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Fractal Hypothesis of the Pelagic Microbial Ecosystem-Can Simple Ecological Principles Lead to Self-Similar Complexity in the Pelagic Microbial Food Web?

Våge S, Thingstad TF - Front Microbiol (2015)

Bottom Line: We discuss a mechanism that could be underlying the formation of repeated patterns at different trophic levels and discuss how this may help understand characteristic biomass size-spectra that hint at scale-invariant properties of the pelagic environment.If the idea of simple underlying principles leading to a fractal-like organization of the pelagic food web could be formalized, this would extend an ecologists mindset on how biological complexity could be accounted for.It may furthermore benefit ecosystem modeling by facilitating adequate model resolution across multiple scales.

View Article: PubMed Central - PubMed

Affiliation: Marine Microbial Ecology Group, Department of Biology, University of Bergen and Hjort Centre for Marine Ecosystem Dynamics Bergen, Norway.

ABSTRACT
Trophic interactions are highly complex and modern sequencing techniques reveal enormous biodiversity across multiple scales in marine microbial communities. Within the chemically and physically relatively homogeneous pelagic environment, this calls for an explanation beyond spatial and temporal heterogeneity. Based on observations of simple parasite-host and predator-prey interactions occurring at different trophic levels and levels of phylogenetic resolution, we present a theoretical perspective on this enormous biodiversity, discussing in particular self-similar aspects of pelagic microbial food web organization. Fractal methods have been used to describe a variety of natural phenomena, with studies of habitat structures being an application in ecology. In contrast to mathematical fractals where pattern generating rules are readily known, however, identifying mechanisms that lead to natural fractals is not straight-forward. Here we put forward the hypothesis that trophic interactions between pelagic microbes may be organized in a fractal-like manner, with the emergent network resembling the structure of the Sierpinski triangle. We discuss a mechanism that could be underlying the formation of repeated patterns at different trophic levels and discuss how this may help understand characteristic biomass size-spectra that hint at scale-invariant properties of the pelagic environment. If the idea of simple underlying principles leading to a fractal-like organization of the pelagic food web could be formalized, this would extend an ecologists mindset on how biological complexity could be accounted for. It may furthermore benefit ecosystem modeling by facilitating adequate model resolution across multiple scales.

No MeSH data available.


Related in: MedlinePlus

Matrix illustrating examples of nested predator-prey and parasite-host interactions repeated at different trophic and phylogenetic levels of resolution, resulting in a fractal-like trophic interaction matrix. Within each upper triangular matrix resulting from nested infection, defense specialized prey are found on the left and competition specialized prey on the right, while generalist predators or viruses with broad prey or host range spectra are found on top and specialized predators or viruses with narrow prey or host range spectra at the bottom. The yellow level represents a level of low phylogenetic resolution, such as plankton functional types (PFTs), where prey may be categorized into small, intermediate and large prey, where small prey are competition specialists and large prey are defense specialists. Predators on this yellow level of PFTs may be generalists eating prey of different sizes or specialists eating prey of a particular size only. The green level within the yellow level of PFTs represents an intermediate level of phylogenetic resolution, such as “species,” whereas the blue level within the green level of “species” represents a high level of phylogenetic resolution, such as “strains.” For a visual distinction of generalist vs. specialist strategies within each level of resolution, interactions with generalist predators or parasites are dark-colored, and those with specialists are light-colored. Modified from Våge (2014).
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Figure 5: Matrix illustrating examples of nested predator-prey and parasite-host interactions repeated at different trophic and phylogenetic levels of resolution, resulting in a fractal-like trophic interaction matrix. Within each upper triangular matrix resulting from nested infection, defense specialized prey are found on the left and competition specialized prey on the right, while generalist predators or viruses with broad prey or host range spectra are found on top and specialized predators or viruses with narrow prey or host range spectra at the bottom. The yellow level represents a level of low phylogenetic resolution, such as plankton functional types (PFTs), where prey may be categorized into small, intermediate and large prey, where small prey are competition specialists and large prey are defense specialists. Predators on this yellow level of PFTs may be generalists eating prey of different sizes or specialists eating prey of a particular size only. The green level within the yellow level of PFTs represents an intermediate level of phylogenetic resolution, such as “species,” whereas the blue level within the green level of “species” represents a high level of phylogenetic resolution, such as “strains.” For a visual distinction of generalist vs. specialist strategies within each level of resolution, interactions with generalist predators or parasites are dark-colored, and those with specialists are light-colored. Modified from Våge (2014).

Mentions: Host-range coevolution is intrinsically driven by the KtW mechanism, where new viruses evolve to control recently established host strains, which had gained improved defense against previously established viruses at the cost of reduced competitive ability (Thingstad et al., 2014). The result are arms-race dynamics, anticipated to occur simultaneously at other trophic levels and levels of phylogenetic resolution within the pelagic plankton food web. On higher trophic levels, we foresee the KtW mechanism to be expressed through predator-prey rather than virus-host interactions, with size-selective grazing (Cyr and Curtis, 1999; Hahn and Höfle, 1999; Thingstad et al., 2010) leading to nested predation networks on the level of plankton functional types. The result is a self-similar trophic interaction structure with subsets of upper triangular infection and predation matrices at different trophic levels and levels of phylogenetic resolution within the pelagic microbial food web (Figure 5).


Fractal Hypothesis of the Pelagic Microbial Ecosystem-Can Simple Ecological Principles Lead to Self-Similar Complexity in the Pelagic Microbial Food Web?

Våge S, Thingstad TF - Front Microbiol (2015)

Matrix illustrating examples of nested predator-prey and parasite-host interactions repeated at different trophic and phylogenetic levels of resolution, resulting in a fractal-like trophic interaction matrix. Within each upper triangular matrix resulting from nested infection, defense specialized prey are found on the left and competition specialized prey on the right, while generalist predators or viruses with broad prey or host range spectra are found on top and specialized predators or viruses with narrow prey or host range spectra at the bottom. The yellow level represents a level of low phylogenetic resolution, such as plankton functional types (PFTs), where prey may be categorized into small, intermediate and large prey, where small prey are competition specialists and large prey are defense specialists. Predators on this yellow level of PFTs may be generalists eating prey of different sizes or specialists eating prey of a particular size only. The green level within the yellow level of PFTs represents an intermediate level of phylogenetic resolution, such as “species,” whereas the blue level within the green level of “species” represents a high level of phylogenetic resolution, such as “strains.” For a visual distinction of generalist vs. specialist strategies within each level of resolution, interactions with generalist predators or parasites are dark-colored, and those with specialists are light-colored. Modified from Våge (2014).
© Copyright Policy
Related In: Results  -  Collection

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Figure 5: Matrix illustrating examples of nested predator-prey and parasite-host interactions repeated at different trophic and phylogenetic levels of resolution, resulting in a fractal-like trophic interaction matrix. Within each upper triangular matrix resulting from nested infection, defense specialized prey are found on the left and competition specialized prey on the right, while generalist predators or viruses with broad prey or host range spectra are found on top and specialized predators or viruses with narrow prey or host range spectra at the bottom. The yellow level represents a level of low phylogenetic resolution, such as plankton functional types (PFTs), where prey may be categorized into small, intermediate and large prey, where small prey are competition specialists and large prey are defense specialists. Predators on this yellow level of PFTs may be generalists eating prey of different sizes or specialists eating prey of a particular size only. The green level within the yellow level of PFTs represents an intermediate level of phylogenetic resolution, such as “species,” whereas the blue level within the green level of “species” represents a high level of phylogenetic resolution, such as “strains.” For a visual distinction of generalist vs. specialist strategies within each level of resolution, interactions with generalist predators or parasites are dark-colored, and those with specialists are light-colored. Modified from Våge (2014).
Mentions: Host-range coevolution is intrinsically driven by the KtW mechanism, where new viruses evolve to control recently established host strains, which had gained improved defense against previously established viruses at the cost of reduced competitive ability (Thingstad et al., 2014). The result are arms-race dynamics, anticipated to occur simultaneously at other trophic levels and levels of phylogenetic resolution within the pelagic plankton food web. On higher trophic levels, we foresee the KtW mechanism to be expressed through predator-prey rather than virus-host interactions, with size-selective grazing (Cyr and Curtis, 1999; Hahn and Höfle, 1999; Thingstad et al., 2010) leading to nested predation networks on the level of plankton functional types. The result is a self-similar trophic interaction structure with subsets of upper triangular infection and predation matrices at different trophic levels and levels of phylogenetic resolution within the pelagic microbial food web (Figure 5).

Bottom Line: We discuss a mechanism that could be underlying the formation of repeated patterns at different trophic levels and discuss how this may help understand characteristic biomass size-spectra that hint at scale-invariant properties of the pelagic environment.If the idea of simple underlying principles leading to a fractal-like organization of the pelagic food web could be formalized, this would extend an ecologists mindset on how biological complexity could be accounted for.It may furthermore benefit ecosystem modeling by facilitating adequate model resolution across multiple scales.

View Article: PubMed Central - PubMed

Affiliation: Marine Microbial Ecology Group, Department of Biology, University of Bergen and Hjort Centre for Marine Ecosystem Dynamics Bergen, Norway.

ABSTRACT
Trophic interactions are highly complex and modern sequencing techniques reveal enormous biodiversity across multiple scales in marine microbial communities. Within the chemically and physically relatively homogeneous pelagic environment, this calls for an explanation beyond spatial and temporal heterogeneity. Based on observations of simple parasite-host and predator-prey interactions occurring at different trophic levels and levels of phylogenetic resolution, we present a theoretical perspective on this enormous biodiversity, discussing in particular self-similar aspects of pelagic microbial food web organization. Fractal methods have been used to describe a variety of natural phenomena, with studies of habitat structures being an application in ecology. In contrast to mathematical fractals where pattern generating rules are readily known, however, identifying mechanisms that lead to natural fractals is not straight-forward. Here we put forward the hypothesis that trophic interactions between pelagic microbes may be organized in a fractal-like manner, with the emergent network resembling the structure of the Sierpinski triangle. We discuss a mechanism that could be underlying the formation of repeated patterns at different trophic levels and discuss how this may help understand characteristic biomass size-spectra that hint at scale-invariant properties of the pelagic environment. If the idea of simple underlying principles leading to a fractal-like organization of the pelagic food web could be formalized, this would extend an ecologists mindset on how biological complexity could be accounted for. It may furthermore benefit ecosystem modeling by facilitating adequate model resolution across multiple scales.

No MeSH data available.


Related in: MedlinePlus