Do you think Speciation can only be observed over millions of years? Explain.

1. Do you think Speciation can only be observed over millions of years? Explain.

2. Do you think species are going extinct, but no new species are forming on Earth? • Yes • No Explain your answer.

3. What is a Species?A Case Study

4. The Apple Maggot Fly Rhagoletispomonella

5. The hawthorn fruit is eaten by the larvae of the hawthorn maggot fly, Rhagoletispomonella. Hawthorn trees are native to North America. 13 mm average Size fruit

6. Rhagoletispomonella lifecycle • The female lays fertilized eggs in the fruit. • Maggots (larvae) emerge from the egg, feed on the fruit, and grow . • Healthy maggots drop from the tree with the fruit and burrow in the soil. Pupation takes place in the soil. 4. Adult maggot flies emerge from the soil and fly to fruit trees, where they mate on the surface of the fruit.

7. But there are parasites! Parasitoid wasps try to lay eggs in the maggot’s body, paralyzing and ultimately killing the maggot.

8. Apples • Domesticated apples (Malusdomesticus) were introduced to North America in the 1600s. They are now the most widely grown fruit in North America. • A typical commercial apple has a diameter of 70 mm.

9. RhagoletisHost Shift ♀ lays eggs on fruit Hawthorn (Crataegusspp) Rhagoletispomonella 1864: First noted apple Infestation (147 years Ago) Apple (Malusdomesticus)

10. Apple vs. Hawthorn:The Maggot’s Viewpoint • The large apple fruit provides 220 times more food than hawthorn fruit. • But the nutritional quality of hawthorn fruit is superior: 52% of hawthorn maggots survive vs. 27% of apple maggots.

11. Apple vs. Hawthorn: The Risk of Attack • Larger fruits of apples are much deeper than hawthorn fruits. • Apple maggots can burrow to avoid parasitoid wasps. • Apple maggots carry fewer parasitoid wasp eggs than hawthorn maggots do.

12. Today: There are Hawthorn & Apple Maggot Flies • Hawthorn and apple maggot flies are physically indistinguishable. • However, they are genetically distinct, with different genetic profiles. • There is no geographic isolation or physical separation between hawthorn and apple maggot flies.

13. Hawthorn & Apple Maggot Flies • Maggot flies tend to mate with their own kind. • Hawthorn maggot flies strongly prefer to mate on and lay fertilized eggs in hawthorn fruit. • Apple maggot flies strongly prefer to mate on and lay fertilized eggs in apple fruit. • There is only a 4-6% hybridization rate between hawthorn and apple maggot flies.

14. Hybrids are viable and fertile. No post-zygotic barriers Rhagoletis Host Shift Apple-raised Hawthorn-raised

15. Timing of Host Fruit Ripening Different ripening time of host fruit leads to temporal separation of apple and hawthorn flies.

16. Based on the information provided, are hawthorn and apple maggot flies separate species? Explain your reasoning.

18. 1. According to the biological species concept, are hawthorn and apple maggot flies separate species?

19. Which information is relevant to the biological species definition? • Hawthorn and apple maggot flies are physically indistinguishable. • There is a 4-6% hybridization rate between hawthorn and apple maggot flies. • Hawthorn and apple maggot flies are genetically distinguishable and have a distinct genetic profiles. • Hawthorn and apple maggot flies strongly prefer to mate and lay fertilized eggs in hawthorns and apples, respectively.

20. Ecological species concept A species is a set of organisms exploiting a single niche. The key aspects of this definition are the resources exploitedand the habitat occupied by the members of a species.

21. 2. According to the ecological species concept, are hawthorn and apple maggot flies separate species?

22. Which information is relevant to the ecological species definition? Explain. • Hawthorn and apple maggot flies are physically indistinguishable. • There is a 4-6% hybridization rate between hawthorn and apple maggot flies. • Hawthorn and apple maggot flies are genetically distinguishable and have a distinct genetic profiles. • Hawthorn and apple maggot flies strongly prefer to mate and lay fertilized eggs in hawthorns and apples, respectively.

23. Morphological species concept A species is a set of individuals with morphological features in common. The key aspect of this definition is the morphology of the members of a species. Individuals of a species are morphologically similar to one another, yet morphologically distinct from individuals from another species.

24. 3. According to the morphological species concept, are hawthorn and apple maggot flies separate species?

25. Which information is relevant to the morphological species definition? • Hawthorn and apple maggot flies are physically indistinguishable. • There is a 4-6% hybridization rate between hawthorn and apple maggot flies. • Hawthorn and apple maggot flies are genetically distinguishable and have a distinct genetic profiles. • Hawthorn and apple maggot flies strongly prefer to mate and lay fertilized eggs in hawthorns and apples, respectively.

26. Phylogenetic species concept A species may be defined by its unique genetic history as a tip of a phylogenetic tree. Species are defined by their unique derived features and shared ancestry.

27. 4. According to the phylogenetic species concept, are hawthorn and apple maggot flies separate species?

28. Which information is relevant to the phylogenetic species definition? • Hawthorn and apple maggot flies are physically indistinguishable. • There is a 4-6% hybridization rate between hawthorn and apple maggot flies. • Hawthorn and apple maggot flies are genetically distinguishable and have a distinct genetic profiles. • Hawthorn and apple maggot flies strongly prefer to mate and lay fertilized eggs in hawthorns and apples, respectively.

29. Reproductive isolation 5. How do two similar species maintain genetic isolation if they come (or remain) in contact with each other?

30. Reproductive isolation Reproductive isolating mechanisms prevent two individuals from distinct species from interbreedingor produce viable and fertile hybrid offspring.

32. Sympatric speciation In sympatric speciation, there is no geographic barrier to gene flow.

33. 6. Explain what type of Speciation is occuring or has occurred with Rhagoletisbased on the evidence given.

34. 7. What reproductive barriers limit interbreeding between hawthorn and apple maggot flies? Explain.

35. Timing of Host Fruit Ripening Different ripening time of host fruit leads to temporal separation of apple and hawthorn flies.

36. 8. Are apple and hawthorn maggot flies a separate species?

37. Genetic divergence Genetic divergence is the accumulation of genetic differences between two populations.

38. Evolutionary Significant Units

39. Factors causing genetic divergence between isolated populations • Founder effect • Mutation • Genetic drift • Differential selection

40. Reproductive isolation Reproductive isolating mechanisms prevent two individuals from distinct species from interbreeding or produce viable and fertile hybrid offspring.

42. Reproductive isolation: Prezygotic barriers • Habitat isolation • Behavioral isolation • Temporal isolation • Mechanical isolation • Gametic isolation

43. geographic isolation ecological isolation temporal isolation gametic isolation mechanical isolation behavioral isolation PRE-reproduction barriers • Obstacle to mating or to fertilization if mating occurs

44. Ecological isolation • Species occur in same region, but occupy different habitats so rarely encounter each other • reproductively isolated 2 species of garter snake, Thamnophis, occur in same area, but one lives in water & other is terrestrial

45. Temporal isolation • Species that breed during different times of day, different seasons, or different years cannot mix gametes • reproductive isolation • sympatric speciation • “same country” Eastern spotted skunk (L) & western spotted skunk (R) overlap in range but eastern mates in late winter & western mates in late summer

46. Behavioral isolation • Unique behavioral patterns & rituals isolate species • identifies members of species • attract mates of same species  • courtship rituals, mating calls • reproductive isolation Blue footed boobies mate only after a courtship display unique to their species

47. Mechanical isolation sympatric speciation? • Morphological differences can prevent successful mating • reproductive isolation Plants Even in closely related species of plants, the flowers often have distinct appearances that attract different pollinators. These 2 species of monkey flower differ greatly in shape & color, therefore cross-pollination does not happen.

48. Mechanical isolation Animals • For many insects, male & female sex organs of closely related species do not fit together, preventing sperm transfer • lack of “fit” between sexual organs: hard to imagine for us… but a big issue for insects with different shaped genitals! Damsel fly penises

49. Gametic isolation • Sperm of one species may not be able to fertilize eggs of another species • mechanisms • biochemical barrier so sperm cannot penetrate egg • receptor recognition: lock & key between egg & sperm • chemical incompatibility • sperm cannot survive in female reproductive tract Sea urchins release sperm & eggs into surrounding waters where they fuse & form zygotes. Gametes of different species— red & purple —are unable to fuse.

50. Reproductive isolation:Postzygotic barriers • Reduced hybrid viability • Reduced hybrid fertility • Hybrid breakdown