Adaptive rewiring aggravates the effects of species loss in ecosystems

Gilljam, David; Curtsdotter, Alva; Ebenman, Bo

doi:10.1038/ncomms9412

Cited by 67 publications

(74 citation statements)

References 69 publications

(77 reference statements)

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“…However, our results only provide a snapshot of community properties in time, with the caveat that intense trophic interactions in fragmented pools are likely to be transient before predators exhaust their preferred food sources (Ledger et al., ). Nonetheless, rewiring of predator–prey linkages following prey loss can be strongly destabilising in freshwater food webs, potentially leading to the extinction of secondary prey species (Gilljam, Curtsdotter, & Ebenman, ). Given that the dominant predators in our mesocosms were generalists (tanypods), and hence likely to be able to exploit alternative prey, the population crashes of prey species we observed may thus have negative implications for network resistance over the longer term.…”

Section: Discussionmentioning

confidence: 99%

Drought intensification alters the composition, body size, and trophic structure of invertebrate assemblages in a stream mesocosm experiment

et al. 2019

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Predicted trends towards more intense droughts are of particular significance for running water ecosystems, as the loss of critical stream habitat can provoke sudden changes in biodiversity and shifts in community structure. However, analysing ecological responses to the progressive loss of stream habitat requires a continuous disturbance gradient that can only be generated through large‐scale manipulations of streamflow. In the first experiment of its kind, we used large artificial stream channels (mesocosms) as analogues of spring‐fed headwaters and simulated a gradient of drought intensity that encompassed flowing streams, disconnected pools, and dry streambeds. We used breakpoint analysis to analyse macroinvertebrate community responses to intensifying drought, and identify the taxa and compositional metrics sensitive to small changes in drought stress. We detected breakpoints for >60% of taxa, signalling sudden population crashes or irruptions as drought intensified. Abrupt changes were most pronounced where riffle dewatering isolated pools. In the remnant wetted habitat, we observed a shift to larger body sizes across the community, primarily driven by irruptions of predatory midge larvae and coincident population collapses among prey species (worms and smaller midges). Our results suggest that intense predation in confined, fragmented stream habitat can lead to unexpected changes in body sizes, challenging the conventional wisdom that droughts favour the small. Pool fragmentation might thus be the most critical stage of habitat loss during future droughts, as the point at which impacted rivers and streams begin to exhibit major shifts in fundamental food web properties.

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Section: Discussionmentioning

confidence: 99%

Drought intensification alters the composition, body size, and trophic structure of invertebrate assemblages in a stream mesocosm experiment

et al. 2019

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“…However, because most plant–pollinator relationships are not strictly specialist (not exclusive; Menz et al, ; Vázquez & Aizen, ), field data show that species often interact with alternative partners in the absence of, or in addition to, favoured partners and loss of a species does not inevitably mean extinction for its partners (Carstensen, Sabatino, Trøjelsgaard, & Morellato, ; Trøjelsgaard, Jordano, Carstensen, & Olesen, ; Tylianakis & Morris, ). Moreover, modelling studies have found large differences in network stability and resilience when nodes are allowed to dynamically rewire (CaraDonna et al, ; Gilljam, Curtsdotter, & Ebenman, ). Given the wide variation in quality, quantity and availability of resource rewards offered by plant species, and behavioural attributes and physiological requirements of pollinators, pollinators’ choices of partners and alternative partners is unlikely to be random (Trøjelsgaard et al, ).…”

Section: How Much and What Type Of Floral Resources Are Necessary To mentioning

confidence: 95%

Network modelling, citizen science and targeted interventions to predict, monitor and reverse bee decline

Lander

2019

Plants People Planet

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Societal Impact Statement The global decline in pollinating insect populations has rightly received widespread news coverage as it imperils ecosystem function and human food security. Reversing and addressing this decline is an urgent global priority. However, in many locations we do not know what species are present, how large or small species populations are, or what types of specific resources the populations require. By adopting novel network analyses approaches and by working with monitoring programs, such as Oxford Plan Bee, we may be able to dramatically improve our ability to predict species extinctions and facilitate targeted conservation action to maintain abundant, diverse and stable pollinator communities. Summary Pollination is fundamentally important to ecosystem function and human food security. Recent reports of dramatic insect declines, and pollinator decline in particular, have increased public awareness and political motivation to act to protect pollinators. This article maps commonly proposed management interventions onto known drivers of bee decline, and identifies forage and nest site provision as a tractable management intervention that can simultaneously address multiple drivers of decline. However, it is recognized that there are gaps in the knowledge of exactly how much and which types of forage resources are necessary to support wild pollinator populations. A novel network analysis approach based on quantified floral resources and pollination services is proposed, which would illuminate the types and quantities of floral resources and pollinators necessary to maintain a diverse and abundant plant–pollinator community. The approach would also facilitate the prediction of species extinctions in plant–pollinator communities and help target conservation interventions. Finally, Oxford Plan Bee is introduced as a new, citizen‐science‐based project to monitor solitary bee populations, and provide empirical data to validate predictions from the proposed network approach. The over‐arching aim of the described network analysis approach and the Oxford Plan Bee project is to facilitate effective, evidence‐based conservation action to protect pollinators and the plants they pollinate into the future.

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“…An important driver of the relationship between richness and connectance, next to spatial dynamics [23], and the capacity of species to change their interactions with other species (e.g. diet shifts[24]), is the diversity of interaction types [25]. Thus, biotic stress, the term used in the present paper to denote effects of species interactions on species richness, by definition plays an important role in shaping the richness-connectance relationship.…”

Section: Introductionmentioning

confidence: 99%

The combined effects of biotic and abiotic stress on species richness and connectance

Kulkarni

Laender

2017

PLoS ONE

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Food web structure and species richness are both subject to biotic (e.g. predation pressure and resource limitation) and abiotic stress (e.g. environmental change). We investigated the combined effects of both types of stress on richness and connectance, and on their relationship, in a predator-prey system. To this end, we developed a mathematical two trophic level food-web model to investigate the effects of biotic and abiotic stress on food web connectance and species richness. We found negative effects of top-down and bottom-up control on prey and predator richness, respectively. Effects of top-down and bottom-up control were stronger when initial connectance was high and low, respectively. Bottom-up control could either aggravate or buffer negative effects of top-down control. Abiotic stress affecting predator richness had positive indirect effects on prey richness, but only when initial connectance was low. However, no indirect effects on predator richness were observed following direct effects on prey richness. Top-down and bottom-up control selected for weakly connected prey and highly connected predators, thereby decreasing and increasing connectance, respectively. Our simulations suggest a broad range of negative and positive richness-connectance relationships, thereby revisiting the often found negative relationship between richness and connectance in food webs. Our results suggest that (1) initial food-web connectance strongly influences the effects of biotic stress on richness and the occurrence of indirect effects on richness; and (2) the shape of the richness-connectance relationship depends on the type of biotic stress.

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Adaptive rewiring aggravates the effects of species loss in ecosystems

Cited by 67 publications

References 69 publications

Drought intensification alters the composition, body size, and trophic structure of invertebrate assemblages in a stream mesocosm experiment

Drought intensification alters the composition, body size, and trophic structure of invertebrate assemblages in a stream mesocosm experiment

Network modelling, citizen science and targeted interventions to predict, monitor and reverse bee decline

The combined effects of biotic and abiotic stress on species richness and connectance

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