Holly
Ilex or holly is a genus of over 570 species of flowering plants in the family Aquifoliaceae, and the only living genus in that family. Ilex has the most species of any woody dioecious angiosperm genus. The species are evergreen or deciduous trees, shrubs, and climbers from tropics to temperate zones worldwide. The type species is Ilex aquifolium, the common European holly used in Christmas decorations and cards.
Description
The genus 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 habitats. It occurs from sea level to more than 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 tall. The type species is the European holly Ilex aquifolium described by Linnaeus. Plants in this genus have simple, alternate glossy leaves, frequently with a spiny leaf margin. The inconspicuous flower is greenish white, with four petals. They are generally dioecious, with male and female flowers on different plants. Plants in the genus have highly similar flowers with a flower preserved in amber suggesting they have been largely unchanged for at least 38−34 million years.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 colour contrast between the bright red of the fruits and the glossy green evergreen leaves. Hence the cut branches, especially of I. aquifolium, are widely used in Christmas decoration. The fruits are generally slightly toxic to humans, and can cause vomiting and diarrhea when ingested. However, they are a food source for certain birds and other animals, which help disperse the seeds. Unfortunately this can have negative impacts as well. Along the west coast of North America, from California to British Columbia, English holly, which is grown commercially, is quickly spreading into native forest habitat, where it thrives in shade and crowds out native species. It has been placed on the Washington State Noxious Weed Control Board's monitor list, and is a Class C invasive plant in Portland.
Etymology
Ilex in Latin means the holm-oak or evergreen oak. Despite the Linnaean classification of Ilex as holly, as late as the 19th century in Britain, the term Ilex was still being applied to the oak as well as the holly – possibly due to the superficial similarity of the leaves. The name "holly" in common speech refers to Ilex aquifolium, specifically stems with berries used in Christmas decoration. By extension, "holly" is also applied to the whole genus. The origin of the word "holly" is considered a reduced form of Old English holen, Middle English Holin, later Hollen.The French word for holly, houx, derives from the Old Low Franconian *hulis. Both are related to Old High German hulis, huls, as are Low German/Low Franconian terms like Hülse or hulst. These Germanic words appear to be related to words for holly in Celtic languages, such as Welsh celyn, Breton kelen and Irish cuileann.
Several Romance languages use the Latin word acrifolium, literally "sharp leaf", hence Italian agrifoglio, Occitan grefuèlh, etc.; the usual Latin form of the word, used as the species name of the European holly, was aquifolium, but acrifolium is thought to have been the original form.
History
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 into Gondwana and Laurasia about 82million 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, mountain formation 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; the earliest records of the distinctive pollen of Ilex are from the Turonian of the Otway Basin of Australia. The earliest fossil holly fruit is known from the Maastrichtian of central Europe. Based on the molecular clock, the common ancestor of most of the extant species probably appeared during the Eocene, about 50million years ago, suggesting that older representatives of the genus belong to now extinct branches. This common ancestor lived in subtropical East Asia and the present worldwide distribution is the result of later migrations. Ilex sinica seems to be the most basal extant species. 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 20million years ago. Most of the last remaining temperate broadleaf 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 areas of extreme cold and aridity and protected by the oceanic influence.
Selected species
- Ilex ambigua - Southeastern USA
- Ilex amelanchier - Southeastern USA
- Ilex anomala
- Ilex aquifolium – European holly, English holly, Christ's thorn
- Ilex canariensis
- Ilex cassine – dahoon holly, cassena
- Ilex coriacea – gallberry
- Ilex cornuta – Chinese holly, horned holly
- Ilex crenata – Japanese holly, box-leaved holly, inutsuge
- Ilex decidua Walter – possumhaw
- Ilex gardneriana
- Ilex glabra L. A.Gray – evergreen winterberry, bitter gallberry, inkberry
- Ilex guayusa
- Ilex integra – mochi tree, Nepal holly
- Ilex kaushue
- Ilex khasiana
- Ilex latifolia – tarajo holly, tarayō
- Ilex mitis
- Ilex montana Torrey & A.Gray – mountain winterberry
- Ilex mucronata M.Powell, Savol., & S.Andrews – mountain holly, catberry
- Ilex opaca – American holly
- Ilex paraguariensis – yerba mate
- Ilex pedunculosa – longstalked holly
- Ilex perado – Macaronesian holly
- Ilex quercetorum
- Ilex rotunda — Kurogane holly
- Ilex rugosa – Tsuru Holly
- Ilex serrata – Japanese winterberry
- Ilex verticillata A.Gray American winterberry
- Ilex vomitoria – yaupon holly
Range
Ilex mucronata, formerly the type species of Nemopanthus, is native to eastern North America. Nemopanthus was treated as a separate genus with eight species. of the family Aquifoliaceae, now transferred to Ilex on molecular data; it is closely related to Ilex amelanchier.
In Europe the genus is represented by a single species, the classically named holly Ilex aquifolium, and in continental Africa by this species and Ilex mitis. Ilex canariensis, from Macaronesia, and Ilex aquifolium arose from a common ancestor in the laurel forests of the Mediterranean. Australia, isolated at an early period, has Ilex arnhemensis. Of 204 species growing in China, 149 species are endemic. A species which stands out for its economic importance in Spanish-speaking countries and in Brazil is Ilex paraguariensis or Yerba mate. Having evolved numerous species that are endemic to islands and small mountain ranges, and being highly useful plants, many hollies are now becoming rare.
Ecology
Often the tropical species are especially threatened by habitat destruction and overexploitation. At least two species of Ilex have become extinct recently, and many others are barely surviving.They are an extremely important food for numerous species of birds, and also are eaten by other wild animals. In the autumn and early winter the fruits are hard and apparently unpalatable. After being frozen or frosted several times, the fruits soften, and become milder in taste. During winter storms, birds often take refuge in hollies, which provide shelter, protection from predators, and food. The flowers are sometimes eaten by the larva of the double-striped pug moth. Other Lepidoptera whose larvae feed on holly include Bucculatrix ilecella, which feeds exclusively on hollies, and the engrailed.
Toxicity
Holly can contain caffeic acid, caffeoyl derivatives, chlorogenic acid, quercetin, quinic acid, kaempferol, tannins, rutin, caffeine, theobromine, and ilicin.Holly berries can cause vomiting and diarrhea. They are especially dangerous in cases involving accidental consumption by children attracted to the bright red berries. Ingestion of over 20 berries may be fatal to children.
Holly leaves, if eaten, might cause diarrhea, nausea, vomiting, and stomach and intestinal problems.
Holly plants might be toxic to pets and livestock.