Lecture 10

Question 1

adaptation (Gould)

Answer 1

trait built by natural selection for its current utility (biological role)

• identified by:
  1) historical origin by natural selection
  2) functional utility towards fitness

Question 2

exaptation

Answer 2

trait whose evolutionary origin has no relation to current utility

Question 3

To test adaptation hypotheses in a phylogenetic context: (general)

Answer 3

• need to be explicit about level of hierarchy

- need to define a selective regime

Question 4

selective regime

Answer 4

aggregate of all biotic and abiotic factors that determine how natural selection will act of character variation (those that are most important)

Question 5

Steps in testing for adaptation with a phylogeny

Answer 5

1) Build the tree
2) score trait(s) of interest
3) score selective regimes
4) Reconstruct history of character changes
5) Reconstruct history of selective regimes
6) assess current utility

Question 6

Scoring selective regimes

Answer 6

• dependent on particular hypothesis being tested, -requires study of spp natural history
• can be extrinsic(environmental) or intrinsic (organismic capabilities)

Question 7

reconstructing history of selective regimes

Answer 7

• can be based on direct paleontological/biogeographic data (uncommon)
• use pars/likelihood to reconstruct ancestral vs derived regimes
• assume shifts in regime are less frequent than cladogenesis

Question 8

assess current utility

Answer 8

• measure fitness differences directly in polymorphic pops
• induce ancestral state experimentally
• test performance theoretically
• compare focal clade to sister group w/ancestral state but derived selective regime

Question 9

Independent contrasts

Answer 9

• method to infer correlations between traits on a phylogeny
• assumptions: tree is correct, branch lengths measured in units of expected change, traits evolve by Brownian
• proceed recursively down tree computing contrasts for each internal node
• each contrast is phylogenetically independent-> (X,Y) values that can be used in regression analysis

Question 10

How to test if changes in one trait influenced by state of another?

Answer 10

Markov model of discrete-trait evolution, consider all combos of two traits