Taxodiaceae

Evolution

In earth's history Taxodiaceae were widespread. They are known since the Jurassic and can be found as fossil from Tertiary times.

Systematics

The Taxodiaceae were circumscribed as one of seven conifer families by Robert Pilger in 1926.

In 1976, James Eckenwalder proposed that the Cupressaceae be merged with the Taxodiaceae, a circumscription which has since become consensus.

Prior to Eckenwalder's merger of the Taxodiaceae and the Cupressaceae, the generally accepted scheme was Pilger's, which split the then-pinaceae into seven families: the Taxaceae, Podocarpaceae, Araucariaceae, Cephalotaxaceae, Pinaceae sensu strictu, Taxodiaceae, and Cupressaceae.

Prior taxonomists had historically also suggested combining the Taxodiaceae and Cupressaceae on the basis of such factors as their gametophytes and embryology, or had otherwise grouped the conifers in unusual ways, but these studies were largely ignored due to questionable methodologies and insufficient evidence. Eckenwalder, however, by gathering vast amounts of morphological data (pertaining to embryology, morphology, anatomy, and chemistry), and computing composite “similarity values” aggregating all of these traits, made a newly convincing case that the Taxodiaceae and Cupressaceae were as similar to each other as groups classed in the same families elsewhere.

Recent papers concur with Eckenwalder, offering supporting genetic evidence, including from the DNA sequencing of rbcL plastids, and ultimately finding that, together, the Cupressaceae sensu strictu and the Taxodiaceae, with the removal of Sciadopitys verticillata, form a monophyletic group.

References

References

1. Tsumura, Y.. (1995-12-01). "Molecular phytogeny of conifers using RFLP analysis of PCR-amplified specific chloroplast genes". Theoretical and Applied Genetics.
2. Pilger, R. (1926). "Coniferae.". A. Engler. Die natürlichen Pflanzenfamilien..
3. Eckenwalder, J. E.. (1976). "Re-evaluation of Cupressaceae and Taxodiaceae: A proposed merger". Madroño.
4. Liu, Xin-Quan. (2022). "Phylogeny and evolution of Cupressaceae: Updates on intergeneric relationships and new insights on ancient intergeneric hybridization". Molecular Phylogenetics and Evolution.
5. Saxton, W. T.. (July 1913). "The Classification of Conifers.". New Phytologist.
6. Brunsfeld, Steven J.. (1994). "Phylogenetic Relationships Among the Genera of Taxodiaceae and Cupressaceae: Evidence from rbcL Sequences". Systematic Botany.