Download The role of intra-specific trait variability in plankton biodiversity: a

The role of intra-specific trait variability in
plankton biodiversity: a game theoretic
and model examination
Susanne Menden-Deuer & Julie Rowlett
Graduate School of Oceanography
University of Rhode Island
[email protected]
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Mathematical Sciences
Chalmers University
[email protected]
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Courtesy of John Delaney
- with modifications
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DEAN JACOBSON ILLUSTRATION
2 Goals:
1. pervasive intra-specific trait variability in physiology,
morphology and behavior in unicellular plankton
2. intra-specific variability matters and is adaptive
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DEAN JACOBSON ILLUSTRATION
Pervasive intra-specific variability…
- growth rate variation as a function of nitrogen source for
strains of phytoplankter Heterosigma akashiwo
ifemer.fr
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Fredrickson et al 2011
Pervasive intra-specific variability…
- variable motility across strains of same phytoplankton
species Heterosigma akashiwo
ifemer.fr
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Harvey et al, in review
Pervasive intra-specific variability…
- variable motility across strains of
Akashiwo sanguinea
Hwan So Yoon
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Menden-Deuer & Montalbano 2015
Pervasive intra-specific variability…
- variable motility across strains of
Akashiwo sanguinea
--> vertically dispersed
population distribution
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Menden-Deuer & Montalbano 2015
Digression: some dinos love turbulence
- variable growth rate across strains of same phytoplankton
species Akashiwo sanguinea
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Menden-Deuer & Montalbano 2015
Pervasive intra-specific variability…
- chemical composition (Moal et al. 1987)
- thermal adaptation (Thomas et al. 2012)
- growth optima (Boyd et al. 2013)
- salinity tolerance (Brand 1984)
- nitrogen fixation (Hutchins et al. 2013)
- ocean acid response (Schaum et al. 2013)
- genetics (Rynearson & Armbrust 2004,Whittaker et al. 2012)
Empirical investigations of intra-specific variability in
plankton physiology, genetics or behavior are rare but
discoveries are frequent
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Paradox of the Plankton
“How is it possible for a number of species to
coexist in a relatively isotropic or unstructured
environment all competing for the same sorts of
materials?”
G. Evelyn Hutchinson 1961
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DEAN JACOBSON ILLUSTRATION
Paradox of the Plankton
“How is it possible for a number of species - with
high intra-specific variability - to coexist in a
relatively isotropic or unstructured environment all
competing for the same sorts of materials?”
G. Evelyn Hutchinson 1961
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DEAN JACOBSON ILLUSTRATION
Environmental Heterogeneity
- Environmental &
observational drivers
- Problems of pattern
and scale of observation
(Levin 1992)
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Rynearson & Armbrust 2005
Many hypotheses advanced
- resource ratio hypothesis (Tilman 1977, 1994)
- chaotic oscillations (Huisman Weissing 1999)
- chaotic fluid motion (Pentek et al. 2000)
- localized competition (Kerr et al. 2002)
- predation/competition
(Record et al. 2013, Cropp and
Norbury 2012)
- latitudinal/seasonal
gradients (Barton et al. 2010)
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Barton et al. 2010
Game theory
- examines outcomes of competitions based on individual interactions
- outcomes depend on behavior of individual
players
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Game theory
- examines outcomes of competitions based on individual interactions
- outcomes depend on behavior of individual
players
- Prisoner’s dilemma famous example:
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Species interactions are cell-cell interactions
- outcomes of ecological interactions are measured at the
population level: abundance, growth rate, distribution
- the processes that result in population dynamics occur at the
individual level: feeding, motility, resource uptake, sex
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Species interactions are cell-cell interactions
- outcomes of ecological interactions are measured at the
population level: abundance, growth rate, distribution
- the processes that result in population dynamics occur at the
individual level: feeding, motility, resource uptake, sex
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Incorporating intra-specific variability
- variability in traits results in species having
some ‘stronger’ and some ‘weaker’ competitors
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Competition with intra-specific variability
- individual based competition model of 2+ species
- intra-specific variability expressed as probability distribution of trait
- randomly choose: competitive ability from probability density
function that reflects variability
uniform pdf
- up to 10,000 individuals
per species
- up to 10,000 generations
Competitive ability
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Competition with intra-specific variability
Probability
- variability results in species having ‘stronger’ and ‘weaker’ than
average competitors
- all identical mean
Competitive ability
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Persistence in 2-species competition
- frequency of 2 species persisted in 100 repeated, randomized
simulations as a function of population size and duration
%
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Menden-Deuer & Rowlett 2014
Persistence in multi-species competition
- population size over time in repeated, multi species competitions
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Menden-Deuer & Rowlett 2014
Persistence in multi-species competition
- population size over time in repeated, multi species competitions
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Menden-Deuer & Rowlett 2014
Persistence in multi-species competition
- 100 species persist
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Menden-Deuer & Rowlett 2014
Probing the role of intra-specific variability
- 14 behavior distributions
- identical mean
- increased variance
- bimodal distributions
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Menden-Deuer & Rowlett, in prep.
Probing the role of intra-specific variability
- 14 behavior distributions
- identical mean
- increased variance
- bimodal distributions
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Menden-Deuer & Rowlett, in prep.
Survival probability
- for each behavior/competitive ability distribution
- survival probability in 100 replicated competitions simulations
- variation in population size and duration
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Menden-Deuer & Rowlett, in prep.
No penalty for type of variability distribution
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Menden-Deuer & Rowlett, in prep.
Probing the role of intra-specific variability
- 14 behavior distributions
- identical mean
- increased variance
- bimodal distributions
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Menden-Deuer & Rowlett, in prep.
Hyper-variability = invulnerable?
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Menden-Deuer & Rowlett, in prep.
Conclusions/Implications
- incorporation of intra-specific variability enhances biodiversity
- diverse variability distributions support survival
- intra-specific variability has adaptive value, independent of
specific formulations: heterogeneity, no. of nutrients
- intra-specific variability may be a mechanism for marine
microbes to acclimate and ultimately adapt to changing ocean
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D. Jacobsen, 1999
Variability an integral trait?
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Illustration Josh Wood
Rynearson & Menden-Deuer, in press
Dennis Hlynsky
Rhode Island School of Design