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Final Exam: Friday, 20 March 2015, 8:00 - 11:00 A.M. In Spieth 2200 = same as lecture room

Final Exam: Friday, 20 March 2015, 8:00 - 11:00 A.M. In Spieth 2200 = same as lecture room Emphasizes last 1/3 of course, but may include carry-over things (e.g., residuals, natural selection, multiple solutions) Format will be similar to previous 2 exams.

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Final Exam: Friday, 20 March 2015, 8:00 - 11:00 A.M. In Spieth 2200 = same as lecture room

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  1. Final Exam: Friday, 20 March 2015, 8:00 - 11:00 A.M. In Spieth 2200 = same as lecture room Emphasizes last 1/3 of course, but may include carry-over things (e.g., residuals, natural selection, multiple solutions) Format will be similar to previous 2 exams

  2. Your Teaching Assistant (Layla Hiramatsu) will hold two extra office hours this week: Thursday, 19 March, 2:00-4:00 P.M. 2378 Spieth Hall You must come with questions to ask,as she will not have any extra review material prepared for you.

  3. Your Professor (Dr. Theodore Garland, Jr.) will also hold two office hours next week: Thursday, 19 March, 9:30-11:30 A.M. 2366 Spieth Hall You must come with questions to ask,as he will not have any extra reviewmaterial prepared for you.

  4. Please remember to fill out course evaluations!

  5. Lecture 19: • Interspecific Comparison and Why Phylogeny Matters

  6. Four General Approaches to Studying Evolution: • Comparisons of Species (or populations) = "The Comparative Method“Shows what has happened in past evolution • Biology of Natural PopulationsShows present evolution in action • 3. Selection ExperimentsShows, experimentally, what might happen during future evolution • 4. Comparison of Real Organisms with Predictions of Theoretical ModelsShows how close selection can get to producing optimal solutions

  7. Three Sampling Schemes for Comparing Species: 1. Do two species differ in the predicted direction? (not adequate) 2. Do multiple sets of species pairs differ in the predicted direction? (acceptable) 3. Does the expected relationship hold across many species? (the most general)

  8. Three Sampling Schemes for Comparing Species: 1. Do two species differ in the predicted direction? (not adequate) Example: what are the respiratory adaptations to living in burrows, where O2 levels can be low and CO2 levels high? Physiologists compared burrowing owls with bobwhite quail. Only the owl usesburrows, and theyare about thesame body size.

  9. But this comparison is ambiguous. Any differences might be attributable to: adaptations to a burrowing habit (owl) carnivory (owl) vs. herbivory (quail) (partial) domestication (quail) nocturnal (owl, mostly) vs. diurnal (quail) or any other aspect of "owlness" or "quailness" (i.e., shared derived features [synapomorphies] of the owl clade or of the quail clade).

  10. Garland, T., Jr., and S. C. Adolph. 1994.Why not to do two-species comparative studies: limitations on inferring adaptation.Physiological Zoology 67:797-828. Four limitations of two-species comparative studies:

  11. A. Independent variable is confounded with species (lineage) membership. The species may differ in many ways and for many reasons, in addition to the one that is of interest (e.g., whether they live in burrows).

  12. B. Species almost always will differ. • The relationship between speciation per se (i.e., the evolution of reproductive isolation) and phenotypic evolution is poorly understood,but the process of speciation itself may result in genetic differentiation that affects various phenotypic traits. • The two species will (by definition) have experienced little or no genetic exchange since the time of their evolutionary divergence, and so, at a minimum, they will have diverged somewhat by random genetic drift alone.

  13. 3. They -- or their ancestors -- will have experienced different environmental conditions and hence different selective regimes, one axis of which is why they were chosen for comparison (e.g., whether they live in burrows). • Therefore, comparing two species is not like comparing two groups of otherwise-identical rats, one of whom received a drug and one of whom received a placebo. • a. The appropriate null hypothesis is not no difference, but rather some difference(s). • b. If difference is presumed to be likely, then you have a 50% chance it will be in the predicted direction, so Type I error rate is 50% not 5%.

  14. Trait Environment C. Degrees of freedom for correlating trait with environment = N - 2 = 0. As soon as you go to three or more species, you are protected from this problem. 3 species, d.f. = 1 2 species, d.f. = 0 Trait Environment

  15. D. Comparison of only two species would not allow inference concerning which state was ancestral. If your definition of "Adaptation" is historical and requires showing that it evolved from a different state, then you cannot infer (e.g., by parsimony) this with only two species. A O O A O O O

  16. Three Sampling Schemes for Comparing Species: 2. Do multiple sets of species pairs differ in the predicted direction? (acceptable) Example: Martin, T. E., P. R. Martin, C. R. Olson, B. J. Heidinger, and J. J. Fontaine. 2000. Parental care and clutch sizes in North and South American birds. Science 287:1482-1485. Background: "The evolutionary causes of small clutch sizes in tropical and Southern Hemisphere regions are poorly understood." Hypothesis: "Alexander Skutch proposed 50 years ago that higher nest predation in the south constrains the rate at which parent birds can deliver food to young and thereby constrains clutch size by limiting the number of young that parents can feed."

  17. Assuming that each taxon is from a different clade, then each pairwise comparison is essentially an independent piece of information. Any difference between two species within a genus (or family) must have arisen since they last shared a common ancestor, and that common ancestor is shared to the exclusion of species in other genera.

  18. So, this method uses phylogenetic information in a simple and incomplete way. And, it does not make use of differences among the species pairs. NorthSouth NorthSouth North South Genus 1 Genus 2 Genus 3

  19. 8 pairs of species to be compared

  20. The AZ species has a larger clutch in each of the 8 cases. paired t-test, P < 0.001

  21. The AZ species experience a higher predation rate in 7 of the 8 cases. paired t-test, P = 0.011

  22. Extended data set with additional species: Overall Conclusion: "Skutch's hypothesis explains clutch size variation within North and South America. However, neither Skutch's hypothesis nor two major alternatives explain differences between latitudes." (Martin et al. 2000)

  23. Three Sampling Schemes for Comparing Species: 3. Does the expected relationship hold across many species? (the most general)

  24. General Procedure for Comparative Study: 1. Measure several species (and/or populations) for some phenotypic trait(s); calculate mean(s). a) Should be raised in common environment or "common garden," and really need at least two generations 2. Characterize environmental features that should indicate variation in the "selective regime" 3. a) Relate interspecific phenotypic variation to environmental variation -- evidence for adaptation? (e.g., clutch size vs. predation rate) b) Relate traits to each other -- elucidate functional relations, allometry, trade-offs, etc.

  25. water shrew water rat muskrat beaver otter mink hippo seal sea lion manatee whales Example:species in several lineages of mammals have become secondarily aquatic, to one degree or another.

  26. Water Shrew Water Rat

  27. Muskrat

  28. Otters of various types, including the Sea Otter (Enhydra lutra)

  29. Mink

  30. The mammals exhibit a gradation in how aquatic they are (some barely, some completely). Not all are members of the same evolutionary lineage (clade), so this habit has evolved multiple times. Allows us to formulate and then test simple adaptive hypotheses. The more aquatic the animal, the more hemoglobin it will have in its blood.

  31. Natural& Sexual Selection Act On Behavior This hypothetical example is essentially trying to relate these levels. Constrain Morphology, Physiology, Biochemistry Deter- mine Organismal Performance Abilities

  32. Hypothetical Example N = 50 d.f. = 48 R = 0.517 1-tailedP < 0.0001 [Hemoglobin] in Blood How Aquatic the Species Is

  33. Real Examples,Some Shown in Previous Lectures (interspecific comparisons are very common in ecological and evolutonary physiology

  34. Natural& Sexual Selection Act On Behavior Constrain Morphology, Physiology, Biochemistry Deter- mine Organismal Performance Abilities

  35. Amphibians that live nearer to the equator have higher thermal tolerances. "These data are consistent with the thesis that congeneric and conspecific populations in different habitats have partially independent evolutionary pathways and that where populations have been displaced from a less to a more uniform environment, characters which are no longer maintained by selection pressure are lost." (p. 100) Snyder, G. K., and Weathers, W. W. 1975. Temperature adaptations in amphibians. American Naturalist 109:93-101.

  36. Natural& Sexual Selection Act On Behavior Constrain Morphology, Physiology, Biochemistry Deter- mine Organismal Performance Abilities

  37. Maximum isometric twitch tension of lizard muscles is positively correlated with PBT across species. "These data are interpreted as indicating that divergence in the thermal adjustments for contractility of muscular tissues are most directly associated with the temperatures characteristically maintained through the behavior of the species rather than to the general geographical (climatic) distribution or phylogenetic position of the species."(p. 1)

  38. More Real Examples ...

  39. Do canids (endurance athletes) have larger hearts than felids (sprinters)?

  40. Do desert animals have greater urine-concentrating ability? 141 species or populations of rodents Habitat coded as Aquatic, Mesic, Semi-desert, Desert Al-kahtani, M. A., C. Zuleta, E. Caviedes-Vidal, and T. Garland, Jr. 2004. Kidney mass and relative medullary thickness of rodents in relation to habitat, body size, and phylogeny. Physiological and Biochemical Zoology 77:346-365. (plus online Appendix B).

  41. Yes, they do. Also note the negative allometric relationshpp.

  42. Do desert animals have reduced basal metabolic rates? Deserts are generally hot and dry, and have low primary productivity. Reduced BMR would reduce needs for food and water, and could reduce chances of overheating. 31 populations/species of deer mice (Peromyscus) were studied. Mass-corrected BMR was correlated with various characteristics of the environment (temperature, precipitation) at or near their point of capture.

  43. 31 Populations of Peromyscus Residual log B.M.R. (ml O2/g x h) r2 = 0.27,2-tailed P < 0.005 Mean July Temperature (oC)

  44. What factors affect size of the testes in primates? Main source is: Harcourt, A. H., P. H. Harvey, S. G. Larson, and R. V. Short. 1981. Testis weight, body weight and breeding system in primates. Nature 293:55-57. See also: Harvey and Pagel (1991) figure 1.3Harvey, P. H., and M. D. Pagel. 1991. The comparative method in evolutionary biology. Oxford University Press, Oxford. 239 pp. http://www.atomicnerds.com/wp-content/uploads/2010/08/Picture1-5.png ChimpBrain Chimp Testicle

  45. Primate Species: Allometry Testes Mass (g) Body Mass (kg)

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