1. How are new species created?
Speciation
How are new species created?

2. What is a species?
According to the biological species concept, a species is a group whose members can breed with each other in nature and produce fertile offspring
It’s all about reproduction!
Problems with this definition?

3. What is speciation?
Speciation is an event that produces two or more separate species.
In a phylogenetic tree, it is represented by a branching point
Example: Drosophila

4. A new species of fruit fly
Example: Fruit flies
A population of wild fruit flies on several bunches of rotting bananas, laying their eggs in the mushy fruit...

5. A new species of fruit fly
Disaster strikes: A hurricane washes the bananas and the fruit flies out to sea. The banana bunch washes up on an island off the coast of the mainland. The two portions of the population, mainland and island, are now too far apart for gene flow to unite them.

6. A new species of fruit fly
The populations diverge: Conditions are slightly different on the island, and the island population evolves under different selective pressures and experiences different random events than the mainland population does.
Food preferences, and courtship displays change over the course of many generations of natural selection.

7. A new species of fruit fly
So we meet again: When another storm brings the island flies back to the mainland, they will not mate with the mainland flies since they've evolved different courtship behaviors.
The few that do mate with the mainland flies, produce inviable eggs because of other genetic differences between the two populations.
Two separate species now exist since genes cannot flow between the populations.

8. Geographic Isolation
Populations are separated by geographic change or dispersal to geographically isolated places
Rivers change course
Mountains rise
Continents drift
Organisms migrate
Roads are built
Note: a barrier for one species may not be a barrier for another species
Add graphics of river, Grand Canyon

9. Small populations face risks
Founder effect: when only a few individuals colonize a new place, genetic variation is low
Genetic drift: changes in gene pool due to chance (which individuals reproduce)
Bottleneck effect: disasters that eliminate a large number of individuals and greatly reduce the gene pool

10. A new species: If a group splits off from the main population
evolves to adapt to its environment
the changes accumulated make it unable to breed with the larger population
Then a new species has been formed

11. Other reasons for reproductive isolation:
Timing: Different breeding seasons
Example: Spotted skunks
Western skunks breed in the fall, Eastern skunks breed in the late winter

12. Other reasons for reproductive isolation:
Behavior: Different courtship or mating behaviors
Example: Eastern and Western Meadowlarks
Different songs

13. Other reasons for reproductive isolation:
Habitat: Adapted to different habitats in the same general location
Example: Stickleback fish in British Columbia
Live in different levels of water, have different diets

14. Other reasons for reproductive isolation:
Others: different reproductive structures, insects only transfer pollen to certain plants, hybrid offspring is sterile

15. Adaptive Radiation
Evolution from a common ancestor that results in diverse species adapted to different environments
Diversification happens quickly
Islands often favor speciation because geographically isolated
Example: Hawaiian honeycreepers

16. Adaptive Radiation
Hawaiian honeycreepers: over 40 species have evolved from 1 common ancestral species
Variation in color and beak shape is related to their habitat and diet

17. Macroevolution Describes dramatic biological changes
Origin of new species
Extinction of species
Formation of major new features (wings, flowers)
Different from microevolution which describes changes in allele frequencies within a population
Mutation+Natural Selection+3.5 billion years = Macroevolution

18. Ensatina Salamanders California salamanders
Live and lay eggs on land
Studied by R.C. Stebbins in the 1940s
You will use his data to map the locations of various subspecies
Video of mating behavior:
Pictures of each subspecies:

19. Ensatina Salamanders

21. Ring Species
All subspecies interbreed with their immediate neighbors EXCEPT at southern end
E. klauberi and E. eschscholtzii do not interbreed
Where should speciation be marked?