Module 1: Evolution MonthDayTopic Sept8Mechanisms of evolution I 11Mechanisms of evolution II 13Speciation 15Macroevolution 18Biodiversity 20The history of plants 22Molecular evolution Exam review First mid-term exam

Microevolution Change in the frequencies of genotypes in a population The formation of new species Macroevolution

Species ASpecies B Time

Species A Species B Species A Species B Species C Time

A species is... a group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.

A species is... a group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.

A species is... a group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.

A species is... a group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.

But what about asexual organisms?

How do new species form? When gene flow ends between natural populations and their gene pool changes

Once a barrier to gene flow is established... populations diverge because of microevolution

How do new species form? 1.Allopatric speciation 2.Sympatric speciation 3.Parapatric speciation

1. Allopatric speciation Literally “other country”

1. Allopatric speciation Literally “other country” Geographic barrier divides population or Part of population crosses barrier and “founds” new population

1. Allopatric speciation Literally “other country” Geographic barrier divides population or Part of population crosses barrier and “founds” new population Most prevalent form of speciation

Allopatric speciation Geographic barrier divides population Gene flow is cut off Microevolution takes over Populations differentiate

Fig. 19-1, p.300

Fig. 19-7d13, p.305 Housefinch (Carpodacus)

Fig. 19-7d12, p.305 Iiwi (Vestiaria coccinea)

2. Sympatric speciation Literally “same country”

2. Sympatric speciation Literally “same country” Species arise from a connected population

2. Sympatric speciation Literally “same country” Species arise from a connected population Most common in plants

2. Sympatric speciation Literally “same country” Species arise from a connected population Most common in plants Occasionally seen in animals

Speciation by polyploidy (plants) Mistake during cell division

Speciation by polyploidy (plants) Mistake during cell division New individual is viable but genetically isolated

Speciation by polyploidy (plants) Mistake during cell division New individual is viable but genetically isolated In plants, individual with new ploidy- level can often self-fertilize

Triticum monococcum (einkorn) T. aestivum (one of the common bread wheats) Unknown species of wild wheat T. turgidum (wild emmer) T. tauschii (a wild relative) 42AABBDD14AA14BB14AB28AABB14DDXX cross-fertilization, followed by a spontaneous chromosome doubling Speciation by polyploidy

Speciation by behavioral change (animals) Parents make “mistake”

Speciation by behavioral change (animals) Parents make “mistake” Young pattern on a new place

Speciation by behavioral change (animals) Parents make “mistake” Young pattern on a new place Young return to place to mate

Speciation by behavioral change (animals) Parents make “mistake” Young pattern on a new place Young return to place to mate No gene flow with original population

3. Parapatric speciation Like allopatric speciation, except boundary is not physical

3. Parapatric speciation Like allopatric speciation, except boundary is not physical Parts of a population experience different conditions

3. Parapatric speciation Like allopatric speciation, except boundary is not physical Parts of a population experience different conditions Natural selection is stronger than gene flow

Bullock’s orioleBaltimore oriole hybrid zone Parapatric speciation

Can species interbreed if they get back together?

Species of European and American sycamores have been separated for 20 million years, yet they can still interbreed

Reproductive barriers between species Prezygotic barriers –barriers that prevent mating

Reproductive barriers between species Prezygotic barriers –barriers that prevent mating Postzygotic barriers –Barriers that operate after mating occurs

Prezygotic barriers Behaviorial isolation Ecological isolation Temporal isolation Mechanical isolation Gametic isolation

Fig. 19-4c, p.302

Fig. 19-4d, p.302

Fig. 19-4e, p.302

Fig. 19-4b, p.302

Fig. 19-4a, p.302

Fig , p.299

Postzygotic barriers Hybrid abnormality Hybrid infertility Low hybrid viability Absence or sterility of one sex

Fig , p.317

What controls the rate at which new species form?

Species richness

What controls the rate at which new species form? Species richness Range size and mobility

What controls the rate at which new species form? Species richness Range size and mobility Behavior, especially mate choice

What controls the rate at which new species form? Species richness Range size and mobility Behavior, especially mate choice Environmental change

What controls the rate at which new species form? Species richness Range size and mobility Behavior Environmental change Life history

What controls the rate at which new species form? Species richness Range size and mobility Behavior Environmental change Life history “Empty space”

Hawaiian silverswords

4 th mass extinction 210 mya: ~65% of species 5 th mass extinction 65 mya: ~76% of species Extraterrestrial impact or volcanism?

What controls the rate at which new species form? Species richness Range size Behavior Environmental change Generation time “Empty space” Innovation

Proportional Changes in Skull Chimpanzee Human Figure 19.14b Page 315