BIOL2610: Biodiversity, Ecology, and Evolution PDF

Name: ________________________________________ BIOL2610: BIODIVERSITY, ECOLOGY AND EVOLUTION PHYLOGENETIC TREES. Today we are working on how to build and interpret a phylogenetic tree. A phylogenic tree is a hypothesis about the evolutionary r...

Name: ________________________________________ BIOL2610: BIODIVERSITY, ECOLOGY AND EVOLUTION PHYLOGENETIC TREES. Today we are working on how to build and interpret a phylogenetic tree. A phylogenic tree is a hypothesis about the evolutionary relationships between groups (in our example these groups are species of animals). We are using a representation of the evolutionary relationships of animals called a cladogram. See an example of a cladogram in FIGURE 1. The lines connecting the animals are called branches and the branches connect at nodes. _____________________________________________________________________________ Co on Tail Black Bear Rabbit Coyote  2.  1. FIGURE 1: CLADOGRAM OF A BLACK BEAR, A COYOTE, AND A COTTONTAIL RABBIT. The nodes 1 and 2 are indicated. _____________________________________________________________________________ To estimate the evolutionary relationships of the animals in FIGURE 1, pick two animal species. Trace the branches from the top of the diagram until the branch connects to the branch that leads to the other species of animal. Species-pairs that join closer to the top of the tree are more closely related than species-pairs that join near the bottom of the tree. The Cottontail Rabbit branch and the Black Bear branch meet at node 1. The Cottontail Rabbit branch and the Coyote branch meet at node 2. Since node 2 is closer to the top of the figure, Cottontail Rabbit and the Coyote are more closely related than Cottontail Rabbit and the Black Bear. An important corollary is that the Black Bear is equally related to the Coyote and the Cottontail Rabbit because to trace from the Black Bear to any other animal in the tree you must go through node 1. Page 1 of 7 Each branch signifies evolutionary transitions (new traits). Each branch indicates evolutionary transitions (traits) that occurred in the ancestor to the species along that branch. You can identify the evolutionary transition on a branch, and all the taxa along that branch have those traits (see FIGURE 2). _____________________________________________________________________________ Co on Tail Black Bear Rabbit Coyote C.  D.   E.  B.  A. FIGURE 2: CLADOGRAM OF A BLACK BEAR, A COYOTE, AND A COTTONTAIL RABBIT. The evolutionary transitions at branches A, B. C, D, and E are indicated. All animals above transition A have four legs, all animals above transition B have pointed ears. Animal that are on the branch labeled C have a large body size. Animal that are on the branch labeled D have a non-retractable claws. Animal that are on the branch labeled E have obligatory nasal breathing. _____________________________________________________________________________ Taxa can be added to cladograms: If you are interested in additional species relationships, they can be added to the cladogram based on their traits. For example, we know that a Jack Rabbit shares many traits with Cottontail Rabbits. In particular, both species of rabbit have four legs, pointed ears, and obligatory nasal breathing. Notice how the addition of one more rabbit does not change the relationships of the other species on the graph. _____________________________________________________________________________ FIGURE 3: CLADOGRAM OF BLACK BEARS, COYOTES, AND COTTONTAIL AND JACK RABBITS. _____________________________________________________________________________ Page 2 of 7 Data to build Cladogram: In order to build a phylogenetic tree, one must tabulate the differences between the species of interest. A table of the relevant species and traits that may be similar or different is useful. We are going to consider the evolutionary transitions at nodes. In our Black Bear. Coyote and Cottontail Rabbit comparison we will consider the traits “four legs” and “pointed ears”. We can code each species with a “0” if the trait is not present and a “1" if the trait is present (TABLE 1). If there is no information about the trait, you may also enter a “?” (this will be treated as a “0” in our data set). _____________________________________________________________________________ TABLE 1: Coded traits of bears, coyotes, or rabbits. FILL IN THE DATA. Black Bear Coyote Cottontail Rabbit 4 legs pointed ears large body size nasal breathing _____________________________________________________________________________ Considering the data from TABLE 1, a cladogram is built by grouping more similar species in shorter branches on the tree. Because Coyotes and Cottontail Rabbit share more traits (4 legs and pointed ears), they have shorter branch lengths than to the Black Bear. Compare the data on TABLE 1 and images on FIGURES 2 and 3. 1. Build your own Cladogram – collecting data: Use the information provided in the species descriptions below to develop your own data set on the species. FILL IN TABLE 2- which is the last page of this handout. Detach the page so you can use the following information to enter data in the table. You will then use your table of coded characteristics to build a phylogenetic tree (page 5 of this hand-out). Some general definitions about birds: The term “fowl” refers to a couple of characteristics in birds including a relatively large number of offspring and precocious (born well developed) young. There are two major groups- land fowl (chickens and pheasants) and waterfowl (ducks and geese). The term “land birds” are birds that spend a majority of their time in a terrestrial habitat. Page 3 of 7 Classification information about Orders of Birds: Peacocks (Galliformes): Peacocks are considered “land fowl” (not waterfowl). They are often used as an example of sexual selection as males have spectacular feather displays. Their bills are adapted to eating grains and have a general shape (not hooked or short). They are not considered land birds or perching birds. Ducks (Anseriformes): Duck feathers have special adaptation for living in/on water. Their bills are also specialized for the aquatic lifestyle, so they are large and flat. Ducks are our example in the waterfowl group, which excludes them from perching or the land birds group. Doves (Columbiformes): A single Dove feather is a symbol of protection. These birds are not considered fowl, land birds or perching birds. Their short pointed bills are adaptations to eating plant seeds. Parrots (Psittaciformes): Parrots are loud birds with very colorful feathers. They are considered land birds. They have large hooked bills that help them eat large fruit. They are not fowl, but are non-perching land-birds. Falcons (Falconiformes): Falcon wing feathers make the shape of a “V” as they are swift fliers that can swoop down and capture animal prey with their hooked bills and tear apart the flesh. They are not considered fowl or perching birds but are “land birds”. Songbirds (Passeriformes): Songbirds are our example of perching birds and are also land birds. Their songs and beautiful feathers maybe be a sexually selected trait (like the feathers in the other “fowl”group). You can see many adaptation of bill size and shape for different feeding habits, but code all the bill feeding characters here as a “0”. 2. Build your own Cladogram – tracing evolutionary transitions: Consider the data from Table 2 to fill in the species on the cladogram in Figure 4. Follow these directions to build your tree. 2.1 What trait does every individual on the tree have? This is the character on the very lowest branch of the tree. 2.2 The next lowest character is splitting birds into “fowl” and “not fowl”. Label these two characters above the first node. 2.3 Follow the “fowl” branch up and fill in the terminal character and taxa. 2.4 Now concentrate on the other major branch. There is only one bird left that is not a land bird. Place that group in the middle branch and fill in the special characteristic. 2.5 Label the taxa on the right, the only “perching bird” group. 2.6 The two groups that are left share on adaptation, fill in that characteristic. 2.7 Fill in the final characteristic that distinguishes the last two taxa and name the fruit eater! Page 4 of 7 _____________________________________________________________________________ FIGURE 4: CLADOGRAM OF ORDERS OF BIRDS _____________________________________________________________________________ When you are finished, be certain that each species box along the top of the tree and each evolutionary transition along the branched are filled in. Page 5 of 7 3. Interpretation: Discuss the phylogenetic trees and these concepts. 3.1 What species is more closely related to Falcons? A. Doves B. Songbirds 3.2 Which is the most closely pair? A. Peacocks and Ducks B. Doves and Songbirds C. Equally related 3.3 What trait is found in Parrots and Falcons, but not songbirds. A. “land birds” B. perching C. hooked bill D. short bill 3.4 Name all the species that have a common ancestor that is considered fowl. 3.5 Name all the species that have a common ancestor that are land birds. 3.6 List the species that do not have feathers. 3.7 Which is most closely related? A. Peacocks and Songbirds B. Peacocks and Parrots C. Equally related 3.8 Did Parrots evolve from Falcons? Explain your answer. Page 6 of 7  PHYLOGENETIC TREES. TABLE 2: CODED TRAITS OF ORDERS OF BIRDS. 1 = CHARACTER PRESENT 0 = CHARACTER ABSENT ? =NO INFORMATION Duck Falcons Songbirds Peacocks Parrots Doves s short bill bill adapted for tearing flesh water fowl land fowl hooked bill feathers fowl not fowl perches land birds Page 7 of 7