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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

(A) Illustrative example of a nested predation and infection fractal with varying numbers of taxa at different levels of resolution. As in Figure 5, within each upper triangular matrix of the fractal, 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. For a visual distinction of interactions with generalist vs. specialist predators or parasites, interactions with generalists are dark-colored and those with specialists are light-colored within each level of resolution. 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 represent an intermediate level of phylogenetic resolution, such as “species,” whereas the blue level represents a high level of phylogenetic resolution, such as “strains.” Adapted from Våge (2014). (B) Sierpinski triangle with a fractal structure similar to the hypothesized nested infection and predation network of the pelagic microbial food web. The Sierpinski triangle was generated by the chaos game as described in Barton (1990).
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Figure 6: (A) Illustrative example of a nested predation and infection fractal with varying numbers of taxa at different levels of resolution. As in Figure 5, within each upper triangular matrix of the fractal, 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. For a visual distinction of interactions with generalist vs. specialist predators or parasites, interactions with generalists are dark-colored and those with specialists are light-colored within each level of resolution. 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 represent an intermediate level of phylogenetic resolution, such as “species,” whereas the blue level represents a high level of phylogenetic resolution, such as “strains.” Adapted from Våge (2014). (B) Sierpinski triangle with a fractal structure similar to the hypothesized nested infection and predation network of the pelagic microbial food web. The Sierpinski triangle was generated by the chaos game as described in Barton (1990).

Mentions: The examples chosen above illustrate the concept that we envision to underlie a fractal-like organization of the pelagic microbial food web. Clearly, natural food webs are far from being as regular as illustrated in Figure 5. The number of taxa between and within different trophic levels varies, and a fractal-matrix as outlined in Figure 6A may be more realistic. Interestingly, however, irrespective of the exact shape of the trophic interaction network, the above described mechanism leads to nested upper triangular interaction matrices with a conspicuous similarity to the well-known Sierpinski triangle (Figure 6B), as discussed below.


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)

(A) Illustrative example of a nested predation and infection fractal with varying numbers of taxa at different levels of resolution. As in Figure 5, within each upper triangular matrix of the fractal, 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. For a visual distinction of interactions with generalist vs. specialist predators or parasites, interactions with generalists are dark-colored and those with specialists are light-colored within each level of resolution. 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 represent an intermediate level of phylogenetic resolution, such as “species,” whereas the blue level represents a high level of phylogenetic resolution, such as “strains.” Adapted from Våge (2014). (B) Sierpinski triangle with a fractal structure similar to the hypothesized nested infection and predation network of the pelagic microbial food web. The Sierpinski triangle was generated by the chaos game as described in Barton (1990).
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Related In: Results  -  Collection

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Figure 6: (A) Illustrative example of a nested predation and infection fractal with varying numbers of taxa at different levels of resolution. As in Figure 5, within each upper triangular matrix of the fractal, 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. For a visual distinction of interactions with generalist vs. specialist predators or parasites, interactions with generalists are dark-colored and those with specialists are light-colored within each level of resolution. 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 represent an intermediate level of phylogenetic resolution, such as “species,” whereas the blue level represents a high level of phylogenetic resolution, such as “strains.” Adapted from Våge (2014). (B) Sierpinski triangle with a fractal structure similar to the hypothesized nested infection and predation network of the pelagic microbial food web. The Sierpinski triangle was generated by the chaos game as described in Barton (1990).
Mentions: The examples chosen above illustrate the concept that we envision to underlie a fractal-like organization of the pelagic microbial food web. Clearly, natural food webs are far from being as regular as illustrated in Figure 5. The number of taxa between and within different trophic levels varies, and a fractal-matrix as outlined in Figure 6A may be more realistic. Interestingly, however, irrespective of the exact shape of the trophic interaction network, the above described mechanism leads to nested upper triangular interaction matrices with a conspicuous similarity to the well-known Sierpinski triangle (Figure 6B), as discussed below.

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