Presentation on theme: "Classification & Phylogeny"— Presentation transcript:
1Classification & Phylogeny General Zoology LS2014Donald Winslow31 January 2011Hickman, Cleveland P., Jr.; Larry S. Roberts; Susan L. Keen; David J. Eisenhour; Allan Larson, and Helen l'Anson Integrated Principles of Zoology, 15th ed., McGraw-Hill, NY. Ch. 10 pp ,
2Approaches to classification Taxonomy (Linnaeus)Classified by similar charactersPheneticsQuantitative approach based on similaritySystematics (cladistics)Based on phylogeny (patterns of descent)Evolutionary taxonomyIncorporates phylogeny and similarity
4Binomial nomenclature Scientific name of a species italicized1st letter of genus name is capitalizedSpecific epithet is all lower-caseExamples:Homo sapiens (human)Sciurus niger (fox squirrel)Branta canadensis (Canada Goose)Junco hyemalis (Dark-eyed Junco)
5Subspecies A subset (lower-order taxon) of a species Trinomial nomenclatureExample: Junco hyemalis mearnsi
6Type specimens & authority Characteristics of a species were historically defined by “type” specimens kept at museums.The taxonomist who names a species is the authority for that species. The name of the authority is often given with the scientific name of the species.Example: Carduus nutans Linnaeus(musk thistle)
7Ancestral & derived characters A character is a morphological feature or other aspect of phenotype.An ancestral character is one that was present in the ancestors of a taxon.A derived character is one that appeared during the evolution of a taxon.
8Homology and homoplasy A homologous character is one that is similar between two taxa because of common descent.A homoplasic (analogous) character is one that is similar between two taxa because of convergent evolution.
9Cladistics Nested hierarchy of lineages within clades Compared with outgroupSynapomorphies useful to define cladesCladogram shows only extant species.Phylogenetic tree includes ancestors.Parsimony used to choose cladogram.Sources of phylogenetic information
10SynapomorphyDerived characterShared by all members of a clade
11ParsimonyThe simplest explanation that is consistent with the evidence is the most likely to be correct.Not necessarily likely to be correct!The cladogram that assumes the fewest character transitions is the most parsimonious.Characters may be morphological, biochemical, behavioral, cytological, etc.
12Biochemical cladistics Uses comparative approachDerives phylogenies from DNA sequencesHickman et al. PpHickman, Cleveland P., Jr.; Larry S. Roberts; Susan L. Keen; David J. Eisenhour; Allan Larson, and Helen l'Anson Integrated Principles of Zoology, 15th ed., McGraw-Hill, NY.
13Types of taxonomic classification MonophylyA monophyletic taxon includes the common ancestor of all members of the taxon and all descendants of that common ancestor.ParaphylyIncludes the common ancestor and some, but not all, descendants of that common ancestor.PolyphylyDoes not include the common ancestor.
15Sister taxaA taxon’s sister taxon is the one that shares the most recent common ancestor.
16Species concepts Basic criteria Typological species concept Common descentSmallest distinct groupingsInterbreedingTypological species conceptBiological species conceptEvolutionary species conceptPhylogenetic species concept
17Typological species concept Fixed & essential featuresDefined by type specimen
18Biological species concept Interbreeding populationReproductively isolated from other populationsDoes not work well for asexual species
19Evolutionary species concept Isolated from other populationsDistinct evolution and fateWorks for asexual species
20Phylogenetic species concept Irreducibly distinct from other groupsAlso works for asexual taxaOften involves splitting taxa into separate species