Announcements

1. Announcements

2. Announcements To what is the adaptation? • They seem too tall for their food • Male heads are disproportionately heavier than females • males use their head as a mace • longer necked males win more contests and females

3. How to answer such questions? • Baseless speculation • Hand-waving speculation • Modeling • Comparative method (correlations) • Experimentation • Which do you prefer?

4. Baseless speculation: the easiest and most widely employed method. We won’t discuss it further. • Modeling: terrific to evaluate complex processes whose components are understood. • Cannot anticipate forces which are not recognized and incorporated into the model. • Comparative method: Negative evidence is useful in rejecting hypotheses, but positive evidence is sometimes spurious (you never know if you’ve identified a cause or a correlate of a cause). • Experiments: incorporate that which is unanticipated. Although this often makes results confusing, it ultimately paves the way for better hypotheses. • Most scientific progress is the result of controlled experimentation.

5. Experiments • Tephritid flies display wing markings that appear to mimic their major predator’s (jumping spider) territorial leg waving display. • H1: the display was selected b/c it scares jumping spiders and decreases predation from them.

6. Experiments • H1: the display was selected b/c it scares jumping spiders and decreases predation from them. Changes (#) from (letter): 1 (A) 1 (B) 1 (B) 1 (D) (neg. control) (pos. control)

7. WT Operation Marks Wave Wave/mark

8. comparative method • sperm competition: multiple ejaculates vying for fertilization success • adaptation: increased sperm production • comparative prediction • testes size will be proportional to incidence of sperm competition

9. comparative method Ha Ho

10. comparative method • are the data independent?

11. n = 6

12. n = 6 • common ancestry makes data non-independent

13. n = 6 • common ancestry makes data non-independent • n=2

14. Phylogenetically independent contrasts • each bifurcation is independent • convert x axis data to contrasts • plot difference (greater – lesser) • leave slope • 3) new regression Felsenstein, ‘85

15. Phylogenetically independent contrasts • how do you contrast non-existing species?

16. Phylogenetically independent contrasts • how do you contrast non-existing species? • extrapolate ancestors from extant descendents • e.g., R from P and Q; • T from O, M, N

17. Phylogenetically independent contrasts n = 17 Hosken, ‘98 When group size evolved toward larger/smaller size, so to did testes size. n = 11

18. Primate testes mass and mating system • multi-male groups • single-male harems • socially monogamous • reviewed in Andersson, 1994 You are here

19. Phenotypic plasticity • Phenotypic variation resulting from (identical genotype) developing in different environments • Can it be adaptive? • Three Daphnia populations: asexual; fish food.10 clones taken from each lake. • Measured: phototaxis after rearing clones with or without fishy smelling water. All clones tested under control (fishless water) conditions. • Is there phenotypic plasticity? • 1) Blaankaart Daphnia most negatively phototactic in response to fish • 2) Blaankaart Daphnia most exposed to fish predation • 3) genetic variation for phototactic behavior? Which populations? • Difference between clones within each population under control conditions; all 3 populations. • 4) Phenotypic plasticity? In which populations • Difference between blue and red (present in all populations) • 5) Is phenotypic plasticity under selection? • When evolved with predators (Blankaart) Daphnia clones all show negative phototaxis. high low zero [fish] lake Controls are ordered lowest to highest

20. Levels of selection • Yeast can respire (through mitochondria) or ferment. • non-respiring mitochondria: contain deletions in their DNA. These mitochondria replicate faster than respiring mitochondria. • Selection within cells favors non-respiring mitochondria • Selection between cells favors respiring mitochondria b/c it is more efficient • H1: non respiring mitochondria are parasites • Test: Start non-respiring cells at intermediate frequency. In large yeast populations competition between yeast will favor respiration. In small yeast populations natural selection among yeast will be less effective (due to ?) and competition among mitochondria will favor parasitic. Yeast mitochondrion respiration non respiration

21. Levels of selection

22. C-value paradox • Size of genome doesn’t correlate strongly with organismal complexity: • single-celled amoeba 670,000,000,000 kb • humans 3,400,000,000 kb • only 2% of human DNA is coding; much of the rest is mysterious • Transposable elements may explain much of the paradox • Sequences that can make copies of themselves that insert elsewhere in genome • Insertion constitutes a mutation and is often deleterious • Transposase protein causes transposition • Parasitic DNA analogous to functionless mitochondria w/ deletions. • Chromosome 22 %of chromosome • 14,000 LINES (long interspersed elements) 13 • 20,188 Alu SINES (short interspersed elements) 16.8 • ~6% of human genome is Alu sequence (300bp, codes for nothing)