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EVOLUTION AND SYSTEMATICS

EVOLUTION AND SYSTEMATICS. http://evolution.berkeley.edu/evolibrary/article/evo_01. Understanding phylogeny. Understanding phylogeny. misconceptions. Evolution produces a pattern of relationships among lineages that is tree-like, not ladder-like. misconceptions.

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EVOLUTION AND SYSTEMATICS

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  1. EVOLUTION AND SYSTEMATICS http://evolution.berkeley.edu/evolibrary/article/evo_01

  2. Understanding phylogeny

  3. Understanding phylogeny

  4. misconceptions Evolution produces a pattern of relationships among lineages that is tree-like, not ladder-like.

  5. misconceptions There is no correlation with level of "advancement."

  6. MISconceptions For any speciation event on a phylogeny, the choice of which lineage goes to the right and which goes to the left is arbitrary.

  7. Misconceptions about humans Humans did not evolve from chimpanzees. Humans are not "higher" or "more evolved" than other living lineages.

  8. CLADE= MONOPHYLETIC POLYPHYLETIC POLYPHYLETIC

  9. Clades are nested within one another — they form a nested hierarchy

  10. Building the tree • Characters • heritable traits  • Comparable across organisms • Morphology, behavior, genetic sequences • Homologous characters

  11. Synapomorphies Basis for grouping taxa together becausethey represent the product of aunique evolutionary event

  12. Convergence - Stem succulence and “spines” in Cactaceae and Euphorbia spp.

  13. Selection of OUTGROUP • Coding of Characters • 0- ancestral • Non-zeros- derived character • Reconstruction of phylogeny • Parsimony analysis

  14. Principle of Parsimony The cladogram that is shortest – has the fewest number of steps (character state changes) – is accepted as most probable, because it minimizes the number of ad hoc hypotheses. “Entia non sunt multiplicanda praeter necessitatem.” (That does not exist which multiplies more than necessary.) Of two or more competing hypotheses, the simplest one is accepted.

  15. eXAMPLE

  16. OUTGROUP 90% Ophiorrhizeae 100% • Strict consensus of 2,023 equally parsimonious trees • 894 evolutionary steps • CI = 0.50 • RI = 0.66 Urophylleae 74% 100% Antherostele

  17. stigma style Morphology of Antherostele • subsessile inflorescence • simple dichasium cyme • inserted at leaf axils • flowers unisexual (dioecious) • Sweet-scented • Rudimentary parts present Female flower Male flower

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