1. POST-reproduction barriers
Prevent hybrid offspring from developing into a viable, fertile adult
reduced hybrid viability
reduced hybrid fertility
hybrid breakdown
zebroid

2. Reduced hybrid viability
sympatric speciation?
Reduced hybrid viability
Genes of different parent species may interact & impair the hybrid’s development
Species of salamander genus, Ensatina, may interbreed, but most hybrids do not complete development & those that do are frail.

3. Reduced hybrid fertility
Even if hybrids are vigorous they may be sterile
Mules are vigorous, but sterile
What’s wrong with having 63 chromosomes?
Odd number! Cannot pair up in meiosis.
Horses have 64 chromosomes
(32 pairs)
Donkeys have 62 chromosomes
(31 pairs)
Mules have 63 chromosomes!

4. sympatric speciation?
Hybrid breakdown
Hybrids may be fertile & viable in first generation, but when they mate offspring are feeble or sterile
In strains of cultivated rice, hybrids are vigorous but plants in next generation are small & sterile.
On path to separate species.

5. Hybrid Examples!

6. In each example, the male parent is listed first, then the female.

7. Donkey + Horse =

8. Mule!

9. Horse + Donkey =

10. Hinny!

11. American Bison + cow =

12. Beefalo!

13. Zebra + Donkey =

14. Zonkey!

15. Goat + Sheep=

16. Geep!

17. Sheep + Goat =

18. Shoat!

19. Grizzly bear + Polar bear =

20. Grolar Bear!

21. Grolar Bear!

22. Lion + Tiger =

23. Liger!

24. Tiger + Lion=

25. Tigon!

26. Camel + llama =

27. Cama!

28. Whale + Dolphin =

29. Wholphin!

30. Chicken + Turkey =

31. Churk!

32. Narwhal + Beluga =

33. Narluga!