-level network indices: normalised degree, closeness centrality, betweenness centrality, and two measures of contribution to modularity (c and z scores). Linear Mixed Models and Linear Regression Models were used to test for differences in species role between native and alien ranges and to predict those roles from the native to the alien range, respectively. Results. Species roles varied considerably across species. Nevertheless, although species lost their native mutualists and gained novel interactions in the alien community, their role did not differ significantly between ranges. Consequently, closeness centrality and normalised degree in the alien range were highly predictable from the native range networks. Main conclusions. Species with high degree and centrality define the core of nested networks. Our results suggest that core species are likely to establish interactions and be core 3 species in the alien range, whilst species with few interactions in their native range will behave similarly in their alien range. Our results provide new insights into species role conservatism, and could help ecologists to predict alien species impact at the community level.
Structure and dynamics of pollination networks: the role of alien plants
Oikos, 2009
Research on ecological communities, and plant–pollinator mutualistic networks in particular, has increasingly benefited from the theory and tools of complexity science. Nevertheless, up to now there have been few attempts to investigate the interplay between the structure of real pollination networks and their dynamics. This study is one of the first contributions to explore this issue. Biological invasions, of major concern for conservation, are also poorly understood from the perspective of complex ecological networks. In this paper we assess the role that established alien species play within a host community by analyzing the temporal changes in structural network properties driven by the removal of non-native plants. Three topological measures have been used to represent the most relevant structural properties for the stability of ecological networks: degree distribution, nestedness, and modularity. Therefore, we investigate for a detailed pollination network, 1) how its dynamics, represented as changes in species abundances, affect the evolution of its structure, 2) how topology relates to dynamics focusing on long-term species persistence; and 3) how both structure and dynamics are affected by the removal of alien plant species. Network dynamics were simulated by means of a stochastic metacommunity model. Our results showed that established alien plants are important for the persistence of the pollination network and for the maintenance of its structure. Removal of alien plants decreased the likelihood of species persistence. On the other hand, both the full network and the subset native network tended to lose their structure through time. Nevertheless, the structure of the full network was better preserved than the structure of the network without alien plants. Temporal topological shifts were evident in terms of degree distribution, nestedness, and modularity. However the effects of removing alien plants were more pronounced for degree distribution and modularity of the network. Therefore, elimination of alien plants affected the evolution of the architecture of the interaction web, which was closely related to the higher species loss found in the network where alien plants were removed.
Invasive plant integration into native plant-pollinator networks across Europe
Proceedings of the Royal Society B: Biological Sciences, 2009
The structure of plant -pollinator networks has been claimed to be resilient to changes in species composition due to the weak degree of dependence among mutualistic partners. However, detailed empirical investigations of the consequences of introducing an alien plant species into mutualistic networks are lacking. We present the first cross-European analysis by using a standardized protocol to assess the degree to which a particular alien plant species (i.e. Carpobrotus affine acinaciformis, Impatiens glandulifera, Opuntia stricta, Rhododendron ponticum and Solanum elaeagnifolium) becomes integrated into existing native plant-pollinator networks, and how this translates to changes in network structure.
Ecology, 2014
ABSTRACT Species introductions have the potential to affect the functionality and stability of ecological communities, but because little is known about how introduced species form novel interactions, these impacts are difficult to predict. We quantified the impacts of species introductions on species interaction networks using five different model scenarios of how a novel species might form plant-pollinator interactions. The network structure was based on experimental manipulations on a community of plants and pollinators and shows that the community was more diverse, ordered, and compartmentalized, but less complex when an invasive plant generalist was present. Our models of species introductions reliably predicted several aspects of novel network structure in the field study. We found that introduced species that become incorporated into the community as generalists (both in the number and frequency of their interactions) have a much larger impact on the structure of plant-pollinator communities than introduced species that integrate into the community with few interactions. Average degree is strongly affected by the number of interactions the novel species forms and whether it competes for interactions, whereas connectance is affected by whether the novel species competes for interactions or adds new interaction partners. The number and size of compartments in the network change only when the novel species adds new interaction partners, while modularity and nestedness respond most to the number of interactions formed by the novel species. This study provides a new approach for understanding the impacts of introduced and invasive species on plant-pollinator communities and demonstrates that it is critical to evaluate multiple structural characters simultaneously as large changes in the fundamental structure of the community may be disguised.
Impact of Alien Plant Invaders on Pollination Networks in Two Archipelagos
PLoS ONE, 2009
Mutualistic interactions between plants and animals promote integration of invasive species into native communities. In turn, the integrated invaders may alter existing patterns of mutualistic interactions. Here we simultaneously map in detail effects of invaders on parameters describing the topology of both plant-pollinator (bi-modal) and plant-plant (uni-modal) networks. We focus on the invader Opuntia spp., a cosmopolitan alien cactus. We compare two island systems: Tenerife (Canary Islands) and Menorca (Balearic Islands). Opuntia was found to modify the number of links between plants and pollinators, and was integrated into the new communities via the most generalist pollinators, but did not affect the general network pattern. The plant uni-modal networks showed disassortative linkage, i.e. species with many links tended to connect to species with few links. Thus, by linking to generalist natives, Opuntia remained peripheral to network topology, and this is probably why native network properties were not affected at least in one of the islands. We conclude that the network analytical approach is indeed a valuable tool to evaluate the effect of invaders on native communities.
Cambridge University Press eBooks, 2012
Invasive alien species are of major concern in the management and conservation of habitats and species worldwide. Recent research has highlighted the importance of alien species' integration into plant-pollinator interactions, and its possible consequences for native species. Here we focus on the implications of alien plant and animal invasion for the pollination and reproductive success of native plants. We review the different mechanisms by which native plants might adapt to novel pollination regimes imposed by invading plants and animals, mainly changes in flower morphology and attractiveness, changes in blooming time and location, and shifts to reproductive modes that are independent of animal visitation. These adaptations may allow some native plant species that are negatively affected by invasive species to survive alongside the invaders. However, not all native plant populations and species are equally likely to undergo such adaptation. We outline the main factors that are likely to affect the potential for such adaptive processes across different taxa and ecosystems, and highlight the need to evaluate these factors in future research. Understanding the mechanisms by which native plants adapt to changing pollination regimes and the main characteristics that allow them to do so may provide an important tool for managing and conserving diversity and functionality in pollination networks.
Urban Ecosystems, 2022
Urban green areas offer diverse flower resources for pollinators. Yet, the role of non-native plant species in local plantpollinator networks is understudied. We explored the effects of plant origin, nationwide distribution, flower color and type on flower visitation by wild bees and honey bees as well as the structure of a plant-pollinator network in a botanical garden in Hungary. Honey bee preferred North American plants over Europeans; it had the highest degree and topological centrality value. The network had similar compactness with its simulated removal from the network model. The species richness and abundance of flower-visiting wild bees did not differ among the plants of different origins and flower color and type. Plant species of different origin, nationwide distribution, and flower color and type had the highest number of direct and indirect links. Our results suggest that non-native plant species can integrate well in diverse botanical gardens and wild bees can adopt these new foraging resources.
Invasive Mutualists Erode Native Pollination Webs
PLOS Biology, 2008
Plant-animal mutualisms are characterized by weak or asymmetric mutual dependences between interacting species, a feature that could increase community stability. If invasive species integrate into mutualistic webs, they may alter web structure, with consequences for species persistence. However, the effect of alien mutualists on the architecture of plant-pollinator webs remains largely unexplored. We analyzed the extent of mutual dependency between interacting species, as a measure of mutualism strength, and the connectivity of 10 paired plant-pollinator webs, eight from forests of the southern Andes and two from oceanic islands, with different incidences of alien species. Highly invaded webs exhibited weaker mutualism than less-invaded webs. This potential increase in network stability was the result of a disproportionate increase in the importance and participation of alien species in the most asymmetric interactions. The integration of alien mutualists did not alter overall network connectivity, but links were transferred from generalist native species to super-generalist alien species during invasion. Therefore, connectivity among native species declined in highly invaded webs. These modifications in the structure of pollination webs, due to dominance of alien mutualists, can leave many native species subject to novel ecological and evolutionary dynamics.