Chapter 12 - Experiments Flashcards
Antlers as weapons Red Deer
RQ: Are antlers weapons used in male competition?
M: collect, weigh antlers shed → blood samples to determine reprod. success (paternity)
R: Avg. Mass → (+) correlated w/ total lifetime breeding success
Weapons size + Mating Success in DUng Beetles
RQ: What is the role of males horn like projection?
H: Large horns → advant → mate comp.
P: Males w/ larger horns = win more fights
M: Staged fighter b/w mates - body size not horn size = recoded outcome + mating success
R: Small Beetles -→ large male / horn = won
Large Beetles → Larger horns won (great diff = increa. chance)
Ornaments + Mate Choice in Peafowl
RQ: Are peacock tails an ornaments used in mate choice?
M: Measured tail length + Male body size, # + Duration of tail displays, # of vocalizations + copulations
- Males had display site - showcase their behaviors to
females
R: + Correlation → defending display site + larger body size + tail size → more successful
- Males w/ high display rates + most ocelli = obtained the most copulations
C: Size isn’t everything → both male + female comp. (prefer males w/ high display rates) = evolution of peacock tails + display rates
Male Mate choice in Pipefish
RQ: How do males select a mate?
H: Prefer females → highest express. sex. selected trait
P: Males spend time + mate more w/ females that display their pattern / ornament the most
M: Day 1 = no interactions, matched M + F for size, recorded how long they spent in front of each F + engagement
Day 2 = interactions, dividers removed → record dancing time, copulations, counted all eggs from males pouch
Results: Total Time + Dancing → shorter latency to dance w/ female, more ornamented female → copulations
C: Females w/ higher ornaments → higher mating success
Origin of Sexually Selected Traits - Sensory Bias Hypothesis in Guppies
RQ: How does a male trait become selected in female mate preference?
H: SBH
P: M+F should be attracted to orange-coloured objects because orange is associated with carotenoids → nutrient that plays key role in immune system function
M: Placed small discs in variety of natural pop. + Lab
R: Strong attraction to orange + red discs → orange b/c of female mating pref.
Female Choice + Nuptial Gifts in Fireflies
RQ: How does the variation in the duration of male flashes affect female choice and fitness?
M: Measured male flash duration and spermatophore size
Created flashes of different lengths and measured female response
R: + correl. b/w M flash duration and
spermatophore mass → F can use this find males w/ largest mass, F respond more freq. → longest flashes
C: F prefer to mate w/ males → longest flash duration → more likely to have larger mass
Female Choice + Territory Quality in Lizards
RQ: How does territory quality affect female choice and fitness? - TQ based on rockiness
M: Larger M → terr. = more rocks, manip. TQ - add/remove, observed female mate chice, measured egg-laying rate + egg mass
R: F pref. improv. terr. → laid eggs sooner + Larger masses
Mate choice + Good Genes in Frogs
RQ: Do females asses male quality on the basis of their vocalizations?
H: Good Gene Hypothesis
M: Captured males, Observed # of matings, collect egg masses + reared in lab, tadpole growth rate + survival, genotyped tadpoles to determine %
R: Males that sired more offspring → tadpoles w. higher growth rates
C: F could be selecting M for more genetic benefits → enhance fitness
Good Genes + Immune System Function in Birds
RQ: How does parasite load affect mate choice?
H: Hamilton - Zuk
P: Females should prefer to mate with males that have the greatest expression of secondary sexual traits
2) High parasite loads will reduce that expression in males
M: 1/2 males → infected w/ intestinal nematodes @ 1 week → control x infected, measured size + colour intensity of comb → mate choice tests → F picks M
R: Parasites affect. the develop. of comb lengths + colour → Paratsit. M = duller, smaller vs control
C: supports prediction of Hamilton-Zuk Hypothesis
Mate choice fitness benefits in spiders
RQ: What is the importance of pheromones as signals of male quality in mate choice?
M: Mate choice experiment in Y test chamber
Phase 1: Two males at end of arms (chemical cues only no visual contact). Foam on the floor prevented tactile signals.
Phase 2: Pheromones of males only at end of arms (on filter paper)
Same female in both phases
Mating - Half females mated with preferred male, half with unpreferred male
R: Phase 2 → F choose pheromone of M in phase 1
F mated w/ pref. M →larger egg sacs → +, heavier eggs + higher hatch rate
C:
Mate Guarding in Warblers
RQ: How effective is mate guarding?
**Females can mate with other men → EPY
M: Capture, identify adults, followed focal males + mates, recorded distance b/w indiv + how often M followed F
R: Males who spent more time mate guarding had fewer extra-pair offspring
Experimentally removed males had more extra-pair offspring
C: Mate guarding can be an effective strategy for increasing paternity assurance
Sperm competition in Tree Swallows
H: paternity assurance can be enhanced through frequent copulations
P: frequent copulation rate would increase paternity for M
M: adults + offspring → marked → blood samples to determine Pat.
R: Increases in copulation rate resulted in decrease of extra- pair offspring
C: Males can reduce paternity loss from sperm competition by increasing their copulation frequency
