Transcript 440sexsel
VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection 1. Meiotic Drive: - Stalk-eyed flies, Cyrtodiopsis dalmanni and C. whitei (Presgraves, et al.1997). • X(d) meiotic drive element on the X chromosome causes female-biased sex ratios • spermatid degeneration of Y-bearing sperm in male carriers of X(d). • balanced by Y-linked and autosomal factors that decrease the intensity of meiotic drive. • Even a Y-linked polymorphism for resistance to drive which reduces the intensity and reverses the direction of meiotic drive. • When paired with X(d), modifying Y chromosomes (Y(m)) cause the transmission of predominantly Ybearing sperm, and on average, production of 63% male progeny. VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection 1. Meiotic Drive: 2. Transposable Elements VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection 1. Meiotic Drive: 2. Transposable Elements these genes replicate themselves independently of cell division... they are gene parasites that make nothing for the cell. yet they increase in frequency relative to other genes in the genome. VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection 1. Meiotic Drive: 2. Transposable Elements 3. 'Selfish' Genes (Richard Dawkins) VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection 1. Meiotic Drive: 2. Transposable Elements 3. 'Selfish' Genes (Richard Dawkins) - genes are the fundamental replicators VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection 1. Meiotic Drive: 2. Transposable Elements 3. 'Selfish' Genes (Richard Dawkins) - genes are the fundamental replicators - genes which confer an advantage, when averaged across other genetic backgrounds, will be selected for. (Analogy of 'crews') VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection 1. Meiotic Drive: 2. Transposable Elements 3. 'Selfish' Genes (Richard Dawkins) - genes are the fundamental replicators - genes which confer an advantage, when averaged across other genetic backgrounds, will be selected for. Analogy of 'crews') - co-adaptive assemblages and non-additive effects are not explained VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection B. Organelle Selection VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection B. Organelle Selection - some mitochondria in yeast are non-respiring parasites - they survive but don't produce much energy for the cell. They reproduce fast in a cell. VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection B. Organelle Selection - some mitochondria in yeast are non-respiring parasites - they survive but don't produce much energy for the cell. They reproduce fast in a cell. - In small populations of yeast, where selection at the organismal level is weak, there is no cost to the cell to reproducing slowly and the parasitic mitochondria dominate within cells. VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection B. Organelle Selection - some mitochondria in yeast are non-respiring parasites - they survive but don't produce much energy for the cell. They reproduce fast in a cell. - In small populations of yeast, where selection at the organismal level is weak, there is no cost to the cell to reproducing slowly and the parasitic mitochondria dominate within cells. - In large populations, where aerobic respiration is advantageous at a cellular level, cells with parasites are selected against and the frequency of parasitic mitochondria is reduced. VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection B. Organelle Selection - some mitochondria in yeast are non-respiring parasites - they survive but don't produce much energy for the cell. They reproduce fast in a cell. - In small populations of yeast, where selection at the organismal level is weak, there is no cost to the cell to reproducing slowly and the parasitic mitochondria dominate within cells. - In large populations, where aerobic respiration is advantageous at a cellular level, cells with parasites are selected against and the frequency of parasitic mitochondria is reduced. - There is a balance of selection at different levels that must be understood to explain the different frequency of parasitic mitochondria. VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection B. Organelle Selection C. Cell Selection VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection B. Organelle Selection C. Cell Selection - Cancerous Tumour - cell division increases, and the effects may be balanced at a higher level (organism). VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection B. Organelle Selection C. Cell Selection D. Organism Selection (Darwinian) VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection B. Organelle Selection C. Cell Selection D. Organism Selection (Darwinian) E. Kin Selection 1. Darwin’s Dilemma …bees make me sad… 2. W. D. Hamilton - 1964 - related individuals that help one another increase their OWN fitness, because their alleles occur within THOSE relatives. 2. W. D. Hamilton - 1964 - related individuals that help one another increase their OWN fitness, because their alleles occur within THOSE relatives. a. Inclusive Fitness several relatives have more of YOUR genes, cumulatively, than YOU do! 1/2 1/2 ½ + ½ + ½ >1 1/2 1 a. Inclusive Fitness 1/2 1/2 1/2 1 If I save myself… AAAAAAAAA !!!!! XX X X XX I save one “set” of my genes… 1/2 1/2 1/2 1 1 If I save my relatives… I save 1.5 sets of my genes. If this has a genetic basis, selection will favor altruism among relatives. What a guy! …ow… 1/2 1/2 1/2 1/2 1 1/2 1/2 3. Examples 1. Helping among relatives – a function of kin selection 3. Examples 1. Helping among relatives – a function of kin selection 3. Examples 1. Helping among relatives – a function of kin selection 3. Examples 2. Haplodiploidy and Social Insects W. D. Hamilton – 1964 rb > c …bees make me sad… VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection B. Organelle Selection C. Cell Selection D. Organism Selection (Darwinian) E. Kin Selection F. Group Selection (Wynne-Edwards) F. Group Selection (Wynne-Edwards) - Can groups replace one another simply by reproductive success?? F. Group Selection (Wynne-Edwards) - Can groups replace one another simply by reproductive success?? - First, it would have to be recognized by it's contradiction with organismal selection. F. Group Selection (Wynne-Edwards) - Can groups replace one another simply by reproductive success?? - First, it would have to be recognized by it's contradiction with organismal selection. - (Sacrifice of fitness at the organismal level with increase at the level of the group). F. Group Selection (Wynne-Edwards) - Can groups replace one another simply by reproductive success?? - First, it would have to be recognized by it's contradiction with organismal selection. - (Sacrifice of fitness at the organismal level with increase at the level of the group). - Altruism is a possible example - sacrifice reproduction for benefit of the group... but it usually doesn't work because f(altruism) declines within the pop if organisms are unrelated! F. Group Selection (Wynne-Edwards) - But – there are caveats with kin selection, too Naked mole-rats: • Live for 31 years • Don’t get cancer; division inhibited by cellcell contact, and have an odd hyaluronan protein…5x larger than humans and cancer-prone species in which the normal form increases rate of metastasis. • MUCH lower mutation rate • Only mammals that are thermoconformers • Eusocial: one ‘queen’, 2-3 males, the rest sterile workers in two size castes. • “Vertebrate of the Year” in 2013 Problem: To show group selection, distinct from individual selection, it must be shown that a net ‘cost’ to the individual is outweighed by a net ‘benefit’ to the group, without invoking relatedness and kin selection. This is different than an individual benefiting MORE by helping the group than by acting selfishly. THIS is still maximizing individual fitness. PRO GROUP: Wilson ANTI GROUP: Pinker VI. Levels of Selection Selection can occur wherever there is differential reproduction among variable entities. A. Gene Selection B. Organelle Selection C. Cell Selection D. Organism Selection (Darwinian) E. Kin Selection F. Group Selection (Wynne-Edwards) G. Species Selection G. Species Selection G. Species Selection - Selection for sexually reproducing species: Parthenogenesis arises spontaneously, but extinctions are rapid due to lack of variation and Muller's rachet. Muller's ratchet is the continuous accumulation of mutations in a lineage. In sexual reproduction, since only 1/2 of the genes are passed from each parent, there is a 50% chance that a deleterious new mutation will be purged from the genome just by chance. And also, even if it is expressed, there will be other organisms in the pop that did NOT receive it and have higher fitness. So, selection can purify this sexual population of the deleterious alleles. But in an asexual lineage, all offspring get the whole genome - even a new deleterious allele. So, there is no way to purge it from the genome. In fact, in Daphnia pulex, asexual lineages accumulate deleterious amino acid substitutions at 4x the rate of sexual lineages (Paland and Lynch 2006, Science 311:990-992). G. Species Selection - Selection for sexually reproducing species: - Parthenogenesis arises spontaneously, but extinctions are rapid due to lack of variation and Muller's rachet. So, extinction rates in parthenogenetic lineages are high... and so most lineages that radiate and produce lots of descendant species are sexual. G. Species Selection - Selection for sexually reproducing species: - Certain lineage are more likely to speciate (beetles - small, tough, and easily isolated...) G. Species Selection - Selection for sexually reproducing species: - Certain lineage are more likely to speciate (beetles - small, tough, and easily isolated...) SO, as a consequence of survival and speciation rate (reproduction), sexual lineages and also more rapidly speciating lineages will leave more species and replace other lineages that die out over time. Sexual Selection - Recognized as a deviation from predictions offered by a strict selection model. In this case, there are different selective pressures on each SEX. Sexual Selection - Recognized as a deviation from predictions offered by a strict selection model. 1. The Basics Sexual Selection 1. The Basics - many species show sexual dimorphism (morph or behav) Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics - many species show sexual dimorphism (morph or behav) - WHY? If adaptive (must be tested), then selective pressures differ Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics - many species show sexual dimorphism (morph or behav) - WHY? If adaptive (must be tested), then selective pressures differ - Some traits appear COSTLY to survival. Darwin (1871) described how showy plumage in birds should decrease survival. In order for it to be ADAPTIVE (increase reproductive success), this COST must be OFFSET by a disproportionate increase in one of the other components of fitness most likely NUMBER of offspring. Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics - many species show sexual dimorphism (morph or behav) - WHY? If adaptive (must be tested), then selective pressures differ - Some traits appear COSTLY to survival. Darwin (1871) described how showy plumage in birds should decrease survival. In order for it to be ADAPTIVE (increase reproductive success), this COST must be OFFSET by a disproportionate increase in one of the other components of fitness most likely NUMBER of offspring. - This is affected by access to mates, number of mates, number of offspring, and quality of offspring. Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics - many species show sexual dimorphism (morph or behav) - WHY? If adaptive (must be tested), then selective pressures differ - Some traits appear COSTLY to survival. Darwin (1871) described how showy plumage in birds should decrease survival. In order for it to be ADAPTIVE (increase reproductive success), this COST must be OFFSET by a disproportionate increase in one of the other components of fitness most likely NUMBER of offspring. - This is affected by access to mates, number of mates, number of offspring, and quality of offspring. - These diffs have to vary BETWEEN SEXES to account for dimorphism... so access to mates must vary, etc. Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics - many species show sexual dimorphism (morph or behav) - WHY? If adaptive (must be tested), then selective pressures differ - Some traits appear COSTLY to survival. Darwin (1871) described how showy plumage in birds should decrease survival. In order for it to be ADAPTIVE (increase reproductive success), this COST must be OFFSET by a disproportionate increase in one of the other components of fitness most likely NUMBER of offspring. - This is affected by access to mates, number of mates, number of offspring, and quality of offspring. - These diffs have to vary BETWEEN SEXES to account for dimorphism... so access to mates must vary, etc. - Darwin (1871) though of two patterns: - Darwin (1871) though of two patterns: Male Contest Female Choice Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) - what is a fundamental difference between most sexes? gamete size Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) - what is a fundamental difference between most sexes? gamete size - in anisogamous species (different sized gametes), the female produces a few large gametes, and the male produces lots of small ones. Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) - what is a fundamental difference between most sexes? gamete size - in anisogamous species (different sized gametes), the female produces a few large gametes, and the male produces lots of small ones. - Thus, the female invests more energy in each gamete, and that may be the tip of the iceberg (fruit, seed, yolk, uterine development, care...) Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) - what is a fundamental difference between most sexes? gamete size - in anisogamous species (different sized gametes), the female produces a few large gametes, and the male produces lots of small ones. - Thus, the female invests more energy in each gamete, and that may be the tip of the iceberg (fruit, seed, yolk, uterine development, care...) - So: Female success is limited by number of offspring she can make Male success is limited by access to/number of mates Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) - what is a fundamental difference between most sexes? gamete size - in anisogamous species (different sized gametes), the female produces a few large gametes, and the male produces lots of small ones. - Thus, the female invests more energy in each gamete, and that may be the tip of the iceberg (fruit, seed, yolk, uterine development, care...) - So: Female success is limited by number of offspring she can raise Male success is limited by access to/number of mates - There should be greater VARIANCE among males in success, so selection for mate acquisition should be stronger in males. Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) C. Tests (Jones 2002) - Newts: # offspring correlates with number of mates in males, not females # offspring male female # mates Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) 3. Tests (Jones 2002) - Pipefish where males incubate young, the pattern is reversed... # offspring female male # mates Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) 3. Tests (Jones 2002) - Pipefish where males incubate young, the pattern is reversed... - SO: reproductive strategy correlates better with INVESTMENT than SEX, per se. # offspring female male # mates Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) 3. Tests (Jones 2002) 4. Conclusions Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) 3. Tests (Jones 2002) 4. Conclusions - Darwin and Bateman said males are competitive, and the only recourse left to females is to be choosy. Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) 3. Tests (Jones 2002) 4. Conclusions - Darwin and Bateman said males are competitive, and the only recourse left to females is to be choosy. - Things are more complex (pipefish, monogamy) Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) 3. Tests (Jones 2002) 4. Conclusions - Darwin and Bateman said males are competitive, and the only recourse left to females is to be choosy. - Things are more complex (pipefish, monogamy) - If one sex is limited by access, that sex should compete. Sexual Selection - not really a level, but recognized in the same way - as a deviation from predictions offered by a strict selection model. 1. The Basics 2. Hypothesis of Parental Investment (Bateman 1948, Trivers 1972) 3. Tests (Jones 2002) 4. Conclusions - Darwin and Bateman said males are competitive, and the only recourse left to females is to be choosy. - Things are more complex (pipefish, monogamy) - If one sex is limited by access, that sex should compete. - The sex NOT limited by access can then be choosey and select mates of the highest QUALITY. Sexual Selection 5. INTRAsexual Competition (for access) Sexual Selection 5. INTRAsexual Competition (for access) - competition for harems, territories Sexual Selection 5. INTRAsexual Competition (for access) - competition for harems, territories - sperm competition Sexual Selection 5. INTRAsexual Competition (for access) - competition for harems, territories - sperm competition - infanticide Sexual Selection 5. INTRAsexual Competition (for access) - competition for harems, territories - sperm competition - infanticide - female mimicry in male subadults and "stealth matings" "sneaker males" FEMALE "Sneaker" male This and other examples Sexual Selection 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating Sexual Selection 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating showy breeding plumage calling displays Sexual Selection 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit - healthy males are better fathers - the redder the male house finch, the healthier it is, and the more food it brings to the nest. 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit - Scorpion fly males bring a 'nuptual gift'... the one with the biggest gift is accepted by the female (who gets this extra energy to make eggs). 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit - Redback spiders - males that give themselves up as meal leave more offspring than those that don't Male mantids eaten during copulation mate longer and transfer more sperm, and females lay more eggs. 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Good Genes" "GOOD GENES" - Bright Plumage means low parasite load - Resistance to parasites has a genetic component - Bright Males - low parasites - offspring with low parasites - increased probability of survival. 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Good Genes" and Symmetry Theory" "GOOD GENES" "SYMMETRY THEORY" - many organisms prefer the most symmetrical mates - this might indicate co-adapted gene complexes that work well together during development. - Moeller demonstrated that offspring of symmetrical males molt earlier and develop sooner than offspring of other males. 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Good Genes" and Symmetry Theory" "GOOD GENES" "SYMMETRY THEORY" - many organisms prefer the most symmetrical mates - this might indicate co-adapted gene complexes that work well together during development. - Moeller demonstrated that offspring of symmetrical males molt earlier and develop sooner than offspring of other males. - And many human studies reveal the same things: - preference for symmetrical mates 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Good Genes" "GOOD GENES" "SYMMETRY THEORY" - many organisms prefer the most symmetrical mates - this might indicate co-adapted gene complexes that Hmmm.... work well together during development 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Good Genes" "GOOD GENES" "SYMMETRY THEORY" - many organisms prefer the most symmetrical mates - this might indicate co-adapted gene complexes that Hmmm.... work well together during development 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Good Genes" "GOOD GENES" "SYMMETRY THEORY" - many organisms prefer the most symmetrical mates - this might indicate co-adapted gene complexes that Hmmm.... work well together during development Hey, It Works!! 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Handicap Theory" - I'm alive, even WITH this HUGE TAIL!!! - I must be awesome!! 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Runaway Selection" - Positive Feedback Loops 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Runaway Selection" - Positive Feedback Loops If long tails are attractive to females for WHATEVER REASON, and they are heritable, then Females should continue to prefer males with long tails, because THEIR SONS will then have long tails and will mate. 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Runaway Selection" - Positive Feedback Loops If long tails are attractive to most females for WHATEVER REASON, and they are heritable, then selection will reinforce this preference because females who select long-tailed males will produce sons with long tails, who will be preferred in the next generation… and daughters with a preference for long tails. 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Runaway Selection" - Positive Feedback Loops If long tails are attractive to females for WHATEVER REASON, and they are heritable, then Females should continue to prefer males with long tails, because THEIR SONS will then have long tails and will mate. Likewise, a female should produce daughters that are attracted to long tails, so that their grandsons will have long tails. May result in SUPERNORMAL STIMULUS - if a long tail is good, a really long tail is GREAT!!! 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Runaway Selection" - Positive Feedback Loops If long tails are attractive to females for WHATEVER REASON, and they are heritable, then Females should continue to prefer males with long tails, because THEIR SONS will then have long tails and will mate. Likewise, a female should produce daughters that are attracted to long tails, so that their grandsons will have long tails. May result in SUPERNORMAL STIMULUS - if a long tail is good, a really long tail is GREAT!!! Why hasn't female choice driven male tail length to that extreme? 6. INTERsexual Selection (Mate Preference) - A behavior or morphology that is only performed during the reproductive season, which increases risk and must then be offset by mating - WHY is it ADAPTIVE for the FEMALE to choose a SHOWY MALE?? 1. Direct Benefit 2. Indirect Benefit - "Runaway Selection" - Positive Feedback Loops If long tails are attractive to females for WHATEVER REASON, and they are heritable, then Females should continue to prefer males with long tails, because THEIR SONS will then have long tails and will mate. Likewise, a female should produce daughters that are attracted to long tails, so that their grandsons will have long tails. May result in SUPERNORMAL STIMULUS - if a long tail is good, a really long tail is GREAT!!! (see long-tailed widowbird example in book). Why hasn't female choice driven male tail length to that extreme? CONSTRAINTS (genetic) and CONTRADICTORY SELECTIVE PRESSURES (energetic, survival, etc.)