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Conceptual figure of a random food web model a without and b with intraspecific variation. Letters next to arrows indicate the strength of that interaction. Food web models are used to build adjacency matrices for food webs c without and d with intraspecific variation. When intraspecific variation is added to food webs, predator-prey interactions and self-limitation remain unchanged while competition within species varies among genotypes and species
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Although the effects of species diversity on food web stability have long been recognized, relatively little is known about the influence of intraspecific diversity. Empirical work has found that intraspecific diversity can increase community resilience and resistance, but few theoretical studies have attempted to use modeling approaches to determi...
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... built on that model by adding intraspecific diversity to each interaction matrix ( Fig. 1), following similar methods to those used to establish interspecific interactions. Although we will use the term "genotypes" to refer to intraspecific diversity throughout this paper, our results apply equally well to ecotypes or any other form of variation within species. We added a row and column to the food web matrix for each ...
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... methods to those used to establish interspecific interactions. Although we will use the term "genotypes" to refer to intraspecific diversity throughout this paper, our results apply equally well to ecotypes or any other form of variation within species. We added a row and column to the food web matrix for each additional genotype in each species (Fig. 1d). For simplicity, intraspecific variation was only added to interaction coefficients governing competition between genotypes of the same species, not to predator-prey interactions among species. Specifically, if there was a predator-prey interaction between two species in the original food web matrix without intraspecific diversity, ...
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... genotypes of the same species, not to predator-prey interactions among species. Specifically, if there was a predator-prey interaction between two species in the original food web matrix without intraspecific diversity, all genotypes of those two species interacted according to the same α ij where i and j represent species (not genotype) identity (Fig. 1). As in May's model, the diagonal elements (here, intragenotype competition) were constant for all genotypes and species. For intraspecific competition among genotypes, interaction strengths were either 0 or a random value with probability 1 -C or C, respectively, to remain consistent with the way species interactions were assigned. The ...
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... intraspecific competition among genotypes, interaction strengths were either 0 or a random value with probability 1 -C or C, respectively, to remain consistent with the way species interactions were assigned. The results based on this scheme hold when all genotypes within a species are allowed to interact with each other, rather than interactions being assigned with probability C, although trends are more difficult to discern as the effect of genotypic richness is more extreme (Supplementary Fig. 1). Hence, our results are robust to the specific scheme used to determine whether genotypes are allowed to interact. ...
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... is unlikely to be due purely to an increase in complexity as models with the same number of taxonomic units (e.g., S = 40 and G = 1 compared with S = 10 and G = 4; Fig. 2), and hence the same number of interactions, were consistently less stable when G was large than when S was. This may be partly because greater genotypic richness shifted the relative balance of inter-and intragenotype competition towards greater relative strength of intergenotype competition in our model ( Supplementary Table 1), which was destabilizing. Empirical work will be required to determine whether or not that shift occurs in real systems. ...
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... The functional stability of ecosystems can be promoted through the diversity of relationships between species and the environment (3), with communities containing suites of species that vary in their responses to environmental gradients better able to stabilise ecosystem properties than communities lacking equivalent response diversity (4). Temporal or spatial variation in the responses of individual populations is similarly expected to contribute to the stability of ecosystems (27), but that contribution is unlikely to be equal among the different classes of response variability: we expect variation in the sign of a response will make the strongest contribution to stability, followed by the uncertainty class and with variable response magnitudes having the smallest impact. Our data demonstrate intra-population response diversity may be the norm rather than the exception, and Author contributions RME designed the study, conducted the analyses and drafted the manuscript. ...
The functional stability of ecosystems depends greatly on interspecific differences in responses to environmental perturbation. However, responses to perturbation are not necessarily invariant among populations of the same species, so intraspecific variation in responses might also contribute. Such inter-population response diversity has recently been shown to occur spatially across species ranges, but we lack estimates of the extent to which individual populations across an entire community might have perturbation responses that vary through time. We assess this using 524 taxa that have been repeatedly surveyed for the effects of tropical forest logging at a focal landscape in Sabah, Malaysia. Just 39 % of taxa - all with non-significant responses to forest degradation - had invariant responses. All other taxa (61 %) showed significantly different responses to the same forest degradation gradient across surveys, with 6 % of taxa responding to forest degradation in opposite directions across multiple surveys. Individual surveys had low power (< 80 %) to determine the correct direction of response to forest degradation for one-fifth of all taxa. Recurrent rounds of logging disturbance increased the prevalence of intra-population response diversity, while uncontrollable environmental variation and/or turnover of intraspecific phenotypes generated variable responses in at least 44 % of taxa. Our results show that the responses of individual species to local environmental perturbations are remarkably flexible, likely providing an unrealised boost to the stability of disturbed habitats such as logged tropical forests.
... It seems that ITV decreases the overall interaction strength of specialist predators and promotes weak interactions (Gibert & Brassil, 2014;Gibert & DeLong, 2017). Because the presence of weak interactions tends to stabilize communities (McCann, 2000;McCann, Hastings, & Huxel, 1998), increased ITV might lead to more stable population dynamics with a higher probability of persistence (Gibert & Brassil, 2014;Gibert, Dell, DeLong, & Pawar, 2015;Wright, Ames, & Mitchell, 2016; but see Noto & Gouhier, 2020). This concurs with the general observation that plasticity favours stability (Mougi & Kishida, 2009). ...
Plasticity‐mediated changes in interaction dynamics and structure may scale up and affect the ecological network in which the plastic species are embedded. Despite their potential relevance for understanding the effects of plasticity on ecological communities, these effects have seldom been analysed. We argue here that, by boosting the magnitude of intra‐individual phenotypic variation, plasticity may have three possible direct effects on the interactions that the plastic species maintains with other species in the community: may expand the interaction niche, may cause a shift from one interaction niche to another or may even cause the colonization of a new niche. The combined action of these three factors can scale to the community level and eventually expresses itself as a modification in the topology and functionality of the entire ecological network. We propose that this causal pathway can be more widespread than previously thought and may explain how interaction niches evolve quickly in response to rapid changes in environmental conditions. The implication of this idea is not solely eco‐evolutionary but may also help to understand how ecological interactions rewire and evolve in response to global change.
... By demonstrating that intraspecific diversity weakens intraspecific competition in the field, this study suggests that one way that intraspecific diversity affects community function is via its effects on competitive interactions. By weakening intergenotype competition, intraspecific diversity can promote coexistence of S. alterniflora genotypes and potentially even community stability, as weaker competition among genotypes may stabilize communities (Noto & Gouhier, 2020). These community-wide impacts are particularly likely to be relevant in low species-diversity systems like salt marshes, where a large proportion of competition in the community is intraspecific competition. ...
Intraspecific diversity can affect the ecological function of communities. Because community function is the outcome of species interactions, understanding how intraspecific diversity affects species interactions may shed light on the mechanism by which intraspecific diversity affects communities. Competition among and within plant species may be particularly important, as the relative strengths of these interactions can influence species coexistence and community stability.
We established a field experiment in a New England salt marsh to determine how plant intraspecific diversity affects both intra‐ and interspecific competition. Focal plants of two species (Spartina alterniflora and Spartina patens) were planted with S. alterniflora neighbours that were either genotypically identical to one another (monoculture) or genotypically distinct (polyculture).
After two growing seasons, S. alterniflora performance was enhanced in the presence of polyculture conspecific neighbours compared to monoculture neighbours, whereas S. patens was not strongly affected by diversity of its S. alterniflora neighbours. This suggests that intraspecific competition was weakened by intraspecific diversity, potentially even shifting to facilitation, but we did not find strong evidence of intraspecific diversity impacting interspecific competition. By weakening competition within species, intraspecific diversity may promote coexistence of genotypes within that species.
Synthesis. The community‐level effects of intraspecific diversity may be mediated in part by its effect on intraspecific competition/facilitation. Furthermore, stronger intraspecific competition and decreased coexistence resulting from reduced diversity may exacerbate ongoing declines in biodiversity in response to global change.
Antarctic biodiversity is affected by seasonal sea-ice dynamics driving basal resource availability. To (1) determine the role of intraspecific dietary variability in structuring benthic food webs sustaining Antarctic biodiversity, and (2) understand how food webs and the position of topologically central species vary with sea-ice cover, single benthic individuals’ diets were studied by isotopic analysis before sea-ice breakup and afterwards. Isotopic trophospecies (or Isotopic Trophic Units) were investigated and food webs reconstructed using Bayesian Mixing Models. As nodes, these webs used either ITUs regardless of their taxonomic membership (ITU-webs) or ITUs assigned to species (population-webs). Both were compared to taxonomic-webs based on taxa and their mean isotopic values. Higher resource availability after sea-ice breakup led to simpler community structure, with lower connectance and linkage density. Intra-population diet variability and compartmentalisation were crucial in determining community structure, showing population-webs to be more complex, stable and robust to biodiversity loss than taxonomic-webs. The core web, representing the minimal community ‘skeleton’ that expands opportunistically while maintaining web stability with changing resource availability, was also identified. Central nodes included the sea-urchin Sterechinus neumayeri and the bivalve Adamussium colbecki, whose diet is described in unprecedented detail. The core web, compartmentalisation and topologically central nodes represent crucial factors underlying Antarctica’s rich benthic food web persistence.
In recent years, evidence has been found that plant-pollinator interactions are altered by land-use and that genetic diversity also plays a role. However, how land-use and genetic diversity influence plant-pollinator interactions, particularly in the Neotropics, where many endemic plants exist is still an open question. Cucurbita pepo is a monoecious plant and traditional crop wide distributed, with high rates of molecular evolution, landraces associated with human cultural management and a history of coevolution with bees, which makes this species a promising model for studying the effect of landscape and genetic diversity on plant-pollinator interactions. Here, we assess (1) whether female and male flowers differences have an effect on the interaction network, (2) how C. pepo genetic diversity affects flower-bee visitation network structure, and (3) what is the effect that land-use, accounting for C. pepo genetic variability, has on pumpkin-bee interaction network structure. Our results indicate that female and male flowers presented the same pollinator community composition and interaction network structure suggesting that female/male differences do not have a significant effect on network evolution. Genetic diversity has a positive effect on modularity, nestedness and number of interactions. Further, the effect of semi-natural areas on nested-ness could be buffered when genetic diversity is high. Our results suggest that considering genetic diversity is relevant for a better understanding of the effect of land-use on interaction networks. Additionally, this understanding has great value in conserving biodiversity and enhancing the stability of interaction networks in a world facing great challenges of habitat and diversity loss.
