- APG Classification system is referred to a Angiosperm Group Classification system
- In the past, many classifications were done by individual botanists or small groups. The result is large numbers of systems such as…
- APG classification systems were published in 1998,2003,2009,2016. These classifications are independent of morphological characters. Less convergent evolution of characters. Many more characters, molecular data, DNA sequences
Principles of the APG system
- The Linnaean system of orders and families should be retained.
- Groups should be monophyletic.
- A broad approach defines the limits of the group’s orders and families. – When feasible, without going against the underlying criterion for monophyly, families with just one genus and orders with only one family are avoided.
- The term “clades” refers to a level above or concurrent with orders and families.
APG I
The main reason existing systems were rejected was that they were not phylogenetic. This classification is primarily based on genetic characteristics. Only a small number of families had been thoroughly investigated in 1998, but the main goal was to get a consensus on the nomenclature of higher orders.
Above the order level, named clades are employed instead of scientific names.
Although there are still 25 families of “uncertain position,” a significant number of taxa whose categorization had previously been ambiguous are assigned positions.
Alternative classifications are provided for some groups. The number of families can be considered separate or merged into a single, more prominent family. The Fumariaceae can be treated as a separate family or as part of the Papaveraceae.
A significant outcome of the classification was the disappearance of the traditional division of flowering plants into two groups, monocots, and dicots.
APG II
The “basal clades” that new orders must accommodate the first system left as families.
- The system now contains many of the previously unplaced families.
- Several significant families are restructured.
APG III
- The outline of the system remains unchanged, but the number of previously unplaced families and genera is significantly reduced. Instead of the 457 families in the APG II system, the APG III system has just 415 families.
APG IV
Using massive gene banks, including those with plastid, mitochondrial, and nuclear ribosomal origins
- The system’s general structure does not alter, but the new orders Boraginales, Dilleniales, Icacinales, Metteniusiales, and Vahliales are now part of it.Boraginales, Dilleniales, Icacinales, Metteniusiales, and Vahliales.
- Two new additional informal major clades – Superrosids & Superasterids are proposed.
- Some previously recognized families are lumped.
JUMP TO THE APG 4 – Green Plant Phylogeny – https://learnplantscience.com/green-plant-phylogeny/
JUMP TO THE Major clades in APG – https://learnplantscience.com/major-clades-in-apg