Winteraceae
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Winteraceae is a primitive family of tropical trees and shrubs including 93 species in five genera. It is of particular interest because it is such a primitive angiosperm family, distantly related to Magnoliaceae, though it has a much more southern distribution. Plants in this family grow mostly in the southern hemisphere, and have been found in tropical to temperate climate regions of Malesia, Oceania, eastern Australia, New Zealand, Madagascar and the Neotropics, with most of the genera concentrated in Australasia and Malesia. The five genera, Takhtajania, Tasmannia, Drimys, Pseudowintera, and Zygogynum s.l. all have distinct geographic extant populations. Takhtajania includes a single species, T. perrieri, endemic only to Madagascar, Tasmannia has the largest distribution of genera in Winteraceae with species across the Philippines, Borneo, New Guinea, Eastern Australia, and Tasmania, Drimys is found in the Neotropical realm, from southern Mexico to the subarctic forests of southern South America, Pseudowintera is found only in New Zealand, and Zygogynum has species in New Guinea and New Caledonia. This family has been estimated to be anywhere from 105 to at least 35 million years ago. Being one of few angiosperms forming persistent tetrads with prominent sculpturing, pollen of Winteraceae is rare but easy to identify in the fossil record.…
Winteraceae is a primitive family of tropical trees and shrubs including 93 species in five genera. It is of particular interest because it is such a primitive angiosperm family, distantly related to Magnoliaceae, though it has a much more southern distribution. Plants in this family grow mostly in the southern hemisphere, and have been found in tropical to temperate climate regions of Malesia, Oceania, eastern Australia, New Zealand, Madagascar and the Neotropics, with most of the genera concentrated in Australasia and Malesia. The five genera, Takhtajania, Tasmannia, Drimys, Pseudowintera, and Zygogynum s.l. all have distinct geographic extant populations. Takhtajania includes a single species, T. perrieri, endemic only to Madagascar, Tasmannia has the largest distribution of genera in Winteraceae with species across the Philippines, Borneo, New Guinea, Eastern Australia, and Tasmania, Drimys is found in the Neotropical realm, from southern Mexico to the subarctic forests of southern South America, Pseudowintera is found only in New Zealand, and Zygogynum has species in New Guinea and New Caledonia. This family has been estimated to be anywhere from 105 to at least 35 million years ago. Being one of few angiosperms forming persistent tetrads with prominent sculpturing, pollen of Winteraceae is rare but easy to identify in the fossil record. Pollen samples found in Gabon may indicate that the family is at least 120 million years old, but the association of these fossils with Winteraceae is uncertain. Oldest unambiguous Winteraceae fossils are from the middle to late Albian of Israel (~110 million years old; described as Qatanipollis). Pollen fossils indicate that the range has been much wider than it is now, reaching north as far as Greenland during the Paleocene (Danian), and disappearing from continental Africa (Cape Peninsula, South Africa) in the Miocene. Equally characteristic is Winteraceae wood, which lacks xylem vessels in contrast to most other flowering plants. Fossil Winteraceae wood has been found in the Late Cretaceous to Paleogene (c. 85–35 million years ago) of Antarctica (Santonian-Campanian), western North America (Central Valley, California; Maastrichian) and Europe (Helmstedt, Germany; Eocene). According to the 1998 APG I system, it did not belong to any order, but it has since been placed in Canellales by the APG II, APG III and APG IV systems.
Description
Members of the family Winteraceae are trees or shrubs. The leaves are alternate, with light green dots and a fragrant aroma. Some are used to produce essential oils. Stipules are absent. Flowers are small, mostly appearing in cymes or fascicles. They have two to six free, valvate sepals, though they are united in Drimys. The Winteraceae have no vessels in their xylem. This makes them relatively immune to xylem embolisms caused by freezing temperatures. In addition, vascular occlusion can occur near the openings of the stomata, preventing excess water from entering. Among all species, the distinctive characters of released pollen tetrads are easily recognized using light and electron microscopy.
References
External links
Chilean Winteraceae Chileflora
Text derived from https://en.wikipedia.org/w/index.php?oldid=1354640868 under CC BY-SA 4.0; modifications have been made.