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
2
Q
what are the three species concepts
A
- morphological species concept
- phylogenetic species concept
- biological species concept
3
Q
morphological species concept - criterion for identifying species
A
phenotypic similarities and differences
4
Q
morphological species concept - strength
A
works for everything (extinct, asexual)
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
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
7
Q
Phylogenetic species concepts - strength
A
Powerful and works for anything with DNA and is testable
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
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
10
Q
biological species concept - strength
A
Reproductive isolation is a meaningful criterion for identifying species bc is confirms lacks of gene flow
11
Q
biological species concept - weakness
A
Cannot use for asexual organisms, fossils, organisms about which little is known about their reproduction
12
Q
why should we care about species concepts?
A
- human health (algal blooms)
- conservation
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
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)
15
Q
biological species concept - what are the reproductive barriers
A
- prezygotic barriers
- postzygotic barriers
16
Q
reproductive barriers - prezygotic barriers
A
- impede mating between species
- no fertilization in the first plce
17
Q
reproductive barriers - postzygotic barriers
A
- fertilization occurs
- produces a hybrid
- prevents hybrid zygote from developing into a viable and fertile adult
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
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
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
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
post zygotic barriers - reduced hybrid viability
- genes may interact in ways that impar hybrid's development or survival
- hybrids are more likely to die
26
post zygotic barriers - reduced hybrid fertility
hybrids survive to adulthood but are not fertile (sterile)
27
post zygotic barriers - hybrid breakdown
- hybrids are produced and the hybrid can produce offspring
- but 2nd generation of offspring is sterile
28
explain the classic model of speciation
1. isolation of population (reduced gene flow)
2. divergence of traits
3. speciation (evolution of reproductive isolation)
29
classic model of speciation - isolation of population (reduced gene flow)
- can be done in 2 ways:
1. allopatric speciation
2. sympatric speciation
30
isolation of population (reduced gene flow) - allopatric speciation
- a population forms a new species while geographically isolated from its parent population
- ex: mountain or river
31
isolation of population (reduced gene flow) - sympatric speciation
a subset of a population forms a new species without geographic separation
32
isolation of population (reduced gene flow): allopatric speciation model - explain the 2 ways of geographical isolation
1. dispersal allopatry
2. vicariance allopatry
33
the allopatric model - dispersal allopatry
- movement of individuals results in physical isolation
- can happen when there is not much gene flow
34
the allopatric model - dispersal allopatry example
- *Drosophila* fly
- each time they colonize a new island, they become a new species
- pattern of relatedness matches the geography of the island
35
the allopatric model - vicariance allopatry
geological events result in isolation of population
36
the allopatric model - vicariance allopatry example
- 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
divergence of traits - what processes cause trait divergence?
- All mechanisms of evolution can contribute to trait divergence between populations (the forces from Hardy-Weinberg)
- but selection makes the strongest contribution
38
divergence of traits - how can selection cause divergence
- natural: when one of the populations occupies a novel environment or uses a novel resource
- sexual: assertive matting
39
divergence of traits - natural selection example
- monkey flower faces different pressures in the coast vs inland
- led to distinct phenotypic and genetic differences
40
divergence of traits - natural + sexual selection example: Cichlid fish
- the fish have diff colors
- Light is filtered through water – only blue goes really far down and it affects visual system of fishes
41
divergence of traits: natural + sexual selection example: Cichlid fish - how does natural selection and sexual selection play a role?
- Natural – drives diff in tuning of female eyes
- Sexual – females can only see blue and mates with blue male
42
divergence of traits: natural + sexual selection example: Cichlid fish - what did researchers find?
- 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
speciation (evolution of reproductive isolation) - define secondary contact
- gene flow is re-established in a hybrid zone (after speciation)
- species come into contact again via migration or geographic changes
44
speciation (evolution of reproductive isolation): secondary contact - when the two populations meet again, can they breed?
- multiple options:
1. no hybrids reproduced
2. unfit hybrids
3. equal or better fitness in hybrids
45
secondary contact - no hybrids reproduced
Suggests that reproductive isolation has evolved, and speciation has occurred
46
secondary contact - unfit hybrids
- Reinforcement selection – postzygotic barrier and selection is reinforcing the barrier
- hybrids are formed but should see a decrease in hybrids overtime
47
secondary contact - equal or better fitness in hybrids
- 3 options:
1. fusion
2. stable hybrid zone
3. hybrid speciation
48
secondary contact: equal or better fitness in hybrids - fusion
- Recently diverged species will fuse back into one
- reversal speciation effect
49
secondary contact: equal or better fitness in hybrids - stable hybrid zone
Continued production of hybrids but still maintain 2 distinct species
50
secondary contact: equal or better fitness in hybrids - hybrid speciation
- hybrid becomes its own species
- 3 species instead of 2
