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 Podocarpus macrophyllus foliage and mature seed cones
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Acmopyle |
Podocarpaceae is a large family of mainly Southern Hemisphere conifers, with 18-19 genera and about 170-200 species of evergreen trees and shrubs. The family is a classic member of the Antarctic flora, with its main centres of diversity in Australasia, particularly New Caledonia, Tasmania and New Zealand, and to a slightly lesser extent Malesia and South America (primarily in the Andes mountains). Several genera extend north of the equator into Indo-China and the Philippines. Podocarpus reaches as far north as southern Japan and southern China in Asia and Mexico in the Americas, and Nageia into southern China and southern India. Two genera also occur in sub-Saharan Africa, the widespread Podocarpus and the endemic Afrocarpus.
Parasitaxus usta is unique as the only known parasitic conifer. It occurs on New Caledonia, where it is parasitic on another member of the Podocarpaceae, Falcatifolium taxoides.
The genus Phyllocladus, here included in Podocarpaceae on genetic evidence, is treated by some botanists in its own family Phyllocladaceae.
Taxonomy
The Podocarpaceae family shows great diversity, both morphologically and ecologically. Its members occur mainly in the southern hemisphere, with most generic variety taking place in New Caledonia, New Zealand and Tasmania. Species diversity of Podocarpus is found mainly in South America and the Indonesian islands, the latter also being rich in Dacrydium and Dacrycarpus species.
Podocarpus L’Hér. ex Pers. (with 107 species) and Dacrydium Sol. ex Forst. are the largest genera. A few genera are common to New Zealand and South America, supporting the view that the Podocarps had an extensive distribution over southern Gondwanaland. The breaking up of Gondwanaland led to large-scale speciation of the Podocarpaceae.
Until 1970 only seven Podocarpaceae genera were recognised - Podocarpus, Dacrydium, Phyllocladus, Acmopyle, Microcachrys, Saxegothaea and Pherosphaera. All the African taxa fell under Podocarpus - P. falcatus, P. elongatus, P. henkelii and P. latifolius. Taxonomists divided Podocarpus species into eight categories based on leaf anatomy (Afrocarpus J. Buchholz & N. E. Gray, Dacrycarpus Endl., Eupodocarpus Endl., Microcarpus Pilg., Nageia (Gaertn.) Endl., Polypodiopsis C.E. Bertrand (non Polypodiopsis Carriére nom. rej. prop.6), Stachycarpus Endl. and Sundacarpus J. Buchholz & N.E. Gray). Studies of embryology, gametophyte development, female cone structure and cytology, led to the belief that the eight categories probably deserved generic status. Researchers agreed on the need to recognize ‘fairly natural groupings which prove to have good geographic and probably evolutionary cohesion’ and took the necessary steps to raise each section to generic status.1
References
- ^ Barker, N.P., Muller, E.M., and Mill, R.R. (2004). A yellowwood by any other name: molecular systematics and the taxonomy of Podocarpus and the Podocarpaceae in southern Africa. South African Journal of Science, 100: 629-632.
- Quinn, C. J. & Price, R. A. Phylogeny of the Southern Hemisphere Conifers. Proc. Fourth International Conifer Conference 129-136 (2003).
External links
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Wikipedia content modification information:
- This page was last modified on 1 December 2008, at 18:37.
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