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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.
first
middle
third
reference
time
reference
reference STATIC
reference
alternate
reference EXO.
reference alternate
reference N.C.
time
• Both the presence and form of niche construction affected adaptation.
Static
Environment
Runs
Negative
Niche
Construction
Transplant
(into Negative
Niche Construction)
Positive
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:
E. moorei
P. rigida
(Lyne, 1996)
(Little, 1990)
– Survival traits (e.g., lignotubers,
thick bark)
– Reproductive traits (serotiny, firecued flowering or germination)
• Such traits have been interpreted
as adaptations to cope with the
presence of fire.
B. attenuata
(Bond & van Wilgen 1996)
W. borbonica
(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
A. fasciculatum
E. globulus
(Simpson, 2003)
(Boden & Fagg, 2003)
The Mutch Hypothesis
If 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
D
D
D
D
D
D
D
D
D
D
D
D
T
D
D
D
D
D
D
D
D
D
D
D
D
(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)
E. ficifolia
(Monroe & Clark, 2003)
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
Removal
– Addition
Dylan
Schwilk
Clip & Leave
• Prescribed burns were set
and temperature and plant
response were measured.
Un-manipulated
calorimeter
pyrometer
Addition
Field Results
• Schwilk found that treatments
with intact dead branches (unmanipulated 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.
Discuss the role of niche construction
in management and conservation:
How might the results of this
experiment influence fire
management policy? Conservation
of fire-adapted plant species?
2000
2001
Niche Construction
Lecture Outline
• Introduction to niche construction
• Niche construction and adaptive landscapes
• Rekindling an old flame
• Experiment on mutual niche construction
• Summary
Coevolution as Mutual Niche Construction
• The new view of evolution
incorporating niche construction
emphasizes the effects
organisms have on their
environment.
• 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).
population (t)
niche
natural
niche
construction
selection construction
population (t+1)
environment
genetic
inheritance
• In this light, coevolutionary
dynamics can be recast as
mutual niche construction.
ecological
genetic
inheritance
• However, one major part of the
environment is other organisms
(e.g., predators, pathogens,
competitors, mutualists).
environment
population (t)
population (t+1)
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”
•
Paterson, Brockhurst and colleagues (2010) propagated phage
F2 with Pseudomonas fluorescens under two treatments:
- “Evolution”: Phage evolves against a constant host.
- “Coevolution”: Phage evolves against a co-evolving host.
•
…
COEVOLUTION
The effects of a coevolutionary arms race on the rate
of molecular evolution can be explored with phage.
EVOLUTION
•
…
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
“Now, here,
you see, it
takes all the
running you
can do, to
keep in the
same place.”
S. Paterson M. Brockhurst
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.