Chapter 17 Processes of Evolution (Sections 17.11 - 17.14)

1. Chapter 17Processes of Evolution (Sections 17.11 - 17.14)

2. 17.11 Allopatric Speciation • In allopatric speciation,a geographic barrier arises and ends gene flow between populations – genetic divergences then give rise to new species • allopatric speciation • Speciation pattern in which a physical barrier that separates members of a population ends gene flow between them

3. Barriers to Reproduction • Whether a geographic barrier can block gene flow depends on whether and how an organism travels (e.g. by swimming, walking, or flying), and how it reproduces (e.g. by internal fertilization or by pollen dispersal) • Example: • When the Isthmus of Panama formed, it cut off gene flow among populations of aquatic organisms in the Pacific and Atlantic oceans

4. Allopatric Speciation in Snapping Shrimp

5. Allopatric Speciation in Snapping Shrimp Alpheus nuttingi (Atlantic) Isthmus of Panama Alpheus millsae (Pacific) Fig. 17.20, p. 272

6. Allopatric Speciation in Snapping Shrimp Atlantic Ocean Mexico Pacific Ocean Isthmus of Panama Columbia Fig. 17.20a, p. 272

7. Allopatric Speciation in Snapping Shrimp Alpheus nuttingi (Atlantic) Fig. 17.20b, p. 272

8. Allopatric Speciation in Snapping Shrimp Alpheus millsae (Pacific) Fig. 17.20b, p. 272

9. Speciation in Archipelagos • Archipelagos are isolated island chains formed by volcanoes, such as the Hawaiian and Galápagos Islands • Archipelagos were populated by a few individuals of mainland species whose descendants diverged over time • Selection pressures within and between the islands can foster even more divergences

10. The Hawaiian Islands

11. Hawaiian Honeycreepers • The first birds to colonize the Hawaiian Islands found a near absence of competitors and predators and an abundance of rich and vacant habitats, which encouraged rapid speciation • The many species of honeycreepers, unique to the Hawaiian Islands, have specialized bills and behaviors adapted to feed on certain insects, seeds, fruits, nectar, or other foods

12. Honeycreeper Diversity

13. Honeycreeper Diversity Akepa (Loxops coccineus) Insects, spiders, nectar; high mountain rain forest Fig. 17.21a, p. 273

14. Honeycreeper Diversity Akekee (Loxops caeruleirostris) Insects, spiders, nectar; high mountain rain forest Fig. 17.21b, p. 273

15. Honeycreeper Diversity Nihoa finch (Telespiza ultima) Insects, buds, seeds, flowers, seabird eggs; rocky or shrubby slopes Fig. 17.21c, p. 273

16. Honeycreeper Diversity Palila Maui (Loxioides bailleui) Mamane seeds, buds, flowers, berries, insects; high mountain dry forests Fig. 17.21d, p. 273

17. Honeycreeper Diversity Maui parrotbill (Pseudonestor xanthophrys) Insect larvae, pupae, caterpillars; mountain forests, dense underbrush Fig. 17.21e, p. 273

18. Honeycreeper Diversity Apapane (Himatione sanguinea) Nectar, caterpillars and other insects, spiders; high mountain forests Fig. 17.21f, p. 273

19. Honeycreeper Diversity Poouli (Melamprosops phaeosoma) Tree snails, insects in understory; last one died in 2004 Fig. 17.21g, p. 273

20. Honeycreeper Diversity Maui Alauahio (Paroreomyza montana) Bark or leaf insects, high mountain rain forest Fig. 17.21h, p. 273

21. Honeycreeper Diversity Kauai Amakihi (Hemignathus kauaiensis) Bark-picker; insects, spiders, nectar; high mountain rain forest Fig. 17.21i, p. 273

22. Honeycreeper Diversity Akiapolaau (Hemignathus munroi) Probes, digs insects from big trees; high mountain rain forest Fig. 17.21j, p. 273

23. Honeycreeper Diversity Akohekohe (Palmeria dolei) Mostly nectar from flowering trees, some insects, pollen; high mountain rain forest Fig. 17.21k, p. 273

24. Honeycreeper Diversity Iiwi (Vestiaria coccinea) Mostly nectar (ohia flowers, some nectar; lobelias, mints), some insects; high mountain rain forest Fig. 17.21l, p. 273

25. ANIMATION: Allopatric speciation on an archipelago To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

26. ANIMATION: Models of speciation To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

27. 17.12 Sympatric and Parapatric Speciation • Populations sometimes speciate even without a physical barrier that bars gene flow between them • In sympatric speciation,populations in physical contact speciate • With parapatric speciation,populations in contact along a common border speciate

28. Sympatric Speciation • Sympatric speciation can occur instantly with a change in chromosome number – many plants are polyploid (e.g. wheat) • Sympatric speciation can also occur with no change in chromosome number (e.g. mechanically isolated sage plants) • sympatric speciation • Pattern in which populations inhabiting the same geographic region speciate in the absence of a physical barrier between them

29. Sympatric Speciation in Wheat

30. Sympatric Speciation in Wheat A Einkorn has a diploid chromosome number of 14 (two sets of 7, shown here as 14 AA). Wild einkorn probably hybridized with another wild species having the same chromosome number (14 BB) about 11,000 years ago. The resulting hybrid was diploid (14 AB). B About 8,000 years ago, the chromo-some number of an AB hybrid plant spontaneously doubled. The resulting species, emmer, is tetraploid: it has two sets of 14 chromosomes (28 AABB). C Emmer probably hybridized with a wild goatgrass having a diploid chromosome number of 14 (two sets of 7 DD). The resulting common bread wheat has six sets of 7 chromosomes (42 AABBDD). spontaneous chromosome doubling T. aestivum (common bread wheat) Triticum mono-coccum (einkorn) Unknown species of Triticum T. turgidum (emmer) T. tauschii (goatgrass) 14 AA X 14 BB 14 AB 28 AABB X 14 DD 42 AABBDD Fig. 17.22, p. 274

31. Examples of Sympatric Speciation • Lake Victoria cichlids (sexual selection) • In the same lake, female cichlids of different species visually select and mate with brightly colored males of their own species • Warblers around the Tibetan plateau (behavioral isolation) • Two populations overlap in range, but don’t interbreed because they don’t recognize one another’s songs

32. Male Cichlids of Lake Victoria

33. Parapatric Speciation • Parapatric speciationmay occur when one population extends across a broad region with diverse habitats • Example: Two species of velvet walking worm with overlapping habitats in Tasmania: Where they interbreed, their hybrids are sterile • parapatric speciation • Speciation model in which different selection pressures lead to divergences within a single population

34. Comparing Speciation Models

35. Key Concepts • How Species Arise • Speciation varies in its details, but it always involves the end of gene flow between populations • Microevolutionary events that occur independently lead to genetic divergences, which are reinforced by reproductive isolation

36. ANIMATION: Sympatric Speciation in Wheat To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

37. 17.13 Macroevolution • A central theme of macroevolution is that major evolutionary novelties often stem from the adaptation of an existing structure for a completely different purpose (exaptation) • exaptation • Adaptation of an existing structure for a completely different purpose; a major evolutionary novelty

38. Patterns of Macroevolution • Macroevolution includes patterns of evolution above the species level, such as one species giving rise to multiple species, origin of major groups, and major extinction events • Four patterns of macroevolution: • Stasis • Adaptive radiation • Coevolution • Extinction

39. Stasis • With the simplest macroevolutionary pattern, stasis,a lineage persists for millions of years with little or no change • Example: Coelacanths • stasis • Evolutionary pattern in which a lineage persists with little or no change over evolutionary time

40. Coelacanth: Fossil and Living

41. Mass Extinctions • More than 99% of all species that ever lived are now extinct • There have been more than twenty mass extinctions, which are simultaneous losses of many lineages, including five catastrophic events in which the majority of species on Earth disappeared • extinct • Refers to a species that has been permanently lost

42. Adaptive Radiation • Inadaptive radiation, a lineage rapidly diversifies into several new species • Adaptive radiation can occur after individuals colonize a new environment that has a variety of different habitats with few or no competitors (e.g. Hawaiian honeycreepers) • adaptive radiation • A burst of genetic divergences from a lineage gives rise to many new species

43. An Example of Adaptive Radiation • This evolutionary tree diagram shows how one ancestral species gave rise to the Hawaiian honeycreepers • Only 41 of many hundreds of species are represented here (orange are extinct)

44. Adaptive Radiation (cont.) • Adaptive radiations also occur after geologic or climatic events eliminate some species from a habitat • Example: Mammals were able to undergo an adaptive radiation after the dinosaurs disappeared

45. Adaptive Radiation (cont.) • A key innovation can result in an adaptive radiation, or rapid diversification into new species • Example: evolution of lungs opened the way for an adaptive radiation of vertebrates on land • key innovation • An evolutionary adaptation that gives its bearer the opportunity to exploit a particular environment more efficiently or in a new way

46. Coevolution • Incoevolution,close ecological interactions between two species cause them to evolve jointly • Over evolutionary time, two species may become so interdependent that they can no longer survive without one another(e.g. the large blue butterfly (Maculinea arion) and red ant (Myrmica sabuleti)) • coevolution • Joint evolution of two closely interacting species • Each species is a selective agent for traits of the other • Each adapts to changes in the other

47. Coevolved Species • The ant eats honey exuded by the butterfly larva and carries it to its nest • The caterpillar lives in the ant nest and eats ant larvae until it pupates

48. Evolutionary Theory • Many biologists disagree about how macroevolution occurs • Dramatic jumps in morphology may be the result of mutations in homeotic or other regulatory genes • Macroevolution may be an accumulation of many microevolutionary events, or it may be an entirely different process

49. Key Concepts • Macroevolution • Patterns of genetic change that involve more than one species are called macroevolution • Recurring patterns of macroevolution include the origin of major groups, one species giving rise to many, and mass extinction

50. ANIMATION: Adaptation to What? To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE