Dog Evolution: Exploring Phylogeny Through Wolves and Cladograms

Original created by Dr. Miriam Ferzli’s team Dog Evolution: A Case Study in Phylogeny A young boy is sitting near the edge of a cave 50,000 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 because 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 10,000 years or so. The dog diverged from a now-extinct population of wolves 40,000-27,000 years ago immediately before the Last Glacial Maximum, when much of the mammoth steppe was cold and dry ( Wikipedia 2022 ). A review of phylogenetics: ● Phylogenies can be based on morphology o Similarity of many morphological characteristics are used (color, shape, size, structure, etc.) ● Most recent phylogenies are based on molecular similarities o E.g. , Similarities of mitochondrial DNA (mtDNA) sequences o More similarities ( i.e. , fewer dissimilarities) = a closer relationship Phylogeny : The study of evolutionary relationships. Think of a phylogeny as a family tree. The following is an example of a phylogenetic tree: Part I: Analyzing a phylogenetic tree 1. Consider the entire phylogenetic tree pictured in Figure 1, a. name the outgroup: __A______ b. name the ingroup: __BCDE______ 1 Species A-D are more similar to each other than they are to either species E or F

Original created by Dr. Miriam Ferzli’s team 2. Indicate by circling, underlining, highlighting, writing here - however you can denote this - where the common ancestor for species B, C, D, E occurs. 3. Indicate by circling, underlining, highlighting, writing here - however you can denote this - where the common ancestor for species D and E occurs. 4. On the phylogenetic tree, label a branch and a node. 5. Indicate by circling, underlining, highlighting, writing here - however you can denote this - where extinct and extant species occur on the tree. Part II: Cladograms Cladograms are diagrams of phylogenetic trees and another way to look at phylogenies. They reconstruct phylogenetic trees by considering various possible pathways of evolution and then proposing plausible trees. The following diagram shows an example of a cladogram as well as several descriptions drawn from the cladogram. Figure 2: Example of a cladogram 2 Species A-D are more similar to each other than they are to either species E or F Species A & B are more similar to each other than they are to any other species Species C & D shared a common ancestor in more recent times than the shared common ancestor of A-D

Original created by Dr. Miriam Ferzli’s team Create a cladogram for domestic dogs, wolves, foxes, and jackals. Part III: Which of the following most closely resembles your cladogram? 3 Dog Wolf Jackal Fox A B C D

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Original created by Dr. Miriam Ferzli’s team 1. According to the molecular evidence shown in the cladogram below, what can you conclude about the ancestry of dogs? They have the same ancestor as grey wolves. 2. What is the outgroup in this example? a. If considering the entire grouping shown, i.indicate where a primitive shared characteristic would occur on this cladogram? ii.indicate where a shared derived characteristic would occur if analyzing the jackal, African wild dog, coyote, domestic dog and gray wolf? Part IV : When you compare wolves with dogs you find: ● Morphological comparisons o Dogs tend to have curled tails, wolves have straight tails. o Dogs tend to have smooth short coats. o Skull shape differs. ● Molecular comparisons o Gray wolves and dogs differ by no more than 0.2% in their mtDNA sequence. o In contrast, gray wolves and coyotes differ by at least 4%. Fill-in-the-blanks for two plausible hypotheses about dog evolution: So how did dogs evolve from wolves? A. Ancestral wolf pups were domesticated intentionally by early humans through ___artificial_________________ selection. B. Ancestral wolf populations experienced _natural__________________ selection forces that favored dog-like characteristics. 4

Original created by Dr. Miriam Ferzli’s team Part V: 1. Based on the hypotheses above, which hypothesis do you think is most plausible? Defend your answer by coming up with arguments for and against each hypothesis: I think A is more probable, since the wolves had to be trained to be eventually be tamed as dogs. In the wild, wolves are a lot more probable to be naturally selected than wolves with dog like features. 2. What characteristic is being selected for in the ancestral wolf population under Hypothesis 2? Loyalty and training 5

Phylogeny dog case study-Dr2 Omkar Apte

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