Process of Speciation Ch 16.3

Intro to Speciation Recall, biologists define a species as a group of individuals that breed and produce fertile offspring Images: http://www.alaskastock.com/Pix/125/FM/BC/125FM_BC0020_001_T.JPG http://smedia.vermotion.com/media/16147/resources/baby-robins-nest-1.jpg http://www.movielandanimals.com/Terry%20With%20Baby%208.JPG

Intro to Speciation Therefore individuals of the same species share a common gene pool. Image:http://www.brooklyn.cuny.edu/bc/ahp/LAD/C21/graphics/C21_GenePool_2.GIF

Intro to Speciation As genetic change occurs in one individual, it can spread through the population via its offspring. Image: http://www.windows.ucar.edu/earth/Life/images/gene_pool_sm.gif

Intro to Speciation If this change increases “fitness” it will soon be found in many within the population. Image:http://www.azfotos.com/flowers_plants/stockphotosalamy/sunflower-picture_AJM55D.jpg

Speciation Defined as- The formation of new species As new species evolve, populations become reproductively isolated

Reproductive Isolation Defined as- When members of two populations cannot interbreed * Breeding can be prevented due to changes in behavior (eating, mating rituals, timing) environment (niches, food source, geographic barriers) or mechanics (breeding, fertilization, development)

Isolating Mechanisms Reproductive isolation can occur as a result of: Behavioral Isolation Geographic Isolation Temporal Isolation Mechanical Isolation

Behavioral Isolation Defined as- the isolating mechanism that operates through differences in courtship behavioral patterns Different mating location, mating time, or mating rituals If one species displays a certain courtship pattern, it won’t be recognized by those of the other species

Behavioral Isolation This is the mechanism which separates wolfs from dogs, their courtship patterns are different in the wild

Behavioral Isolation Meadowlarks Western Eastern

(Different mating songs) Behavioral Isolation Difference in courtship rituals Western and Eastern Meadowlark (Different mating songs) Images: http://i.pbase.com/u42/tmurray74/upload/27341017.CRW_7115_RJ.JPG http://www.sacsplash.org/cimages/meadowlark.jpg

Behavioral Isolation Different species of bowerbird construct elaborate bowers and decorate them with different colors in order to woo females. The Satin bowerbird (left) builds a channel between upright sticks, and decorates with bright blue objects, while the MacGregor’s Bowerbird (right) builds a tall tower of sticks and decorates with bits of charcoal. Evolutionary changes in mating rituals, such as bower construction, can contribute to speciation.

Behavioral Isolation Feeding Habits - change in food preference Fruit flies switched from Hawthorn fruit to Apple fruit introduced from England No gene flow occurs now because they eat, mate, and lay their eggs on different hosts (fruit). Images: http://images.google.com/imgres?imgurl=http://www.nd.edu/~biology/images/Feder6.gif&imgrefurl=http://www.nd.edu/~biology/JeffreyFeder.shtml&h=338&w=462&sz=100&hl=en&start=7&tbnid=hIbq3aExEYjf4M:&tbnh=94&tbnw=128&prev=/images%3Fq%3DHawthorn%2Bmaggot%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG

Geographic Isolation When two populations are separated physically when their original habitat becomes divided by barriers such as rivers, mountains, or bodies of water Image: http://images.google.com/imgres?imgurl=http://evolution.berkeley.edu/evosite/evo101/images/drosophila_experiment.gif&imgrefurl=http://evolution.berkeley.edu/evosite/evo101/VC1fEvidenceSpeciation.shtml&h=403&w=321&sz=16&hl=en&start=1&tbnid=uyn5icCbfLr_gM:&tbnh=124&tbnw=99&prev=/images%3Fq%3DGeographic%2BIsolation%26gbv%3D2%26svnum%3D10%26hl%3Den

Geographic Isolation Another Example of Speciation due to Geographic Isolation (Colorado River – 10,000 years ago) Images: http://content.answers.com/main/content/wp/en/thumb/9/93/200px-Kaibab-squirrel.jpg http://images.google.com/imgres?imgurl=http://dwrcdc.nr.utah.gov/rsgis2/images/Photos/sciuaber.jpg&imgrefurl=http://dwrcdc.nr.utah.gov/rsgis2/Search/Display.asp%3FFlNm%3Dsciuaber&h=266&w=342&sz=34&hl=en&start=7&tbnid=fGqhsBGh6own9M:&tbnh=93&tbnw=120&prev=/images%3Fq%3Dabert%2Band%2BKaibab%2Bsquirrel%26gbv%3D2%26svnum%3D10%26hl%3Den Abert Squirrel (Sciurus aberti) Kaibab Squirrel (Sciurus aberti kaibabensis) Grand Canyon

Geographic Isolation Island/Bodies of water Separated the Galapagos finches, tortoises, iguanas, and other species Island/Bodies of water

Geographic Isolation Speciation in action? In the summer of 1995, at least 15 iguanas survived Hurricane Marilyn on a raft of uprooted trees. They rode the high seas for a month before colonizing the Caribbean island, Anguilla. Evolutionary biologists would love to know what happens next: will the colonizing iguanas die out, will they survive and change only slightly, or will they become reproductively isolated from other Iguana iguana and become a new species? http://images.google.com/imgres?imgurl=http://evolution.berkeley.edu/evosite/evo101/images/drosophila_experiment.gif&imgrefurl=http://evolution.berkeley.edu/evosite/evo101/VC1fEvidenceSpeciation.shtml&h=403&w=321&sz=16&hl=en&start=1&um=1&tbnid=uyn5icCbfLr_gM:&tbnh=124&tbnw=99&prev=/images%3Fq%3Dgeographic%2Bisolation%26um%3D1%26hl%3Den%26rls%3DGGLB,GGLB:1969-53,GGLB:en%26sa%3DN

Temporal Isolation Two or more species reproduce at different times. The time periods could differ simply by hours, or by seasons Image: http://www.pbs.org/wnet/nature/orchids/images/wallpaper/orchids_large.jpg

Temporal Isolation If one species reproduces in the spring, while the other reproduces in the fall, the two species aren’t able to breed Image: http://www.pbs.org/wnet/nature/orchids/images/wallpaper/orchids_large.jpg

Temporal Isolation Example: 3 similar species of orchid in same forest release pollen on different days (can not pollinate one another) Image: http://www.pbs.org/wnet/nature/orchids/images/wallpaper/orchids_large.jpg

Mechanical Isolation Deals with the actual mechanics of the reproductive organs Occurs when there is incompatibility in structure of the male and female sex organs

Mechanical Isolation Isolates species by preventing mating between two different species Isolation also occurs when the gametes of the two species are chemically incompatible Prevents fertilization

Galapagos Island Finches Darwin’s Discovery Galapagos Island Finches Image: http://www.rit.edu/~rhrsbi/GalapagosPages/Pictures/LandBirds/FinchTypes.jpeg

Darwin’s Discovery The finches looked so different he thought they were blackbirds, warblers, & other kinds of birds. After returning home, an ornithologist told him they were all finches Image:http://www.intelligentdesignnetwork.org/images/Finches.jpg

Darwin’s Discovery He then hypothesized: They had descended from a common ancestor. Natural selection shaped the beaks as they adapted to eat different foods Image: http://focus.hms.harvard.edu/2006/090106/images/Nature_finches.jpg

Reproductive Isolation Concept Map 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

Testing Natural Selection in Nature Two testable assumptions 1. Sufficient Variation among species 2. Natural Selection due to “fitness” of the variation Peter and Rosemary Grant

Testing Natural Selection in Nature What the Grant’s Finch Research Showed: There is great variation among inheritable traits During drought, food becomes scarce or gone and big beaks more likely to survive. Big beak birds tend to mate with other big beak birds, resulting in increase in average beak size of the population The next generation of finches had bigger beaks than the generations before Images: http://content.answers.com/main/content/wp/en/9/97/Darwin's_finches.jpeg

Testing Natural Selection in Nature After 20 years of banding & measuring finches, the Grants had demonstrated that evolutionary changes in finch beak size & shape occur rapidly in response to severe environmental changes in the Galapagos Image: http://explore-evolution.unl.edu/images/grant1.jpg Peter and Rosemary Grant (Princeton University)

Speciation of Finches in the Galapagos Islands B South America a) Founders Arrive b) Separation of Populations c) Changes in the Gene Pool E Speciation in the Galapagos finches occurred by: a) Founders Arrive A few finches travel from South America to one of the islands. There, they survive and reproduce. b) Separation of Populations Some birds from species A cross to a second island. The two populations no longer share a gene pool. c) Changes in the Gene Pool Seed sizes on the second island favor birds with larger beaks. The population on the second island evolves into a population, B, with larger beaks. d) Reproductive Isolation If a few population-B birds cross back to the first island, they will not mate with the birds of population-A. The gene pools are now separate. Populations A and B are separate species. e) Ecological Competition As species A ad B compete for seeds on the first island, they continue to evolve. A new species, C, may evolve. Some members of the original species B may travel to a new island. f) Continued Evolution The process continues, leading to the formation of all 13 finch species on the Galapagos. D B A C A C A B B B d) Reproductive Isolation e) Ecological Competition f) Continued Evolution

Follow these Steps as Review of Speciation in Darwin’s Finches 1. Founders Arrive on an Island 2. Separation of Population (some birds of species A cross to another island) 3. Change in Gene Pool (natural selection causes species A & B to evolve.) 4. Reproductive Isolation (now even if species A & B appear in same locale, gene pool remains isolated) 5. Ecological Competition (increase difference as species A & B compete.) 6. Continued Evolution