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An extended patch-dynamic framework for food chains in fragmented landscapes

View Article: PubMed Central - PubMed

ABSTRACT

Habitat destruction, a key determinant of species loss, can be characterized by two components, patch loss and patch fragmentation, where the former refers to the reduction in patch availability, and the latter to the division of the remaining patches. Classical metacommunity models have recently explored how food web dynamics respond to patch loss, but the effects of patch fragmentation have largely been overlooked. Here we develop an extended patch-dynamic model that tracks the patch occupancy of the various trophic links subject to colonization-extinction-predation dynamics by incorporating species dispersal with patch connectivity. We found that, in a simple food chain, species at higher trophic level become extinct sooner with increasing patch loss and fragmentation due to the constraint in resource availability, confirming the trophic rank hypothesis. Yet, effects of fragmentation on species occupancy are largely determined by patch loss, with maximal fragmentation effects occurring at intermediate patch loss. Compared to the spatially explicit simulations that we also performed, the current model with pair approximation generates similar community patterns especially in spatially clustered landscapes. Overall, our extended framework can be applied to model more complex food webs in fragmented landscapes, broadening the scope of existing metacommunity theory.

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Artificial fragmented landscapes consisting of two patch types (black – suitable, white – unsuitable) in a square lattice of size L × L = 100 × 100 cells with each cell representing one patch, differentiated by varying both patch availability (s) and connectivity (qs/s).Each image shows a typical configuration for the given properties. In the special case with qs/s = s, both patch types are randomly distributed (marked with red square), while the cases of qs/s > s and qs/s < s respectively represent spatially clustered and over-dispersed patterns of suitable patches.
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f1: Artificial fragmented landscapes consisting of two patch types (black – suitable, white – unsuitable) in a square lattice of size L × L = 100 × 100 cells with each cell representing one patch, differentiated by varying both patch availability (s) and connectivity (qs/s).Each image shows a typical configuration for the given properties. In the special case with qs/s = s, both patch types are randomly distributed (marked with red square), while the cases of qs/s > s and qs/s < s respectively represent spatially clustered and over-dispersed patterns of suitable patches.

Mentions: Currently, the patch-dynamic model developed by Pillai et al.29, however, still ignores details of the spatial arrangement of patches (e.g., patch fragmentation), which have been proven empirically to affect species persistence343536. Using a single population model, Liao et al.910 already showed that species with contrasting dispersal abilities respond differently to patch fragmentation, with shorter-range dispersers responding more negatively than longer-range dispersers. Yet, Pillai et al.29 assumed global dispersal (i.e., uniform in space) for all species regardless of their trophic levels, which is relatively restrictive as species at different trophic levels often display distinct dispersal traits. For example, higher trophic level species tend to exhibit longer-range dispersal in nature3738. Thus, the role of patch fragmentation in mediating the relationships between food webs and species dispersal remains untested and vaguely understood. Furthermore, we are still far from constructing mathematical models that predict how patch loss and spatial fragmentation separately act and interact in modifying food web dynamics, particularly along the axis of species dispersal ranges at different trophic levels. To address this problem, we propose an extended food chain model that incorporates both landscape fragmentation (see illustration in Fig. 1) and species dispersal, based on the modelling framework of Pillai et al.29. With this model, we investigate how metacommunities with different dispersal ranges at different trophic levels respond to patch availability and spatial connectivity.


An extended patch-dynamic framework for food chains in fragmented landscapes
Artificial fragmented landscapes consisting of two patch types (black – suitable, white – unsuitable) in a square lattice of size L × L = 100 × 100 cells with each cell representing one patch, differentiated by varying both patch availability (s) and connectivity (qs/s).Each image shows a typical configuration for the given properties. In the special case with qs/s = s, both patch types are randomly distributed (marked with red square), while the cases of qs/s > s and qs/s < s respectively represent spatially clustered and over-dispersed patterns of suitable patches.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016810&req=5

f1: Artificial fragmented landscapes consisting of two patch types (black – suitable, white – unsuitable) in a square lattice of size L × L = 100 × 100 cells with each cell representing one patch, differentiated by varying both patch availability (s) and connectivity (qs/s).Each image shows a typical configuration for the given properties. In the special case with qs/s = s, both patch types are randomly distributed (marked with red square), while the cases of qs/s > s and qs/s < s respectively represent spatially clustered and over-dispersed patterns of suitable patches.
Mentions: Currently, the patch-dynamic model developed by Pillai et al.29, however, still ignores details of the spatial arrangement of patches (e.g., patch fragmentation), which have been proven empirically to affect species persistence343536. Using a single population model, Liao et al.910 already showed that species with contrasting dispersal abilities respond differently to patch fragmentation, with shorter-range dispersers responding more negatively than longer-range dispersers. Yet, Pillai et al.29 assumed global dispersal (i.e., uniform in space) for all species regardless of their trophic levels, which is relatively restrictive as species at different trophic levels often display distinct dispersal traits. For example, higher trophic level species tend to exhibit longer-range dispersal in nature3738. Thus, the role of patch fragmentation in mediating the relationships between food webs and species dispersal remains untested and vaguely understood. Furthermore, we are still far from constructing mathematical models that predict how patch loss and spatial fragmentation separately act and interact in modifying food web dynamics, particularly along the axis of species dispersal ranges at different trophic levels. To address this problem, we propose an extended food chain model that incorporates both landscape fragmentation (see illustration in Fig. 1) and species dispersal, based on the modelling framework of Pillai et al.29. With this model, we investigate how metacommunities with different dispersal ranges at different trophic levels respond to patch availability and spatial connectivity.

View Article: PubMed Central - PubMed

ABSTRACT

Habitat destruction, a key determinant of species loss, can be characterized by two components, patch loss and patch fragmentation, where the former refers to the reduction in patch availability, and the latter to the division of the remaining patches. Classical metacommunity models have recently explored how food web dynamics respond to patch loss, but the effects of patch fragmentation have largely been overlooked. Here we develop an extended patch-dynamic model that tracks the patch occupancy of the various trophic links subject to colonization-extinction-predation dynamics by incorporating species dispersal with patch connectivity. We found that, in a simple food chain, species at higher trophic level become extinct sooner with increasing patch loss and fragmentation due to the constraint in resource availability, confirming the trophic rank hypothesis. Yet, effects of fragmentation on species occupancy are largely determined by patch loss, with maximal fragmentation effects occurring at intermediate patch loss. Compared to the spatially explicit simulations that we also performed, the current model with pair approximation generates similar community patterns especially in spatially clustered landscapes. Overall, our extended framework can be applied to model more complex food webs in fragmented landscapes, broadening the scope of existing metacommunity theory.

No MeSH data available.


Related in: MedlinePlus