Food web persistence in fragmented landscapes

Liao, Jinbao; Bearup, Daniel; Blasius, Bernd

doi:10.1098/rspb.2017.0350

Cited by 32 publications

(41 citation statements)

References 67 publications

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“…Thus, a larger branch contains more patches (illustrated in Figure 1; Muneepeerakul, Weitz, Levin, Rinaldo, & Rodriguez-Iturbe, 2007). The population of a given branch, and the system as a whole, can be regarded as proportional to the number of colonised patches within it (Liao, Bearup, & Blasius, 2017a;Liao, Bearup, & Blasius, 2017b;Liao et al, 2017). This framework allows us to model both within-branch colonisation-extinction processes and the effects of dispersal between branches.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

Spatial variation in branch size promotes metapopulation persistence in dendritic river networks

Shen

Bearup

et al. 2019

Freshwater Biology

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1. Despite years of attention, the dynamics of species constrained to disperse within riverine networks are not well captured by existing metapopulation models, which often ignore local dynamics within branches.2. We develop a modelling framework, based on traditional metapopulation theory, for patch occupancy dynamics subject to local colonisation-extinction dynamics within branches and regional dispersal between branches in size-structured, bifurcating riverine networks. Using this framework, we investigate whether and how spatial variation in branch size affects species persistence for dendritic systems with directional dispersal, including one-way (up-or downstream only) and two-way (both up-and downstream) dispersal.3. Variation in branch size generally promotes species persistence more obviously at higher relative extinction rate, suggesting that previous studies ignoring differences in branch size in real riverine systems might overestimate species extinction risk. 4. Two-way dispersal is not always superior to one-way dispersal as a strategy for metapopulation persistence especially at high relative extinction rate. The type of dispersal that maximises species persistence is determined by the hierarchical level of the largest, and hence most influential, branch within the network. When considering the interactive effects of up-and downstream dispersal, we find that moderate upstream-biased dispersal maximises metapopulation viability, mediated by spatial branch arrangement. 5. Overall, these results suggest that both branch-size variation and species traits interact to determine species persistence, theoretically demonstrating the ecological significance of their interplay. K E Y W O R D Sdownstream dispersal, local branch dynamics, metapopulation model, spatial branch-size heterogeneity, upstream dispersal | 427 MA et Al.

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Section: Theoretical Frameworkmentioning

confidence: 99%

Spatial variation in branch size promotes metapopulation persistence in dendritic river networks

Shen

Bearup

et al. 2019

Freshwater Biology

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“…Given that top-down regulation can stabilise food webs [24,57], the loss of top predators might entail unpredictable consequences for adjacent trophic levels, destabilise food webs, reduce species diversity and trophic complexity and ultimately compromise ecosystem functioning [23,24]. In addition to the trophic position of a species, the trophic structure of the food web has also been shown to be an important aspect (see [11]). Our results suggest that bottom-up energy limitation caused by dispersal mortality due to habitat isolation can be a critical factor driving species loss and the reduction of trophic complexity.…”

Section: The Biggest Losersmentioning

confidence: 99%

“…A general observation and prediction is that large-bodied predators at high trophic levels which depend on sufficient food supplied by lower trophic levels are most sensitive to fragmentation, and thus, might respond more strongly than species at lower trophic levels [4,5]. However, most conclusions regarding the effect of fragmentation are based on single species or competitively interacting species (see references within [6][7][8], but see for example [9][10][11] for food chains and simple food web motifs). There is thus limited understanding how species embedded in complex food webs with multiple trophic levels respond to habitat fragmentation [4,[12][13][14][15], even though these networks are a central organising theme in nature [16,17].…”

Section: Introductionmentioning

confidence: 99%

The biggest losers: Habitat isolation deconstructs complex food webs from top to bottom

Häussler

Ryser

Stark

et al. 2018

Preprint

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Habitat fragmentation is threatening global biodiversity. To date, there is only limited understanding of how the different aspects of habitat fragmentation (habitat loss, number of fragments and isolation) affect species diversity within complex ecological networks such as food webs. Here, we present a dynamic and spatially-explicit food web model which integrates complex food web dynamics at the local scale and species-specific dispersal dynamics at the landscape scale, allowing us to study the interplay of local and spatial processes in metacommunities. We here explore how the number of habitat patches, i.e. the number of fragments, and an increase of habitat isolation, affect the species diversity patterns of complex food webs (α-, β-, γ-diversity). We specifically test whether there is a trophic dependency in the effect of these to factors on species diversity. In our model, habitat isolation is the main driver causing species loss and diversity decline. Our results emphasise that large-bodied consumer species at high trophic positions go extinct faster than smaller species at lower trophic levels, despite being superior dispersers that connect fragmented landscapes better. We attribute the loss of top species to a combined effect of higher biomass loss during dispersal with increasing habitat isolation in general, and the associated energy limitation in highly fragmented landscapes, preventing higher trophic levels to persist. To maintain trophic-complex and species-rich communities calls for effective conservation planning which considers the interdependence of trophic and spatial dynamics as well as the spatial context of a landscape and its energy availability.

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“…Habitat loss refers to a 65 decrease in the amount of suitable habitat whereas fragmentation per se implies a decrease in the 66 spatial autocorrelation of suitable habitat (Jackson and Fahrig, 2013;Fahrig, 2017). It is important to 67 study both effects independently, as each has a distinct effect on species performance within multi-68 trophic food webs (Liao, Bearup and Blasius, 2017). Habitat loss generally has negative effects on 69 species survival, whereas fragmentation might promote species coexistence within a trophic level by 70 lowering competition and between trophic levels by providing refuges Fahrig, 2013, 71 2015;Fahrig, 2017;Liao, Bearup and Blasius, 2017;Fletcher Jr et al, 2018).…”

Section: Introduction 25mentioning

confidence: 99%

“…It is important to 67 study both effects independently, as each has a distinct effect on species performance within multi-68 trophic food webs (Liao, Bearup and Blasius, 2017). Habitat loss generally has negative effects on 69 species survival, whereas fragmentation might promote species coexistence within a trophic level by 70 lowering competition and between trophic levels by providing refuges Fahrig, 2013, 71 2015;Fahrig, 2017;Liao, Bearup and Blasius, 2017;Fletcher Jr et al, 2018). So far, theoretical studies 72 have demonstrated that large individuals can be selected with increasing levels of isolation and 73 habitat fragmentation due to their high gap-crossing ability (Etienne and Olff, 2004;Hillaert, 74 Hovestadt, et al, 2018).…”

Section: Introduction 25mentioning

confidence: 99%

Habitat loss and fragmentation increase realized predator-prey body size ratios

Hillaert

Vandegehuchte

Hovestadt

et al. 2018

Preprint

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In the absence of predators, habitat fragmentation favours large body sizes to facilitate gap crossing. The size of primary consumers is, however, also shaped by top‐down effects as predators select prey of a certain size. Therefore, higher trophic levels should be taken into consideration when studying the effect of habitat loss and fragmentation on size distributions of herbivores. We built a model to study the effect of habitat loss and fragmentation within a tri‐trophic food chain. Body size is directly linked to movement capacity and metabolic processes and considered as a master trait under selection. We show that basal resources accumulate locally if a predator causes top‐down control of the herbivore. Due to this increasing spatiotemporal variability in resource availability, larger herbivores are selected than in scenarios without predator as they are able to move further. As predators cause herbivores to be intrinsically much larger than the optimal sizes selected by habitat fragmentation in the absence of predators, habitat fragmentation is no longer a significant driver of herbivore size. However, there is selection for increased predator size with habitat fragmentation as herbivores become less abundant, hence favouring gap‐crossing ability of the predator. Since herbivore and predator body size respond differently to habitat loss and fragmentation, realized predator–herbivore body size ratios increase along this fragmentation gradient. Our model demonstrates how feedbacks between the abundance, body size and mobility of predators and prey ultimately determine body size distributions in food webs. These new insights shed light on the impact of habitat destruction and fragmentation on overall food web structure. A free Plain Language Summary can be found within the Supporting Information of this article.

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Food web persistence in fragmented landscapes

Cited by 32 publications

References 67 publications

Spatial variation in branch size promotes metapopulation persistence in dendritic river networks

Spatial variation in branch size promotes metapopulation persistence in dendritic river networks

The biggest losers: Habitat isolation deconstructs complex food webs from top to bottom

Habitat loss and fragmentation increase realized predator-prey body size ratios

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