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Evolution > Sexual Selection II (intersexual) > Flashcards

Sexual Selection II (intersexual) Flashcards

1
Q

what does a sexual signal say? What info might receivers get from it?

A
  • readiness to mate
  • quality or health of mate
  • can show if they are related
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2
Q

examples of intersexual selection

A
  1. red-collared widowbirds
  2. gray tree frogs
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3
Q

intersexual selection examples - red-collared widowbirds

A
  • researchers experimentally changed tail length by cutting it off
  • females like long tails
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4
Q

intersexual selection examples: red-collared widowbirds - what was the result

A
  • long-tails are not good for the male
  • but it still has it bc females like long tails
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5
Q

intersexual selection examples: red-collared widowbirds - what does the results mean?

A

females are making mating decisions based on signal even if the signal has a cost

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6
Q

intersexual selection examples - gray tree frogs

A
  • female frogs are choosy and prefer males giving longer calls
  • longer-calling males are more likely to find mates
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7
Q

what are the hypotheses for why receiver preferences evolve

A
  1. null model
  2. sensory bias
  3. resource acquisition hypothesis
  4. honest signal/good genes
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8
Q

hypotheses for receiver preferences evolution - null model

A
  • assumes preferences are arbitrary (no benefits to sender or reciever)
  • outcome: runaway sexual selection
  • ornamentation continues to get more ‘bigger’ without stopping
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9
Q

hypotheses for receiver preferences evolution : null hypothesis - what is runaway sexual selection

A
  • assumes that both sexual preference in females and ornamentation in males are genetically variable and heritable
  • all about genetics
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10
Q

hypotheses for receiver preferences evolution : null hypothesis - bird example

A
  • first need variation in preference and display
  • then assortative matting where a connection begins to form in preference and display
  • if selection favors one of them, it will move the other
  • can graph this relationship
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11
Q

null hypothesis: bird example - adding natural selection to graph

A
  • optimal display for reproduction is graphed
  • optimal display for survival is graphed
  • average display is a compromise between the two lines (equilibrium line)
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12
Q

null hypothesis: bird example - adding drift to graph

A
  • drift wll push the population off of the equilibrium
  • they will eventually move back
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13
Q

null hypothesis: bird example - how is runaway selection seen on the graph

A
  • trait correlations will be off the equilibrium line and cannot get back to it
  • they will instead move further and further from the mean
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14
Q

null hypothesis - example of this happening in a natural setting

A
  • crickets
  • male songs and the female preferences are strongly correlated
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15
Q

null hypothesis: cricket example - how are female preferences and male songs correlated

A
  • male signal and female preference linked
  • found via QTL mapping
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16
Q

null hypothesis: cricket example - what was the finding

A

Each population is at a different stage of the runaway process

17
Q

hypotheses for receiver preferences evolution - sensory bias

A
  • Receivers have to take into account all sensory input not just mating
  • But sometimes a mating signal can co-opt an existing sensory bias
  • Does not need to have a benefit to the receiver, only to the sender
18
Q

sensory bias - water mite example

A
  • water mites sense vibrations to find food
  • Male water mites make vibrations and females think its food and then they mate
19
Q

sensory bias - guppies example

A

Females like orange males bc they need carotenoids (orange coloration) for food

20
Q

sensory bias - why does it require ‘time travel’ to study?

A
  • Cannot witness it in real time
  • Researchers use tree comparative approach to see if female response to signal had evolved before the males started signaling
21
Q

hypotheses for receiver preferences evolution - resource acquisition hypothesis

A
  • Receiver benefits from acquisition of resources
  • sender also gets benefits via offspring
22
Q

resource acquisition hypothesis - examples

A
  • gift giving
  • mate cannibalism
  • parenting
23
Q

resource acquisition hypothesis - gift giving (nuptial gifts)in Bittacus apicalis (hanging male flies)

A
  • Female gets to lay more eggs the bigger the gift is
  • beneficial bc in this species, hunting/foraging is dangerous
  • Male gets more offspring and they are more likely to survive
24
Q

resource acquisition hypothesis - mate cannibalism

A
  • in many animals, nuptial gifts have evolved into mate cannibalism
  • where some male spiders throw themselves into the female’s mouth after co-population
  • usually in environments were hunting/foraging is dangerous and resources are limited
25
Q

resource acquisition hypothesis - parenting in Threespined stickleback

A
  • males make a nest and care for eggs and young
  • Females can assess how good they are with how they treat the nest with treating eggs
26
Q

hypotheses for receiver preferences evolution - honest signals/good genes

A
  1. good genes model
  2. handicap hypothesis
  3. sexy sons model
27
Q

honest signals/good genes - good genes model

A
  • females obtain better genes for their offspring
  • bc the displays could indicate good genes
28
Q

honest signal/good genes: good genes model - grey tree frog example

A
  • females prefer longer calls
  • offspring of males with longer calls do have higher fitness
  • suggests that fathers have better genes and the call is a honest signal of male quality
29
Q

honest signal/good genes: good genes model - human example

A
  • humas have major histocompatibility complex (MHC)
  • having more diversity is good for the immune system
30
Q

good genes model: human example - results sweaty t-shirt experiment

A
  • women not on oral contraceptives chose t-shirt that had a more dissimilar MHC than them
  • woman on oral contraceptives chose similar MHC
  • this is bc contraceptives mimics pregnancy and it means women do not need to find mates
31
Q

good genes model - challenges

A
  • causes directional selection that reduces variation
  • all males will try to be cheaters even if they do not have good genes
  • BUT if the signal is too costly than it will remain an honest signal and only high quality males will have it (handicap hypothesis)
32
Q

honest signals/good genes - handicap hypothesis

A
  • suggests that reliable signals must be costly to the signaler
  • costing the signaler something that could not be afforded by an individual with less of a particular trait
33
Q

honest signals/good genes: good genes model - when can sexual selection act?

A
  • before, during, and after co-population
  • before: signals
  • during: genital arms race
  • after: sperm competition and control females have on fertilization
34
Q

honest signals/good genes - sexy sons hypothesis

A

genes from the more attractive male will make the females sons more attractive

35
Q

honest signals/good genes - good genes vs sexy sons hypothesis

A
  • good genes: good for natural selection on offspring
  • sexy sons: good for sexual selection on offspring

Evolution (18 decks)

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