Until recently, figworts were the 8th largest family of flowering plants (angiosperms), containing 275 different generations
Now less than half of the species remain in the figwort family – which is now the 36th largest among angiosperms.
- This was problematic as many of the figwort plants were too dissimilar in structure to function as a meaningful grouping
- Taxonomists attempt to group plant species by using information from many sources, such as floral and fruit morphology, embryology, wood anatomy, leaf architecture, cytology, genetic and fossil records
- Lack of uniquely defining traits raises the possibility that the figwort family are not monophyletic (i.e. contain only one clade)
- Some researchers suggested that the figwort family are polyphyletic (i.e. contains more that on clade)
- DNA sequencing of three chloroplast genes, researchers were able to determine that there were significant differences in lineage. Therefore, the entire figwort family was reclassified into six monophyletic families. However, no classification is ever complete or universally accepted and more refinements are likely in the future.
Now less than half of the species remain in the figwort family – which is now the 36th largest among angiosperms.
Reclassification of Figworts (Family Scrophulariaceae)
Nature of Science:
5.4.NOS: Falsification of theories with one theory being superseded by another- plant families have been reclassified as a result of evidence from cladistics.
Objective:
5.4.NOS: Falsification of theories with one theory being superseded by another- plant families have been reclassified as a result of evidence from cladistics.
Objective:
- Outline the reason why biological theories may change with time.
Falsification of theories with one theory being superseded by another—plant families have been reclassified as a result of evidence from cladistics.
The use of DNA sequences to classify organisms has been an important breakthrough in classification. Previously, species were classified primarily on morphology (physical characteristics), which works some of the time but is less useful in other situations. Thus seemingly unrelated organisms have been grouped more closely together and those that were thought to be very closely related have been found to be more distant. Carl Woese used gene sequencing to not only overturn the existing dogma of the 5-Kingdom system, but to also propose that Archaea are more closely related to humans (eukaryotes) than to other prokaryotic bacteria. This was a major paradigm shift in microbiology and has since been recognised as “…one of the 20th century’s landmark achievements in biology…” by Dr. Nigel Goldenfeld (“Carl Woese | Carl R. Woese Institute For Genomic Biology”).
In another example (as stated in 5.4.A2), the Figwort family of flowering plants, underwent a dramatic recent reclassification. The figworts were a large family classified under the family Scrophulariaceae and included the popular snapdragons and foxgloves. Using three genes found in the chloroplast, researchers were able to determine that there were significant differences in lineage and so an entire family had to be reclassified into six families. See Olmstead et al. (2001), full text available online, for the full scientific story.
The use of DNA sequences to classify organisms has been an important breakthrough in classification. Previously, species were classified primarily on morphology (physical characteristics), which works some of the time but is less useful in other situations. Thus seemingly unrelated organisms have been grouped more closely together and those that were thought to be very closely related have been found to be more distant. Carl Woese used gene sequencing to not only overturn the existing dogma of the 5-Kingdom system, but to also propose that Archaea are more closely related to humans (eukaryotes) than to other prokaryotic bacteria. This was a major paradigm shift in microbiology and has since been recognised as “…one of the 20th century’s landmark achievements in biology…” by Dr. Nigel Goldenfeld (“Carl Woese | Carl R. Woese Institute For Genomic Biology”).
In another example (as stated in 5.4.A2), the Figwort family of flowering plants, underwent a dramatic recent reclassification. The figworts were a large family classified under the family Scrophulariaceae and included the popular snapdragons and foxgloves. Using three genes found in the chloroplast, researchers were able to determine that there were significant differences in lineage and so an entire family had to be reclassified into six families. See Olmstead et al. (2001), full text available online, for the full scientific story.