Autapomorphy

Phylogenetic similarities: These phylogenetic terms are used to describe different patterns of ancestral and derived character or trait states as stated in the above diagram in association with synapomorphies.[1]

• Homoplasy in biological systematics is when a trait has been gained or lost independently in separate lineages during evolution. This convergent evolution leads to species independently sharing a trait that is different from the trait inferred to have been present in their common ancestor.^[9][10][11]
  • Parallel Homoplasy – derived trait present in two groups or species without a common ancestor due to convergent evolution.^[12]
  • Reverse Homoplasy – trait present in an ancestor but not in direct descendants that reappears in later descendants.^[13]
• Apomorphy – a derived trait. Apomorphy shared by two or more taxa and inherited from a common ancestor is synapomorphy. Apomorphy unique to a given taxon is autapomorphy.^{[14][15][16][17]}
  • Synapomorphy/Homology
    – a derived trait that is found in some or all terminal groups of a clade, and inherited from a common ancestor, for which it was an autapomorphy (i.e., not present in its immediate ancestor).
  • Underlying synapomorphy – a synapomorphy that has been lost again in many members of the clade. If lost in all but one, it can be hard to distinguish from an autapomorphy.
  • Autapomorphy – a distinctive derived trait that is unique to a given taxon or group.[3]
• Symplesiomorphy
  – an ancestral trait shared by two or more taxa.
  • Plesiomorphy – a symplesiomorphy discussed in reference to a more derived state.
  • Pseudoplesiomorphy – is a trait that cannot be identified as neither a plesiomorphy nor an apomorphy that is a reversal.^[18]
• Reversal – is a loss of derived trait present in ancestor and the reestablishment of a plesiomorphic trait.
• Convergence – independent evolution of a similar trait in two or more taxa.
• Hemiplasy^[19][20]

References