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botany > Evolution of plant diversity > Flashcards

Evolution of plant diversity Flashcards

1
Q

gene flow

A

= exchange of genes between populations (Genaustausch)

  • role in creating and maintaining plant taxa unclear
  • interruption of gene flow in 1 species needed somehow to split into 2 species
  • nature of gene flow betw/within plant species not criterion for their recognition!
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2
Q

hybridization / interspecific gene flow – dual role in speciation

A
  • may reduce diversity by merging species

- can lead to speciation esp. when coupled with polyploidy

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3
Q

2 levels of evolution

A

anagenesis - accumulation of changes w/in a lineage

cladogenesis - changes that lead to formation of splitting of 1 lineage in to 2 (of primary interest to systematacists)

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4
Q

reproductive isolating barriers

A 
premating (vor der Befruchtung)
vs. 
postmating/prezygotic 
vs. 
postmating/postzygotic
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5
Q

premating reproductive isolating barriers

A

prevention of successful mating

temporal - seasonal, diurnal
habitat
floral - behavioral, structural
reproductive mode - self-fertilization, agamospermy (asexuelle Bildung v Samen, Nachkommen=Klon)

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6
Q

geographic separation

A
  • often considered a reproductive isolating barrier
  • individuals / populations that are geographically far apart could reproduce if not for that isolation; considered part of the same species
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7
Q

postmating/prezygotic reproductive isolating barriers

A

incompatability - pollen style

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8
Q

postmating/postzygotic reproductive isolating barriers

A

incompatability - seed

hybrid inviability (failure to reach reproductive maturity / Fortpflanzungsreife, geschlechtliche Reife?)

hybrid floral isolation (absence of effective pollinators)

hybrid sterility

hybrid breakdown (problems in later-generation hybrids)

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9
Q

possible origins of reproductive isolating barriers

A
  • as 2 species diverge from a common ancestor, accumulated genetic changes diminish likelihood of successful reproduction
  • premating isolation: result of natural selection against wastage of gametes on unsuccessful matings with other species (gegen Verschwendung der Gameten)
  • premating isolation: reduction of competition for animal pollinators
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10
Q

hybridization (esp interspecific)

A
  • critically impt in plant evolution, prevalent in plants
  • source of novel gene combinations, as mechanism of speciation
  • often associated with habitat disturbance
  • ecological adaptations that isolate species may be broken down (new pests, predators, environmental ‘disasters) – creates habitat suitable for hybrids?
  • reduced competition in the wake of disturbance - favors growth of hybrids
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11
Q

evolutionary consequences of hybridization

A

(1) reinforcement of reproductive isolating mechanisms
(2) formation of a hybrid swarm through reproduction by hybrids at one site (gene flow limited to one or few sites where the species grow together)
(3) fusion of 2 species through interspecific gene flow (introgression); permanent incorporation of genes of one species into another species
(4) creation of genetic diversity and adaptation
(5) evolution of new species

1, 2 – maintenance of biodiversity
3 – destruction of biodiversity
4, 5 – creation of biodiversity

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12
Q

consequences of introgression

A

(1) may lead to merging of different species
(2) transfer of genetic material from one species to other without merging –> genetic diversity increased in introgressed species
(3) stabilized introgressants may form a new species

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13
Q

F1 intermediacy

A
  • through hybridization
  • characters governed just by one or few genes do now show intermediacy
  • chemical and molecular characters more likely than morphological characters to yield predicable expression in hybrids
  • other processes that can result in this: mutation, phenotypic plasticity, an evolutionary trend
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14
Q

biological species concept

A

definition of species as:
group of interfertile individuals

  • dominates zoological literature
  • test of infertility cannot be applied unambiguously in plants
  • gene flow as diversifying force when there is gap in the gene flow
  • gene flow varies greatly among plant groups
  • reproductive communites: from one/few indiv to morphologically heterogeneous assemblages (when hybridization occurs bew morphologically divergent groups)
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15
Q

plant species not reproductively isolated?

A

common view

studies: plant species actually more likely to represent reproductively isolated lineages

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16
Q

recognition species concept (RSC)

A
  • also focuses on role of gene flow (like BSC)
  • gene flow as a cohesive force, maintaining similarity of individuals within a species (Gemeinsamkeiten/Ähnlichkeiten bleiben erhalten)
17
Q

phenetic species concept

A
  • rests on overall similarity of members of a species (allg Ähnlichkeit zw. Individ. einer Gruppe)
  • separated from other species by gap in variation
18
Q

evolutionary species concept

A
  • centers on recognition of evolutionary lineages

- does not clearly prescribe how these lineages to be defined

19
Q

phylogenetic species concepts (PSC)

A
  • ascendancy of phylogeny as organizing principle has motivated such concepts
  • similarity: species recognized as taxa that mark the boundary between reticulate relationships
  • boundary unfortunately often blurred
  • term ambiguous. NOT used in this book
    (at least 3 different criteria have been used to advance this concept)
20
Q

apomorphy species concept

A
  • a type of phylogenetic species concept
  • monophyly as criterion
  • a species contains all the descendants of one ancestral population, identifiable by apomorphies
  • inappropriate criterion below species level
  • reticulate, nonhierarchical and nondivergent relationships are incompatible with grouping by monophyly
21
Q

diagnosability species concept

A
  • a type of phylogenetic species concept
  • criterion = diagnosability
  • phylogenetic species = the smallest aggregation of populations (sexual) or lineages (asexual) diagnosable by a unique combination of character states in comparable individuals
  • uncertainty about what constitutes diagnosability
  • diagnosability = character based concept
22
Q

genealogical species concept (BSC)

A
  • a type of phylogenetic species concept
  • historically based concept
  • criterion = basal exclusivity
  • exclusivity: members of a group must be more related to one another than to any organisms outside the group
  • exclusivity may be determined by gene coalescence

botany (6 decks)

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