not necessarily on purpose: domestication and speciation in the canidae family
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Not Necessarily on Purpose: Domestication and Speciation in the Canidae Family. Tom Horvath Department of Biology SUNY College at Oneonta. 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: - PowerPoint PPT PresentationTRANSCRIPT
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Not Necessarily on Purpose: Domestication and Speciation
in the Canidae Family
Tom HorvathDepartment of Biology
SUNY College at Oneonta
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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.2
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Dog Breeds
“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? 3
The winner of Best of Show at the 2009 Westminster Dog Show was a Sussex Spaniel.
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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…. 4
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20,000 years ago, a boy looked out of a cave …
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The Family Canidae
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Jackal(Black-backed jackal)
Fox (Kit fox, Red fox)
Wolf(Gray wolf)
African wild dog
Members of the Family
Canidae
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Domestic dogs look like they are more closely related to wolves than other
canids.Siberian husky(domestic dog)
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Gray wolf
Coyote
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Of course, looks can be deceiving!
Phylogenetic analyses are more convincing.
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Gray wolf Domestic dog(Lhasa apso)
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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) =
a closer relationship 10
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PhylogenyThe study of evolutionary relationships– Think of it as a family tree
A B C D
Species A, B, C & D all exist in modern times
Recenttime
Pasttime
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PhylogenyThe study of evolutionary relationships– Think of it as a family tree
Sp A Sp B Sp C Sp D
Common ancestorof both C & D, but not A & B
Uniqueancestorof D only
Common ancestorof A, B, C & D 12
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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
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Cladograms are another way to look at phylogenies
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Species A
Species BSpecies C
Species D
Species E
Species FSpecies 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 FSpecies C & D shared a common ancestor in more recent times than the shared common ancestor of A-D 15
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In Groups: Discuss relationships and create a cladogram for:
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Domestic dog Fox
JackalWolf
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CQ#2: Which of the following most closely resembles your cladogram?
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Dog
Wolf
JackalFox
DogWolf
JackalFox
Dog
Wolf
Jackal
Fox
Dog
WolfJackal
Fox
A.
C. D.
B.
E. Wow, mine looks like none of these
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Canid Phylogeny
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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 is the most likely ancestor of the domestic dog.
D. The domestic dog is the most evolved of the canids.
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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%.20
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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 dog-like characteristics.
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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.
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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.
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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.
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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.
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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.
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What did humans give dogs?
• Easy access to high-quality food.• A safe “home” to raise pups.• What else…
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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.
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Phylogeny of Domestic Dog Breeds – Result of Artificial
Selection
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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
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