Ilex, or holly, is a genus of approximately 400 to 600 species of flowering plants in the family Aquifoliaceae, and the only living genus in that family. The species are evergreen and deciduous trees, shrubs, and climbers from tropics to temperate zones worldwide. The genus Ilex is widespread throughout the temperate and subtropical regions of the world. It includes species of trees, shrubs, and climbers, with evergreen or deciduous foliage and inconspicuous flowers. Its range was more extended in the Tertiary period and many species are adapted to laurel forest habitat. It occurs from sea level to more than 2,000 meters with high mountain species. It is a genus of small, evergreen trees with smooth, glabrous, or pubescent branchlets. The plants are generally slow-growing with some species growing to 25m tall.
The phylogeography of this group provides examples of various speciation mechanisms at work. In this scenario ancestors of this group became isolated from the remaining Ilex when the Earth mass broke away from Gondwana and Laurasia about 82 million years ago, resulting in a physical separation of the groups and beginning a process of change to adapt to new conditions. This mechanism is called allopatric speciation. Over time survivor species of the holly genus adapted to different ecological niches. This led to reproductive isolation, an example of ecological speciation. In the Pliocene, around five million years ago, the formation of the new orogeny[clarification needed] diversified the landscape and provided new opportunities for speciation within the genus.
The fossil record indicates that the Ilex lineage was already widespread prior to the end of the Cretaceous period. Based on the molecular clock the common ancestor of most of the extant species probably appeared during the Eocene, about 50 million years ago, suggesting that older representatives of the genus belong to now extinct branches. The laurel forest covered great areas of the Earth during the Paleogene, when the genus was more prosperous. This type of forest extended during the Neogene, more than 20 million years ago. Most of the last remaining temperate evergreen forests are believed to have disappeared about 10,000 years ago at the end of the Pleistocene. Many of the then existing species with the strictest ecological requirements became extinct because they could not cross the barriers imposed by the geography, but others found refuge as a species relict in coastal enclaves, archipelagos, and coastal mountains sufficiently far from the extreme cold and aridity and protected by the oceanic influence.
Plants in this genus have simple, alternate glossy leaves, typically with a spiny toothed, or serrated leaf margin. The inconspicuous flower is greenish white, with four petals. They are generally dioecious, with male and female flowers on different plants, although there are exceptions.
The small fruits of Ilex, although often referred to as berries, are technically drupes. They range in color from red to brown to black, and rarely green or yellow. The "bones" contain up to ten seeds each. Some species produce fruits parthenogenetically, such as the cultivar 'Nellie R. Stevens'. The fruits ripen in winter and thus provide winter color contrast between the bright red of the fruits and the glossy green evergreen leaves. Hence the cut branches are widely used in Christmas decoration. The fruits are generally slightly toxic to humans, and can cause vomiting and diarrhea when ingested. The berries of various species contain Theobromine, a compound similar to caffeine. In very small doses, theobromine and other caffeines only mildly stimulate the nervous system. However larger amounts can cause dizziness, stomach pain, nausea, diarrhea, elevated pulse rate, and low blood pressure, as well as drowsiness.
Berries attract birds that eat them after the frosts have reduced toxicity. However, if household pets ingest Holly, they are very liable to be poisoned, and it is a very good idea to keep holly decorations out of reach of pets and/or children.
Several holly species are used to make caffeine-rich herbal teas. Ilex paraguariensis is boiled for the popular reinvigorating drinks The South American Yerba Mate, and Chimarrão, and steeped in water for the cold Tereré. Ilex guayusa is used both as a stimulant and as an admixture to the entheogenic tea ayahuasca; its leaves have the highest known caffeine content of any plant. In North and Central America, Ilex vomitoria (Yaupon) was used by southeastern Native Americans as a ceremonial stimulant and emetic known as "the black drink". As the name suggests, the tea's purgative properties were one of its main uses, most often ritually. Ilex glabra is a milder substitute for Yaupon and does not have caffeine. In China, the young leaf buds of Ilex kudingcha are processed in a method similar to green tea to make a tisane called kǔdīng chá (roughly "bitter spikeleaf tea").
Between the thirteenth and eighteenth centuries, before the introduction of turnips, holly was cultivated for use as winter fodder for cattle and sheep. Less spiny varieties of holly were preferred, and in practice the leaves growing near the top of the tree have far fewer spines making them more suitable for fodder.
Holly was also once among the traditional woods for Great Highland bagpipes before tastes turned to imported dense tropical woods such as cocuswood, ebony, and African blackwood.
Article excerpt is from Wikipedia.org under the Creative Commons License.
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