Linking the green and brown worlds through nonconsumptive predator effects

Sitvarin, Michael I.; Rypstra, Ann L.; Harwood, James D.

doi:10.1111/oik.03190

Cited by 31 publications

(15 citation statements)

References 123 publications

(203 reference statements)

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“…Another potential explanation could be nonconsumptive effects of abundant mesopredatory stickleback at low piscivore biomass (landscape of fear) changing grazer behaviour from feeding to hiding, thus boosting algal biomass. Such behavioural effects are increasingly recognized to affect both green and brown food webs [65,66].…”

Section: Discussionmentioning

confidence: 99%

A cross-scale trophic cascade from large predatory fish to algae in coastal ecosystems

Donadi

Austin²,

Bergström

et al. 2017

Proc. R. Soc. B.

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Trophic cascades occur in many ecosystems, but the factors regulating them are still elusive. We suggest that an overlooked factor is that trophic interactions (TIs) are often scale-dependent and possibly interact across spatial scales. To explore the role of spatial scale for trophic cascades, and particularly the occurrence of cross-scale interactions (CSIs), we collected and analysed food-web data from 139 stations across 32 bays in the Baltic Sea. We found evidence of a four-level trophic cascade linking TIs across two spatial scales: at bay scale, piscivores (perch and pike) controlled mesopredators (three-spined stickleback), which in turn negatively affected epifaunal grazers. At station scale (within bays), grazers on average suppressed epiphytic algae, and indirectly benefitted habitat-forming vegetation. Moreover, the direction and strength of the grazer-algae relationship at station scale depended on the piscivore biomass at bay scale, indicating a cross-scale interaction effect, potentially caused by a shift in grazer assemblage composition. In summary, the trophic cascade from piscivores to algae appears to involve TIs that occur at, but also interact across, different spatial scales. Considering scale-dependence in general, and CSIs in particular, could therefore enhance our understanding of trophic cascades.

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Section: Discussionmentioning

confidence: 99%

A cross-scale trophic cascade from large predatory fish to algae in coastal ecosystems

Donadi

Austin²,

Bergström

et al. 2017

Proc. R. Soc. B.

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“…One‐third out of more than 30 studies documenting detrital‐based trophic cascades in temperate ecosystems occurred in streams (Sitvarin et al. ). In contrast, we are aware of only one prior report of a detrital‐based trophic cascade in a tropical stream (Andrade et al.…”

Section: Discussionmentioning

confidence: 99%

Landscape patterns in top‐down control of decomposition: omnivory disrupts a tropical detrital‐based trophic cascade

Simon

Binderup

Flecker

et al. 2019

Ecology

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Detrital‐based trophic cascades are often considered weak or absent in tropical stream ecosystems because of the prevalence of omnivorous macroconsumers and the dearth of leaf‐shredding insects. In this study, we isolate top‐down effects of three macroconsumer species on detrital processing in headwater streams draining Trinidad's northern mountains. We separated effects of different macroconsumers by experimentally manipulating their temporal access to isolated benthic habitat over the diel cycle. We found no evidence that omnivorous macroconsumers, including a freshwater crab (Eudaniela garmani) and guppy (Poecilia reticulata), increased leaf decomposition via consumption. By contrast, above a waterfall excluding guppies, the insectivorous killifish, Anablepsoides hartii, reduced the biomass of the leaf‐shredding insect Phylloicus hansoni 4‐fold, which consequently reduced leaf decomposition rates 1.6‐fold. This detrital cascade did not occur below the barrier waterfall, where omnivorous guppies join the assemblage and reduce killifish densities; here killifish had no significant effects on Phylloicus or decomposition rates. These patterns of detrital processing were also observed in upstream–downstream comparisons in a landscape study across paired reaches of six streams. Above waterfalls, where killifish were present, but guppies absent, leaf decomposition rates and Phylloicus biomass were 2.5‐ and ~35‐fold lower, respectively, compared to measurements below waterfalls. Moreover, the strength of top‐down control by killifish is reflected by the 20‐ and 5‐fold reductions in variability (±SE) surrounding mean Phylloicus biomass and leaf decomposition rates in upstream relative to downstream reaches where no top‐down control was detected. Findings show a clear, detrital‐based trophic cascade among killifish, a leaf‐shredding insect, and leaf decomposition rates. Results also show how omnivorous guppies disrupt this cascade by depressing killifish densities, thereby releasing invertebrate shredders from predation, and significantly increasing decomposition rates. Moreover, this combination of direct and indirect trophic interactions drives patterns in decomposition rates in stream networks at a landscape scale, resulting in significantly lower rates of decomposition above vs. below barrier waterfalls. Our findings reveal that omnivory can result in significant indirect effects on a key ecosystem process, illustrating the importance of these hidden trophic pathways in detrital‐based systems and suggesting that resource control in tropical systems may be even more complex than previously envisioned.

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“…For instance, superfluous killing (Maupin and Riechert, 2001), could result in mortality for a prey item without consumption by the predator. Predator-induced behavioral changes (decreased feeding rates and reproduction) can also negatively affect prey populations without consumption by the predator (Brown et al, 1999;Preisser and Bolnick, 2008;Preisser et al, 2005;Schmitz et al, 1997;Sitvarin et al, 2016). Despite these limitations, molecular gut content analysis is a useful tool for visualizing food web linkages especially when coupled with abundance data (Furlong, 2015).…”

Section: Molecular Gut Content Analysismentioning

confidence: 99%

Spring Forward: molecular detection of early season predation in agroecosystems

Athey

Dreyer

Kowles³

et al. 2016

Food Webs

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Agroecosystems undergo disturbance early in the season and host simple food webs that are often comprised of pests, generalist predators, and alternative prey. This is a critical time because predator: pest ratios are highest, in favor of predators, and most likely to affect the trajectory of pest populations, a concept we describe as early season predation. Conservation biological control of these pests utilizes on-farm management schemes to increase predator populations, in part, by providing or enhancing alternative resources. These resources may include beneficial alternative prey that sustains predators prior to pest arrival, but if predator affinity for these alternative prey is strong, pest suppression may be disrupted. Early in the season, when the abundance of pests is low compared to alternative prey, predators do not typically consume prey in direct proportion to their relative abundance, often feeding at disproportionately high rates on "rare" prey items. Therefore, molecular tools, such as gut content analysis, have been used to reveal trophic linkages and decouple the relationship between prey abundance and consumption. Using molecular techniques, numerous studies across different agroecosystems have determined that early season predation occurs regularly and may contribute to pest control and is probably most effective for pests with the potential for exponential population growth, where suppression early in the season may be essential to prevent these outbreaks. Studies incorporating molecular tools and field studies can provide insight for growers to create successful conservation biological control programs utilizing generalist predators in early season predation.

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Linking the green and brown worlds through nonconsumptive predator effects

Cited by 31 publications

References 123 publications

A cross-scale trophic cascade from large predatory fish to algae in coastal ecosystems

A cross-scale trophic cascade from large predatory fish to algae in coastal ecosystems

Landscape patterns in top‐down control of decomposition: omnivory disrupts a tropical detrital‐based trophic cascade

Spring Forward: molecular detection of early season predation in agroecosystems

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