The dilemma of binary or weighted data in interaction networks

Miranda, Patrícia Nakayama; Ribeiro, José Eduardo Lahoz da Silva; Luna, Pedro; Silva, Izaias Brasil da; Delabie, Jacques Hubert Charles; Dáttilo, Wesley

doi:10.1016/j.ecocom.2018.12.006

Cited by 41 publications

(41 citation statements)

References 52 publications

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“…We used qualitative data (i.e. binary data expressed as interaction presence/absence) to build the networks, aiming to describe interaction distribution within the community (Miranda et al., 2019). We also tested a quantitative analysis using moss biomass as a proxy of abundance.…”

Section: Methodsmentioning

confidence: 99%

Cryptic interactions revisited from ecological networks: Mosses as a key link between trees and hummingbirds

Fontúrbel

Osorio²,

Riffo‐Donoso

et al. 2020

Functional Ecology

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1. Ecological interactions are the glue of biodiversity, structuring communities and determining their functionality. However, our knowledge about ecological interactions is usually biased against cryptic interactions (i.e. overlooked interactions involving inconspicuous species). Mosses are a neglected component in community ecology despite being diverse and abundant in boreal and temperate forests. Therefore, the cryptic relationships of trees as hosts for epiphytic mosses, and vertebrates using mosses as nesting material, may have important consequences for community structuring. 2. We built species-and individual-based ecological networks to characterise treemoss associations in 120 tree individuals representing 13 species, which hosted 19 moss species. We also used those ecological networks to simulate the effects of non-random extinctions due to selective logging, to assess the presence of moss species in hummingbird nests (30 nests), whether these mosses were a subset of those found on the trees if moss diversity varies with tree height and whether these moss-tree relationships are phylogenetically constrained. 3. We found a nested pattern in the tree-moss network. Taller trees were the most connected, with tree height positively related to number of moss species, network degree and centrality. Extinction simulations showed changes in network topology, with the strongest effect from the removal of the most connected tree species. However, tree and moss networks were not influenced by phylogenetic relatedness. The hummingbird Sephanoides sephaniodes selectively collected mosses; the moss species used as nesting material by hummingbirds were a subset of available species. These complex relationships among trees, birds and mosses underpin the importance of neglected components in the community. 4. We found that tree-moss associations were non-random, showing a positive relationship between tree height and moss diversity. Those associations are the reflection of preferences beyond relative abundances in the forest, and the removal of certain tree species (due to selective logging) may have cascade effects in the community. Furthermore, the lack of phylogenetic correspondence suggests that tree-moss associations are governed by ecological factors (host tree preferences). Moss-hummingbird associations are non-random, as hummingbirds (that pollinate | 227 Functional Ecology FONTÚRBEL ET aL.

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Section: Methodsmentioning

confidence: 99%

Cryptic interactions revisited from ecological networks: Mosses as a key link between trees and hummingbirds

Fontúrbel

Osorio²,

Riffo‐Donoso

et al. 2020

Functional Ecology

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“…Understanding how different approaches to estimate interaction strength may influence network structure has generated much debate in the interaction literature (e.g. [22,44–46]). The commonly used measure of interaction strength in plant-pollinator systems is based on the frequency of encounters between individual plants and pollinators.…”

Section: Discussionmentioning

confidence: 99%

Interaction strength in plant-pollinator networks: Are we using the right measure?

et al. 2019

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Understanding how ecological networks are assembled is important because network structure reflects ecosystem functioning and stability. Quantitative network analysis incorporates measures of interaction strength as an estimate of the magnitude of the effect of interaction partners on one another. Most plant-pollinator network studies use frequency of interaction between individual pollinators and individual plants (encounter) as a surrogate of interaction strength. However, the number of flowers visited per encounter may strongly vary among pollinator and plant species, and therefore not all encounters are quantitatively equivalent. We sampled plant-pollinator interactions in a Mediterranean scrubland and tested whether using a measure of interaction strength based on the number of flowers visited resulted in changes in species (species strength, interaction species asymmetry, specialization) and network descriptors (nestedness, H2’, interaction evenness, plant generality, pollinator generality) compared to the encounter-based measure. Several species (including some of the most abundant ones) showed important changes in species descriptors, notably in specialization. These changes were especially important in plant species with large floral displays, which became less specialized with the visit-based measure of interaction strength. At the network level we found significant changes in all properties analysed. With the encounter-based approach plant generality was much higher than pollinator generality (high specialization asymmetry between trophic levels). However, with the visit-based approach plant generality was greatly reduced so that plants and pollinators had similar levels of generalization. Interaction evenness also decreased strongly with the visit-based approach. We conclude that accounting for the number of flowers visited per encounter provides a more ecologically relevant measure of interaction strength. Our results have important implications for the stability of pollination networks and the evolution of plant-pollinator interactions. The use of a visit-based approach is especially important in studies relating interaction network structure and ecosystem function (pollination and/or exploitation of floral resources).

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“…Analyses were conducted using the packages lme4 [39] and lmerTest [40], for LM and robustlmm package [41] for robust regressions in R [33]. Because network analyses based on binary and weighed matrices might lead to different results [42], we repeated all the analyses based only on binary data (electronic supplementary material, figure S5 and table S6). This did not change any results and below we only present the results for the quantitative networks.…”

Section: Methodsmentioning

confidence: 99%

Integrating plant species contribution to mycorrhizal and seed dispersal mutualistic networks

et al. 2019

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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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The dilemma of binary or weighted data in interaction networks

Cited by 41 publications

References 52 publications

Cryptic interactions revisited from ecological networks: Mosses as a key link between trees and hummingbirds

Cryptic interactions revisited from ecological networks: Mosses as a key link between trees and hummingbirds

Interaction strength in plant-pollinator networks: Are we using the right measure?

Integrating plant species contribution to mycorrhizal and seed dispersal mutualistic networks

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