The Effect of Niche Construction: A Digital Experiment• A population of Avidians evolved (mutations

yield new instructions) over three periods, each defined by which tasks were rewarded (the environment).

• Runs with negative niche construction in the middle trimester ended with significantly higher fitness than paired static runs.

Negative Niche

Construction

Positive Niche

Construction

Transplant (into Negative

Niche Construction)

first middle third

time

reference STATICreferencereference

reference alternate reference EXO.

reference referencealternate N.C.

• Both the presence and form of niche construction affected adaptation.

StaticEnvironment

Runs

time

Niche Construction Niche Construction

Lecture Outline

• Introduction to niche construction

• Niche construction and adaptive landscapes

• Rekindling an old flame

• Experiment on mutual niche construction

• Summary

Fire and Plants• Wildfire is a recurring event in

many vegetation systems.

• Plants in fire-prone ecosystems have a remarkable suite of traits to persist:– Survival traits (e.g., lignotubers,

thick bark)– Reproductive traits (serotiny, fire-

cued flowering or germination)

• Such traits have been interpreted as adaptations to cope with the presence of fire.

(Lyne, 1996)

E. moorei (Little, 1990)

P. rigida

B. attenuata W. borbonica (Bond & van Wilgen 1996) (Bond & van Wilgen 1996)

Flammability

• Certainly climate affects the fire regime of a given vegetation

• However, as fuel, the plants also influence the nature and intensity of fire.

• Traits exist in many fire-prone species which enhance their flammability:– Retention of dead branches– Possession of volatile

compounds– Fine branching patterns– Schleromorphic leaf structure

(Boden & Fagg, 2003)

E. globulus(Simpson, 2003)

A. fasciculatum

The Mutch HypothesisIf plants possess traits to persist in a

fire-prone environment, then there

may be selection for characteristics

that enhance flammability.(Mutch, 1970)

• Mutch ado about nothing? Criticisms of the Mutch hypothesis:

– It is difficult to see how a more flammable variant would invade a less flammable population of conspecifics

(Snyder 1984, Troumbis & Trabaud 1989)

– Flammability is a side-effect of selection for other traits (e.g., volatile oils are selected because they deter herbivores)

(Snyder 1984, Bond & van Wilgen, 1996)

– Flammability is not a trait of individuals, but an emergent property of populations.

(Snyder 1984, Troumbis & Trabaud 1989)(Monroe & Clark, 2003)

E. ficifolia

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D

D

D

D

D

D

D

D

D

D

D

D

D

D

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D D D

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A Bright Idea: Testing Flammability as Niche Construction• Can the traits of plants influence the intensity and biological

effects of wildfire at a local scale?

• Schwilk (2003) executed a field experiment to gauge whether the retention of dead branches by chamise shrubs (Adenostoma fasciculatum) affected fire intensity and effects.

• Four replicated treatments were established:– Unmanipulated– Removal– Clip and leave– Addition

DylanSchwilk

Un-manipulated

Removal Clip & Leave

Addition

• Prescribed burns were set and temperature and plant response were measured.

calorimeter pyrometer

Field Results• Schwilk found that treatments

with intact dead branches (un-manipulated and addition) had significantly higher temperatures than treatments with dead branches removed.

• Schwilk found that the density of seedlings of another species (C. cuneatus) was highest in treatments with dead branches.

• This is evidence that flammability is a niche construction trait.

20002001

Discuss the role of niche constructionin management and conservation:

How might the results of this experiment influence firemanagement policy? Conservationof fire-adapted plant species?

Niche Construction Niche Construction

Lecture Outline

• Introduction to niche construction

• Niche construction and adaptive landscapes

• Rekindling an old flame

• Experiment on mutual niche construction

• Summary

population (t)

population (t+1)

niche construction g

enetic

inh

eritance

natural selection

environment (t)

environment (t+1)

ecolo

gical

inh

eritance

Coevolution as Mutual Niche Construction• The new view of evolution

incorporating niche construction emphasizes the effects organisms have on their environment.

• However, one major part of the environment is other organisms (e.g., predators, pathogens, competitors, mutualists).

• In this light, coevolutionary dynamics can be recast as mutual niche construction.

• Here, we focus on cases where two interacting species have an antagonistic interaction.

• Niche construction by one species induces new niche construction in the other (i.e., a construction arms race).

gen

etic in

heritan

ce

population (t)

population (t+1)

nicheconstruction

Red Queen Dynamics in Microbial Populations• Red Queen principle:

When a population is interacting (antagonistically) with another evolving population, continual evolutionary

change is necessary just to “stay in the game”

• The effects of a coevolutionary arms race on the rate of molecular evolution can be explored with phage.

S. Paterson M. Brockhurst

• Paterson, Brockhurst and colleagues (2010) propagated phage 2 with Pseudomonas fluorescens under two treatments:

- “Evolution”: Phage evolves against a constant host.

- “Coevolution”: Phage evolves against a co-evolving host.

• Compared to the Evolution treatment, coevolved phage:- Possessed a higher rate of molecular evolution- Displayed greater divergence between and within replicates- Displayed greater variation at loci involved in host adhesion

… …EVO

LUTI

ON

COEV

OLU

TIO

N

“Now, here, you see, it takes all the running you can do, to keep in the same place.”

Niche Construction Niche Construction

Lecture Outline

• Introduction to niche construction

• Niche construction and adaptive landscapes

• Rekindling an old flame

• Experiment on mutual niche construction

• Summary

Summary • Through their physiology, development and behavior, organisms alter the world in which they live– this process is called “niche construction.”

• Incorporation of niche construction offers a different evolutionary perspective, where the effects organisms have on their environment can feed back to influence future evolution.

• Niche construction can involve physical perturbation or relocation, can be inceptive or counteractive, and can have negative or positive fitness consequences.

• Niche construction is now being explored in mathematical modeling, computer simulations, laboratory experiments and field studies:

- Niche construction can affect the evolution of cognition. - Niche construction can affect the process of adaptation.- Niche construction can be demonstrated in the field.- Coevolution can be seen as a form of mutual niche construction and shown to affect rates of evolution in antagonistic interactions.