Natural Selection, Evolution, and Ecology

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Transcript Natural Selection, Evolution, and Ecology

Natural Selection, Evolution,
and Evolutionary Ecology
Dr. James Danoff-Burg
Columbia University
Levels of Ecological
Explanation

Ultimate
– Evolutionary influences

Proximate
– Human influences
– Abiotic changes
– Biotic interactions
Most ecologists explore the last three levels
Progress of Ecological Inquiry?
 Explore
 If
 If
plausible ultimate answers
one is supported, stop
no ultimate answers are supported,
explore proximate answers
Rationale
 Need
to pitch the question at the right
level
 Example
– Why are Penguins only in the Southern
Hemisphere?
– Proximate - insufficient food, too many
predators, lack of shelter, etc.
– Ultimate - historical and thus evolutionary
distribution --> favored at present
Two EvolEcol Branches
 Intraspecific
– Relative selective value of different traits
– Origin of intraspecific diversity
 Interspecific
– Behavioral ecology (comparative studies)
– Systematics and phylogeny
Common feature of all branches - Evolution!
Evolution
 Change
through time within a lineage
 Mechanisms / Producers of Variation
– Genetic drift
– Phenotypic plasticity
– Natural Selection
Natural Selection  Evolution
Natural Selection
 Proposed
by Darwin and Wallace
 Evolutionary mechanism
 One way that variation exists and is
maintained in a population
 Value is relative to local competitors
 Only a negative action
– Only selection AGAINST a form of a trait
– Never selection for a trait
Intraspecific Variation
 Possible
sources:
– Genetic drift
– Phenotypic plasticity
– Natural Selection
 How
to differentiate between them?
– Genetic fixation / continuity through lineages
– Use traits that do not change in response to
changes in environment
Today’s Activity

How do changes in a resource gradient affect
intraspecific diversity?
– Are these changes due to natural selection?

Choose an organism with the following
characteristics:
–
–
–
–
Low vagility
Does not disperse aerially
Clearly marked adult stage
Traits under study do not change
Activity Tasks
Plan activity
 Collect data and enter into eBiome
 Analyze our data
 Wait for data from other sites
 Jointly analyze all data
 Make conclusions about relationship
 Posit future studies to distinguish between
evolutionary mechanisms

Planning - To be Determined:
 Environmental
variable
 Experimental organism
 Organismal trait for study
 Statistical technique to use, justify