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Angiosperm Classification From Linnaeus to the Angiosperm Phylogeny Group and beyond. Historical concepts of relationships Linnaeus’ artificial classifications Natural classifications Molecular and Phylogenetic Revolution. Premolecular classification Artificial Natural Phylogenetic.
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PhylogeneticThe building up of a natural classification: APG versus earlier classifications
Perception of plant form has to be seen in a philosophical context as the encounter of man with plants
Either as a man-centered approach…
or as a perception of the real nature of things…
Early natural history work was motivated by the need to contemplate and understand ‘Gods work’
His merit is that he showed that the basic unit of natural classification is not the individual but the species- a species is hold together by sex
Artificial sexual system (based entirely on reproductive structures)
Systema Naturae - the Linnean hierarchy
Phylum Spermatophyta (seed plants)
Division Magnoliophyta (flowering plants)
Class Magnoliopsida (Dicotyledons)
Genus Prunus Species Prunus avium L.
Each entity within the hierarchy is called a taxon (plur. taxa)
These classifications were termed natural because they rejected Linnaeus artificial system, but used combinations of a limited number of characters
Concept of “natural classification” in pre-Darwinian very different from ours - non evolutionary
Woody apetalous plants are primitive (Amentiferae) - advanced = increase in complexity
Woody Magnolia-like plants are primitive (Ranales) - advanced = increase in simplicity
Abundant use of phylogenetic trees: Bessey 1915, Cronquist 1981, Takhtajan 1997, Thorne 1992
Dahlgrenogram: Dahlgren 1975
Ranales most primitive Asteridae most derived
His ideas are greatly influential for twentieth century evolutionary
Subclasses are connected to each other by level of primitiveness and
Good didactic system and well documented: Families and genera of
Flowering plants (1981)
Dahlgren used a wide variety of chemical characters that he mapped on ‘Dahlgrenograms’ (a horizontal section of a tree in time.
Even if the number of characters used in the systems increased considerably over the years, the lack of a well-defined methodology for analysing data made the system more intuitive than synthetical.
The introduction of the cladistic methodology helped to solve this dilemma.
A summary of the major groups that occurred in greater than 50% of the 1000 jackknife replicates (from Soltis et al. 2000).
Basal Eudicot grade
Simplified phylogenetic tree of APG II
Gatekeeper: Hugh D. Wilson
The selection options on this page, and the menu bar below, provide various paths for exploration or comparison of four systems of flowering plant classification. Selection of a Family name will query an index of web links relating to that Family or included taxa. This 'gateway' system - eventually to include all vascular plants - is under constant revision. Current options (menu bar at the base of this page) include:
Cronquist A 'top down' view of the Cronquist System, starting with the Class/Subclass array and links to Cronquist Subclass pages. This system is used by our course text and the lab herbarium.
Takhtajan An entry to the Takhtajan System, starting with the Class/Subclass array that links to Takhtajan Subclass pages.
Thorne A similar starting view of the Thorne System, with the Subclass, Superorder selection and resolution to Subfamily on Superorder pages.
Informal elements of the Angiosperm Phylogeny Group system, with family listings in ordinal sequence where possible and full linkage to family placements of the other systems.
Select Family An alphabetical selection menu that leads to listings of family names with links to either Cronquist or Thorne classification systems or, for non-flowering vascular plants, direct access to internet data for the family via queries to a full text index of URLs.
Home Open this page. Handy if pursuit of family-level links (generated by selection of linked Family names) should lead far afield.