28 October 2021
Females: big gametes, low (and fixed) number, low reproductive rate
e.g. human females: born with 1-2 million/oocytes (eggs), ovulate around 400 times in lifetime. Typically ca 20 follicles mature each month, but only a single follicle is ovulated. The rest undergo follicular atresia.
Males: small gametes, high (and produced continously) number, high reproductive rate e.g. human males
Schedwill P, Eggert AK, Moller JK (2018) How burying beetles spread their seed: The Coolidge effect in real life. Zool Anz 273:210-217. doi: 10.1016/j.jcz.2018.01.002
The President Coolidge and Mrs. Coolidge were being shown [separately] around an experimental government farm. When [Mrs. Coolidge] came to the chicken yard she noticed that a rooster was mating very frequently. She asked the attendant how often that happened and was told, “Dozens of times each day.” Mrs. Coolidge said, “Tell that to the President when he comes by.” Upon being told, the President asked, “Same hen every time?” The reply was, “Oh, no, Mr. President, a different hen every time.” President: “Tell that to Mrs. Coolidge.”
The way to increase reproductive success (fittnes): females: increase in the rate of food consumption/processing -> offspring production males: increase in the numer of matings
Variation in male and female reproductive potential results in sexual selection, in which males compete with each other, and females become choosy in which males to mate with (the higher slope the higher selective force)
Where one sex invest in offspring considerably more than the other, individuals of the latter will compete for the former (Trivers 1972)
DEF: the advantage which certain individuals have over other individuals of the same sex and species solely in respect of reproduction/Darwin/
stronger than natural selection, as it frequently drives trait values beyond their naturally selected optima largely acts on only half the population (usually males) - the quantitative paradox of sexual selection two mechanisms - competition for mates and mate choice Hosken DJ, House C (1998) Sexual Selection. Curr Biol 21:62–65 Elephant seals: extreme sexual dimorphism (males > (5-6x) females) dominance hierarchy established thru posturing/vocalizing/fights unsuccessful males may not mate at all, successful males have harems of 30-100 females Casey C, Charrier I, Mathevon N, Reichmuth C (2015) Rival assessment among northern elephant seals : evidence of associative learning during male – male contests Subject Category : R Soc Open Sci Elephant seals: Haley M, Deutsch C, Boeuf B (1994) Size, dominance and copulatory success in male northern elephant seals, Mirounga anusirostris. Anim Behav 48:1249-1260 Assumption: the atractive trait and preferance for this trait has to be heritable
Females choose physically attractive male -> produce physically atractive sons (and dauthers with the preference) -> has more grandchildren, because other choosy females will prefer their attractive, sexy sons (and daughter will mate with atractive males) -> self-reinforcing coevolution of both trait and preference
DEF: becasue of intersexual conflict males evolve traits to stimulate females into mating suboptimally (e.g., at a rate so high that it reduces female fitness). Females evolve “resistance” to the traits, and males then evolve novel or exaggerated traits.
Assumptions: Chase-away selection? Ligon JD, Zwartjes PW (1995) Ornate plumage of male red junglefowl does not influence mate choice by females. Anim Behav 49:117-125 Lande R (1981) Models of speciation by sexual selection on polygenic traits. Proc Natl Acad Sci U S A 78:3721-3725 DEF: animals of greater biological fitness signal this status through handicapping behaviour or morphology that effectively lowers this quality. DEF: Persistent female choice for particular male trait values should erode genetic diversity in male traits and thereby remove the benefits of choice, yet choice persists Getty T (1998) Reliable signalling need not be a handicap. Anim Behav 56:253-255 DEF: sexual ornaments are indicators of parasite- and disease-resistance Moller AP (1990) Effects of a Haematophagous Mite on the Barn Swallow (Hirundo rustica) Evolution 44: 771-784 Moller AP (1990) Effects of a Haematophagous Mite on the Barn Swallow (Hirundo rustica) Evolution 44: 771-784 Moller AP (1990) Effects of a Haematophagous Mite on the Barn Swallow (Hirundo rustica) Evolution 44: 771-784 Evidence, eg. guppies Martin CH, Johnsen S (2007) A field test of the Hamilton-Zuk hypothesis in the Trinidadian guppy (Poecilia reticulata). Behav Ecol Sociobiol 61:1897Effect of basic sex differences
Bateman principle (1948)
Differential parental investments
Sexual selection
Sexual selection - WN/fighting
Sexual selection - WN/fighting
Sexual selection - WN/fighting
Sexual selection: BTWN/atractiveness
Sexual selection: BTWN/atractiveness
Epigametic traits
Sexy son hypothesis (Fisher 1930)
Run-away selection
Lande model (1981)
Chase-away selection (Holland and Rice 1998)
Paradox of rooster plumes
Run/Chase-away and Ratchet model
Handicap hypothesis (Zahavi 1975)
Lek paradox
Handicap - Grafen model
Handicap - Getty model
Hamilton-Zuk hypothesis (Zahavi 1975)
* Hamilton WD, Zuk M (1982) Heritable true fitness and bright birds: A role for parasites? Science (80) 218:384-387
* Balenger SL, Zuk M (2014) Testing the Hamilton-Zuk hypothesis: Past, present, and future. Integr Comp Biol 54:601-613 Hamilton-Zuk hyp - Moller’s test
Hamilton-Zuk hyp - Moller’s test
Hamilton-Zuk hyp - Moller’s test
Hamilton-Zuk hypothesis (Zahavi 1975)
