Connectance of species interaction networks and conservation value: Is it any good to be well connected?

Heleno, Rúben; Devoto, Mariano; Pocock, Michael J. O.

doi:10.1016/j.ecolind.2011.06.032

Cited by 85 publications

(67 citation statements)

References 40 publications

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“…Our results suggest that, despite both Connectance and Weighted Connectance of seed dispersal networks may be stable even with a low sampling effort, they are of limited use if we want to compare at least similar seed dispersal networks. Moreover, despite its wide use in ecological network studies and apparent robustness to sample size, Connectance seems to have no relation between its value and the network conservation status (Heleno, Devoto, & Pocock 2012). Further work is required to confirm the extent of this generalization.…”

Section: Network Propertiesmentioning

confidence: 99%

Sampling completeness in seed dispersal networks: When enough is enough

Costa

Silva

Ramos

et al. 2016

Basic and Applied Ecology

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Ecological networks are an increasingly popular tool to explore community assembly rules and frame practical conservation issues. However, most described networks vary largely in sampling effort, hampering the distinction of true biological patterns from artefacts caused by poor sampling. Identifying entire seeds in the droppings of mist-netted birds is generally considered a preferred sampling method for building unbiased, quantitative seed dispersal networks. We retrieved seeds from the droppings of 936 mist-netted birds captured during five days in seven sites in Portugal and estimated sampling completeness as the diversity of seed species, disperser species, and links detected with respect to those predicted by Chao 2 estimator. In one of those sites, sampling effort was extended to 25 days to evaluate the sensitivity of ten network structure descriptors to increasing sampling effort. After five sampling days we detected 93% of the seed species, 97% of the disperser species, and 79% of the links predicted by Chao 2, however sampling for 25 days resulted in the detection of more seeds, dispersers, and links than those estimated at day 5. Most network descriptors only began to stabilize around day 8, except for Connectance and Weighted Connectance that stabilized earlier. Similarly, only after 8 days most networks descriptors significantly departed from the confidence interval estimated by null models exclusively constrained by species abundances, thus reflecting independent ecological patterns. Nestedness was the only exception, as it never departed from the null models. We suggest that Chao 2 may slightly underestimate the real diversity and that in our case at least eight sampling days were needed to build a sound seed dispersal network as 67% of the seeds, 88% of the dispersers, and 71% of the links were detected. Our results have important implications for the interpretation of seed dispersal networks because under-sampled networks may produce biased descriptors that do not suitably characterize the focal communities. ZusammenfassungÖkologische Netzwerke werden immer beliebter als eine Methode, um die 'assembly rules' für Gemeinschaften zu untersuchen und praktische Naturschutzregeln zu entwerfen.

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Section: Network Propertiesmentioning

confidence: 99%

Sampling completeness in seed dispersal networks: When enough is enough

Costa

Silva

Ramos

et al. 2016

Basic and Applied Ecology

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“…This raises the question of the relationship between network stability and network degradation. A greater stability can be a signature of pristine communities, but also of already eroded communities [44].…”

Section: Discussion (A) Emerging Pollination Patterns In the Galápagomentioning

confidence: 99%

Invaders of pollination networks in the Galápagos Islands: emergence of novel communities

et al. 2013

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The unique biodiversity of most oceanic archipelagos is currently threatened by the introduction of alien species that can displace native biota, disrupt native ecological interactions, and profoundly affect community structure and stability. We investigated the threat of aliens on pollination networks in the species-rich lowlands of five Galápagos Islands. Twenty per cent of all species (60 plants and 220 pollinators) in the pooled network were aliens, being involved in 38 per cent of the interactions. Most aliens were insects, especially dipterans (36%), hymenopterans (30%) and lepidopterans (14%). These alien insects had more links than either endemic pollinators or non-endemic natives, some even acting as island hubs. Aliens linked mostly to generalized species, increasing nestedness and thus network stability. Moreover, they infiltrated all seven connected modules (determined by geographical and phylogenetic constraints) of the overall network, representing around 30 per cent of species in two of them. An astonishingly high proportion (38%) of connectors, which enhance network cohesiveness, was also alien. Results indicate that the structure of these emergent novel communities might become more resistant to certain type of disturbances (e.g. species loss), while being more vulnerable to others (e.g. spread of a disease). Such notable changes in network structure as invasions progress are expected to have important consequences for native biodiversity maintenance.

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“…One of the most generally accepted rule on food web connectance is that food webs display an average low connectance of about 0.11 (Havens 1992;Martinez 1992;Dunne et al 2002b), which is however still relatively high compared to that of other real-world networks (Dunne et al 2002b). Since connectance has been used by May (1972May ( , 1973) as a descriptor of network complexity, it has become central to early works on the complexity-stability debate (De Angelis 1975;Pimm 1980bPimm , 1984 and continues to be widely used as a descriptor for network structure (Havens 1992;Dunne et al 2002a;Olesen and Jordano 2002;Tylianakis et al 2010;Heleno et al 2012;Poisot and Gravel 2014). Depending on the way stability is defined, the quality of empirical datasets, or the methods used to generate theoretical networks, contradiction has been observed in the relationship between network stability and connectance.…”

Section: Connectancementioning

confidence: 99%

Complexity and stability of ecological networks: a review of the theory

et al. 2018

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Our planet is changing at paces never observed before. Species extinction is happening at faster rates than ever, greatly exceeding the five mass extinctions in the fossil record. Nevertheless, our lives are strongly based on services provided by ecosystems, thus the responses to global change of our natural heritage are of immediate concern. Understanding the relationship between complexity and stability of ecosystems is of key importance for the maintenance of the balance of human growth and the conservation of all the natural services that ecosystems provide. Mathematical network models can be used to simplify the vast complexity of the real world, to formally describe and investigate ecological phenomena, and to understand ecosystems propensity of returning to its functioning regime after a stress or a perturbation. The use of ecological-network models to study the relationship between complexity and stability of natural ecosystems is the focus of this review. The concept of ecological networks and their characteristics are first introduced, followed by central and occasionally contrasting definitions of complexity and stability. The literature on the relationship between complexity and stability in different types of models and in real ecosystems is then reviewed, highlighting the theoretical debate and the lack of consensual agreement. The summary of the importance of this line of research for the successful management and conservation of biodiversity and ecosystem services concludes the review.

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Connectance of species interaction networks and conservation value: Is it any good to be well connected?

Cited by 85 publications

References 40 publications

Sampling completeness in seed dispersal networks: When enough is enough

Sampling completeness in seed dispersal networks: When enough is enough

Invaders of pollination networks in the Galápagos Islands: emergence of novel communities

Complexity and stability of ecological networks: a review of the theory

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