Outline 16-3: The Process of Speciation 1/15/2019

I. Speciation A. Formation of new species 1/15/2019 I. Speciation A. Formation of new species 1. A species is a group of organisms that breed with one another and produce fertile offspring. 2. The gene pools of two populations of a species must become separated for them to become new species. 1/15/2019

They will have separate gene pools. 1/15/2019 3. As new species evolve, two populations can become so different from each other that the populations eventually become reproductively isolated from each other a. When members of two populations cannot interbreed & produce fertile offspring, reproductive isolation has occurred. They will have separate gene pools. 1/15/2019

a. Behavioral Isolation 1/15/2019 4. Reproductive isolation can develop in a variety of ways: a. Behavioral Isolation Organisms are capable of inter- breeding but have differences in courtship rituals or other reproductive strategies. Examples: Meadowlarks, blue-footed boobies, albatross, firefly flash patterns 1/15/2019

Eastern & Western Meadowlarks have different mating songs 1/15/2019 Song Song Eastern & Western Meadowlarks have different mating songs Blue-footed boobies have specific courtship rituals

Firefly flash patterns 1/15/2019

b. Geographic Isolation 1/15/2019 b. Geographic Isolation Two populations are separated by geographic barriers such as rivers or mountains & thus can’t interbreed Examples: Kaibab & Abert squirrels Wrasse fishes 1/15/2019

1/15/2019 Grand Canyon

Kaibab squirrel Abert’s squirrel 1/15/2019 Kaibab squirrel Abert’s squirrel

Wrasses separated by Isthmus of Panama 1/15/2019 Wrasses separated by Isthmus of Panama

Occurs when two or more species reproduce at different times. 1/15/2019 c. Temporal Isolation Occurs when two or more species reproduce at different times. Examples: Wood & leopard frogs mate at different times; orchids release pollen on different days 1/15/2019

Amphibian temporal isolation 1/15/2019

Orchid temporal isolation 1/15/2019 Orchid temporal isolation Release pollen on different days

II. Natural Selection in Darwin’s finches 1/15/2019 II. Natural Selection in Darwin’s finches

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 Beaks became larger & more massive at such times 1/15/2019 A. Studied by Peter & Rosemary Grant (1973 - 1998) 1. Results of Study: a. During wet years, when food is plentiful, bird beak size doesn’t matter much (All beaks work on plentiful small, soft seeds) b. During dry years, plants make fewer seeds & more of them are larger and harder to open  Beaks became larger & more massive at such times 1/15/2019

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III. Speciation in Darwin’s Finches 1/15/2019 III. Speciation in Darwin’s Finches A. Occurred by: 1. founding of a new population 2. geographic isolation 3. changes in new population's gene pool 4. reproductive isolation 5. ecological competition B. This is an example of adaptive radiation. 1. Single species evolves into several different ones 1/15/2019

Speciation in Darwin's Finches 1/15/2019 DON’T COPY THIS!! Founders Arrive  A few finches —species A—travel from South America to one of the Galápagos Islands. There, they survive and reproduce. Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species.

Speciation in Darwin's Finches 1/15/2019 Speciation in Darwin's Finches Geographic Isolation Some birds from species A cross to a second island. The two populations no longer share a gene pool. Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species.

Speciation in Darwin's Finches 1/15/2019 Changes in the Gene Pool Seed sizes on the second island favor birds with large beaks. The population on the second island evolves into population B, with larger beaks. Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species.

Speciation in Darwin's Finches 1/15/2019 Reproductive Isolation Population B birds cross back to first island. They will not mate with birds from Pop. A. A & B are now separate species. Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species. B

Speciation in Darwin's Finches 1/15/2019 Ecological Competition Species A & B compete for seeds on first island & continue to evolve differences. New species - C - may evolve. Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species. B C

Speciation in Darwin's Finches 1/15/2019 Continued Evolution These processes continue across the entire Galapagos island chain until 13 species evolved. G D E Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species. B F C