2. P i = A i + D i + E i V P = V A + V D + V E + some other stuff (covariances) Parents Offspring What is parental phenotype? P i = A i + D i + E iP What is offspring phenotype? O i = 1/2 A i + E iO Cov O,P = 1/2 V A + 1/2 Cov (A,D) + 1/2 Cov (A,E P ) + Cov (A,E O ) + Cov (D,E O ) + Cov (E P,E O ) Cov O,P = 1/2 V A + “G by E terms” + covariance in environment

3. Sibling Siblings have the same parents They have resemblance through both parents---AND it is possible for both to get the same alleles. In that case their phenotypes will be influenced by Dominance in the same way. Cov siblings = 1/2 V A + 1/4 V D

4. Mid-Parent Offspring How does a population respond to selection? On average, Offspring = h 2 Parents If we only allow some parents to breed (e.g. above the mean) Then the offspring will be larger. By how much?  offspring = h 2  Parents R = h 2 s

5. Mean of ParentsThreshold for Survival Mean of Surviving Parents Mean of Offspring s R R = h 2 s Often: h 2 = R / s

6. s -- Selection Differential With a single gene the change in phenotype is the change in allele frequency: With a quantitative trait: R = h 2 s

7. Selection differentials How big are selection differentials? R = h 2 s

8. Or resemblance among relatives How much heritability is there? Why is that important? How do traits differ?

9. Graph of successive generations of phenotype. Change in ‘oil content’ = R = h 2 s R 1 ~ R 30 ~ R 70 Closer look shows decline in rate of change

10. the selection differential and the selection gradient: s, selection differential = X S - X , selection gradient = slope of best fit line for relative fitness, w, as a function of trait value, z  = [cov(w, z)]/var (z) s = cov (w, z) the selection gradient enables measurement of selection independent of trait size (otherwise, larger trait=stronger selection) important when considering multiple traits simultaneously

11. Different Types of Selection

12. Directional Selection in the Blackcap, Sylvia atriacapilla

13. novel route

14. change in migratory direction is heritable, h 2 : 0.58 – 0.9

15. non-migratory

16. number of 30-minute periods of migratory restlessness populations from southern Germany are migratory, those from the Canary Is. are not

17. artificial selection increased and decreased migratory tendency

18. Stabilizing selection in the goldenrod gallfly, Eurosta solidiginis females insert an egg into a goldenrod bud larva induces gall formation ---> protection summer: parasitoid wasps winter (pupa): woodpeckers and chickadees infer predator from type of damage to gall 16 populations, each for four years measure galls of survivors and dead each spring  sources of mortality  intensity, direction of selection

19. parasitoids attack small galls; birds attack large galls

20. opposing directional selection is equivalent to stabilizing selection

21. Stabilizing selection in the goldenrod gallfly, Eurosta solidiginis females insert an egg into a goldenrod bud larva induces gall formation ---> protection summer: parasitoid wasps winter (pupa): woodpeckers and chickadees infer predator from type of damage to gall 16 populations, each for four years measure galls of survivors and dead each spring ---> sources of mortality ---> intensity, direction of selection *great variation in intensity of selection among populations and among years

22. Disruptive Selection in the large cactus finch, Geospiza conirostris

23. Geospiza conirostris on Genovese Is. four dry season feeding modes: bark-stripping to obtain arthropods cracking seeds of Opuntia helleri extracting seeds from ripe Opuntia fruits to obtain the surrounding arils tearing open rotting Opuntia pads to obtain arthropods

24. extracting seeds from ripe Opuntia fruits to obtain the surrounding arils tearing open rotting Opuntia pads to obtain arthropods Grant 1986

25. stripping bark to obtain insects and other arthropods

26. Geospiza conirostris on Genovese Is. four dry season feeding modes: bark-stripping to obtain arthropods cracking seeds of Opuntia helleri extracting seeds from ripe Opuntia fruits to obtain the surrounding arils tearing open rotting Opuntia pads to obtain arthropods birds that stripped bark had significantly deeper beaks than those that did not birds that cracked seeds had significantly larger beaks than those that did not birds that opened opuntia fruits had significantly longer bills than those that fed on arils in already opened fruits

27. seed-size hardiness feeding efficiency resource gradient utilization efficiency

28. Evolution of correlated characters selection acts on individuals, not traits few traits are completely independent— e.g., forelimbs and hindlimbs similar developmental pathways, similar genes e.g., size of red shoulder patch on a Red-Winged Blackbird pigment precursor may be involved in multiple biochemical pathways ---> many loci, many traits genetic correlations pleiotropy (one gene, many traits) polygeny (many genes, one trait)

29. linkage disequilibrium can produce genetic correlations locus A only affects trait z 1, locus B only affects trait z 2 D = 0 D = +0.15 D = -0.15 no positive negative correlation correlation correlation

30. pleiotropy can produce genetic correlations locus A (with additive alleles) affects both trait z 1 and z 2 phenotypic correlations may also arise from environmental effects r G and r E positive r G no r G both positive negative r E negative r E

31. initial selection study --- measure several features problems of interpretation: how important is what you’ve measured? observe change in trait -- selection on measured trait -- selection on a correlated trait that wasn’t measured failure of trait to change -- no selection -- no additive variance -- opposing selection -- genetic correlation easy to measure phenotypic variance and covariance but only genetic variance and covariance relevant to evolution

32. Evolution of correlated characters selection on any trait can be partitioned into a direct component (changes due to phenotypic/genotypic variation in the trait) and an indirect component due to genetic covariation with other traits the magnitude and direction of direct selection may differ from overall selection because of indirect effects consequently: a trait may change solely because of selection on some other trait -- correlated response to selection a trait may fail to change (despite measurable selection) because of opposing selection on some other, correlated trait --- constraints on trait evolution

33. Model for quantitative trait evolution single trait: R = h 2 samount of phenotypic change (R), depends on amount of V A (h 2 ) and strength of selection (s) several traits:  z = GP -1 s z is the trait vector (z 1 z 2 z 3 …z n ) = G  s is still selection differential (z – z s ) G, P are the genotypic and phenotypic variance-covariance matrices  is the selection gradient s i = 3 P ij  ij = P i1  1 + P i2  2 + P i3  3 + …… + P in  n direct indirect   is the partial regression coefficient

35. Directional natural selection on Geospiza fortis in 1976-77 and 1984-86. standardized selection coefficients differential gradient s  SE 1976-77 (n=632) weight +0.74 +0.4770.146 wing length +0.72 +0.4360.126 tarsus length +0.43 +0.0050.110 bill length +0.54 -0.1440.174 bill depth +0.63 +0.528 0.214 bill width +0.53 -0.4500.197 1984-86 (n=549) weight -0.11 -0.0400.101 wing length -0.08 -0.0150.084 tarsus length -0.09 -0.0470.076 bill length -0.03 +0.2450.095 bill depth -0.16 -0.135 0.136 bill width -0.17 -0.1520.125 Grant & Grant 1995 Evolution 49:241

36. Evolutionary genetics of feeding behavior in the garter snake, Thamnophis elegans two populations: coastal -- eat slugs inland -- no slugs occur; eats fish and aquatic amphibians (Arnold 1981)

37. feeding response to slugs is influenced by genes coastal – eat slugsinland – avoid slugs

38. Genetic correlations between responses to different prey odors in two populations of Thamnophis elegans Hyla Batrachoseps Taricha fish slug leech Hyla --- 1.10 -0.24 0.18 0.88 1.01 Batrachoseps 0.81 --- 0.07 1.00 1.34 0.98 Taricha-0.45 0.57 --- 0.09 -0.55 -0.88 fish 0.89 1.27 0.02 --- 0.59 0.84 slug-0.03 0.56 -0.79 0.19 --- 0.89 leech 0.07 0.77 -0.01 -0.38 0.89 --- coastal = above diagonal; inland = below diagonal

39. Response to slugs (food) avoid accept Response to leeches (risk)

40. Response to slugs (food) avoid accept Response to leeches (risk) H L

41. Response to slugs (food) avoid accept Response to leeches (risk) H L Selection against eating leeches is stronger than selection for eating slugs (slugs are rare)

42. Response to slugs (food) avoid accept Response to leeches (risk) H L Selection for eating slugs is stronger than selection against eating leeches (slugs are common)

43. Traits may not evolve independently because of genetic correlations due to pleiotropy or linkage disequilibirum A trait may change as a consequence of direct selection, or as a correlated response to selection on a different trait A trait undergoing selection may fail to change because of a constraint operating through a genetically correlated character Partial regression is a statistical method that enables us to separate direct selection on a trait (  ) from total selection (s) The selection gradient (  ) and the selection differential (s) may differ in magnitude and sign