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19 Cards in this Set
- Front
- Back
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Define:
Speciation |
The formation of a new species from a pre-existing species
Occurs at the branching events in a phylogeny (cladogram) |
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What are the 4 main modes of speciation?
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1) Allopatric
2) Parapatric 3) Sympatric 4) Hybridization |
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Define:
Allopatric speciation |
Populations become separated by a physical barrier and then evolve reproductive barriers.
Outlined by Ernst Mayr. *The most common* mode of speciation. Two types: - Vicariant speciation - Peripatric speciation |
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What is the most common of the 4 modes of speciation?
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ALLOPATRIC
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Define:
Vicariant speciation |
A form of allopatric speciation.
Population is divided into two widespread populations by a physical barrier - e.g. changes in courses of rivers, mountain-building events, Volcanism, glaciation, environmental changes |
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What are some different types of barriers that can lead to vicariant speciation?
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Changes in courses of rivers
Mountain-building events Volcanism Glaciation Environmental changes |
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What were 2 examples given for vicariant speciation?
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1) Speciation in 6 pairs of freshwater fish in southeastern U.S.
- split into a western and eastern clade. 2) Snapping shrimp - Separated on either side of the Isthmus of Panama |
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Define:
Peripatric speciation |
A type of allopatric speciation.
A colony disperses from a widespread population to a new area and evolves reproductive isolation. |
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What plays a large role in accelerating the process of peripatric speciation (once the initial move happens)
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Genetic Drift
The new population is small, thus genetic drift will have a large influence. |
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What organism (and geographic location) was used as an example for Peripatric Speciation?
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Hawaiian fruit flys across the Hawaiian Islands.
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Summarize the characteristics of Vicariant Speciation (3 points) and Peripatric Speciation (3 points)
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Vicariant Speciation
- Physical barrier - No dispersal - Results in 2 large populations Peripatric speciation: - Physical barrier - Dispersal - Results in 1 large and 1 small population |
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Define:
Parapatric speciation |
Strong selection causes a continuous population to diverge
Populations are contiguous (boundaries are in contact) No physical barrier present Divergent selection may be strong enough to overcome gene flow; reproductive isolation may evolve. |
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What organism was used as an example for Parapatric Speciation?
What caused it? |
Grass species: Anthoxanthum odoratum
Evolved different flowering times due to natural selection from mine wastes. Evolution of reproductive isolation over a short distance. |
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Define:
Sympatric Speciation |
Evolution of reproductive isolation within a randomly mating population
No geographic separation. |
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What organismz were used as examples for sympatric speciation?
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Pyrenestes - Seedcracker Finches.
Insect host switching trees (Apply fly maggot) |
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Define:
Hybridization Speciation |
Two parental species hybridize and produce offspring that can breed with each other, but are reproductively isolated from the parent species.
*Important in plants to get new species. Rare in animals. Chromosomal barriers may isolate offspring from the parents. |
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Define:
Speciation by polyploidy |
A type of hybridization speciation.
- Errors in mitosis or meiosis result in diploid gametes instead of the normal haploid gametes - Individuals with diploid gametes mate with each other and produce polyploid offspring - Resulting individuals can not breed with progenitors (parents), but can breed with each other. |
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A single genetic event resulting in *instantaneous speciation* is an example of what type of speciation?
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Polyploidy.
A type of hybridization speciation. |
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What are the 2 types of Allopatric speciation?
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1) Vicariant Speciation
2) Peripatric Speciation |
