Process of Speciation

1. Process of Speciation Ch 16.3

2. Intro to Speciation Recall, biologists define a species as a group of individuals that breed and produce fertile offspring

3. Intro to Speciation Therefore individuals of the same species share a common gene pool.

4. Intro to Speciation As genetic change occurs in one individual, it can spread through the population via its offspring.

5. Intro to Speciation If this change increases “fitness” it will soon be found in many within the population.

6. Speciation • Defined as- The formation of new species • As new species evolve, populations become reproductively isolated

7. Reproductive Isolation • Defined as- When members of two populations cannot interbreed * Breeding can be prevented due to changes in behavior (eating, mating rituals, timing) environment (niches, food source, geographic barriers) or mechanics (breeding, fertilization, development)

8. Isolating Mechanisms Reproductive isolation can occur as a result of: • Behavioral Isolation • Geographic Isolation • Temporal Isolation • Mechanical Isolation

9. Behavioral Isolation • Defined as- the isolating mechanism that operates through differences in courtship behavioral patterns • Different mating location, mating time, or mating rituals • If one species displays a certain courtshippattern, it won’t berecognized bythose of the other species

10. Behavioral Isolation • This is the mechanism which separates wolfs from dogs, their courtship patterns are different in the wild

11. Meadowlarks Behavioral Isolation Western Eastern

12. Behavioral Isolation • Difference in courtship rituals Western and Eastern Meadowlark (Different mating songs)

13. Behavioral Isolation Different species of bowerbird construct elaborate bowers and decorate them with different colors in order to woo females. The Satin bowerbird (left) builds a channel between upright sticks, and decorates with bright blue objects, while the MacGregor’s Bowerbird (right) builds a tall tower of sticks and decorates with bits of charcoal. Evolutionary changes in mating rituals, such as bower construction, can contribute to speciation.

14. Behavioral Isolation • Feeding Habits - change in food preference Fruit flies switched from Hawthorn fruit to Apple fruit introduced from England No gene flow occurs now because they eat, mate, and lay their eggs on different hosts (fruit).

15. Geographic Isolation • When two populations are separated physically when their original habitat becomes dividedby barriers such as rivers, mountains, or bodies of water

16. Geographic Isolation • Another Example of Speciation due to Geographic Isolation (Colorado River – 10,000 years ago) Abert Squirrel (Sciurus aberti) Kaibab Squirrel (Sciurus aberti kaibabensis) Grand Canyon

17. Geographic Isolation • Separated the Galapagos finches, tortoises, iguanas, and other species Island/Bodiesof water

18. Geographic Isolation • Speciation in action? • In the summer of 1995, at least 15 iguanas survived Hurricane Marilyn on a raft of uprooted trees. • They rode the high seas for a month before colonizing the Caribbean island, Anguilla. • Evolutionary biologists would love to know what happens next: • will the colonizing iguanas die out, • will they survive and change only slightly, or • will they become reproductively isolated from other Iguana iguanaand become a new species?

19. Temporal Isolation • Two or more species reproduce at different times. • The time periods could differ simply by hours, or by seasons

20. Temporal Isolation • If one species reproduces in the spring, while the other reproduces in the fall, the two species aren’t able to breed

21. Temporal Isolation Example: 3 similar species of orchid in same forest release pollen on different days (can not pollinate one another)

22. Mechanical Isolation • Deals with the actual mechanics of the reproductive organs • Occurs when there is incompatibility in structure of the male and female sex organs

23. Mechanical Isolation • Isolates species by preventing mating between two different species • Isolation also occurs when the gametes of the two species are chemically incompatible • Prevents fertilization

24. Darwin’s Discovery Galapagos Island Finches

25. Darwin’s Discovery The finches looked so different he thought they were blackbirds, warblers, & other kinds of birds. After returning home, an ornithologist told him they were all finches

26. Darwin’s Discovery He then hypothesized: • They had descended from a common ancestor. • Natural selection shaped the beaks as they adapted to eat different foods

27. Geographic isolation Behavioral isolation Temporal isolation Physical separation Behavioral differences Different mating times Concept Map Reproductive Isolation results from Isolating mechanisms which include produced by produced by produced by which result in Independentlyevolving populations which result in Formation ofnew species

28. A A A A B E A A A D B C C B B B Speciation of Finches in the Galapagos Islands Galapagos Islands South America a) Founders Arrive b) Separation of Populations c) Changes in the Gene Pool d) Reproductive Isolation e) Ecological Competition f) Continued Evolution