Reproductive Behaviour & Mating Systems Flashcards

1
Q

sexual selection

A
  • process that depends on the advantage certain individuals have over others of the same sex and species in relation to reproduction
  • involves intra- and inter-sexual selection
  • plays a role in majority of mating systems
  • related to natural selection
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2
Q

intra-sexual selection

A
  • members of one sex compete with each other for access to the other sex (competition for motes)
  • In most species, males compete for females -> females tend to be more choosy due to the high amounts of energy they invest in having offspring (energy is critical for reproduction!)
  • Related to type and number of gametes produced by each sex (female gametes/eggs are larger and more scarce, limited number -> more of a valuable resource than sperm)
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3
Q

Bateman Principal

A
  • falls under category of intra-sexual selection
  • States that females are the choosier sex because:
    • Their gametes are eggs -> energetically expensive
    • Female reproductive success is limited, compared to the male
    • As a result of females being the “choosier” in mate selection, this is expected to translate into increased variance in reproductive success in males
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4
Q

factors influencing intrasexual selection

A
  • Environment
  • Cognitive ability
  • Species differences
  • Could be other factors too?
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5
Q

competition for mates

A
  • Dangerous bouts between males to gain access to females
  • “Battles to the death” are less common
  • Result: winner gains mating opportunities
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6
Q

intersexual selection

A
  • individuals of one sex choose which individuals of the other sex to take as mates (mate choice)
  • Less research on this: easier to study intrasexual; in the past evolutionary biologists didn’t acknowledge importance of mate selection by females (nowadays, research examining female mate selection predominates)
  • Includes female selection of a male and male selection of a female
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7
Q

epigametic sexual characteristics

A
  • Secondary sexual traits that are favoured by sexual selection as a result of their effect of mate choice
  • Strategies employed by males to attract females:
    • Ornamental plumage
    • Bright colouration
    • Courtship displays/dances
    • Courtship songs (ie. Male drosophila/fruit flies sing to females via wing vibration – pulse song)
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8
Q

types of pairing/mating systems

A
  • Monogamous pairing (1 male + 1 female)
  • Polygamous paring (1 male + multiple females)
  • Polyandrous pairing (1 female + multiple males)
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9
Q

what type(s) of parings/mating systems is sexual selection strongest in? Why?

A
  • polygamous and polyandrous pairings
  • higher because if sexual selection deems 1 animal to be a good mate, there are much more mating opportunities for them in those mating systems
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10
Q

how is sexual selection related to natural selection?

A
  • fitness consequences
  • If trait x confers a mating and fertilization advantage, trait x will increase in the population and males with trait x will produce more offspring
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11
Q

models of sexual selection (female mate selection)

A
  • direct benefits model
  • good genes model
  • runaway selection model
  • sensory exploitation model
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12
Q

direct benefits model

A
  • Sexual selection favours females who have a genetic predisposition to select mates that provide them with tangible resources
    • Resources: increase fecundity
  • – Food, safe habitat, parental care of offspring, etc.
  • – Females that select males who provide them with resources will benefit – over time, numbers of choosier females will increase
  • ex. Scorpionflies
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13
Q

Scorpionfly example (direct benefits model)

A
  • Thornhill et al hypothesized that female mate selection is influenced by male presentation of “nuptial gift”
  • Results: females do select males based on presentation of large prey; larger prey = longer copulation; males without gifts rejected
  • Why:
    • Nutritional benefit -> larger gift = less time spent hunting
    • Females selecting males with large gifts produce more eggs and have longer lifespans
    • Longer copulation -> more sperm transfer -> more offspring
  • Risks for the male in gift presentation: More dangerous to hunt for large prey
  • Strong selection have resulted in additional male-specific behaviours:
    • Male will catch small prey and discard it if it’s not likely to win over the female
    • Prey theft by males -> male mimics behaviour of a female and then steals the prey delivered to them
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14
Q

good genes model

A
  • Sexual selection involving females choosing mates with good genes
  • Cheaters exist -> males making it appear that they have good genes
    • Sexual selection does favour male cheating behaviours, but honest indicators are more favoured over evolutionary time since they’re a true indication of male genetic quality
    • Females can distinguish because honest traits cost more energetically, so hard to fake/cheat
  • ex. Pronghorn antelopes
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15
Q

what are “good genes”? How are they determined?

A
  • Good genes:
    • Code for favourable traits
    • Passed on to the offspring
    • Fitness advantage
  • Exact nature of good genes is environment-dependent:
    • High predation: genes resulting in strong anti-predator behaviour
    • Scarce food sources: genes resulting in successful foraging abilities
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16
Q

pronghorn antelopes (good genes model)

A
  • Byers et al: observational study in Montana -> tracked females and recorded mating pairings; tracked offspring and measured their survival
  • Hypothesis: females base their mate selection on “good genes” that improve survival of offspring
  • Results: females travel long distances to visit reproductively active males with harems (group of female animals sharing a single mate), observe male’s ability to protect harem -> males w/large harems = better protectors -> offspring have better survival rates
17
Q

runaway selection model

A
  • Involves relationship between alleles on 2 different loci (positions on a chromosome)
    • Ex. Subset of females prefer bright-coloured males, remaining females have no preference; males will therefore have colour variation (more vs. Less colourful)
  • – Assumption: Loci for both the female preference and the male colouration are found in both male and female with preference for colourful mates -> over time, these genes become linked -> the frequency of both change together
18
Q

sensory exploitation model

A
  • Model hypothesis: when a male trait first emerges, it will be preferred by females due to initiation of a neurobiological response already in place in females (not related to mate selection)
  • Hypothetical example:
    • Bird species prefers red berries (energy-rich food)
    • Females better able to locate red berries = higher survival and reproduction
    • Natural selection: favours ability of males to hone in on berries
    • Mutation arises in males: results in red feathers
    • Female expected to prefer males with red feathers: neurocircuitry in place to prefer red colouration
    • Note: preference for red must come first
19
Q

primate example (sensory exploitation model)

A
  • Females prefer males with red fur/facial skin
  • Experimental question: is there a sensory base for preference?
    – Most mammals have 2 types of photoreceptor cones in the eye -> dichromatic vision
    — Subset of primates has 3 types of photoreceptor cones in the eye -> trichromatic vision -> red/orange detected
    Trichromatic vision improves abilities in detecting red-orange food-> primates withtrichromatic vision show preference for red-orange foods
    – Did female mating preference for red colouration in males arise due to trichromatic vision and the effects on foraging?
  • Experiment by Fernandez et al.: used primate data examining colour vision and red fur/face colour -> Phylogenetic data supports this hypothesis