Systematics, Taxonomy and Conservation. Part I: Build a phylogenetic tree Part II: Apply a phylogenetic tree to a conservation problem

Transcription

1 Systematics, Taxonomy and Conservation Part I: Build a phylogenetic tree Part II: Apply a phylogenetic tree to a conservation problem

2 What is expected of you? Part I: develop and print the cladogram there is only one most parsimonious configuration Part II: Answer each question succinctly Timing: Today: Get started Next Tues: Review of progress Next Thurs: Due

3 PART I: BUILD A PHYLOGENETIC TREE

4 Cladogram terminology Morphe means form in Greek: apomorphy, plesiomorphy both mean a certain kind of form. Plesio means near in Greek so plesiomorphies are near the ancestral type. Apo means away from in Greek so apomorphies are away from the ancestral type. Syn- comes from a Greek root meaning with. Clad comes from the Greek meaning branch cladogram, clade, cladistics, all have to do with branch diagrams. Phyl comes from phulon, a Greek word for tribe or race. Many tribes vs. one tribe. Poly means many and mono means one, so polyphyletic vs. monophyletic.

5 Concepts Taxonomy The creation of classifications for organisms Creation of names for groups Systematics an attempt to understand the evolutionary relationships among living things allows making testable, falsifiable hypotheses about how things evolved Cladistics is the method for inferring relationships among organisms.

6 Fundamental idea of cladistics A members of a group share a common evolutionary history more closely related to each other than to other organisms not in their group. These groups share unique features not present in their more distant relatives. These shared derived characteristics are called synapomorphies.

7 All families of winged flies have unique set of hind wings: halteres

8 Assumptions 1. Organisms are related by descent from a common ancestor 2. There is a bifurcating pattern of cladogenesis; that is, when speciation happens, it generates two new lineages where there was one before 3. Change in characteristics occurs in lineages over time and can be passed on to descendants

9 How do we do a cladistic analysis? Choose a group of organisms plus an outgroup - a taxon closely related to the group you are studying but that does not belong to it. Determine the characters, or features, of the organisms and examine each taxon to determine the character states. Determine the polarity of characters; that is, whether each character state is primitive or derived. If a character state is present in the outgroup, then it is provisionally assumed it is the primitive state of the character. Group taxa by synapomorphies, or shared derived characteristics. Remember, shared primitive characteristics, or symplesiomorphies, are not phylogenetically informative.

10 In practice Draw your results as a cladogram a branching diagram that represents an evolutionary tree Two species that share a branch are closer relatives than species that do not share that branch Tick marks on the branches indicate the evolution of a synapomorphy Every species above the tick mark shares the synapomorphy

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12 Your exercise Unite taxa by synapomorphies Construct the cladogram including all the groupings you found Label each change between primitive and derived states for each character Count the total changes

13 An example not the answer!

14 PART II: APPLY A PHYLOGENETIC TREE TO A CONSERVATION PROBLEM

15 Map of Galapagos including shell types of giant tortoises typical to each island

16 Generalized phylogenetic relationships among giant Galapagos tortoises PINTA 1 ind. Volcan Wolf "Alien type 1 ESPANOLA 1,000 inds. SANTA FE Extinct (bone fragment) SAN CRISTOBAL 3,000 inds SANTA CRUZ FATAL 40 inds FLOREANA Extinct (bone fragment) Volcan Wolf "Alien type 2 ISABELA WOLF VOLCANO 12,000 inds SANTIAGO 2000 inds PINZON 800 inds SANTA CRUZ - CERRO MONTURA 3 inds SANTA CRUZ LA RESERVA 5000 inds ISABELA DARWIN VOLCANO 400 inds ISABELA ALCEDO VOLCANO 6000 inds Volcan Wolf "Alien type 3 ISABELA SIERRA NEGRA VOLCANO 100 inds ISABELA CERRO AZUL 1,000 inds Chilensis - outgroup

17 Six questions to address with the tortoise tree 1. The sole surviving tortoise from Pinta island was always kept in captivity with individuals from Volcan Wolf? Were they the best option? If the Pinta tortoises are indeed extinct which population would be the best option to restore tortoises to Pinta (and why?) 2. Santa Cruz / Cerro Fatal is in very small numbers and was just discovered is it a significant taxon worth saving? It will cost a lot of money and time to do so. Is it worth it? 3. Santa Cruz / Cerro Montura is nearly extinct. Should a last ditch effort be made to rescue it? Note that this population occurs right beside an anchorage whalers used to use commonly. It will cost a lot of money and time to do so. Is it worth it? 4. The Sierra Negra is heavily affected by poachers by the Cerro Azul population is secure does poaching on Sierra Negra pose a substantial risk for loss of genetic diversity in giant Galapagos tortoises? 5. Whalers left a large mix of giant tortoises on Volcan Wolf that do not fit neatly into the local population these are call aliens. Which of the alien samples are of most interest to conservation, which the least, and why? 6. The Santa Fe species has long been extinct. For an analog species to restore tortoises as ecosystem engineers on Santa Fe island, which extant taxon might be most appropriate?

18 What is expected of you? Part I: develop and print the cladogram there is only one most parsimonious configuration Part II: Answer each question succinctly Timing: Today: get started Tues: Review of progress Thurs: Due