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Trinity Term 1 > Angiosperm mating systems and pollination > Flashcards

Angiosperm mating systems and pollination Flashcards

1
Q

Mating (breeding) system:

A

the way in which a group of organisms is structured in relation to its reproductive behaviour

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2
Q

Why is cosexuality adaptive?

A

optimises the benefits of animal pollination

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3
Q

The majority of flowers are

A

cosexual

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4
Q

Angiosperm mating system definition

A

Structural and physiological features of the flower

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5
Q

Angiosperm pollination system definition

A

Structural features of the flower and inflorescence – adaptations for pollination

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6
Q

What is one factor contributing to angiosperm success?

A

variety of mating systems

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7
Q

Describe the factors influencing mating system evolution

A
  • immobility
  • inbreeding depression
  • reproductive assurance
  • optimal allocation of male and female reproductive effort (maintenance of sexual polymorphisms)
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8
Q

Most angiosperms

A

outcross

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9
Q

What is reproductive assurance?

A

if mates or pollinators are scarce, it is better to self or reproduce asexually

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10
Q

apomixis

A
  • asexual reproduction
  • vegetative
  • agamospermy
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11
Q

Give some angiosperm sexual dimorphisms

A

dioecy, gynodioecy

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12
Q

Describe angiosperm hermaphroditism

A
  • ~96% flowering plants
  • flowers co-sexual or unisexual
  • monoecious
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13
Q

Describe the triangle of mating system interfaces

A
  • reproductive assurance at apomixis
  • reproductive assurance at inbreeding
  • inbreeding depression at outbreeding
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14
Q

Inbreeding

A
  • autogamy
  • selfing (can be facultative or obligate)
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15
Q

Obligate autogamy

A

cleistogamy

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16
Q

Outbreeding

A
  • panmixis
  • can be facultative or obligate (self-incompatibility or dioecy)
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17
Q

In co-sexual flowers

A

autogamy is always possible

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18
Q

Describe some adaptations for autogametic avoidance

A
  • dichogamy
  • herkogamy
  • dicliny
  • SI: plants able to recognize and reject their own pollen
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19
Q

dichogamy

A
  • separation of sexual organs in time
  • protandry
  • protogyny
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20
Q

protandry

A

stamens mature before carpels/pistils

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21
Q

protogyny

A

or carpels/pistils mature before stamens

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22
Q

herkogamy

A
  • separation of sexual organs in space
    – style length polymorphisms
  • bizarre flowers e.g. Coryanthes sp. (Bucket Orchids)
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23
Q

Give some style length polymorphisms

A

distyly and tristyly

24
Q

Describe dicliny

A
  • sexual polymorphisms
  • plants are dioecious, monoecious, gynodioecious or gynomonoecious
25
Q

dioecious

A

male or female

26
Q

monoecious

A

unisexual flowers on same plant are male and female

27
Q

gynodiecious

A

combinations of unisexual and co-sexual plants

28
Q

gynomonoecious

A

unisexual and co-sexual flowers on same plant

29
Q

Describe SI

A
  • self-incompatibility
  • the ability of a plant to recognize and reject self or self-related pollen
  • pre-zygotic barrier: incompatible pollen is recognized and rejected before the pollen tube reaches the ovule
  • ~65% of hermaphrodite angiosperms
  • visualised with fluorescent stain aniline blue which stains callose
30
Q

Describe genetic control of SI

A
  • usually controlled by a single locus (S) with multiple alleles: S1, S2, S3 etc
  • highly polymorphic: populations maintain around 40 S alleles by negative frequency-dependent selection
  • Self (or cross with shared S alleles)
31
Q

Describe the two main genetic types of SI:

A
  • GSI
  • SSI
32
Q

Describe SSI

A
  • sporophytic SI
  • incompatibility phenotype of pollen determined by diploid genome of its parental sporophyte
  • S alleles show dominance in pistil and ‘in’ pollen
33
Q

Describe GSI

A
  • gametophytic SI
  • incompatibility phenotype of pollen determined by its own haploid genome
  • S alleles are co-dominant in pistil
34
Q

List some GSI lineages

A
  • Solanaceae (Potato family)
  • Rosaceae
  • Plantaginaceae
  • Campanulaceae
  • Papaveraceae (Poppy)
  • Poaceae (Grasses)
35
Q

List some SSI lineages

A
  • Brassicaceae
  • Asteraceae
  • Convolvulaceae (Ipomoea sp.)
  • Betulaceae
  • Caryophyllaceae
  • Malvaceae
36
Q

Describe distyly in Primula and Primulaceae

A
  • two S alleles: S (dominant) and s (recessive/null)
  • 388/426sp. = distylous
  • pin = ss
  • thrum = Ss
  • 50% Ss, 50% ss
37
Q

Pin

A

long-styled morph

38
Q

Thrum

A

short-styled morph

39
Q

Describe the heteromorphic S locus

A
  • ‘supergene’
  • controls SI and morphological characters (style length, stamen position)
40
Q

Give a pin and thrum species

A

Limonium meyeri

41
Q

Describe autogamy

A
  • selfing within outbreeding groups = common across all angiosperm lineages
  • 35-40% co-sexual angiosperms able to self fertilize
  • 20% = habitual selfers
42
Q

List some autogamous angiosperms

A
  • Cardamine hirsuta (Brassicaceae)
  • Arabidopsis thaliana (Brassicaceae)
43
Q

Describe the genetic consequences of selfing

A
  • recessive individuals are candidates for inbreeding depression
  • genetic variation declines with time
44
Q

Inbreeding depression can be studied in

A

SI obligate outcrossers

45
Q

Describe inbreeding depression

A

recessive alleles are ‘purged’ and dominant alleles are fixed in homozygotes

46
Q

Why don’t habitual selfers suffer from inbreeding depression?

A

homozygous at most loci

47
Q

Describe the advantages of autogamy

A
  1. Reduces male expenditure and removes the ‘costs of outbreeding’
  2. Optimizes reproductive assurance when:
    a.) Pollinators are scarce or unreliable
    b.) Plants are ‘pioneers’ or colonizers (Bakers Law)
    c.) Populations pass through ‘bottlenecks’ (threat of extinction)
48
Q

Describe the evolution of autogamy in Eichhornia paniculata

A
  • Brazil (outcrossing population)
  • Nicaragua (selfing population)
  • once selfing established, selection favours reduction in: flower size, pollen production, nectar production; disappearance of adaptations for herkogamy, dichogamy, dicliny
49
Q

Describe the disadvantages of autogamy

A
  • decreases (but also maintains) genetic diversity
  • cannot adapt to changing environmental conditions
  • ‘Evolutionary dead end’
50
Q

Describe apomixis (agamospermy)

A
  • production of fertile seeds in the absence of sexual fusion between gametes
51
Q

Give some agamospermous lineages

A
  • Taraxacum sp. (Asteraceae)
  • Alchemilla sp. (Rosaceae)
  • Rubus sp. (Rosaceae)
52
Q

Demonstrating Agamospermy in a dandelion (Taraxacum officinale)

A
  • emasculate bud
  • all offspring are clones and reproductively isolated
53
Q

Describe gametophytic agamospermy

A
  • diploid egg cell forms embryo
  • other diploid cells becomes embryo(s)
  • pollination may be needed for endosperm formation
54
Q

Describe sporophytic agamospermy

A
  • embryo sac haploid
  • egg cell fertilised and diploid embryo forms
  • polar nuclei fertilised: triploid endosperm
  • sexual embryo aborts and diploid embryo forms one or more cells of nucellus
55
Q

Describe the advantages of agamospermy

A
  • reproductive assurance
  • avoids costs of meiosis
  • transmits 100% mothers genes to offspring
  • fixes well-adapted genotypes
  • frequently maintains/fixes new hybrids/polyploids
56
Q

Describe the disadvantages of agamospermy

A
  • unable to escape from disadvantageous mutations (‘Muller’s Ratchet’)
  • unable to recombine advantageous mutations
  • very narrow niche tolerance
  • inability to adapt: evolutionary dead-end

Trinity Term 1 (38 decks)

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