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Drosera anglica

2007 Schools Wikipedia Selection. Related subjects: Plants

               iDrosera anglica
           Scientific classification

   Kingdom: Plantae
   Order:   Caryophyllales
   Family:  Droseraceae
   Genus:   Drosera
   Species: D. anglica

                                Binomial name

   Drosera anglica
   Huds.

   Drosera anglica (syn. Drosera longifolia L., English sundew, Great
   sundew) is an insectivorous plant species belonging to the sundew
   genus. It is a temperate species with a generally circumboreal range,
   although it does occur as far south as Japan, southern Europe, and
   Kaua'i (Hawaiian Island), where it grows as a subtropical sundew. It is
   thought to originate from an amphidiploid hybrid of D. rotundifolia and
   D. linearis, meaning that a sterile hybrid between these two species
   doubled its chromosomes to produce fertile progeny which stabilized
   into the current D. anglica.

Morphology

   A large D. anglica plant with hand for size comparison
   Enlarge
   A large D. anglica plant with hand for size comparison

   Drosera anglica is a perennial herb which forms an upright, stemless
   rosette of generally linear-spatulate leaves. As is typical for
   sundews, the laminae are densely covered with stalked mucilaginous
   glands, each tipped with a clear droplet of a viscous fluid used for
   trapping insects. The lamina, which is 15-35  mm long, is held
   semi-erect by a long petiole, bringing the total leaf size to 30-95 mm.
   Plants are green, coloring red in bright light. In all populations
   except those in Kaua'i, D. anglica forms winter resting buds called
   hibernacula. These consist of a knot of tightly curled leaves at ground
   level, which unfurl in spring at the end of the dormancy period. The
   root system is weak and penetrates only a few centimeters, serving
   mainly as an anchor and for water absorption. Nitrogen is in short
   supply in bogs and trapping and digesting insects provides an alternate
   source.

   D. anglica flowers in the summer, sending up peduncles 6-18 cm. long
   bearing several white flowers which open individually. Like other
   sundews, the flowers have five sepals, petals, and stamens. The petals
   for this species are 8-12 mm long, and the flowers have branched
   2-lobed styles. The black ovoid seed forms in a dehiscent capsule and
   is 1 to 1½ mm long.

Carnivory

   A D. anglica leaf bent around a trapped fly
   Enlarge
   A D. anglica leaf bent around a trapped fly

   Like all sundews, D. anglica uses stalked mucilaginous glands called
   tentacles which cover its laminae to attract, trap, and digest small
   arthropods, usually insects. These are attracted by a sugary scent
   exuded by the glands, and upon alighting on the plant adhere to the
   sticky drops of mucilage. Although most of its prey consists of small
   insects such as flies, bulkier insects with large wings are also
   caught. Small butterflies, damselflies, and even dragonflies can become
   immobilized by the plant's sticky mucilage.

   The plant's initial response to contact with prey consists of
   thigmotropic (movement in response to touch) tentacle movement, with
   tentacles bending toward the prey and the centre of the leaf to
   maximize contact. D. anglica is also capable of further movement, being
   able to bend the actual leaf blade around prey to further the digestion
   process. Tentacle movement can occur in a matter of minutes, whereas
   the leaf takes hours or days to bend. When something gets caught, the
   tentacles touching the prey exude additional mucilage to mire down the
   prey, which eventually dies of exhaustion or is asphyxiated as the
   mucilage clogs its tracheae. Once the prey has been digested and the
   resulting nutrient solution has been absorbed by the plant, the leaf
   unfurls, leaving only the prey's exoskeleton behind.

Habitat

   D. anglica growing on a quaking bog in the Wallowa Mountains of Oregon
   Enlarge
   D. anglica growing on a quaking bog in the Wallowa Mountains of Oregon

   D. anglica grows in open, non-forested habitat with wet, often
   calcium-rich soils. These include bogs, marl fens, quaking bogs, cobble
   shores, and other calcareous habitats. This tolerance of calcium is
   relatively rare in the rest of the genus. D. anglica is often
   associated with various sphagnum mosses, and many times grows in a soil
   substrate that is entirely composed of living, dead, or decomposed
   sphagnum. The sphagnum wicks moisture to the surface while
   simultaneously acidifying it. What soil nutrients are not seeped away
   by the constant moisture are often used up by the sphagnum or made
   unavailable by the low soil pH. Since nutrient availability is low,
   competition from other plants is diminished, allowing the carnivorous
   English sundew to flourish.

Distribution

   World distribution of D. anglica
   Enlarge
   World distribution of D. anglica

   D. anglica is one of the most widely distributed sundews in the world.
   It is generally circumboreal, meaning that it is found at high
   latitudes around the globe. In a few areas, however, it is found
   farther south, particularly in Japan, southern Europe, the Hawaiian
   island of Kaua'i, and California. Plants from the Hawaiian population
   are generally smaller than normal and do not experience a winter
   dormancy period. Its natural habitat includes 12 U.S. states, including
   Alaska, and 11 Canadian provinces and territories. The altitudinal
   range is from 5  m to at least 2000 m.

Special origins

   All North American Drosera species except for D. anglica have a
   chromosome count of 2n=20. In 1955, Wood noted that D. anglica had a
   chromosome count of 2n=40, and hypothesized that it was of hybrid
   amphidiploid origin. Since the leaf morphology of D. anglica is an
   intermediary between that of D. rotundifolia and D. linearis and the
   two occur sympatrically in several locations, Wood conjectured that D.
   anglica likely originated from a hybrid between these two.

   All North American Drosera species produce sterile hybrids. The natural
   hybrid D. rotundifolia × D. linearis (conventionally but incorrectly
   referred to as Drosera ×anglica), is also sterile but is
   morphologically similar to the modern D. anglica. Errors in meiosis
   during ovule and pollen production, however, can result in a chromosome
   doubling which can allow for viable seed to be produced. The resulting
   plants, known as amphiploids, would be fertile. Woods noted that this
   appeared to be an ongoing process with D. anglica speciating from D.
   rotundifolia × D. linearis through amphidiploidy in multiple locations.
   The question remains as to why D. anglica is so widespread, whereas the
   range of D. linearis is limited to the Great Lakes region of North
   America. The greater adaptability of D. anglica to varied habitat
   conditions could be a major factor.

Hybrids

   Several naturally occurring hybrids involving D. anglica exist. These
   include:
   D. anglica × capillaris   = D. × anpil
   D. anglica × filiformis   = D. × anfil
   D. anglica × linearis
   D. anglica × intermedia   = D. × anterm
   D. anglica × spatulata    = D. × nagamoto
   D. linearis × anglica     = D. × linglica
   D. rotundifolia × anglica = D. × obovata

   These are all sterile. In addition, several man-made hybrids have been
   made.

Gallery

   Tropical form from Kaua'i, Hawaii

   A dense carpet of flowering D. anglica on a quaking bog

   An atypical D. anglica flower with 6 petals

   Several damselflies ensnared by some English Sundews

   D. anglica growing in a mountain bog, British Columbia, Canada

   Retrieved from " http://en.wikipedia.org/wiki/Drosera_anglica"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
