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Sem 2: Behavioural ecology > Week 6 > Flashcards

Week 6 Flashcards

1
Q

What is sexual selection?

A

= Adaptations generated by intraspecific interactions and competitions
= Adaptations associated with the struggle to reproduce

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2
Q

What is the quote by Darwin about sexual selection?

A

‘the advantage which certain individuals have over other individuals of the same sex and species, in exclusive relation to reproduction’

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3
Q

What is the relationship between sexual and natural selection?

A

Sexual selection and natural selection can be distinct
Traits that are attractive to mates because they constrain survival and only occur in the competing sex

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4
Q

What is an example of sexual selection trait increasing risk of extinction?

A

Megaloceros giganteus (Irish Elk)
Increase in male horn length increases risk of extinction

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5
Q

What is an example of sexual selection trait being aligned with natural selection?

A

Black grouse
Male (sexually selected) mating success on the lek correlates with (naturally selected) survival
So traits associated with enhanced survival can also be attractive to mates

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6
Q

Why does sexual selection occur?

A

BATEMAN PRINCIPLE
POTENTIAL REPRODUCTIVE RATE VARIANCE
Female dominated PARENTAL INVESTMENT

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7
Q

What is the quote by Robert trivers about the occurance of sexual selection?

A

‘…the sex whose typical parental investment is greater than that of the opposite sex will become a limiting resource for that sex.’

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8
Q

What is an overview about why sexual selection occurs?

A

THEREFORE (IN GENERAL) SELECTION ON LIMITED MALES TO COMPETE AND LIMITING FEMALES TO CHOOSE

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9
Q

What is intrasexual selection?

A

INDIVIDUALS OF THE SAME SEX (USUALLY MALES) COMPETE FOR MATINGS eg elephant seals

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10
Q

What is intersexual selection?

A

INDIVIDUALS OF ONE SEX (USUALLY FEMALES) CHOOSE MATING PARTNERS FROM THE OTHER SEX eg male peacock spiders dancing to attract female spider

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11
Q

Can both inter and intrasexual selection occur?

A

Males may compete intra-sexually for an inter-sexual result
Red deer stags compete intra-sexually during the rut and establish dominance hierarchy for territories
Hinds choose males and territories inter-sexually
= mate choice dynamics within polygyny

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12
Q

What are direct benefits of mate selecting for females?

A

Parental care, protection from a predator and access to resource

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13
Q

What are indirect benefits of mate selecting for females?

A

Improve reproductive success or offspring quality

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14
Q

What is conspecific recognition?

A

Avoidance of hybridisations which may be less fertile/infertile

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15
Q

What selects for mate chouce and discrimination?

A

Mate choice & discrimination evolves more rapidly in sympatric (overlapping) than allopatric (isolated) Drosophila species pairs

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16
Q

What is an example of Prunella modularis (dunnock)?

A

Male dunnocks help with raising chicks
DNA barcoding to identify whether alpha or beta male fathered each offspring. This is a mixed-paternity brood
The more opportunity the beta male had to mate with the female (exclusive access) the more he contributes to feeding brood

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17
Q

What are the pros of polygyny and polyandry in dunnocks?

A

Polyandry here allows female to increase number and quality of offspring, by ensuring paternal investment.
For ana lpha male, at least 60% of brood need to be fathered by him for cooperative polyandry to be favourable.
Alpha male wins out in polygyny, female and beta male win in polyandry – which may be why polyandry persists, but alpha males chase away beta males.

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18
Q

What is an example of male sacrifice in mating?

A

Male redback spiders often actively sacrifice themselves while mating
Females benefit from an extra meal
Males feed their own offspring, and achieve greater sperm transfer

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19
Q

Why does male sacrifice occur in male redback spiders?

A

This strategy may have evolved since males suffer extreme mortality risks while mate-searching 80% of males do not encounter a mate.

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20
Q

Why does male sacrifice persist in male redback spiders?

A

Rare to find a mate, so although males have physiological capability to remate, it’s unlikely they will have opportunity.
Therefore, they are selected to maximise number/success of offspring in any mating opportunity.
Males that allow themselves to be cannibalized transfer more sperm & provide nutrients for their offspring

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21
Q

Does courtship effort display fertility?

A

Male display rate reveals ejaculate characteristics in the Trinidadian guppy Poecilia reticulata

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22
Q

What is a direct benefit in males for staying around?

A

Cuckold: husband of adulterous wife.
Biologically a cuckold is a male who invests in the offspring of others (due to extra-pair paternity)
Seen in house sparrow, Passer domesticus

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23
Q

What are the models for why sexual selection choose when there are no direct benefits?

A

Runaway sexual selection
Good genes
Parasie mediated
Compatible genes

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24
Q

What is an overview of the runaway selection?

A

FISHER (1930)
FEMALE PREFERENCES FOR PARTICULAR (NATURALLY-SELECTED / ARBITRARY) TRAITS
GENETIC LINK BETWEEN MALE TRAIT AND FEMALE PREFERENCE
SONS CARRYING THE TRAIT GAIN SUCCESS
TRAITS FIX IN POPULATION AND FEMALE GENES FOR TRAIT CHOICE PERSIST
RUNAWAY EXAGGERATION OF THE TRAIT

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25
Q

What is an overview of the good genes model?

A

TRAITS ARE COSTLY TO DEVELOP / CARRY – THEY ARE A HANDICAP (ZAHAVI 1975)
CARRYING THE HANDICAP IS AN HONEST SIGNAL OF INDIVIDUAL MALE ‘QUALITY’
HANDICAP IS EITHER ‘STANDARD’ AND ACTS AS A ‘SURVIVAL FILTER’….
….OR HANDICAP IS CONDITION-DEPENDENT AND BETTER MALES CARRY BIGGER HANDICAPS
BEING FATHERED BY MALES THAT CAN CARRY THE HANDICAP WILL CAPTURE BETTER GENES

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26
Q

What is an overview of the parasite mediated sexual selection?

A

HAMILTON & ZUK (1985)
PARASITE LOAD IS A MAJOR & GENERAL PROBLEM
SIGNAL IS LINKED TO PARASITE RESISTANCE
BEING FATHERED BY MALES WITH EVIDENT SIGNALS WILL CAPTURE BETTER RESISTANCE GENES

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27
Q

What is an overview of the compatible gene hypothesis?

A

MATE CHOICE BENEFITS IN CHOOSING GENOTYPES THAT COMPLEMENT SELF
GENERAL BENEFIT TO AVOID OUTBREEDING (e.g. similar to self to avoid hybridisation)
GENERAL BENEFIT TO AVOID INBREEDING (e.g. different to self to avoid inbreeding)
SPECIFIC BENEFIT AT PARTICULAR LOCI / COMPLEXES (e.g. the Major Histocompatibility Complex (MHC) for immunorecognition)

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28
Q

How are all the theories about sexual selection linked?

A

CO-EVOLUTION OF LINKED FEMALE PREFERENCE IMPORTANT IN RUNAWAY MODELS
COST OF SIGNAL MORE IMPORTANT IN HANDICAP MODELS
SPECIFICITY OF SIGNAL TO IMMUNITY IMPORTANT IN PARASITE RESISTANCE MODELS
COMPATIBILITY FOCUSED ON MALE-FEMALE RELATEDNESS

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29
Q

How do all of these signal good genes?

A

Sexy sons
General quality
Parasite resistance
Compatibility

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30
Q

What is an example of runaway selection?

A

Male ornamentation varies across different populations of Trinidadian guppy (affected by predation)
Observational comparison of male trait and ‘naïve’ female preference across 7 different populations
Naïve females prefer their own population’s male ornamentation characteristics
= Evidence that female preference genes co-evolved with male trait

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31
Q

What are naive female trinidadian guppies

A

Naïve females = separated from males before maturity (and before colour patterns develop), reared in female-only group

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32
Q

What is an example of sexual dimorphism in insects?

A

Stalk eye flies
Male dimorphism in eye stalk lengths
Males with bigger eye stalks win in competition for resources and mates

33
Q

How did they test for selection for stalk eye length in stalk eye flies?

A

Artificial selection to increase or decrease male eyespan in different lines,
Test female preference in those lines for that ‘short’ or ‘long’ eye span males
= Evidence that female preference genes experimentally co-evolved with male trait expression

34
Q

What is the famous example of the good genes hypothesis?

A

Peacock tails are extravagant and composed of eyespots which vary in size
Females prefer bigger males carrying bigger eyespots
Peafowl experimentally single-paired to males with different tail eyespot traits
Peacocks provide nothing to females except sperm / gene
Sons and daughters grew bigger when fathered by males carrying bigger eyespots
Chick groups sired by big-eyed fathers had better % survival in Whipsnade Park

35
Q

What is an example of parasite mediated sexual selection?

A

Swallows & mites
Males with longer and more symmetrical tails find mates quicker
Offspring from males with (naturally) longer tails have fewer mites – even when translocated to other nests.
More mites one year -> shorter tail the next year.

36
Q

What is an example of compatible genes?

A

Mate choice for the major histocompatibility complex

37
Q

What is the MHC?

A

A large chromosomal region crossing over 200 genes that play a role in immune recognition - differntiation between self and non self
High polymorphic, probably due to heteroygote advantage and/or selection for rare types

38
Q

How does the MHC influence mate choice?

A

Influences odour through either microbial flora or concerntrations of volatile acids
Experimental observations that when mice are allowed to mate, there are more heterozygous offspring than you would expect from random mating – suggesting mate choice for heterozygous offspring.

39
Q

Why is MHC selected heterozygosity important?

A

Heterozygosity at the MHC confers an immune advantage in mice
Higher survival of heterozygotes under pathogen challenge
Higher growth of heterozygotes under pathogen challenge

40
Q

What are the wider benefits to sexual selection?

A

Sexual selection could help to purge mutation load (bad genes) from lineages if….
Mutations influence male mating success in the face of competition and choice
OR
Mutations are more deleterious in males than females because of sexual selection
If either applies, then the average successful father should carry less mutations than the average male

41
Q

How did they show the benefits of sexual selection?

A

High sexual selection population of Tribolium castaneum vs Low sexual selection in a population of Tribolium castaneum
They were allowed to breed
10+ years and 95 generations they were forced through multiple extinction events (population bottle neck, heat or low food ie no yeast) for 5 generations and had there population tracked)

42
Q

What were the conclusions about the results for the important of sexual selection?

A

High sexual selection backgrounds resist extinction
By generation 15 low sexual selection had gone extinct compared to high sexual selection line which had a population fitness of ~25

43
Q

What is sperm competition?

A

The competition within a single female between the sperm from two or more males over the fertilisation of the ova

44
Q

When does sperm competition only occur?

A

Selection arises when sperm from two or more males compete for a females ova

45
Q

How wide spread is polyandry?

A

Across 203 natural populations, 160 species across all taxa shows that it is quite widely spread, though with varying amounts
Some level of polyandry is the norm

46
Q

How does sperm longevity impact sperm competition?

A

How likely sperm overlap and compete

47
Q

What are examples of different levels of sperm longevity?

A

Fish - Seconds
Humans - 3-5 days
Birds - days to weeks
Most insects - weeks to months
Bats - weeks to month
Solenopsis (Hymenoptera) - >5 years

48
Q

What was R.Trivers quote about sperm competiton?

A

In a sense all male:male competition is just so much sperm competition

49
Q

How does sexual selection link heavily to sperm competition?

A

Male:male competition is ultimately:
Avoid sperm competition
Enhance the sucess of self’s sperm

50
Q

How can you test for sperm competition?

A

Control female x Male with distictive identifiable trait (marker male)
The bred there offspring with organisms with the trait you are investigating
Replicate crosses and mating order, then genotype to compare the male success

51
Q

What is an example of testing for sperm competition success?

A

Control females bred with clubbed antennae (Tribolium)
Their offspring where bred with males that were inbred or not The impacts inbreeding has on sperm competition

52
Q

What were the results of the experiment on inbreeding on Tribolium sperm competion?

A

First males produced fewer offspring than second males
In both first and second males the inbred males produced fewer offspring than not inbred

53
Q

How can you show sperm competition with external fertilisation?

A

But in a bucket with water make sure conditions are correct
Mix and then genotype the offspring to see which were more sucessful

54
Q

What is an example of sperm competiton on external fertilisation?

A

Farmed salmon vs Wild salmon
In all group sizes farmed salmon produced more offspring than wild salmon

55
Q

What are adaptation to sperm competition?

A

Behaviour
Genitalia
Gonads
Ejaculates
Spermatozoa

56
Q

What are adaptation to spermatozoa?

A

Number
Size
Motility
Polymorphism
Cooperation
Gigantism

57
Q

What is an example of behavioural adaptation for sperm competition?

A

Mate guarding - damselfly
Male will guard female to prevent female from copulating with other males
Pressure finding new to female to mate with vs guarding current female

58
Q

What is the mate guarding behaviour like in soapberry bug populations?

A

Plasticity in male mate guarding depending on risk of sperm competition form operational sex ratio
More females to males = less mate guarding
More males to females = more mate guarding

59
Q

What are method for males to manipulate female behaviour to reduce sperm competition?

A

Anti aphrodisiac - males cover female in antiaphrodiasic to put males off - seen in butterflies
Seminal fluid - proteins inserted that makes females less receptive to mating and can cause females to lay eggs earlier - seen in drosophilia
Mating plug - seal up females to prevent males from mating which will fall off after a couple days so it doesnt prevent egg laying

60
Q

What is an example removal of rival sperm?

A

Seen in Mnais pruinose (damselfly) which in stage 1 removes sperm and then transfers in its own sperm

61
Q

What was the experiment for damselfly sperm removal?

A

Interrupted mating experiments show the different stages of copulation involved in sperm removal
More stage 1 inflexions less sperm in total
More stage 3 inflexions more sperm from male

62
Q

What is the advantage of sperm removal?

A

Sperm removal allows fertilisation precedence to be almost 100% in some odonates

63
Q

What was an example of spermatigenesis physiology being impacted by mating type?

A

Bonobo - 168g testes
Chimpanzee - 149g testes
Human - 34g testes
Gorilla - 23g
Group living organisms have bigger relative testes compared to both single male or pair living species

64
Q

How does sperm number change with increased sperm competiton?

A

Plodia interpunctella (indiameal moth)
Polyandry goes up with adult density (OSR)
Higher density results in bigger volume of testes meaning males produce and ejaculate more sperm

65
Q

What is the raffle principle?

A

Copula duration = number of sperm transferred
More transferred = more fertilisations = relative sperm number important

66
Q

How can sperm size vary across organisms?

A

Mammalian sperm morphology
Harvest mouse, human and African elephant have similar sized sperm
Platypus sperm is massive
Porcupine sperm is tiny

67
Q

What causes a variaiton in sperm size?

A

Bigger sperm are more competitive so more sperm competition means selective pressure on bigger sperm

68
Q

Why is big sperm a paradox?

A

Anisogamy –> should be more advantgaous to produce more smaller sperm

69
Q

Why do sperm get bigger with competition?

A

Not really known. Investment in sperm quality traits evolving within quantity

70
Q

What was an competitiveness experimentally approached?

A

Tribolium beetles
Evolved 4 beetle in lab for 77 generation under either female biased OSRs (low sperm competitive) or male biased OSRs (higher sperm competition)
Then compared compteititvely with marker male offspring against both groups each being first of not first

71
Q

What were the results of the competitiveness between female and male biased OSRs?

A

Male-biased OSRs became more competitive and their sperm got bigger

72
Q

What is an experimental approach for importance of sperm motility?

A

Atlantic salmon
Sperm reach peak speed soon after activation
Males with faster sperm win ie most likely to be 1st down micropyle

73
Q

What is an example of sperm polymorphism?

A

Butterflies and moths produce two distinct sperm types eupyrene (fertile, 10%) and apyrene (nonfertile, 90%)

74
Q

What was the function of the sperm polymorphism?

A

Female Pieris napi butterflies remate depending on numbers of apyrene sperm not eupyrene sperm in storage
Being full of sperm prevented remating not matter sperm type eg sperm dertility

75
Q

What is the function of apyrene sperm?

A

Apyrene sperm as ‘cheap filler’ in female storage - alternative gametic strategy for sperm competition

76
Q

What is an example of sperm cooperation?

A

Wood mouse
Hooks on head to form sperm trains
Bigger sperm trains are faster

77
Q

What is an example of gigantic sperm?

A

Drosophila bifurca - 58.3 mm long much bigger than fly
Significant associayion between sperm length and female sperm storage size across Drosophila species

78
Q

What is an experiment were sperm tract and sperm size are related traits?

A

Drosophila - evolve females with long and short tracts and males with long and short sperm (these then competited against each other)
Long sperm more competitive in female long tracts than short female tracts
Short sperm more competitive in female short tracts than long female tracts

Sem 2: Behavioural ecology (11 decks)

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