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Evolution > Speciation > Flashcards

Speciation Flashcards

1
Q

what is a species

A
  • multiple definitions
  • smallest evolutionarily independent unit
  • interbreeding populations that evolve independently of other populations
  • a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding
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2
Q

what are the three species concepts

A
  1. morphological species concept
  2. phylogenetic species concept
  3. biological species concept
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3
Q

morphological species concept - criterion for identifying species

A

phenotypic similarities and differences

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4
Q

morphological species concept - strength

A

works for everything (extinct, asexual)

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5
Q

morphological species concept - weakness

A
  • cryptic species
  • groups that were or are actually independent of one another appear to be members of the same species based on morphological similarity
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6
Q

Phylogenetic species concepts - criterion for identifying species

A
  • monophyly (Lineage has all descendants and a common ancestor)
  • if it cannot be distinguished phylogenetically, it will be considered a single species
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7
Q

Phylogenetic species concepts - strength

A

Powerful and works for anything with DNA and is testable

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8
Q

Phylogenetic species concepts - weakness

A
  • Need good DNA and understanding of it
  • Different inputs used to build the tree results in differing phylogenies and conflicting species designations
  • would double the number of named species and might create confusion
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9
Q

biological species concept - criterion for identifying a species

A
  • Emphasizes reproductive isolation and barriers
  • Members are interbreeding and producing viable offspring and do not breed with other species
  • it is the legal definition of a species under the endangered species act
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10
Q

biological species concept - strength

A

Reproductive isolation is a meaningful criterion for identifying species bc is confirms lacks of gene flow

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11
Q

biological species concept - weakness

A

Cannot use for asexual organisms, fossils, organisms about which little is known about their reproduction

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12
Q

why should we care about species concepts?

A
  1. human health (algal blooms)
  2. conservation
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13
Q

why should we care about species concepts? - human health

A
  • red tides: can kill fishes and people
  • different species of dinoflagellates cause this
  • but some species do not cause human health issues
  • need to identify which do and do not
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14
Q

why should we care about species concepts? - conservation

A
  • endangered species act uses the biological species concepts
  • but different concept can determine which species are on the act
  • mammals and birds are overrepresented (invertebrates)
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15
Q

biological species concept - what are the reproductive barriers

A
  • prezygotic barriers
  • postzygotic barriers
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16
Q

reproductive barriers - prezygotic barriers

A
  • impede mating between species
  • no fertilization in the first plce
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17
Q

reproductive barriers - postzygotic barriers

A
  • fertilization occurs
  • produces a hybrid
  • prevents hybrid zygote from developing into a viable and fertile adult
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18
Q

types of prezygotic barriers

A
  • no mating attempted:
    1. habitat isolation
    2. temporal isolation
    3. behavioral isolation
  • mating attempt:
    1. mechanic isolation
  • copulation has occurred:
    1. gametic isolation
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19
Q

prezygotic barriers - habitat isolation and example

A
  • 2 species in diff habitat and do not encounter each other
  • no interaction
  • ex: apple maggot fly mates and feeds on red apples, hawthorn fly mates and feeds on grapes
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20
Q

prezygotic barriers - temporal isolation and example

A
  • species breed during different times
  • example: western spotted skink and eastern spotted skunk. habitat overlaps but one breeds in winter and the other in summer
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21
Q

prezygotic barriers - behavioral isolation and example

A
  • courtship rituals that attract mates and other behaviors cause species to only mates with their own
  • example: blue footed boobies pick up their feet and stomp. this reveals blue feet to females
22
Q

prezygotic barriers - mechanical isolation and example

A
  • mating is attempted
  • not successful bc morphological differences prevent copulation
  • example: snails cannot get their genitalia to touch if their shells do not spin in the same direction
23
Q

prezygotic barriers - gametic isolation and examples (2 here)

A
  • copulation has occurred
  • but sperm and egg are not compatible
  • example (1): red and purple sea urchins release eggs into water but the gametes will not fuse if its red an purple bc of proteins on the egg
  • example (2): species that has internal fertilization, the sperm may not survive in reproductive tract of female
24
Q

types of postzygotic barriers

A
  • fertilization has occurred:
    1. reduced hybrid viability
    2. reduced hybrid fertility
    3. hybrid breakdown
25
Q

post zygotic barriers - reduced hybrid viability

A
  • genes may interact in ways that impar hybrid’s development or survival
  • hybrids are more likely to die
26
Q

post zygotic barriers - reduced hybrid fertility

A

hybrids survive to adulthood but are not fertile (sterile)

27
Q

post zygotic barriers - hybrid breakdown

A
  • hybrids are produced and the hybrid can produce offspring
  • but 2nd generation of offspring is sterile
28
Q

explain the classic model of speciation

A
  1. isolation of population (reduced gene flow)
  2. divergence of traits
  3. speciation (evolution of reproductive isolation)
29
Q

classic model of speciation - isolation of population (reduced gene flow)

A
  • can be done in 2 ways:
    1. allopatric speciation
    2. sympatric speciation
30
Q

isolation of population (reduced gene flow) - allopatric speciation

A
  • a population forms a new species while geographically isolated from its parent population
  • ex: mountain or river
31
Q

isolation of population (reduced gene flow) - sympatric speciation

A

a subset of a population forms a new species without geographic separation

32
Q

isolation of population (reduced gene flow): allopatric speciation model - explain the 2 ways of geographical isolation

A
  1. dispersal allopatry
  2. vicariance allopatry
33
Q

the allopatric model - dispersal allopatry

A
  • movement of individuals results in physical isolation
  • can happen when there is not much gene flow
34
Q

the allopatric model - dispersal allopatry example

A
  • Drosophila fly
  • each time they colonize a new island, they become a new species
  • pattern of relatedness matches the geography of the island
35
Q

the allopatric model - vicariance allopatry

A

geological events result in isolation of population

36
Q

the allopatric model - vicariance allopatry example

A
  • Isthmus of Panama divided the Atlantic and Pacific Ocean
  • 15 species of snapping shrimp on each side
  • all look really similar but when comparing morphological and phylogenetic species concepts the sister species are divided by the two sides (they are different species)
37
Q

divergence of traits - what processes cause trait divergence?

A
  • All mechanisms of evolution can contribute to trait divergence between populations (the forces from Hardy-Weinberg)
  • but selection makes the strongest contribution
38
Q

divergence of traits - how can selection cause divergence

A
  • natural: when one of the populations occupies a novel environment or uses a novel resource
  • sexual: assertive matting
39
Q

divergence of traits - natural selection example

A
  • monkey flower faces different pressures in the coast vs inland
  • led to distinct phenotypic and genetic differences
40
Q

divergence of traits - natural + sexual selection example: Cichlid fish

A
  • the fish have diff colors
  • Light is filtered through water – only blue goes really far down and it affects visual system of fishes
41
Q

divergence of traits: natural + sexual selection example: Cichlid fish - how does natural selection and sexual selection play a role?

A
  • Natural – drives diff in tuning of female eyes
  • Sexual – females can only see blue and mates with blue male
42
Q

divergence of traits: natural + sexual selection example: Cichlid fish - what did researchers find?

A
  • tested what filtered light (muddy water) does to the tuning of eyes and mating preferences
  • When water is clear – females see well, and mating (sexual selection) was stronger
43
Q

speciation (evolution of reproductive isolation) - define secondary contact

A
  • gene flow is re-established in a hybrid zone (after speciation)
  • species come into contact again via migration or geographic changes
44
Q

speciation (evolution of reproductive isolation): secondary contact - when the two populations meet again, can they breed?

A
  • multiple options:
    1. no hybrids reproduced
    2. unfit hybrids
    3. equal or better fitness in hybrids
45
Q

secondary contact - no hybrids reproduced

A

Suggests that reproductive isolation has evolved, and speciation has occurred

46
Q

secondary contact - unfit hybrids

A
  • Reinforcement selection – postzygotic barrier and selection is reinforcing the barrier
  • hybrids are formed but should see a decrease in hybrids overtime
47
Q

secondary contact - equal or better fitness in hybrids

A
  • 3 options:
    1. fusion
    2. stable hybrid zone
    3. hybrid speciation
48
Q

secondary contact: equal or better fitness in hybrids - fusion

A
  • Recently diverged species will fuse back into one
  • reversal speciation effect
49
Q

secondary contact: equal or better fitness in hybrids - stable hybrid zone

A

Continued production of hybrids but still maintain 2 distinct species

50
Q

secondary contact: equal or better fitness in hybrids - hybrid speciation

A
  • hybrid becomes its own species
  • 3 species instead of 2

Evolution (18 decks)

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