Entomology 301 Lecture

• Phylogeny is a hypothesis of evolutionary relationships among organisms.

Systematics

• The study of biological diversity and the relationships among organisms through time.

  • Document, identify, describe species and classify them to provide a taxonomic concept (hypothesis).

  • Understand the evolutionary history of the organisms to provide the pattern of evolution.

• Phylogenetic tree is a hypothesis based on all available data (taxa and characters).

Phylogenetic Tree Research

• Timeline of phylogenetic research and publications (1904-2016).

Basic Structure of a Phylogenetic Tree

• Key components:

  • Terminals (Taxa)

  • Outgroup

  • Ingroup

  • Node

  • Branch

  • Root

• Characters: Apomorphy vs. Plesiomorphy.

• Autapomorphy: uniquely derived character.

• Synapomorphy: shared derived character.

• Symplesiomorphy: shared ancestral character.

• The concept of synapomorphy and symplesiomorphy is context-dependent.

Monophyletic, Paraphyletic, and Polyphyletic Groups

• Monophyletic group: A group of organisms which includes the most recent common ancestor of all of its members and all of the descendants of that most recent common ancestor.

• Paraphyletic group: A group of organisms which includes the most recent common ancestor of all of its members, but not all of the descendants of that most recent common ancestor.

• Polyphyletic group: A group of organisms which does not include the most recent common ancestor of those organisms; the ancestor does not possess the character shared by members of the group.

• The goal of a phylogenetic analysis is to recover a monophyletic clade grouped by synapomorphies.