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Evolution of and by Phenotypic Plasticity
When should plasticity evolve?
1) when there is environmental heterogeneity that is predictable by reliable cues, or
when time lag is not an issue
2) parents or offspring actually experience environmental heterogeneity
3) selection favors different phenotypes in different environments
Comparative approaches may be used to test these predictions on an interspecific
level: Q: Are phylogenetic comparitive approaches really appropriate tests for these
predictions? (Justin)
Van Buskirk (2002):
Has adaptive plasticity evolved in pond-dwelling anurans given:
1) Coarse grained spatial and temporal variation in predation
2) Are there cues, or is time lag unimportant?
3) Do individuals only experience one environment?
Methodology: are there phylogenetically independent correlations between
behavior/morphology and environmental heterogeneity, and how many times can one use
PCA in a single manuscript?
Results: Morphology correlates, albeit weakly, with environmental heterogeneity, and
behavior does not.
Q: How does this inform us on the conditions under which morphological and behavioral
plasticity are expected? (Amber)
Q: The behaviors studied are stereotyped and easily identifiable in each species, but if
different species have different behavioral strategies are interspecific comparisons
appropriate? (Me)
Q: Does the negative correlation between tail depth and tail length necessarily imply a
constraint? (Willow)
Experimental evolution in heterogeneous environments:
-Do temporal environmental fluctuations lead to the evolution of plasticity?
Leroi et al. (1994) – E. coli and variable temperatures
Q: Is this really an example of a Darwinian monster?
If control lines were selected for the same number of generations at constant 42
and 32C wouldn’t they outperform the experimental lines in their respective
thermal environments? (Will)
Would the ancestor maintained at 37 degrees have higher fitness than the
experimental lines at 37C? (Jon)
Reboud and Bell (1997) – Chlamydomonas and variable light conditions
Q: Does the spatial component of this experiment really represent spatial heterogeneity,
or is it also temporal? (Amber)
-Does plasticity evolve in response to novel environments?
Travisano et al. (1995)- E. coli and variable nutrient environments
Q: Do the results really indicate that plasticity has evolved in response to the maltose
and lactose (novel) media (Will and Marty)?
Q: How are evolutionary theories being biased by drawing conclusions based primarily
on model organisms with short generation times? (Jennifer)
Evolution of Life Histories, Phenotypic Novelties, and Speciation
-How do we incorporate reaction norms into macroevolutionary theory?
Leclaire and Brandle (1994) – colonization of novel host by rose-hip flies
Q: Were flies pre-adapted to the novel host, or did plasticity evolve subsequently? If it
was not a pre-adaptation, how does this change the role of host-use plasticity in the
evolution of the flies? (Tara)
Q: If flies were pre-adapted, is this an example of exaptation? Can both adaptive and
non-adaptive plasticity serve as a “pool of variability” for potential exaptation? (Jon)
Shine (1995) – Viviparity and thermal environments of offspring
Q: Is the plasticity Pigliucci is referring to plasticity of the parental environment or
plasticity of development in the offspring? (Jon)
Wimberger (1994) – plastic jaw morphology in fishes
Q: Is the developmental control of continuous variation really that different from the
control of dichotomous variation, i.e. could the same fundamental mechanisms be
involved? (Willow)
West-Eberhard (1989) – The bipedal goat
Q: Will we be overthrown by a mutant goat revolution?
-Is plasticity really a useful concept in macroevolution?
Q: As in the goat example, it appears that phenotypic novelties induced by plastic
responses could play a prominent role in species diversification. Can plasticity provide
an explanation for much of the life history variation that we see at the species level?
Q: Can the roles that plasticity and genetic differentiation play in macroevolution be
disentangled? (Marty)
The Role of Phenotypic Plasticity in Evolution:
Q: Do the physical properties of bio-molecules really predispose phenotypes to be
plastic? (Jennifer)
Q: Point (4) on page 213 – Variation in reaction norms may be compatible with the idea
of periods of accelerated evolution in punctuated equilibrium, but how does it explain the
periods of stasis? (Ted)
Q: What role might plasticity play when species are faced with a cataclysmic event?