Cupressaceae
Systematics
Systematics
Cupressaceae includes two families, recently merged. As a whole family, the Cupressaceae includes 29 genera and approximately 145 extant species of conifer s. The Cupressaceae (now known as the cypress family) is found in both the Northern and Southern hemisphere. The Taxodiaceae side of the family, now known as the redwood family, includes 10 genera and 15 species. The redwood family is found mainly in the Northern hemisphere.
There are some differences within the Cupressaceae family. The cypress family has inverted ovules and modified leaves on it's apical meristem shoots. The redwood family lacks these synapomorphies. Similarities between the two families include a similarly fused bract scale complex in ovulate cones and pollen that has a shallow functional germination furrow. Both families also have decussate leaf phylotaxy (leaves in opposite pairs).
A chemical analysis that may be proof of the two families being one is evidence given in the 1976 Eckenwalder study which states that the redwood genera is as similar to each other as to the cypress genera. The study compared the two families and found that they were 90% similar overall. When they were compared to other families, the similarities were only 29-59%.
These are all reasons supporting the merger of the two families into one, the family Cupressaceae. The name of the group takes that of the cypress group due to the fact that it is an older family and therefore takes precedence. The cypress family has been around since the late Triassic, while the redwood family has only been around since the mid-Jurassic.
Evidence from various studies shows that the redwood group is actually the main group. This means that the cypress group only forms a subgroup of the Cupressaceae. It has been suggested that the Cupressaceae forms a lineage distinct from other conifers. Another finding is that within the redwood group, there are at least four subgroups, one of which is the cypress group. Also, cladistic analysis shows that the redwoods and cypresses form a monophyletic grouping. Even with all this evidence, the regrouping of families--a relatively new idea--is being hotly debated.
Among the other conifers, the closest relative to the Cupressaceae family is the Sciadopitys. This is determined by synapomorphies such as both families having the same number of ovules per cone scale. However, the difference between the leaf and shoot morphologies between the two groups is enough to separate them into distinct families.
Source: Watson, F. D. Cupressaceae Bartlett: Redwood or Cypress Family. Oxford University Press, Inc., NY, NY :1993.
Hart, J. A. Cladistic Analysis of Conifers. Journal of Arnold Arboretum, v.68, n.3, (1987) p.269.
Buchholz, J.T. Generic and Subgeneric Distribution of Coniferales. Botanical Gazette v.110, n.1 (1948).
Miller, C. Mesozoic Conifers. Botanical Review v.43, n.2 (1977).
