Speciation Flashcards
1
Q
Allopatric speciation
A
- split habitat prevents gene flow
- founder/bottleneck effect: sudden drop in population causes a new allele distribution
2
Q
Selection effects
A
- directional: from one end to the other
- disruptive: centralized alleles are less frequent, periphery is more frequent
- stabilizing: already frequent allele becomes more stable
3
Q
Sympatric speciation
A
- same habitat, but ecological adaptations/behavior changes lead to reproductive isolation
- e.g. blackcap birds breed in EU and migrate to Spain in the winter; NOW, some move up to UK , due to assortative mating effects
- would mean that natural selection is directly acting on a population to encourage reproductive isolation
- history: allopatric speciation period must be highly unlikely
4
Q
Why are there so many species?
A
- ecological changes might introduce new niches
- mating isolation by time/method
5
Q
Pre/postzygotic barriers
A
- pre: habitat, temporal, behavioral, mechanical, gametic
- post: reduced hybrid viability, fertility issues, hybrid breakdown in F2 or later
6
Q
Hybrid zones (what are they; 3 types?)
A
- regions where genetically distinct populations meet and reproduce
1. FUSING: high gene flow and interfertility -> new species
2. REINFORCEMENT: mating results in loss of fitness, so speciation is reinforced
3. STABILITY: limited gene flow, negligible effects, little change
7
Q
What reinforces inviability between carrion and hooded crows?
A
Inverted chromosome regions make it so that crossing over is prohibited. When they do occur, genetic information is likely to remain linked.
8
Q
Phlox and cline theory
A
- evidence of stronger reproductive isolation in sympatric conditions by difference in flower color
- cline theory: stronger natural selection means phenotypic changes are more geographically abrupt