Download CH - NIMBioS

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
Bacterivores
Studied by:
Addicot, Istock, Bradshaw,
Ellison and Gotelli, Kneitel
and Miller, Hoekman, many
others
Dominant Bacterivores Species in Sarracenia
Habrotrochus
flagellates
ciliates
Colpoda (CA)
Bodo (BO)
Mosquito larvae
bacteriovores
Sarraceniopus gibsonii
Eimeriidae
(BFC)
bacteria
dead bugs
Poterioochromonas
(CH)
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
Effect of
CH
BO
BFC
CA
Mosquito larvae
-1.00* -1.00* -1.00*
protozoa
bacteria
dead bugs
Effect on
CH
BO
-0.02
BFC
-0.05 -0.10+
CA
0.13*
competitive
ability rank
-0.53* -0.14*
0.00
-0.16+
-0.09
CH < BO < BFC = CA
Evolution of Interaction Strengths
WEEK 2
CH
CH
BO
BO
BFC
CA
CH
BO
-1.00* -1.00* -1.00*
CH
-0.53* -0.14*
BO
-0.08
-0.16+
BFC
0.15
0.05
CA
0.09
-0.15
-0.02
BFC -0.05 -0.10+
CA
WEEK 7
0.13* 0.00 -0.09
log( comp)  log( mono)
CI 
log( mono)
increased competitive effect
CA
-0.86+ -0.56* -0.50*
-0.12* -0.10*
-0.30
-0.08
WEEK 12
CH
BO
BO
BFC
-0.36* -0.14
CH
less competitive effect
BFC
-0.06
-0.22
-0.09* -0.02
BFC -0.14* -0.35
CA
CA
-0.08 -0.28* -0.16*
-0.12*
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?
A model of evolution with substitutable resources
Resource-use matrix
Per-capita interaction matrix
resources
7
8
2
0
1
1
3
9
species
2
1
U
5
1
A
1.0
1.09 0.50 0.20
0.89
1.0
0.71 0.63
0.36 0.15
1.0
0.84
0.13 0.12 0.39
1.0
n


K i    ij N j 

i1
Population growth dN i  r N 
i i
dt
Ki

A model of evolution with substitutable resources
Resource-use matrix
Per-capita interaction matrix
resources
1
1
3
9
species
2 .1 7
1 8
U
5 2
1 0
A
1.0
1.09 0.50 0.20
0.89
1.0
0.71 0.63
0.36 0.15
1.0
0.84
0.13 0.12 0.39
1.0
n


K i    ij N j 

i1
Population growth dN i  r N 
i i
dt
Ki

A model of evolution with substitutable resources
Resource-use matrix
Per-capita interaction matrix
resources
1
1
3
9
species
2 .1 7
1 8
U
5 2
1 0
A
1.0
1.08 0.50 0.20
0.90
1.0
0.72 0.63
0.36 0.15
1.0
0.84
0.14 0.12 0.39
1.0
n


K i    ij N j 

i1
Population growth dN i  r N 
i i
dt
Ki

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.
terHorst, Miller, and Power model
• 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 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.
Evolution of Predation Tolerance
WEEK 2
CH
CH
BO
BO
BFC
CA
Pred
CH
BO
-1.00* -1.00* -1.00* -0.48*
CH
-0.53* -0.14* -0.24*
BO
-0.08
-0.16+ -0.28+
BFC
0.15
0.05
-0.02
CA
0.09
-0.15
-0.02
BFC -0.05 -0.10+
CA
WEEK 7
0.13* 0.00 -0.09
BFC
CA
Pred
-0.86+ -0.56* -0.50* -0.15
-0.12* -0.10* -0.14
-0.30 -0.20*
-0.08
-0.21
WEEK 12
CH
Increased effect
BO
BFC
-0.36* -0.14
CH
Less effect
BO
-0.06
-0.08 -0.28* -0.16*
Pred
-0.22 -0.34*
-0.09* -0.02
BFC -0.14* -0.35
CA
CA
-0.17+
-0.12* -0.29*
-0.37*
Biogeography detail on community
Patterns within a Field
Buckley, et al. 2004
Succession in Sarracenia leaves
Mosquito larvae
protozoa
bacteria
dead bugs
WEEKS
High Predation
Low Competition
Low Predation
High Competition
0.22
6
0.2
5
Cell Area (x 10-3mm2)
Population Growth Rate
Evolution of Colpoda in competition
0.18
0.16
0.14
0.12
0.1
Monoculture
Competition
Selection Environment
4
3
2
1
0
Monoculture
Competition
Selection Environment
terHorst selection experiments in the laboratory show that Colpoda evolve
faster growth rates and smaller size when in competition.
terHorst, 2011. J. Evol. Biol. 24:36-46
Evolution of Colpoda with predation by Wyeomyia
terHorst selection experiments in the laboratory show that Colpoda evolve
when in predation.
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.