Taxonomy & Systemacs • These give us the background to understand the evoluon of: – Morphology – Physiology – Ecology – Life History – Geography – Etc. What are they? • Taxonomy? • Systemacs? The goals of systemacs… • Determining relaonships • Understanding evoluonary history • Describing biodiversity • This is an incredibly challenging enterprise! Why? • It is primarily an historical and inferenal science. • Relaonships become obscured as me passes. Ancestry • Regardless, evoluonary history makes us what we are today. – 50,000 years of Homo sapiens – 4-6 my as homonids – 12-18 my as great apes – 85 my as primates – 125 my as eutherians – 210 my as mammals – 525 my as vertebrates Arthropod Ancestry • Insects are shaped by 400 my of history (as insects) as well. • But now we have to sort out (who knows how many?) millions of species. The earliest known insect fossil, Rhyniognatha hirsti Phylogenecs • Systemasts group taxa Class Insecta based on the principle of Order 1 descent with Family A Family B Genus A modificaon. 1 Genus B1 Genus A Genus B • Sort taxa into a hierarchy 2 2 Genus A of Orders, Families, and 3 Genus B3 Genera. Order 2 Family C Family D Genus C1 Genus D1 Genus C2 Genus D2 Genus C3 Genus D3 Phylogenecs Genus A1 • Systemasts group Genus A2 taxa based on the Family A Order 1 principle of descent Genus A3 with modificaon. Genus B1 • Sort taxa into a Genus B2 hierarchy of Orders, Family B Genus B Family, and Genera. 3 Genus C • The goal is to 1 construct these so Genus C2 that this hierarchy Family C Order 2 Genus C reflects evoluonary 3 Genus D1 history. Family D Genus D2 Genus D3 Phylogenecs • Therefore, we want our groups to be monophylec. • Not paraphyle-c. • Not polyphyle-c. Phylogenecs • You will have a beer understanding of each individual group by learning about its: – Evoluonary history – Selecve pressures – Differences from close relaves • Note that Figure 7.2 in your book is the best current working hypothesis of the insect Tree of Life But it is an hypothesis 3rd Edition: 4th Edition: 5th Edition: Phylogenecs Review Change through time Change through time Relative position is the only thing that matters! Nodes, Tips, Internodes Sister groups: The two taxa on either side of a split. Polytomies: When resoluon of the branching diagram is difficult. Outgroups: Not part of the group in queson, but is closely related to the group. Outgroups Terminology. • Phylogenies are based on shared, derived (or unique) homologous features. These are known as apomorphies. • Synapomorphies are traits that are unique, derived, and indicate relaonships. They denote clades. • Autapomorphies are traits that are unique and derived, but do not indicate relaonships. They denote ps. • Plesiomorphies are traits shared by a number of groups, and are inherited from ancestors older than the last common ancestor. They do not denote clades. Synapomorphies, Autapomorphies, & Plesiomorphies • Insects are a very well-supported monophylec group. • Numerous recognized synapomorphies. • Let’s consider two traits: ectognathy and wings. How about metamorphosis? Are three pairs of legs a defining feature of Insecta? How or how not? Tree-thinking questions: Which is most closely related to a dragonfly: wasps, true bugs, or stoneflies? Tree-thinking questions: Which is most evolved: Lepidoptera, Orthoptera, or Ephemeroptera? Phylogenec Analysis • How do we reconstruct phylogenec trees? • Based on using characters to test hypotheses of phylogenec relaonships. • Remember that the branching diagram is the hypothesis. CHARACTERS • A set of alternave condions (character state) that are considered able to evolve one to another. • For phylogenies, these are consistent within taxa, but vary among taxa. • Must search for and evaluate homologous structures. – Must follow Recognion Criteria of Homology: 1. Similarity in posion 2. Detailed resemblance 3. Connuance through intermediate forms CHARACTERS • Types of Characters: • Morphological – Must be products of Characters evoluonary process • Physiological characters – Must be heritable • Molecular characters – What kinds of things fall under this? • Behavioral characters • Ecological characters • Geographic characters CHARACTERS A simple rule for hypothesis tesng • The more data, the beer! – This applies to tesng phylogenec relaonships as well: the more characters, the beer – Also, the more character systems, the beer. Phylogenec Analysis • How do we reconstruct phylogenec trees? • Based on using characters to test hypotheses of phylogenec relaonships. • Remember that the branching diagram is the hypothesis. Phylogenec Analysis 1. A set of data (character X taxon matrix) 2. A set of possible evoluonary trees 3. A means of evaluang the alternave trees given the data. Phylogenec Analysis 1. A set of data • Idenfy homologous (character X taxon characters and matrix) delineate alternave 2. A set of possible character states. evoluonary trees 3. A means of evaluang the alternave trees given the data. Phylogenec Analysis 1. A set of data • These are the alternave (character X taxon hypotheses. matrix) • There are a tremendous number of alternave 2. A set of possible hypotheses (e.g. with 10 evoluonary trees species, there are 3. A means of 34,459,425 possible trees) evaluang the alternave trees n!(n − 1)! given the data. 2n−1 Phylogenec Analysis 1. A set of data • Based on distribuon of using shared derived characters (character X taxon (apomorphies) to idenfy clades. matrix) • Evaluated based on maximum parsimony or maximum 2. A set of possible likelihood as the opmality evoluonary trees criterion. 3. A means of evaluang the alternave trees given the data. Which tree is preferred? • We should first invesgate the • Parsimony simplest explanaon for observed character state • Maximum- distribuons. likelihood • Minimizes the number of evoluonary events on a tree. • Maximizes apomorphic characters while mimizing homoplasious characters. Which tree is preferred? • Parsimony A – Data matrix & alternave hypotheses. B – Minimize character changes on the trees. C B Head Legs Dorsum Wings black blue orange red A A C C B A C B Which tree is preferred? • Parsimony A – Minimize character changes on the trees. B – Do so for every C character. B – Count the number of changes. A – Which is most parsimonious? C C A B Which tree is preferred? • Parsimony • Similar, but now • Maximum-likelihood opmality no longer based on principle of parsimony. • Opmality based on specified model of evolu.on. • Generally applied to molecular data. • Uses external informaon. The Insects • For now, don’t get bogged down in the details. • Today we’ll focus on the big picture and use this as a starng point for touring some of the major milestones in insect evolu.on. 1 2 3,4 5,6 Time 9 7 8 Evoluonary Milestones • Pre-adaptaons: life on land… • Each number corresponds 1. Six legs, three body to a new or improved regions. physical characterisc 2. Ectognathous mouthparts. (perhaps a mutaon or a 3. Wings. novel adaptaon) that 4. Metamorphosis. proved to have selecve 5. Foldable wings. value and was passed on 6. Indirect flight muscles. to succeeding 7. Concentraon of ganglia. generaons. 8. Sucking mouthparts. • These are cumulave. 9. Complete metamorphosis. Hexapoda 1 Six legs Three body regions • ‘Lumpers’ put all of these into the Insecta. • ‘Spliers’ separate into two classes: Entognatha & Insecta (a.k.a. Ectognatha). Entognatha • Mouthpart appendages recessed within pouch on head. Dipluran Proturan Collembolan Entognatha • Monophyly with Insecta under queson. • What features do they have in common with Insecta? Nardi et al Science 2003 Delsuc et al Science 2003 November 2014 2.5 gigabases of DNA Misof et al. Science Hexapoda monophyletic but Entognatha paraphyletic Insecta 2 ‘Apterygota’ Archaeognatha: Bristletails Paraphyletic grade of plesiomorphically wingless true insects Zygentoma:Silverfish ‘Apterygota’ What kind of development do they have? With whom do they share this? Is is plesiomorphic or derived? Pterygota 3,4 These milestones are intimately linked. What are they? Pterygota 3,4 These are synapomorphies for Pterygota. What is the plesiomorphic state for each character within the Pterygota? What is the derived state for each character? Paleoptera Monophyletic? Flight? Wings? Paleoptera Only two lineages currently But 6-8 lineages, numerous species from Carboniferous & Permian Neoptera 5,6 Milestones 5 & 6 are synapomorphies for the Neoptera. Both involved in flight. Likely provided significant advantages. The Neopteran radiaon 5,6 • Diversified and dominated in the Carboniferous. • With evoluon of conifers, boomed into three main clades: Polyneoptera, Paraneoptera, Endopterygota Polyneoptera • 10 insect orders that have remained largely unspecialized. • Mostly scavengers and herbivores. • Plesiomorphic mouthparts with mandibles for chewing or grinding solid food. Milestone 7 • Associated with a reducon in the number of abdominal 7 segments and the concentraon of neural ssue into a single abdominal ganglion • Both of these represent a departure from the primive body form of Polyneoptera in which each segment of the body was innervated by a separate pair of ganglia. • Synapomorphy for Paraneoptera + Endopterygota = the Phalloneoptera Milestone 8 • Paraneopteran lineage is 8 disnguished by adaptaons of the mouthparts for consuming liquid food by rasping and sucking or by piercing and sucking. • These insects are grouped into four orders: Hemiptera, Thysanoptera, ‘Psocoptera’, and Phthiraptera. Milestone 9: Endopterygota • Includes all insects that