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What is the Linnaean System of Taxonomy?. Levels of taxonomy: Kingdom , Phylum (or Division ); Class ; Order ; Family ; Genus and Species Today, all levels are intended to reflect evolutionary relatedness Developed by Carolus Linnaeus (mid 1700s), a Swedish botanist
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What is the Linnaean System of Taxonomy? • Levels of taxonomy: Kingdom, Phylum (or Division); Class; Order; Family; Genus and Species • Today, all levels are intended to reflect evolutionary relatedness • Developed by Carolus Linnaeus (mid 1700s), a Swedish botanist • Binomial Nomenclature (Linnaeus, 1758) • Each species receives a unique scientific name in Latin (common names differ by location and change over time) • Latin is a dead language (will not change), and is used internationally • Scientific names always two words (Genus species), always underlined or italicized (versus longer description in Latin); second name not used alone, lower case, often describes location species found or in honor of person • Tomato (pre-Linnaeus): Solanum caule inermi herbaceo, foliis pinnatis incises • Descriptions of Newly Discovered Species • Often identified based on their physical structure (Morphological Species Concept); taxonomists attempt to include genetic comparisons and ecological descriptions also (e.g., habitat) • Holotype and Paratypes: first known specimen and subsequent specimens described in peer-reviewed scientific journal
How are Phylogenetic Relationships Determined? • Clade: an ancestral species and all of its descendents (a “branch on the Tree of Life”) • Cladistics: systematic analysis of clades and their relationships to other clades; focuses on the evolutionary innovations that define branch points in evolution (synapomorphies: shared, derived traits) • Parsimony: convergence considered more rare than homology; tree that results in fewest number of steps considered most parsimonious • Techniques • Often heavy computer memory requirements for statistical tests (bootstrapping, Monte Carlo simulations, tests of monophyly) • If multiple trees result with equal significance, relationships remain unresolved (a “bush” or polytomy) • Any single resulting tree still considered a hypothesis; best if consistent with other independent evidence (e.g., the fossil record) • Character states entered for multiple traits (ex. horns present = 1, horns absent = 0); taxa that share more homologies considered more closely related; nucleotide or amino acid sequences often used (eliminates potential bias in choice of characters)
The Evolution of Inflation in Pufferfishes Phylogenetic trees can be produced via DNA comparisons (relatively free from subjective choices of characters). Behaviors of interest then “mapped” onto tree.
