Evolution of the niche in protozoan Communities

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


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


€

U =

2 7 1

1 8 1

5 2 3

1 0 9


€

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


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 Powers. 2011. Evol. Ecol. Res. 12:843-854.


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.

Documents

Evolution of the niche in protozoan Communities