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Podocarpaceae is a family of conifers conisisting of 7 genera -- Phyllocladus, Podocarpus, Dacrydium, Saxegothaea, Microcachyrys, Microstrobos, and Acmopyle -- and 150 species. It is the most important conifer family in the southern hemisphere. Members of this family are natives of the tropics, subtropics and warm temperate regions of southern Africa, South America, and New Zealand, with a few species extending to Central America, the West Indies, India, China, Japan, Malaysia and the Philipines.
Podocarpus, the largest genus, includes evergreen trees and shrubs commonly called podocarps or yellow woods. With about 110 species, it is not only the largest genus in the family, but also the largest among all living conifers. The genus is unique in having the only known coniferous parasitic species, P. ustus, which parasitizes Dacrydium taxoides, another member of the Podocarpaceae.
Podocarps are important timber trees in their native areas. In South Africa for example, yellow-wood (Podocarpus latifolius) is the chief source of fine timber. They have also found their way into use as ornamental shrubs.
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Podocarp diversity : On the left, a stand of Dacrydium trees. On the right is a closeup of the foliage of Podocarpus amarus; notice the broad leaves, which are not found in most conifers.
The leaves of this family demostrate great diversity, varying in color, size, and anatomy. The color of young leaves is often red or rose-colored. At a more mature stage, they become light green. The size of the leaves range from small and scale-like to up to 35 cm long and 5 cm wide. The anatomy of leaves in this family provides some of the basis for the sectioning of genera.
An especially unusual podocarp is Phyllocladus. This genus, which includes 7 species, is unusual in that its photosynthetic organs are flattened, celery-leaf-like "phylloclades" instead of leaves. Another odd feature is that its ovules are partially enveloped in an "aril" -- a structure found only in the podocarps and Taxaceae among conifers.
The seed cones are uniform in their attachment to the primary axis and can reach sizes up to 6 cm long. Extending from each cone scale, the structure that supports the cone, is one large elongate ovule (the precursor to a seed). Sometimes, the ovule is inverted early on, eventually becoming erect, with a short, cup-like aril (ie. Dacrydium).
Seed cones in Podocarpaceae have a short, stout stalk with two or four "bracts", of which only one develops; a bract is a modified leaf. In many species, a bract fuses with the upper part of a stalk to produce a lightly colored fleshy receptacle where the seed matures. In some species, this fleshy receptacle is edible.
The seeds in this family are not all identical to one another. Sometimes, they are solitary and found within a fleshy receptacle, as in Acmopyle. In Podocarpus, the seeds have a fleshy outer coat and are borne on a woody or fleshy receptacle. Still further variation can be seen in Microcachrys. In this genus, the seed is surrounded at its base by a fleshy, scarlet aril.
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Podocarp reproductive diversity : On the left is Prince Albert's Yew (Saxegothaea conspicua) from Chile. The generic name derives from Saxe-Coburg-Gotha, the family name of Prince Albert, consort to Queen Victoria. On the right is Podocarpus nivalis, a tiny alpine podocarp from Australasia; the red "berries" are individual seeds enclosed in a fleshy aril.
Some of the significant Podocarpaceae finds have been: Stalagma, Nothodacrium, Mataia, Sqasamastrobus, and Trisacocadus. Stalgma is from the Upper Triassic of China. It has a single, inverted seed. Northodacrium is from the Jurassic of Antartica; it is unique as a woody conifer that has no division of vegetative parts into long and short shoots. Mataia is from the Jurassic of Australia and New Zealand. It is unique for having leaves which are helically arranged but twisted at the base to form two rows. Sqasamastrobus is from the Early Cretaceous of Baquero Formation, Argentina; its ovulate cones are terminal and bear bract-scales, each containing a single seed. Trisacocladus is from the Lower Cretaceous of Argentina; its pollen grains have three (rather then two) sacci extending from the distal portion of the grain.
For more information on Podocarps try the Botanical Dermatology Database or the Floridata site on Podocarpus macrophyllus
Chaw, Shu-Miaw, Huanh-Mo Sung, Huei Long, Zharkikh, & Wen-Hsiung Li. 1995. The phylogenetic positions of the conifer genera Amentotaxus, Phyllocladus, and Nageia inferred from 18S rRNA sequences. Journal of Molecular Evolution 41 (2): 224-230.
Dallimore, I.S. and Bruce Jackson. 1967. A Handbook of Coniferae and Ginkgoaceae. St Martins Press: New York.
Hora, Bayard. 1981. The Oxford Encyclopedia of Trees of the World. Oxford University Press: Oxford, New York, Toronto, Melbourne.
Johnson, Hugh. 1973. International Book of Trees - A Guide and Tribute to the Trees of Our Forests and Gardens. Mitchell Beazley Publishers Limited: New York.
Penhallow, David. 1907. A Manual of the North American Gymnosperms. Ginn and Company Publishers: Boston.
Sporne, K.R. 1965. The Morphology of Gymnosperms- The Structure and Evolution of Primitive Seed Plants. Hutchinson University Library: London.
Taylor, Edith and Thomas N. Taylor. 1993. The Biology and Evolution of Fossil Plants. Prentice Hall: Englewood Cliffs, NJ.
