Effects of model choice, network structure, and interaction strengths on knockout extinction models of ecological robustness

Bane, Miranda; Pocock, Michael J. O.; James, Richard

doi:10.1002/ece3.4529

Cited by 13 publications

(17 citation statements)

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“…Understanding direct and indirect threats to ecosystem services from species losses is a key question in the ecology of ecosystem services 17 , 27 . Robustness is one way to measure how species losses and associated secondary extinctions will impact food webs 12 , 28 , 29 ; and here, we investigate the consequences of these secondary extinctions for ecosystem services. Extending robustness analyses to ecosystem services, we further our understanding of how indirect threats from secondary species extinctions will impact ecosystem services.…”

Section: Discussionmentioning

confidence: 99%

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An ecological network approach to predict ecosystem service vulnerability to species losses

et al. 2021

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Human-driven threats are changing biodiversity, impacting ecosystem services. The loss of one species can trigger secondary extinctions of additional species, because species interact–yet the consequences of these secondary extinctions for services remain underexplored. Herein, we compare robustness of food webs and the ecosystem services (hereafter ‘services’) they provide; and investigate factors determining service responses to secondary extinctions. Simulating twelve extinction scenarios for estuarine food webs with seven services, we find that food web and service robustness are highly correlated, but that robustness varies across services depending on their trophic level and redundancy. Further, we find that species providing services do not play a critical role in stabilizing food webs – whereas species playing supporting roles in services through interactions are critical to the robustness of both food webs and services. Together, our results reveal indirect risks to services through secondary species losses and predictable differences in vulnerability across services.

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Section: Discussionmentioning

confidence: 99%

“…Following Bane et al 29 , food web robustness ( R F ) is calculated as the Area Under the Curve (AUC, Supplementary Fig. 5 ), using , where x is the proportion of target species directly removed (i.e., primary extinctions) and y is the proportion of susceptible species that did not go secondarily extinct (Fig.…”

Section: Methodsmentioning

confidence: 99%

An ecological network approach to predict ecosystem service vulnerability to species losses

et al. 2021

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“…Specifically, the observed decrease of nestedness is a possible symptom of instability 5 because specialist species are less connected to the generalist network core 30 . Concurrently, the length, suggesting that trait matching is relevant in defining modules 21,43,44 ; nestedness being predicted by the interaction of morphological matching and sugar amount in the nectar, which confirms that trait matching allows an efficient resource gathering 45,46 ;…”

Section: Discussionmentioning

confidence: 68%

An empirical attack tolerance test alters the structure and species richness of plant-pollinator networks

Biella

Akter

Ollerton

et al. 2020

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Ecological network theory hypothesizes a link between structure and stability, but this has mainly been investigated in-silico. In an experimental manipulation, we sequentially removed four generalist plants from real plant-pollinator networks and explored the effects on, and drivers of, species and interaction extinctions, network structure and interaction rewiring. Our results indicate that cumulative species and interaction extinctions increased faster with generalist plant loss than what was expected by co-extinction models, which predicted the survival or extinction of many species incorrectly. In addition, network nestedness decreased, modularity increased, and opportunistic random interactions and structural unpredictability emerged, which are all indicators of network instability and fragility.Conversely, interaction reorganization (rewiring) was high, asymmetries between network levels emerged as plants increased their centrality. From the experimental manipulations of real networks, our study shows how plant-pollinator network structure has low stability and changes towards a more fragile state when generalist plants are lost. IntroductionInteractions are organized in complex networks, and the way these structures react to disturbance is crucial for understanding network functioning, their ability to buffer negative impacts and also for their conservation 1-4 . This is usually verified with "attack tolerance tests" that assess the functionality of a system after knocking out its important components 5 . In ecology, such tests usually consist in removing all species in one trophic level and then in assessing how many species in another level lost all interactions 6,7 . So far, in pollination networks, this has been addressed mainly theoretically with numerical simulations that show a higher rate of pollinator extinction when highly linked plants are removed 7-10 . However, these theoretical predictions were not compared to empirical data from similar manipulations, which is urgently needed to assess their reliability 11 . Manipulative experiments of plant-pollinator networks can illuminate the factors maintaining network stability and the processes of network reorganization. For instance, previous experiments removing only one generalist plant 12,13 showed that networks are quite stable to this loss, and that other species occupy the role in the network of the removed species. Conversely, when multiple invasive plants are removed, network interaction diversity and generalisation are impacted 14 , indicating that losing multiple species can strongly affect real networks. Moreover, after disturbance, network stability could depend on the amount of interaction rewiring 18 , i.e. foragers' ability to use alternative resources after depletion or disappearance of those previously used 15-17 . Rewiring and the establishment of interactions between plants and pollinators may be regulated by several ecological drivers, such as species trait matching 19,20 , flower's rewards 21,22 or species abundances 23,24 . Sim...

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“…In our study, after removing generalist plants from real plant pollinator networks, the cumulative number of disappeared species and interactions increased more than expected from co‐extinction models. Previous studies have only used in‐silico estimation of extinctions (Bane, Pocock, & James, 2018; Evans, Pocock, & Memmott, 2013; Kaiser‐Bunbury, Muff, Memmott, Müller, & Caflisch, 2010; Vanbergen, Woodcock, Heard, & Chapman, 2017), but our experiment clarifies that TCM, SCM and REW models underestimated species extinction rates, and the rate of false positives and false negatives was high in relation to the identity of the species that were lost. Furthermore, these models underestimated the rate of interaction loss, an issue that has been already pointed out (Santamaría, Galeano, Pastor, & Méndez, 2016).…”

Section: Discussionmentioning

confidence: 99%

An empirical attack tolerance test alters the structure and species richness of plant–pollinator networks

et al. 2020

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Ecological network theory hypothesizes that the structuring of species interactions can convey stability to the system. Investigating how these structures react to species loss is fundamental for understanding network disassembly or their robustness. However, this topic has mainly been studied in‐silico so far. Here, in an experimental manipulation, we sequentially removed four generalist plants from real plant–pollinator networks. We explored the effects on, and drivers of, species and interaction disappearance, network structure and interaction rewiring. First, we compared both the local extinctions of species and interactions and the observed network indices with those expected from three co‐extinction models. Second, we investigated the trends in network indices and rewiring rate after plant removal and the pollinator tendency at establishing novel links in relation to their proportional visitation to the removed plants. Furthermore, we explored the underlying drivers of network assembly with probability matrices based on ecological traits. Our results indicate that the cumulative local extinctions of species and interactions increased faster with generalist plant loss than what was expected by co‐extinction models, which predicted the survival or disappearance of many species incorrectly, and the observed network indices were lowly correlated to those predicted by co‐extinction models. Furthermore, the real networks reacted in complex ways to plant removal. First, network nestedness decreased and modularity increased. Second, although species abundance was a main assembly rule, opportunistic random interactions and structural unpredictability emerged as plants were removed. Both these reactions could indicate network instability and fragility. Other results showed network reorganization, as rewiring rate was high and asymmetries between network levels emerged as plants increased their centrality. Moreover, the generalist pollinators that had frequently visited both the plants targeted of removal and the non‐target plants tended to establish novel links more than who either had only visited the removal plants or avoided to do so. With the experimental manipulation of real networks, our study shows that despite their reorganizational ability, plant–pollinator networks changed towards a more fragile state when generalist plants are lost. A free Plain Language Summary can be found within the Supporting Information of this article.

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Effects of model choice, network structure, and interaction strengths on knockout extinction models of ecological robustness

Cited by 13 publications

References 35 publications

An ecological network approach to predict ecosystem service vulnerability to species losses

An ecological network approach to predict ecosystem service vulnerability to species losses

An empirical attack tolerance test alters the structure and species richness of plant-pollinator networks

An empirical attack tolerance test alters the structure and species richness of plant–pollinator networks

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