How are new species created? Speciation How are new species created?

Warmup: Get out your learning targets paper In the warmup section of your lab book: Create a concept map using at least 12 of the terms listed in part b) on the front side

Share current events article Notes: Directional selection, stabilizing, disruptive Genetic Drift Founder Effect Speciation Ensatina eschscholtzii salamanders Create a scenario… Homework

Natural Selection on Polygenic Traits Low mortality, high fitness Directional Selection High mortality, low fitness Food becomes scarce Individuals at one end of curve have higher fitness Range of phenotypes shifts

Natural Selection on Polygenic Traits Individuals near center of curve have highest fitness Keeps center of curve at same position and narrows graph Stabilizing Selection Low mortality, high fitness High mortality, low fitness Selection against both extremes keeps curve narrow and in same place Percentage of Population Birth Weight

Natural Selection on Polygenic Traits Disruptive Selection Largest and smallest seeds become more common Population splits into two subgroups specializing in different seeds. Low mortality, high fitness Number of Birds in Population Number of Birds in Population High mortality, Low fitness Beak Size Beak Size Individuals at upper and lower ends of the curve have higher fitness than individuals in the middle Selection acts strongly against individuals of the intermediate type

Speciation Speciation = formation of new species Species = group of organisms that breed with one another and produce fertile offspring As new species evolve, populations become reproductively isolated from each other Members of same species share same gene pool Genetic change that occurs in one individual can spread through the population Gene pools must become separated for speciation to occur When two population cannot interbreed and produce fertile offspring, reproductive isolation has occurred

Isolating Mechanisms (lacewing interactive) Behavioral Isolation Differences in courtship rituals or other reproductive strategies Geographic Isolation Two populations separated by geographic barrier such as rivers, mountains or bodies of water Temporal Isolation Two or more species reproduce at different times of the day or year

Reproductive Isolation results from Isolating mechanisms which include Behavioral isolation Temporal isolation Geographic isolation produced by produced by produced by Behavioral differences Different mating times Physical separation which result in Independently evolving populations which result in Formation of new species

Speciation In a phylogenetic tree, it is represented by a branching point Example: Drosophila

A new species of fruit fly Example: Fruit flies http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_42 A population of wild fruit flies on several bunches of rotting bananas, laying their eggs in the mushy fruit...

A new species of fruit fly Disaster strikes: A hurricane washes the bananas and the fruit flies out to sea. The banana bunch washes up on an island off the coast of the mainland. The two portions of the population, mainland and island, are now too far apart for gene flow to unite them.

A new species of fruit fly The populations diverge: Conditions are slightly different on the island, and the island population evolves under different selective pressures and experiences different random events than the mainland population does. Food preferences, and courtship displays change over the course of many generations of natural selection.

A new species of fruit fly So we meet again: When another storm brings the island flies back to the mainland, they will not mate with the mainland flies since they've evolved different courtship behaviors. The few that do mate with the mainland flies, produce inviable eggs because of other genetic differences between the two populations. Two separate species now exist since genes cannot flow between the populations.

Geographic Isolation Populations are separated by geographic change or dispersal to geographically isolated places Rivers change course Mountains rise Continents drift Organisms migrate Roads are built Note: a barrier for one species may not be a barrier for another species Add graphics of river, Grand Canyon

Small populations face risks Founder effect: when only a few individuals colonize a new place, genetic variation is low Genetic drift: changes in gene pool due to chance (which individuals reproduce) Bottleneck effect: disasters that eliminate a large number of individuals and greatly reduce the gene pool

Genetic Drift Section 16-2 Sample of Original Population Descendants Founding Population A Founding Population B

Genetic Drift Section 16-2 Sample of Original Population Descendants Founding Population A Founding Population B

Genetic Drift Section 16-2 Sample of Original Population Descendants Founding Population A Founding Population B

A new species: If a group splits off from the main population evolves to adapt to its environment the changes accumulated make it unable to breed with the larger population Then a new species has been formed

Other reasons for reproductive isolation: Timing (Temporal Isolation): Different breeding seasons Example: Spotted skunks Western skunks breed in the fall, Eastern skunks breed in the late winter http://s190.photobucket.com/albums/z257/americanwildlife/Mammal/Z-western-spotted-skunk1.jpg http://www.redorbit.com/modules/reflib/article_images/42_7de29e7e859b48896129c3d380d3cfbb.jpg

Other reasons for reproductive isolation: Behavior (Behavioral Isolation): Different courtship or mating behaviors Example: Eastern and Western Meadowlarks Different songs

Other reasons for reproductive isolation: Habitat: Adapted to different habitats in the same general location Example: Stickleback fish in British Columbia Live in different levels of water, have different diets http://ecoreb.org/imgs/o_gasacu2.jpg

Other reasons for reproductive isolation: Others: different reproductive structures, insects only transfer pollen to certain plants, hybrid offspring is sterile http://www.birkenholz.com/IMAGES/MuleColt05Right.jpg

Speciation of Darwin’s Finches Founders Arrive Separation of Populations Changes in the Gene Pool Reproductive Isolation Ecological Competition Continued Evolution

Speciation in the Andes (Ecuador) Hummingbird video Explain the hypothesis presented by the scientists profiled in this segment to explain the process of speciation in hummingbirds and possibly other species. How does this hypothesis differ from the traditional view that speciation often requires geographic separation of populations? Why were the researchers collecting blood from the populations they studied? Discuss at least two possible analyses that could be performed on those samples and, identify at least two different questions that might be answered with sufficient data.

Ensatina Salamanders California salamanders Live and lay eggs on land Studied by R.C. Stebbins in the 1940s You used his data to map the locations of various subspecies Video of mating behavior: http://evolution.berkeley.edu/evolibrary/article/0_0_0/devitt_07 Pictures of each subspecies: http://www.indiana.edu/~ensiweb/lessons/stepsal4.html http://evolution.berkeley.edu/evolibrary/article/0_0_0/devitt_02

Ring Species All subspecies interbreed with their immediate neighbors EXCEPT at southern end E. klauberi and E. eschscholtzii do not interbreed Where should speciation be marked? http://evolution.berkeley.edu/evolibrary/article/side_0_0/biospecies_01#ring

Did you get it? Watch this! Link to video about Ensatina salamanders in California (3 minutes) http://www.youtube.com/watch?v=PjcFSy1KCTI

Do Now! Devise a scenario in which a particular type of selection leads to speciation. Use the 5 tenants of natural selection What type of selection is at work?

Homework Read section 17-4 in your textbook (pg. 435-440), Patterns in Evolution Answer the three learning targets for this section (#3, 4 and 5 under chapter 17) from your LEARNING TARGETS paper.