Lecture 14 Flashcards
1
Q
Sexual Dimorphism
A
- Phenomenon in which individuals of different sexes of same species have different genotypes and phenotypes
- Differences in gametes(anisogamy)
- Differences in reproductive organs
- Other sex associated phenotypic differences
2
Q
Males and Females
A
- Genetic males(XY, ZZ): Sperm producers
- Gametic females(XX, ZW): Egg producers
3
Q
Sexual Selection
A
- Sexually selected traits function to enhance mating success
- Subset of natural selection but it can be useful to consider them separately
4
Q
Increase fitness
A
- Natural and Sexual Selection increase fitness through survival, reproductive rate, number and quality of mates
5
Q
Types of sexual selection
A
- Intrasexual selection: competition
- Intersexual selection: choosiness
6
Q
What determines strength of sexual selection
A
- Operational sex ratio -> mating competition -> sexual selection
7
Q
What determines operational sex ratio
A
- Anything that alters the receptivity of one sex to mating, or potential for remating
8
Q
What drives differences in potential reproductive rates(PRR)
A
- Egg: resource-rich, few, large
- Sperm: inexpensive, many, small
9
Q
Parental Investment Theory
A
- Sexes of some species differ in their reproductive investment
- Each offspring in these species is produced from a sperm and egg
- Members of the sex that invest little in offspring will compete among themselves to mate with members of the sex that invest in more offspring
10
Q
Difference in investment between the sexes
A
- Males: fitness limited by access to fertilizable gametes
- Females: fitness limited by access to resources
11
Q
If males are limited by access to mates, and females arent as much
A
- High variance in mating success will lead to high variance in fitness
- High variance in mating success will lead to relatively lower variance in fitness
12
Q
Intrasexual selection: competition
A
- Pre-copulatory: # of copulations
- Post-copulatory: success of copulations
13
Q
Manifestations of competition: pre-copulatory
A
- Fighting behavior
- Social status
- Territoriality
14
Q
Manifestations of competition: post-copulatory
A
- Mate guarding
- Copulation duration
- Sperm removal
- Sperm plugs
- Anti-aphrodisiacs
15
Q
Alternative reproductive strategies
A
- 3 male strategies in side-blotched lizards
- orange, blue, yellow
- Vary in frequency over time
- Orange: defend large territories, extremely aggressive towards all males
- Blue: defend smaller territories, detect and root out yellow males
- Yellow: “sneaker male” (on orange). Mimic throat color and behavior of receptive females
- Orange attacks and defeat blue, Blue detect and defeat yellow, Yellow fools orange. Success of each strategy in obtaining mates is dependent on frequency of other strategies in population
16
Q
Empirical data
A
- If orange is common, yellow will increase
- If blue is common, orange will increase
- If yellow is common, blue will increase
17
Q
Results
A
- Blue was numerically dominant in 1991
- In 1992, orange increase while blue decreases
- By 1994, yellow starts to increase at expense of orange
- Blue returns to numerical dominance by 1995
- Fitness of strategy is highest when strategy is rare in the population -> selection is negative frequency dependent
