Pontic rhododendron

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Pontic rhododendron
Pontic rododendron struik (Rhododendron ponticum) .jpg

Pontic Rhododendron ( Rhododendron ponticum )

Systematics
Class : Bedecktsamer (Magnoliopsida)
Asterids
Order : Heather-like (Ericales)
Family : Heather family (Ericaceae)
Genre : Rhododendrons ( Rhododendron )
Type : Pontic rhododendron
Scientific name
Rhododendron ponticum
L.
Flowers of Rhododendron ponticum

The Pontic Rhododendron , rarely Pontic Alpine Rose, ( Rhododendron ponticum ) is a species of the heather family. It is native to Southern Europe and Southwest Asia .

description

R. ponticum is an upright shrub with heights of two to five, exceptionally up to eight meters, on the Iberian Peninsula only up to three meters. The growth begins monopodially , older specimens branch, whereby the shoots bend to the side and then form extensive thickets. The twigs are green when young and change color to yellowish to red to gray-brown with age. The leaves are evergreen , 8 to 22 (-25) inches long and 2 to 9 inches wide. They are elongated, elliptical to lanceolate with a wedge-shaped base and a pointed apex, the entire leaf margin is slightly rolled down, the upper side of the leathery leaves is dark green and shiny, the underside of the leaf is noticeably lighter than the upper side. The leaves are glabrous on both sides and hairless, the leaf blade is about ten times as long as the petiole.

The weakly zygomorphic flowers sit in compact, short terminal clusters with about eight to fifteen individual flowers each, they are short stalked. The sepal lobes are short and inconspicuous, triangular to rounded. The corolla is about four to six inches long, with a basal flower tube and five somewhat longer bell- to funnel-like corolla lobes, the top one being somewhat larger and often brown-orange spotted or striped. The petals are quite variable in color from pink to purple-violet, rarely white. The ten stamens are weakly curved and slightly hairy in the outer half, and the stylus is long and bent.

The fruit is a lignified capsule 1.5 to 1.8 centimeters long, which remains on the plant for up to three years, with numerous small seeds .

The species can be distinguished from other wild species within its range by the relatively large, bare leaves on both sides. Cultivated plants form numerous hybrids and cannot easily be determined by species.

Systematics

The Pontic Rhododendron belongs to the subgenus Hymenanthes , which comprises a good 200 species with a distribution focus in China and Southeast Asia, and thus almost a quarter of the species diversity within the genus. It forms the subsection Pontica with about 10 other species , the species of which occur in warm-temperate areas of North America, southwest and northeast Eurasia. The subsection Pontica in its previous definition is probably not monophyletic. It is possible that some species go back to hybridization events with species from other sections of the subgenus.

Two subspecies are described:

  • Rhododendron ponticum subsp. ponticum , occurring from Bulgaria eastwards to Georgia
  • Rhododendron ponticum subsp. baeticum (Boiss. & Reut.) Hand.-Mazz. from Spain and Portugal There are three small relic areas, in humid , rainy mountain areas north of the Strait of Gibraltar, with the largest population in the Sierra del Aljibe , a foothill of the Sierra Morena . It is a relic occurrence that today can almost only reproduce vegetatively. The following are given as distinguishing features: leaves somewhat smaller and narrower, the inflorescence axis hairy. Plants with this combination of characteristics occasionally appear in the area of ​​the typical subspecies, so that not all botanists recognize the subspecies.

The botanist Joseph Pitton de Tournefort described the species during his travels to the Middle East from 1700 to 1702. Therefore it was named by Linnaeus with the species name "ponticum" after the ancient name of the Black Sea Pontos Euxeinos . At the other end of its natural range, Linné's friend and correspondent Claes Alströmer found him together with Oleander . This double specification is taxonomically problematic, as type material in the Linnés Herbarium is only available from Spain. So, according to the rules of nomenclature, the Spanish subspecies should actually receive the name ponticum . This is why some botanists have applied to the ICBN to write down the names of the subspecies in their current use.

According to the genetic data, the feral populations in Great Britain and Ireland come from the Iberian Peninsula, not the Black Sea. In addition, crossings of the (American) Rhododendron catawbiense and Rhododendron maximum were found in the overgrown stands , especially in the northern parts of the range, so that the cold resistance of the Scottish occurrences may be due to this.

distribution

The Pontic Rhododendron has three disjoint natural ranges. The main area of ​​distribution is the mountain range of the Pontic Mountains south of the Black Sea in Turkey and the eastern adjacent western Caucasus , in Georgia and Russia. It grows here in the undergrowth of forests, but also forms bushes up to the subalpine altitude, above 2400 meters. Far apart from this occurrence, there is a small area in the mountains of Lebanon, along the banks of rivers. The occurrence in the Pontic Mountains continues to Europe in a small area in the Strandscha Mountains and the easternmost Balkan Mountains in southeast Bulgaria. Here the Pontic rhododendron grows in the undergrowth of the forests of the oriental beech .

On the Iberian Peninsula, it occurs in the southwest, in three relict areas in the mountains, up to heights of 850 (rarely up to 1000) meters. It grows here in the undergrowth of forests in acidic locations, often in stream valleys near waters. Locations are the Serra de Monchique and Serra de Vouzela in Portugal and the Sierra del Aljibe in the province of Cádiz in Spain.

Historical distribution

Fossil evidence shows that the species was much more widespread over most of southern and western Europe before the maximum of the last glaciation or 20,000 years ago. Quaternary fossil finds from the Alps are mostly attributed to this species, but have also been recognized as a separate species Rhododendron sordellii Tralau .

Cultivation and use

Close up of Rhododendron ponticum

Rhododendron ponticum subsp. baeticum is one of the most commonly cultivated rhododendrons in Western Europe. It is used as an ornamental plant itself , but more often as a grafting base on which more attractive rhododendrons are grafted . The plants were first grown in Great Britain in the 1760s by Joachim Conrad Loddiges (1738–1826), the founder of an important gardening business in the 18th and 19th centuries. They became widespread in the late 18th and early 19th centuries with the emerging trade in horticultural products. The roots produce unrefined saplings, which often overgrow the refined plant.

The Pontic honey made from nectar and pollen can be very toxic and cause hypotension and bradycardia in people who have consumed sufficient amounts . The effect is due to toxic diterpenes ( grayanotoxins ).

Invasive species

It is considered an invasive species in the UK , Ireland , Belgium , the Netherlands and Austria, and Madeira . Evidence from France , Norway , Poland , Russia and Slovakia is also known.

The plant's rash, along with its high seed production, led to it being the invasive species in much of Western Europe and parts of New Zealand. The management or control of the stocks is a key nature conservation measure in such areas. Nature conservation organizations in Great Britain meanwhile consider R. ponticum to be a "serious problem" in the native Atlantic oak forests of the western Highlands in Scotland as well as in Wales and in the heathland in southern England , which overgrow the native flora. Strategies for complete elimination have been developed, including knocking off the above-ground parts with subsequent herbicide treatment. However, the injection of herbicides into individual plants is considered to be more precise and effective.

A recent study showed the nectar's toxic effects on honey bees ( Apis mellifera ), which killed individual individuals within hours of ingestion. It also paralyzed bees of the species Andrena carantonica , a solitary grave bee. After ingesting the nectar, the bees were paralyzed and showed excessive cleaning or other abnormal behavior. They also ate less food than individuals in a control group. In contrast, the dark bumblebee ( Bombus terrestris ) was not affected by the nectar of the Pontic rhododendron.

Individual evidence

  1. ↑ a b DA Webb: Ericaceae. In TG Tutin VH Heywood, NA Burges, DM Moore, DH Valentine, SM Walters, DA Webb (editors): Flora Europaea. Vol. III Diapensiaceae to Myoporaceae. Cambridge University Press, 1972. ISBN 0-521-08489-X . Page 9.
  2. ↑ JR Cross (1975): Rhododendron Ponticum L. (Biological Flora of the British Isles). Journal of Ecology 63 (1): 345-364.
  3. ↑ EG Bobrov, EA Bush, NA Bush, An.A. Fedorov, SG Gorshkova, AA, Grossgeim, VI Grubov, AN Krishtofovich, IA Linchevskii, EG Pobedimova, AI Poyarkova, OI Rozhkova, BK Shishkin, EI Shteinberg, LA Smol'yaninova, VN Vasil'ev: Flora of the USSR edited by Botanical Institute VL Komarov of the Academy of Sciences of the USSR, translated by N. Landau, the Israel Program for Scientific Translations, Jerusalem 1967. Vol. XVIII: Metachlamydiae. Pages 28–29. online by archive.org
  4. ↑ Richard I. Milne, Chantel Davies, Ruby Prickett, Lucy H. Inns, David F. Chamberlain (2010): Phylogeny of Rhododendron subgenus Hymenanthes based on chloroplast DNA markers: between-lineage hybridization during adaptive radiation? Plant Systematics and Evolution 285: 233-244. doi: 10.1007 / s00606-010-0269-2
  5. ↑ a b S. Castroviejo et al. (editors): Flora Iberica. Plantas vasculares de la Península Ibérica e Islas Baleares. Vol. IV: Cruciferae to Monotropaceae. Real Jardín Botánico, Madrid 2003. ISBN 84-00-06221-3 , on page 508.
  6. ↑ José A. Mejías, Juan Arroyo, Fernando Ojeda (2002): Reproductive ecology of Rhododendron ponticum (Ericaceae) in relict Mediterranean populations. Botanical Journal of the Linnean Society 140: 297-311.
  7. ^ Richard Ian Milne: Molecular Systematics of Rhododendron ponticum L. and its close allies. Thesis, University of St. Andrews, School of Biological and Medical Sciences, 1998.
  8. ↑ Alice M. Coats: "Rhododendron" . In: Garden Shrubs and Their Histories 1964 (1992).
  9. ↑ P. Pablo Ferrer-Gallego & Emilio Laguna (2018): Proposal to conserve the name Rhododendron ponticum (Ericaceae) with a conserved type. Taxon 67 (6): 1226-1227. doi: 10.12705 / 676.32
  10. ↑ Richard I. Milne & Richard J. Abbott (2000): Origin and evolution of invasive naturalized material of Rhododendron ponticum L. in the British Isles. Molecular Ecology 9: 541-556.
  11. ↑ N. Zazanashvili, R. Gagnidze & G. Nakhutsrishvili (2000): Main types of vegetation zonation on the mountains of the Caucasus. Acta Phytogeographica Suecica 85: 7-16.
  12. ↑ J. Stephan, D. Issa (2017): Riparian woody vegetation distribution along ecological gradients in an East Mediterranean stream. Plant Sociology 54, Suppl. 1: 47-52. doi: 10.7338 / pls2017541S1 / 07
  13. ↑ Rossen Tzonev, Marius Dimitrov, Milan Chytry, Veska Roussakova, Dobromira Dimova, Chavdar Gussev, Dimitar Pavlov, Vladimir Vulchev, Antonina Vitkova, Georgi Gogoushev, Petrich, Ivajlo Nikolov, Daniela Borisova, Anna Ganeva (2006): Beech forest communities in Bulgaria . Phytocoenologia 36 (2): 247-279.
  14. ↑ Ali Kavgacı, Münevver Arslan, Ümit Bingöl, Neslihan Erdoğan, Andraž Čarni (2012): Classification and phytogeographical differentiation of oriental beech forests in Turkey and Bulgaria. Biologia 67 (3): 461-473. doi: 10.2478 / s11756-012-0029-6
  15. ^ AV Pérez Latorre & B. Cabezudo (2006): Phenomorphology and eco-morphological characters of Rhododendron lauroid forests in the Western Mediterranean (Iberian Peninsula, Spain). Plant Ecology 187: 227-247 doi: 10.1007 / s11258-005-6574-0
  16. ↑ Hans Tralau: About Rhododendron ponticum and the fossil occurrences of the closely related Rhododendron Sordellii. Phyton, Annales Rei Botanicae, Horn - 10 (1/2): 103 - 109. download
  17. ^ Andrew Wallace Hayes: Principles and methods of toxicology . CRC Press, 2007, ISBN 978-0-8493-3778-9 .
  18. ^ PE Hulme: Delivering Alien Invasive Species Inventories for Europe . 2006. Accessed June 4, 2019.
  19. ↑ Rhododendron ponticum . In: EPPO Global Database . Retrieved June 4, 2019.
  20. ^ New flora and fauna for old . In: The Economist , December 21, 2000. Archived from the original on July 28, 2001. Retrieved December 14, 2008. 
  21. ↑ Rhododendron: A killer of the Countryside . Offwell Woodland & Wildlife Trust. 2004. Retrieved May 30, 2010.
  22. ↑ BREAKTHROUGH IN BATTLE AGAINST PROBLEM PONTICUM . Forestry Commission . July 30, 2004. Archived from the original on March 5, 2011. Retrieved on May 30, 2010.
  23. ↑ Erin Jo Tiedeken, Paul A. Egan, Philip C. Stevenson, Geraldine A. Wright, Mark JF Brown, Eileen F. Power, Iain Farrell, Sharon M. Matthews, Jane C. Stout: Nectar chemistry modulates the impact of an invasive plant on native pollinators . In: Functional Ecology . 30, No. 6, November 2015, pp. 885-893. doi : 10.1111 / 1365-2435.12588 .

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