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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

Nested interaction matrix illustrated by the example of five different host and virus groups. Positive infections are represented by a color-filled tile. Nested interactions results in a triangular matrix, in this case upper triangular with defense specialized hosts that are infected by few viruses only on the left and competition specialized hosts that are infected by most viruses on the right. Generalist viruses with a broad host range spectrum, able to infect all host groups, are on top (dark-colored interactions), and specialized viruses with a narrow host range able to infect few host groups only are at the bottom (light-colored interactions). Modified from Våge (2014). The same type of nested interaction matrix is conceivable from predator-prey interactions, where predators play the role analogous to viruses and prey to hosts.
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Figure 4: Nested interaction matrix illustrated by the example of five different host and virus groups. Positive infections are represented by a color-filled tile. Nested interactions results in a triangular matrix, in this case upper triangular with defense specialized hosts that are infected by few viruses only on the left and competition specialized hosts that are infected by most viruses on the right. Generalist viruses with a broad host range spectrum, able to infect all host groups, are on top (dark-colored interactions), and specialized viruses with a narrow host range able to infect few host groups only are at the bottom (light-colored interactions). Modified from Våge (2014). The same type of nested interaction matrix is conceivable from predator-prey interactions, where predators play the role analogous to viruses and prey to hosts.

Mentions: The KtW mechanism is, according to the proposed hypothesis, responsible for an emergent, fractal like organization of trophic interactions in the pelagic microbial food web. For illustration, we first consider virus-host interactions, which represent “trophic interaction networks” at the highest level of phylogenetic resolution (i.e., on the levels of species and strains). Virus-host interactions tend to be highly specific (Lima-Mendez et al., 2015), but infection networks within a particular host community are characterized by varying infection and susceptibility ranges for viruses and hosts. Oftentimes, these infection networks can be summarized as nested infection patterns (Flores et al., 2011; Jover et al., 2013). In nested infection networks, generalist viruses represent the most evolved viral strains, infecting nearly all host strains within the host community, while specialist viruses represent more ancient strains able to infect ancient host strains only. Typically, ancient host strains are infected by most viruses including ancient types, whereas the more evolved host strains are defense specialists, susceptible to few, evolved viruses only. The resulting infection matrix is upper triangular (Figure 4). Nested infection can arrive through expanded host range coevolution, where hosts evolve to become resistant against existing viruses, while viruses evolve to infect the ever increasing number of newly evolved host strains (Lenski and Levin, 1985; Buckling and Rainey, 2002). The cost of being a generalist virus is assumed to be reduced virulence in terms of lower adsorption coefficients, while defensive, evolved host strains pay with lower competitive abilities (Flores et al., 2011).


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)

Nested interaction matrix illustrated by the example of five different host and virus groups. Positive infections are represented by a color-filled tile. Nested interactions results in a triangular matrix, in this case upper triangular with defense specialized hosts that are infected by few viruses only on the left and competition specialized hosts that are infected by most viruses on the right. Generalist viruses with a broad host range spectrum, able to infect all host groups, are on top (dark-colored interactions), and specialized viruses with a narrow host range able to infect few host groups only are at the bottom (light-colored interactions). Modified from Våge (2014). The same type of nested interaction matrix is conceivable from predator-prey interactions, where predators play the role analogous to viruses and prey to hosts.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664636&req=5

Figure 4: Nested interaction matrix illustrated by the example of five different host and virus groups. Positive infections are represented by a color-filled tile. Nested interactions results in a triangular matrix, in this case upper triangular with defense specialized hosts that are infected by few viruses only on the left and competition specialized hosts that are infected by most viruses on the right. Generalist viruses with a broad host range spectrum, able to infect all host groups, are on top (dark-colored interactions), and specialized viruses with a narrow host range able to infect few host groups only are at the bottom (light-colored interactions). Modified from Våge (2014). The same type of nested interaction matrix is conceivable from predator-prey interactions, where predators play the role analogous to viruses and prey to hosts.
Mentions: The KtW mechanism is, according to the proposed hypothesis, responsible for an emergent, fractal like organization of trophic interactions in the pelagic microbial food web. For illustration, we first consider virus-host interactions, which represent “trophic interaction networks” at the highest level of phylogenetic resolution (i.e., on the levels of species and strains). Virus-host interactions tend to be highly specific (Lima-Mendez et al., 2015), but infection networks within a particular host community are characterized by varying infection and susceptibility ranges for viruses and hosts. Oftentimes, these infection networks can be summarized as nested infection patterns (Flores et al., 2011; Jover et al., 2013). In nested infection networks, generalist viruses represent the most evolved viral strains, infecting nearly all host strains within the host community, while specialist viruses represent more ancient strains able to infect ancient host strains only. Typically, ancient host strains are infected by most viruses including ancient types, whereas the more evolved host strains are defense specialists, susceptible to few, evolved viruses only. The resulting infection matrix is upper triangular (Figure 4). Nested infection can arrive through expanded host range coevolution, where hosts evolve to become resistant against existing viruses, while viruses evolve to infect the ever increasing number of newly evolved host strains (Lenski and Levin, 1985; Buckling and Rainey, 2002). The cost of being a generalist virus is assumed to be reduced virulence in terms of lower adsorption coefficients, while defensive, evolved host strains pay with lower competitive abilities (Flores et al., 2011).

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