Evolution of the niche in protozoan Communities
William Bartram, ~1780
Outline
1. Who am I?
1. What QUESTIONS am I interested in?
2. What TECHNOLOGY do I use?
3. Example of a project
4. Motivation: Why I use (or want to use) the individual-based approach?
5. Challenges: What prevents me from (or makes it difficult to) use the individual-based approach?
6. Opportunities: What (else) the individual-based approach could be used for?
Ecology and Evolution of Species Patterns using Pitcher Plants
Food web within Pitcher Plants
Studied by:Addicot, Istock, Bradshaw,Ellison and Gotelli, Kneitel and Miller, Hoekman, many others
Bacterivores
Dominant Bacterivores Species in Sarracenia
Colpoda (CA)
Eimeriidae(BFC)
Bodo (BO)
Poterioochromonas(CH)
flagellates ciliates
Mosquito larvae
bacteriovores
bacteria
dead bugs
Habrotrochus
Sarraceniopus gibsonii
Evolution in ecological time scale
What role does past or current evolution play in determining species patterns? In this system, we can quantify evolution over successional time scales because of the fast generations times.
Competitive Hierarchy in Protozoa in Two Week-old Community
Mosquito larvae
protozoa
bacteria
dead bugs
CH < BO < BFC = CAcompetitiveability rank
CH BO BFC CA
CH -1.00* -1.00* -1.00*
BO -0.02 -0.53* -0.14*
BFC -0.05 -0.10+ -0.16+
CA 0.13* 0.00 -0.09
Effect of
Effe
ct o
n
CH BO BFC CA
CH -1.00* -1.00* -1.00*
BO -0.02 -0.53* -0.14*
BFC -0.05 -0.10+ -0.16+
CA 0.13* 0.00 -0.09
WEEK 2 WEEK 7
WEEK 12
CH BO BFC CA
CH -0.86+ -0.56* -0.50*
BO -0.08 -0.12* -0.10*
BFC 0.15 0.05 -0.30
CA 0.09 -0.15 -0.08
CH BO BFC CA
CH -0.36* -0.14 -0.22
BO -0.06 -0.09* -0.02
BFC -0.14* -0.35 -0.12*
CA -0.08 -0.28* -0.16*
Evolution of Interaction Strengths
€
CI =log(comp) − log(mono)
log(mono)
less competitive effect
increased competitive effect
Conclusions
• There is no evidence for pairwise niche convergence or divergence among competitors in this community.
• Our fundamental view of species’ niche overlap driving evolution of competitors may need revision.
• What is really evolving? While we measure interaction traits, we have no knowledge of the mechanisms involved.
NIMBioS Question 1: At the level of individual cells, what traits or characters are actually evolving?
€
U =
2 7 1
1 8 1
5 2 3
1 0 9
€
A =
1.0 1.09 0.50 0.20
0.89 1.0 0.36 0.15
0.71 0.63 1.0 0.84
0.13 0.12 0.39 1.0
species
Resource-use matrix Per-capita interaction matrix
€
dN i
dt= riN i
K i − α ijN ji=1
n
∑ ⎛
⎝ ⎜
⎞
⎠ ⎟
K iPopulation growth
resources
A model of evolution with substitutable resources
€
U =
2 7 1
1 8 1
5 2 3
1 0 9
species
Resource-use matrix Per-capita interaction matrix
Population growth
.1
€
A =
1.0 1.09 0.50 0.20
0.89 1.0 0.36 0.15
0.71 0.63 1.0 0.84
0.13 0.12 0.39 1.0
€
dN i
dt= riN i
K i − α ijN ji=1
n
∑ ⎛
⎝ ⎜
⎞
⎠ ⎟
K i
resources
A model of evolution with substitutable resources
€
U =
2 7 1
1 8 1
5 2 3
1 0 9
A model of evolution with substitutable resources
€
A =
1.0 1.08 0.50 0.20
0.90 1.0 0.36 0.15
0.72 0.63 1.0 0.84
0.14 0.12 0.39 1.0
resources
species
Resource-use matrix Per-capita interaction matrix
Population growth
.1
€
dN i
dt= riN i
K i − α ijN ji=1
n
∑ ⎛
⎝ ⎜
⎞
⎠ ⎟
K i
terHorst, Miller, and Power model
One species diverges to specialize on Resource 1
Two species converge to specialize on Resource 1
terHorst, Miller, and Powers. 2011. Evol. Ecol. Res. 12:843-854.
• Convergence is an evolutionary outcome of competition of >2 species
• Convergence or divergence can occur when there is sufficient selection and genetic variation to converge before extinction occurs.
terHorst, Miller, and Power model
terHorst, Miller, and Powers. 2011. Evol. Ecol. Res. 12:843-854.
terHorst, Miller, and Power model
A problem is that the model essentially acts through group selection. It creates variation in resource use among populations, then selections the population that has the highest growth rate.
This form of modeling competitors has been shown to be inaccurate.
NIMBioS Question 2: What is the best way to model the simultaneous evolution of competitors, based on selection on individuals?
Outline
1. Who am I?
1. What QUESTIONS am I interested in?
2. What TECHNOLOGY do I use?
3. Example of a project
4. Motivation: Why I use (or want to use) the individual-based approach?
5. Challenges: What prevents me from (or makes it difficult to) use the individual-based approach?
6. Opportunities: What (else) the individual-based approach could be used for?
This work has been significantly supported by the National Science Foundation
Thanks to the many students that either marked leaves and sucked up pitcher plants out in the miserable heat or counted protozoa in the very cold Miller lab, including Amber Roman, Casie Reed, Fani Gruber, John Mola, and Heather Wells.
CH BO BFC CA Pred
CH -1.00* -1.00* -1.00* -0.48*
BO -0.02 -0.53* -0.14* -0.24*
BFC -0.05 -0.10+ -0.16+ -0.28+
CA 0.13* 0.00 -0.09 -0.02
WEEK 2 WEEK 7
WEEK 12
CH BO BFC CA Pred
CH -0.86+ -0.56* -0.50* -0.15
BO -0.08 -0.12* -0.10* -0.14
BFC 0.15 0.05 -0.30 -0.20*
CA 0.09 -0.15 -0.08 -0.21
CH BO BFC CA Pred
CH -0.36* -0.14 -0.22 -0.34*
BO -0.06 -0.09* -0.02 -0.17+
BFC -0.14* -0.35 -0.12* -0.29*
CA -0.08 -0.28* -0.16* -0.37*
Evolution of Predation Tolerance
Less effect
Increased effect
Biogeography detail on community
Buckley, et al. 2004
WEEKS
High PredationLow Competition
Low PredationHigh Competition
Mosquito larvae
protozoa
bacteria
dead bugs
Succession in Sarracenia leaves
terHorst selection experiments in the laboratory show that Colpoda evolve faster growth rates and smaller size when in competition.
Evolution of Colpoda in competition
terHorst, 2011. J. Evol. Biol. 24:36-46
terHorst selection experiments in the laboratory show that Colpoda evolve when in predation.
Evolution of Colpoda with predation by Wyeomyia
terHorst, Miller and Levitan, 2010. Ecology 91:629-636
Poorer get rich and rich get poorer
Results, again
• Poorer competitors evolve to be better competitors (effect and response)
• Better competitors evolve to be poorer competitors (effect and response)
• All the species are converging on an intermediate competitive ability
• But, NOT convergence as described before, driven by reciprocally increased competitive interactions
• No evidence of a competition/predation trade-off.