Topic 2: Systematics I What is the difference between taxonomy, classification, systematics? Why is systematics important? Terminology of systematics What are important terms related to cladograms, groups & characters? What are homology and homoplasy? What is the difference between anagenesis & cladogenesis? What are the schools of thought of systematics? What are taxonomy, classification, and systematics? __________________ – The naming of organisms and their categorization. _________________ – The arrangement of organisms into groups based on trait similarity (justifying the groups). __________________ – The clustering of groups or organisms based on a unifying set of principles (evolutionary, or otherwise). 1 How would you taxonomize, classify and systematize this cuttlery? © www.visualdicationary.com 1 Taxonomy – naming and categorizing Elk Wrasse Crested Gecko Japalura Monitor Dog Boa Goby Fly Solefugid Photos © K.P. Bergmann Classification – categorization based on similarity Mammals Fishes Arthropods Squamates Photos © K.P. Bergmann Systematics – clustering of taxa based on unifying principles Photos © K.P. Bergmann 1 What are taxonomy, classification, and systematics? Taxonomy and classification are used to ________________ things Systematics is used to ___________ things Why is systematics important? “Nothing in biology makes sense except in the light of evolution.” - Dobzhansky, 1973. “The task of systematics is the creation of a general reference system and the investigation of the relations that extend from it to all other possible and necessary systems in biology.” - Hennig, 1950 (1966). What aspects of biology are informed by systematics? 2 Why is systematics important? Provides a framework for comparing species Accounts for ________ ______________ of species Species pairs spent different amount of time evolving ___________________ ___________________ Photos © K.P. Bergmann Why is systematics important? Informs about direction of evolution, how species can be compared The Evolution of Fur 2 Species 3 Species ____________________ _________________________ ____________________ _________________________ Photos © K.P. Bergmann The Terminology of Systematics Anatomy of a “Cladogram” Operational Taxonomic Unit (OTU) • Sister group • Dichotomous Topology • Polytomy • Rooted vs unrooted Modified from Pough et al., 2002. Fig. 1-3. 1 What are the types of taxonomic groups? What are characters? ____________________ – A group containing A character can comprise any quality or an ancestor and all of its descendents quantity that can be compared between the ____________________ – A group containing taxa under study. some, but not all, of an ancestor’s descendents ____________________ – A group containing taxa that lack a common ancestor The Terminology of Systematics – What are the different types of characters? Types of Characters Sarcopterygii Tetrapoda Amniota _______________ – An ancestral feature, (Lobe-finned common to taxa in the ingroup and outgroup fishes) Plesiomorphy Two sets of Shoulder 2 bones in paired fins girdle zygopodium _______________ – A shared derived feature, common to clusters of taxa of the ingroup Synapomorphy Shoulder 2 bones in Cleidoic egg girdle zygopodium _______________ – A unique derived feature, diagnostic of a taxon (OTU) in the ingroup Autapomorphy Of Tetrapoda: Of Amniota: 2 bones in Cleidoic egg zygopodium What are character states? What is character polarity? Character States – ___________________ of a Polarity – A character is polarized when the ancestral state character in the taxa being studied is determined These represent the variation that is analyzed This can give us information about the order of by systematic methods character state transformation Round Slitted Slit & pin-hole Approaches: _______________________ e.g. Pupil Clues from ontogeny shape Ancestral state widespread © K.P. Bergmann 1 What is character polarity? What do we mean by homology & homoplasy? Polarity – A character is polarized when the ancestral state is determined Homology – The fundamental similarity of a __________________________ is most prevalent character between taxa within a group Gives information about the order of character state transformation Specifically, for a character to be valid, structures compared between taxa must be of the ______________________________ (comparing apples to apples) © K.P. Bergmann What is homoplasy & how does it differ What do we mean by homology & homoplasy? from homology? Homology – comparing apples to apples. Homoplasy – The similarity of a character or structure between taxa due to _______________ Homoplasy can obscure relationships between taxa by leading to erroneous Statements of homology of characters, or Coding of character states Modified from Linzey, 2001. What is homoplasy? What is parsimony? Homoplasy is also an important evolutionary phenomenon Parsimony – The guiding principle of science, stating that the _____________ Gekko vittatus Anolis cuvieri Prasinohaema virens explanation that fits the _____________ is most likely the correct explanation © K.P. Bergmann © USDA © Afco Zoological Suppliers Williams and Peterson, 1982. 2 What is the difference between What are the different schools of cladogenesis & anagenesis? systematics? Anagenesis Cladogenesis – An evolutionary ____________ Systematics – The clustering of groups or event, where new taxa Cladogenesis organisms based on a unifying set of arise from a common principles (evolutionary, or otherwise) ancestor If the system is based on evolution, then it is Anagenesis – Evolutionary phylogenetic change in a lineage through time (________________ These underlying principles are typically evolution ______________) and parsimony What are the different schools of systematics? 1. Evolutionary Systematics (phylogenetic) 2. Phenetics (not phylogenetic) 3. *Cladistics (= “Phylogenetic Systematics”) 4. *Model-based approaches (phylogenetic) * Currently used approaches 3.