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Today… • Turn in your Hardy Weinberg labs & practice problems • Turn in PKU Case Study • Test corrections due FRIDAY • Today – Speciation & Cladograms! 1 The Origin of Species Mom, Dad… There’s something you need to know… I’m a MAMMAL! 2010-2011 Speciation • Changes in allele frequency are so great that a new species is formed • Can be slow and gradual or in “bursts” • Extinction rates can be rapid and then adaptive radiation follows when new habitats are available Correlation of speciation to food sources Seed eaters Flower eaters Insect eaters Rapid speciation: new species filling niches, because they inherited successful adaptations. Adaptive radiation So…what is a species? • Population whose members can interbreed & produce viable, fertile offspring • Reproductively compatible Distinct species: songs & behaviors are different enough to prevent interbreeding Eastern Meadowlark Western Meadowlark How do new species originate? • When two populations become reproductively isolated from each other. • Speciation Modes: – allopatric • geographic separation • “other country” – sympatric • still live in same area • “same country” Allopatric Speciation Physical/geographical separation of two populations Allele frequencies diverge After a length of time the two population are so different that they are considered different species If the barrier is removed interbreeding will still not occur due to pre/post zygotic isolation Sympatric Speciation Formation of a new species without geographic isolation. Causes: – Pre-zygotic barriers exist to mating – Polyploidy (only organism with an even number of chromosomes are fertile…speciation occurs quickly) – Hybridization: two different forms of a species mate in common ground (hybrid zone) and produce offspring with greater genetic diversity than the parents….eventually the hybrid diverges from both sets of parents Sympatric Speciation Gene flow has been reduced between flies that feed on different food varieties, even though they both live in the same geographic area. Pre-zygotic Isolation Sperm never gets a chance to meet egg •Geographic isolation: barriers prevent mating •Ecological isolation: different habitats in same region •Temporal isolation: different populations are fertile at different times •Behavior Isolation: they don’t recognize each other or the mating rituals •Mechanical isolation: morphological differences •Gamete Isolation: Sperm and egg do not recognize each other PRE-Zygotic barriers • Obstacle to mating or to fertilization if mating occurs geographic isolation behavioral isolation ecological isolation temporal isolation mechanical isolation gametic isolation Post Zygotic Isolation • Hybrid Inviability – the embryo cannot develop inside the mothers womb • Hybrid Sterility – Adult individuals can be produced BUT they are not fertile • Hybrid Breakdown – each successive generation has less fertility than the parental generation Evolutionary Time Scale • Microevolution – changing of allele frequencies in a population over time. • Macroevolution – patterns of change over geologic time. Determines phylogeny – Gradualism – species are always slowly evolving – Punctuated equilibrium – periods of massive evolution followed by periods with little to no evolution Patterns of Evolution • Divergent Evolution (adaptive radiation) • Convergent Evolution – Two or more species that share a common environment but not a common ancestor evolve to be similar Is it a shark or a dolphin?? Coevolution • Two or more species reciprocally affect each other’s evolution – predator-prey • disease & host – competitive species – mutualism • pollinators & flowers Not Necessarily on Purpose: Domestication and Speciation in the Canidae Family Did Dogs Co-evolve with Humans? 16 Who is Who’s Best Friend? The dog is said to be a man’s (human’s) best friend, but it could also be said that we are a dog’s best friend. Objectives: – How to interpret phylogenetic diagrams. – Understand how natural selection can work on a population to cause speciation. – Distinguish between natural and artificial selection. 17 Dog Breeds The winner of Best of Show at the 2009 Westminster Dog Show was a Sussex Spaniel. “Stump” the spaniel competed against 170 other breeds of domestic dog (an intraspecies competition). Where do so many breeds come from? How did the species we recognize as the domestic dog arise? 18 The start of our story… A young boy is sitting near the edge of a cave 20,000 years ago. He has just taken out the garbage from the group’s previous day’s activities. The garbage consists of mostly bones and scraps of food from a recent successful hunt. As dusk approaches, the wolves start to arrive. The boy is not frightened. He has seen the wolves many times before. In fact, their arrival is almost ritualistic. They move in from the forest and wait until all the humans have gone into the cave for the night. The boy notices that the same wolf is the first one to get to the good scraps. It doesn’t immediately run off when it sees the boy. Domestic dogs wouldn’t appear on the scene for another 5,000 years…. 19 20,000 years ago, a boy looked out of a cave … 20 The Family Canidae 21 Jackal (Black-backed jackal) Members of the Family Canidae Fox (Kit fox, Red fox) Wolf (Gray wolf) African wild dog 22 Domestic dogs look like they are more closely related to wolves than other canids. Siberian husky (domestic dog) Gray wolf Coyote 23 Of course, looks can be deceiving! Gray wolf Domestic dog (Lhasa apso) Phylogenetic analyses are more convincing. 24 Phylogenetic Analysis • Phylogenies can be based on morphology – Similarity of many morphological characteristics are used (color, size, structure, etc.) • Most recent phylogenies are based on molecular similarities – E.g., similarities of mitochondrial DNA (mtDNA) sequences – More similarities (i.e., fewer dissimilarities) = 25 a closer relationship Phylogeny The study of evolutionary relationships – Think of it as a family tree A B C D Recent time Species A, B, C & D all exist in modern times Past26 time Phylogeny The study of evolutionary relationships – Think of it as a family tree Sp A Sp B Sp C Sp D Unique ancestor of D only Common ancestor of both C & D, but not A & B Common ancestor of A, B, C & D 27 CQ#1: Which statement can be made about this phylogeny? A. Species A, B, and C are extinct. B. Species C & D shared a common ancestor more recently than B & D. C. Species D will display the most advanced morphological characteristics. D. Species D is most closely related to Species A. E. Species D evolved from Species C. Sp A Sp B Sp C Sp D 28 CQ#1: Which statement can be made about this phylogeny? A. Species A, B, and C are extinct. – ALL MODERN B. Species C & D shared a common ancestor more recently than B & D. C. Species D will display the most advanced morphological characteristics. – Just different D. Species D is most closely related to Species A. – Just, no. E. Species D evolved from Species C. – common ancestor only Sp A Sp B Sp C Sp D 29 Cladograms are another way to look at phylogenies 30 Species A Species B Species C Species D Species E Species F Species A & B are more similar to each other than they are to any other species Species A-D are more similar to each other than they are to either species E or F Species C & D shared a common ancestor in more recent times than the 31 shared common ancestor of A-D In Groups: Discuss relationships and create a cladogram for: Domestic dog Fox Wolf Jackal 32 CQ#2: Which of the following most closely resembles your cladogram? A. Dog B. Wolf C. Dog Jackal Wolf Jackal Fox Fox Dog D. Dog Wolf Jackal Wolf Fox Jackal Fox 33 E. Wow, mine looks like none of these Canid Phylogeny 34 CQ#3: According to the molecular evidence shown in the cladogram, which statement is most true? A. Foxes and wolves are closely related. B. Domestic dogs and wolves are as closely related to each other as they are to coyotes. C. Out of the canids tested, a Gray wolf shares the most recent ancestor of the domestic dog. D. The domestic dog is the most evolved of the canids. 35 CQ#3: According to the molecular evidence shown in the cladogram, which statement is most true? A. Foxes and wolves are closely related. – B. Domestic dogs and wolves are as closely related to each other as they are to coyotes. C. Out of the canids tested, a Gray wolf shares the most recent ancestor of the domestic dog. D. The domestic dog is the most evolved of the canids. 36 Comparing wolves with dogs • Morphological comparisons (examples) • Dogs tend to have curled tails, wolves have straight tails. • Dogs tend to have smooth short coats. • Skull shape differs. • Molecular comparisons • Gray wolves and dogs differ by no more than 0.2% in their mtDNA sequence. • In contrast, gray wolves and coyotes differ by at least 4%. 37 How did dogs evolve from wolves? Competing hypotheses – Ancestral wolf pups were domesticated intentionally by early humans – Artificial selection. – Ancestral wolf populations experienced natural selection forces that favored doglike characteristics. 38 Hypotheses 1 – Artificial Selection • Arguments for – It makes intuitive sense that ancestral wolves could be domesticated easily since they are so dog-like. Early humans would have intentionally bred ancestral wolves. • Arguments against – Why would any human want to deal with an animal that avoids humans? – Modern wolves can not be “domesticated” by training alone. It takes intensive and sophisticated selective breeding. 39 Hypothesis 2 – Natural Selection • Canids are very resourceful & would have found human waste piles good foraging – wolves were living close to humans. • Wolves are shy, skittish animals – only “adventurous” wolves would have stayed close to the waste piles while humans were around. • The “adventurous” wolves were the best fed and hence had high fitness. 40 CQ#4: What is fitness in the evolutionary sense? A. Being the strongest and most able to get food. B. Being able to survive and reproduce more successfully than others. C. Being the most aggressive and fending off potential predators. D. Being the smartest and remembering where the best food resources are. 41 CQ#4: What is fitness in the evolutionary sense? A. Being the strongest and most able to get food. B. Being able to survive and reproduce more successfully than others. C. Being the most aggressive and fending off potential predators. D. Being the smartest and remembering where the best food resources are. 42 CQ#5: What characteristic is being selected for in the ancestral wolf population under Hypothesis 2? A. Ability to interact with humans. B. Capability of eating human waste. C. Behaviors that lead to tolerance of humans being around. D. Inability to run away from humans. 43 CQ#5: What characteristic is being selected for in the ancestral wolf population under Hypothesis 2? A. Ability to interact with humans. B. Capability of eating human waste. C. Behaviors that lead to tolerance of humans being around. D. Inability to run away from humans. 44 A Plausible Series of Events • Those ancestral wolves that tended to tolerate humans would have had the best access to high-quality food (scraps). • Canids likely would have protected their scrap piles from other invading animals and possibly even strange humans. 45 What did humans give dogs? • Easy access to high-quality food. • A safe “home” to raise pups. • What else… 46 CQ#6: What did the first "dogs" give humans that is the most significant in evolutionary terms? A. An efficient garbage disposal. B. An affectionate pet. C. An early warning system that someone or something was approaching. 47 CQ#6: What did the first "dogs" give humans that is the most significant in evolutionary terms? A. An efficient garbage disposal. B. An affectionate pet. C. An early warning system that someone or something was approaching. 48 Epilogue • Molecular data suggest multiple “domestications” in multiple areas. • Canids artificially selected for tameness also showed characteristics common to domestic dogs: – Curled tails – Mottled coats – Floppy ears 49 Cladogram Activity • If you don’t finish in class, it will be homework due NEXT time. 50