Lecture 6: Speciation

Question 1

Biological Species Complex (BSC)

What makes different species according to BSC?

Answer 1

Defines species as infividuals in populations that can breed and produce fertile offspring

They are reproductively isolated from one another

Question 2

Horses and donkeys can mate and have offspring (mules). What makes them different according to BSC

Answer 2

Male mules dont produce sperm that is capable of fertilizing an egg. Their offspring are not fertile!

Question 3

What is the difference between prezyogtic barriers and postzygotic barriers?

Answer 3

Prezygotic- prevent fertilization from taking place
Postygotic- occur when there is mating but either the viability or the fertility of the hybrid is reduced

Question 4

What are the 5 types of prezygotic barriers and give a brief description

Answer 4

1. Temporal isolation: breed at different times
2. Behavioral isolation: male must “act properly” to mate
3. Mechanical isolation: male and female genitalia are incompatible
4. Genetic isolation: Egg and sperm are incompatible
5. Habitat Isolation: Populations are isolated, breed in different habitats

Question 5

Postzygotic Isolation Types

Answer 5

1. Hybrid Inviability: Fertilized offspring die before birth
2. Hybrid Sterility: Perfectly good but cannot reproduce

Question 6

Morphospecies Concept

Answer 6

Organisms that look “different enough” represent different species

Question 7

Phylogenic Species

Answer 7

Species are differnet if you look on a phylogeny and the species are in different places
aka the smallest monophyletic groups

Question 8

Allopatric Speciation

What are the different types?

Answer 8

Speciation that Takes place due to geographical isolation vicariance
dispersal- A group of individuals move to another location
Vicariance- Geographical isolation due to chance seperation

Question 9

What are the steps of Allopatric Speciation

Answer 9

1. Seperation of species
2. Mutation
3. Natural Selection
4. Genetic Drift
5. Reproductive isolation

Question 10

Sympatric Speciation

What are the two types?

Answer 10

Speciation not due to geographical isolation
1. Sympatric Speciation due to Ecological niche: Occurs when there is divergent selection (differences in closely related species)
2. Internal Sympatric Speciation: Chromosomal mutations that cause a reproductive barrier (POLYPLOIDY)

Question 11

What is the example of whales in regards to Symaptric Speciation?

Answer 11

There are two types of whales; resident and transient whales. Residents travel in large groups whereas transient travel in small groups. They don’t intermate often which is an example of Ecological nice.

Question 12

What are the 5 possible outcomes when isolated populations come back in contact?

Answer 12

1) Fusion of Populations
2) Extinction
3) Reinforcement
4) Hybrid zones
5) Speciation

Question 13

Fusion of the populations

Example

Answer 13

The two populations freely interbreed
Ex. Openwater whitefish fuse with sympatric bottom of water whitefish population after the introduction of invasive open water competitor

Question 14

Extinction of one population

Answer 14

Poorer competitor is driven to extinction
Ex. Open water whitefish may go extinct after fusion with bottom of water witefish.

Question 15

Reinforcement of divergence

Answer 15

If hybrid offspring have low fitness, reinforcement of the distinction between the two populations occurs
Ex. Fruit flies that occupy the same geographic areas

Question 16

Hybrid zone formation

Answer 16

Regions where populations are in contact and have fertile and viable offspring
Ex. The hybrid zone between hermit and warblers appear to have moved over time

Question 17

Formation of new species

Answer 17

Sometimes hybrids can themselves become separate species from the hybrid species
Ex. Hybridization between sunflowers gave rise to a new species with unique characteristics