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1 BIO171 Discussion Handout: Frogs and Phylogeny Objectives After doing the pre-discussion exercise, discussion exercise, and reviewing the material from discussion and lecture, students will be able to recognize examples, explain the knowledge, and use the knowledge in applications: 1. Phylogenies are used to communicate evolutionary history and ancestor/descendant relationship of a group of organisms 2. Monophyletic groups are groups of organisms that consist of an ancestor and ALL descendant species of that ancestor 3. Define the concepts on the vocabulary list and explain them in their own words You will be able to 1. Draw or choose a phylogeny consistent with a given evolutionary narrative 2. Use a phylogeny to discover and describe the relationships among taxa 3. Identify monophyletic groups and named, non-monophyletic groups 4. Use a matrix of character states and parsimony to infer the chronology of evolutionary changes 5. Given a specific phylogeny, give examples of the concepts on the vocabulary list Prepare yourself for your discussion activities this week ● Do all the preparation for Lecture 19, as required for the quiz due on March 26. o Read the reading guide for Lecture 19 and learn the vocabulary. Pay special attention to Lecture 19 in the coursepack, which include the “Phylogeny Concept Primer” (Canvas Files>Lecture Slides, RGs and Guiding Qs>Unit 4). o Baum, D.A. 2004. “Lec19 Introduction to phylogenetic trees and tree thinking ” (in Canvas Files>Lecture Slides, RGs and Guiding Qs>Unit 4). o Learn the learning objectives for Lecture 19 and write out ideas for the guiding questions. ● Complete the DPA. Illnesses and other circumstances The guidelines for what to do in an emergency or extraordinary circumstance or illness are here: https://umich.instructure.com/courses/575097/pages/discussion-illness-and-other- circumstances

2 Prompts for This Week’s Discussion Activities Discussion Preparation Assignment (Discussion Canvas Page, graded) These questions will be on your Discussion Canvas Page in an assignment. This is graded for completion; reasonable “wrong” answers are OK. You must answer the question that is asked. One point is awarded for fully completing this assignment. Question 1 Consider Fig. 22.21 in How Life Works (Dinosaurs and birds, p. 485). Note that the crocodile group is the outgroup of the group that contains all the other animals in the tree. a. Give an example of a monophyletic group in this phylogeny : b. Explain what makes this group monophyletic : Question 2 What is the difference between an ancestral trait and a shared, derived trait ? If needed, refer to Figure 23.2 “The family tree of the lesser and great apes” (p. 492) in How Life Works , in your answer. Question 3 Consider Fig. 31.1 “Phylogenetic tree of land plants” (p. 686) in How Life Works . One monophyletic group on this tree is the Vascular Plants and their Most Recent Common Ancestor (MRCA). i. For the Vascular Plants, what is a shared, derived trait ?____ ii. For the Vascular Plants, name one ancestral trait :___ Question 4 Draw a phylogenetic tree with at least 4 tips. On this tree, draw and label 1) an extinct lineage 2) two sister taxa 3) living (extant) taxa 4) the evolution of a trait 5) the oldest point on the tree (the root) 6) a monophyletic group (circle this group). Attach your drawing or insert your drawing into a file.

3 Main Exercise Worksheet (do this during class) 1. What is a shared, derived trait of the group, Eukarya? 2. Is the group called “Prokaryotes” a monophyletic group? Why or why not? (Hint: Review the Tree of Life from Lecture 1.) 3. How can the skills of building and/or reading a phylogeny be applied in a field other than evolutionary biology? This question is asking about uses other than studying the evolution of taxa. (Hint: Look in Lecture 19.) For this exercise, it is helpful to know that frogs usually cannot move across saltwater, because their skin is very permeable. Saltwater dehydrates frogs. The evolution of taxa is affected by geography, and geography changes. The image below shows the break-up of the super-continent, Gondwana. Much of the land that was in the supercontinent is now the continent of Africa. A phylogenetic tree is a diagram that tells a hypothesized story about the evolution of a group of organisms. 4. Based on the following narrative of the evolutionary history of Asian, African, and European frogs: A. Draw a phylogeny that illustrates the story told in the text. The first step is completed for you, below. ● As you do this, use as many terms from the lecture on phylogeny as possible and answer the bolded questions. B. Calibrate speciation events on the phylogeny. This means that you mark the time in earth’s history when the speciation occurred. C. Name the groups and tips on the phylogeny. D. Annotate the phylogeny with important information to help you understand the story.

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4 I. About 130 million years ago (MYA), the landmass that would become present day Madagascar, Seychelles and India (M-S-I landmass) separated from the supercontinent Gondwana. A species of frogs living in Gondwana was divided into two separate populations by this geologic event (see “A” above). This geographic separation caused gene flow to cease between populations and speciation followed. ● Discuss with your small group and instructor: What do we call a bifurcation in a group that leads to 2 new groups? II. The group of frogs that remained on Gondwana evolved and diverged into many species, becoming modern day African ground frog species. Draw one line representing this entire African ground frog group, do not diagram the radiation of African ground frogs. You should also: ● Time-calibrate the separation of the Gondwana frogs and the MSI frogs. ● Label the M-S-I group (hint: This is not at a tip on the phylogeny; this group will include several tips.) ● Note the one line representing the African ground frog group. III. At least one species that drifted with the M-S-I landmass split into more species when Madagascar separated from India and Seychelles about 88 MYA. At least one population drifted away on the land mass that would become Madagascar and became a new species. The descendant species of this ancestral species still live on Madagascar. (See 88MYA image above.) ● Label one line representing the Madagascar frog group at its tip . We will NOT diagram the radiation of frogs on the island of Madagascar . ● Time-calibrate the appropriate node(s) on your diagram . 130 MYA present Gon. Frogs Gon. Frogs MSI Frogs Allopatric speciation

5 IV. At least one species of India-Seychelles (I-S) frogs was divided into many small populations when there was a massive volcanic event about 65 MYA. The lava flows from this eruption left many high-altitude, small areas of frog habitat (refugia) separated by dry rocky areas that the frogs could not survive in or travel across. The frog populations in most of these refugia became extinct. However, 3 refugia populations survived and each became a separate species and, later, evolved into groups of species. That is, speciation events followed this geographic separation. ● Discuss with your small group and instructor: What is the term for a node where one group splits into more than 2 groups? ● Time-calibrate this node on your phylogeny. ● Label the refugia groups as “refugium” and put a Ⴕ on the extinct groups . V. At least one of these refugium groups became separated from the Indian landmass when the Seychelles Islands drifted away from India within about 1 million years after the volcanic event. Descendant species of this refugium group still live on the Seychelles. We drew one line representing the Seychelles group, we did not diagram the radiation of frogs on the Seychelles islands . ● Label the Seychelles group at its tip . VI. A second refugium species on the Indian landmass evolved to spend most of their adult life in the trees, while the third refugium species on the Indian landmass remained ground dwelling. We drew one branch to begin the “tree dwelling Indian frog group” and another to begin the “ground dwelling Indian frog group”. ● Use these words to describe what happened in the paragraph: character state, derived trait, most recent common ancestor, ancestral trait. ● Label the Indian ground dwelling frogs (Not a tip, yet.) ● Label the Indian tree-dwelling frogs (Not a tip yet.)

6 VII. Some of the tree dwelling and ground dwelling Indian frog species dispersed into Asia. Populations of both tree-dwelling and ground-dwelling frogs became established in Asia. The Indian subcontinent collided with the Eurasian landmass about 56 MYA. This is the cause of the Himalaya mountain range. Eventually, the Himalaya mountain range grew very tall and separated India from the rest of Asia, such that the Asian and Indian populations of each species were geographically isolated from each other. When speciation begins with the cessation of gene flow because of a geographic barrier, we call this a “vicariance” event and the speciation is allopatric speciation. (This is a preview of later material.) ● Calibrate the geographic splits of the tree-dwelling and ground-dwelling groups. ● You can now label one tip as the “ground dwelling Indian frogs” and another tip as the “tree dwelling Indian frogs.” ● Label the tree-dwelling groups in Asia. (No tips yet.) VIII. From Asia, some tree frog populations dispersed overland to Africa and established an isolated population of African tree frogs. Speciation followed, partially due to changes in geography that isolated the Asian and African populations from each other. At present, there are many species of African tree frogs, but we collapsed this radiation into one branch. ● Label one tip as the Asian tree frogs. ● Label one tip as the African tree frogs. ● You should already have a tip labeled as the Indian tree frogs. IX. Some of the Asian ground frogs dispersed to Europe and established an isolated European ground frog population. Speciation followed, partially due to changes in geography that isolated the Asian and European populations from each other. At present, there are many species of European ground frogs; however, we collapsed this group into one branch. ● Label one tip as the Asian ground frogs. ● Label one tip as the European ground frogs. ● You should already have a tip labeled as the Indian ground frogs. ● Discuss with your small group and instructor: Where are the African ground frogs on your phylogeny?

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7 Narrative adapted and figure copied from Bossuyt, F. and M.C. Milinkovitch (2001) Amphibians as indicators of early tertiary "out-of-India" dispersal of vertebrates. Science 292(5514):93-5. 5. Using the trait matrix below, map the character state changes onto the phylogeny you drew. Assume the ancestral traits of the frogs in Gondwana were: 1. ground dwelling 2. ate insects 3. gray skin 4. no cold tolerance 5. no poison Hints: 1) You should already have a phylogeny drawn based on the information from the first page. If you do not, draw that first. Check your phylogeny with an instructor before you do any trait mapping. 2) Pick ONE trait (one column) to work with at a time. Use the principle of parsimony to determine the most parsimonious way in which this trait could have evolved. 3) Work top to bottom within each column, NOT left to right. Habitat Primary diet Skin color Cold tolerance Presence of poison Asian tree frogs Tree Small vertebrates Green No No African tree frogs Tree Insects Green No No Indian tree frogs Tree Small vertebrates Green No No Asian ground frogs Ground Insects Brown Yes Yes European ground frogs Ground Worms Brown Yes No Indian ground frogs Ground Insects Brown Yes No Seychelles ground frogs Ground Insects Brown No No Madagascar ground frogs Ground Insects Gray No No African ground frogs Ground Insects Gray No Yes

8 Discussion Questions – Do these after you build the phylogeny and map traits. 6. Are African tree frogs more closely related to African ground frogs or to Indian ground frogs? Explain your answer. (Hint: How long ago did African tree frogs share a common ancestor with African ground frogs? With Indian ground frogs?) 7. Look at the matrix on the page above and at the phylogenetic tree that you created, are any of these shared, derived traits of any monophyletic group(s)? If so, state the group(s) for which these are monophyletic traits. 8. How would you describe the evolutionary relationships of modern African, Asian, and Indian tree frogs? Use these terms in your answer: common ancestor, shared, derived trait(s), monophyletic (or not monophyletic). 9. Which of the following is a/are monophyletic group(s)? Explain your answer. A. Tree frogs B. African frogs C. Indian frogs 10. Give an example of a similarity between two frog taxa that is likely due to analogy, rather than homology. 11. The different diets of tree frogs could have evolved by convergent evolution or a reversal (evolution back to the ancestral state). A. For the hypothesis of convergent evolution , indicate where on the tree the dietary changes took place. B. Consider the place on the tree where you hypothesize convergent evolution. Propose an equally parsimonious arrangement that, instead of convergence, hypothesizes one change in diet followed by a second change back to the ancestral character state. 12. In this exercise, you were given the ancestral character state for all the traits of interest on this phylogenetic tree. How do evolutionary biologists figure out what the ancestral character state is? Hint: Look at slide 1926.

WK13+disc+handout+frogs+and+phylogeny+STDT

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