Drosera anglica
Encyclopedia
Drosera anglica, commonly known as the English sundew or Great sundew, is a carnivorous 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 the island of Kauai
in Hawaii
, 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.
herb which forms an upright, stemless rosette
of generally linear-spatulate leaves. As is typical for sundew
s, 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 (0.590551181102362–1.4 in) 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 (2.4–7.1 in). 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 odorless, nectar-less flowers do not rely on insect pollinators for pollination, rather setting seed well through self-pollination (autogamy). The black ovoid seed forms in a dehiscent capsule and is 1 to 1½ mm long.
Like all sundews, D. anglica uses stalked mucilaginous
gland
s 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 center 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.
fen
s, 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.
s 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 Kauai
, and California. Plants from the Hawaii, where it is known as mikinalo, 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.
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.
in 1778. It has frequently been confused with the other circumpolar long-leaf Drosera, D. intermedia. This confusion was fueled by the resurfacing of an older name, D. longifolia (described by Carl Linnaeus in 1753), which was regarded as being too ambiguous in description and had been applied to specimens of both D. anglica and D. intermedia. Herbarium specimens were also a mix of the two species. These points led Martin Cheek
to propose D. longifolia for rejection as a species name in 1998. The proposal was accepted and the taxon listed as rejected in 1999.
These are all sterile. In addition, several man-made hybrids
have been made.
Carnivorous plant
Carnivorous plants are plants that derive some or most of their nutrients from trapping and consuming animals or protozoans, typically insects and other arthropods. Carnivorous plants appear adapted to grow in places where the soil is thin or poor in nutrients, especially nitrogen, such as acidic...
species belonging to the sundew
Sundew
Drosera, commonly known as the sundews, comprise one of the largest genera of carnivorous plants, with at least 194 species. These members of the family Droseraceae lure, capture, and digest insects using stalked mucilaginous glands covering their leaf surface. The insects are used to supplement...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
. It is a temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
species with a generally circumboreal range, although it does occur as far south as Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, southern Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, and the island of Kauai
Kauai
Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...
in Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
, where it grows as a subtropical sundew. It is thought to originate from an amphidiploid hybrid of D. rotundifolia
Drosera rotundifolia
Drosera rotundifolia is a species of sundew, a carnivorous plant often found in bogs, marshes and fens...
and D. linearis
Drosera linearis
Drosera linearis, commonly called the slenderleaf sundew, is a sundew found in the Great Lakes region of North America, in Canada and the United States, such as in Michigan....
, meaning that a sterile hybrid between these two species doubled its chromosomes to produce fertile progeny which stabilized into the current D. anglica.
Morphology
Drosera anglica is a perennialPerennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...
herb which forms an upright, stemless rosette
Rosette (botany)
In botany, a rosette is a circular arrangement of leaves, with all the leaves at a single height.Though rosettes usually sit near the soil, their structure is an example of a modified stem.-Function:...
of generally linear-spatulate leaves. As is typical for sundew
Sundew
Drosera, commonly known as the sundews, comprise one of the largest genera of carnivorous plants, with at least 194 species. These members of the family Droseraceae lure, capture, and digest insects using stalked mucilaginous glands covering their leaf surface. The insects are used to supplement...
s, the laminae are densely covered with stalked mucilaginous glands
Mucilage
Mucilage is a thick, gluey substance produced by most plants and some microorganisms. It is a polar glycoprotein and an exopolysaccharide.It occurs in various parts of nearly all classes of plant, usually in relatively small percentages, and is frequently associated with other substances, such as...
, each tipped with a clear droplet of a viscous fluid used for trapping insects. The lamina, which is 15–35 mm (0.590551181102362–1.4 in) 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
Hibernaculum
Hibernaculum can refer to:* Hibernaculum , the location chosen by an animal for hibernation...
. These consist of a knot of tightly curled leaves at ground level, which unfurl in spring at the end of the dormancy
Dormancy
Dormancy is a period in an organism's life cycle when growth, development, and physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be closely associated with environmental conditions...
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
Peduncle (botany)
In botany, a peduncle is a stem supporting an inflorescence, or after fecundation, an infructescence.The peduncle is a stem, usually green and without leaves, though sometimes colored or supporting small leaves...
6–18 cm (2.4–7.1 in). 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 odorless, nectar-less flowers do not rely on insect pollinators for pollination, rather setting seed well through self-pollination (autogamy). The black ovoid seed forms in a dehiscent capsule and is 1 to 1½ mm long.
Carnivory
Mucilage
Mucilage is a thick, gluey substance produced by most plants and some microorganisms. It is a polar glycoprotein and an exopolysaccharide.It occurs in various parts of nearly all classes of plant, usually in relatively small percentages, and is frequently associated with other substances, such as...
gland
Gland
A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream or into cavities inside the body or its outer surface .- Types :...
s called tentacles which cover its laminae to attract, trap, and digest
Digest
Digest can refer to any of the following:*A condensed collection or compendium of writings:**Pandects, or "The Digest", a digest of Roman law**A tax 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
Damselfly
Damselflies are insects in the order Odonata. Damselflies are similar to dragonflies, but the adults can be distinguished by the fact that the wings of most damselflies are held along, and parallel to, the body when at rest...
, and even dragonflies can become immobilized by the plant's sticky mucilage.
The plant's initial response to contact with prey consists of thigmotropic
Thigmotropism
Thigmotropism is a movement in which an organism moves or grows in response to touch or contact stimuli. The prefix thigmo- θιγμος comes from the Greek for "touch". Usually thigmotropism occurs when plants grow around a surface, such as a wall, pot, or trellis. Climbing plants, such as vines,...
(movement in response to touch) tentacle movement, with tentacles bending toward the prey and the center 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
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....
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
Invertebrate trachea
The invertebrate trachea refers to the open respiratory system composed of spiracles, tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues....
. 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
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
behind.
Habitat
D. anglica grows in open, non-forested habitat with wet, often calcium-rich soils. These include bogs, marlMarl
Marl or marlstone is a calcium carbonate or lime-rich mud or mudstone which contains variable amounts of clays and aragonite. Marl was originally an old term loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay...
fen
Fen
A fen is a type of wetland fed by mineral-rich surface water or groundwater. Fens are characterised by their water chemistry, which is neutral or alkaline, with relatively high dissolved mineral levels but few other plant nutrients...
s, quaking bogs, cobble shores, and other calcareous
Calcareous
Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...
habitats. This tolerance of calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
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
Soil pH
The soil pH is a measure of the acidity or basicity in soils. pH is defined as the negative logarithm of the activity of hydrogen ions in solution. It ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic and above 7 is basic. Soil pH is considered a master variable in soils as it...
. Since nutrient availability is low, competition from other plants is diminished, allowing the carnivorous English sundew to flourish.
Distribution
D. anglica is one of the most widely distributed sundewSundew
Drosera, commonly known as the sundews, comprise one of the largest genera of carnivorous plants, with at least 194 species. These members of the family Droseraceae lure, capture, and digest insects using stalked mucilaginous glands covering their leaf surface. The insects are used to supplement...
s 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 Kauai
Kauai
Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...
, and California. Plants from the Hawaii, where it is known as mikinalo, 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 chromosomeChromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
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
Drosera rotundifolia
Drosera rotundifolia is a species of sundew, a carnivorous plant often found in bogs, marshes and fens...
and D. linearis
Drosera linearis
Drosera linearis, commonly called the slenderleaf sundew, is a sundew found in the Great Lakes region of North America, in Canada and the United States, such as in Michigan....
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
Drosera rotundifolia
Drosera rotundifolia is a species of sundew, a carnivorous plant often found in bogs, marshes and fens...
× D. linearis (conventionally but incorrectly referred to as Drosera ×anglica), is also sterile but is morphologically
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
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
Drosera rotundifolia
Drosera rotundifolia is a species of sundew, a carnivorous plant often found in bogs, marshes and fens...
× 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
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
region of North America. The greater adaptability of D. anglica to varied habitat conditions could be a major factor.
Botanical history
Drosera anglica was first described by William HudsonWilliam Hudson (botanist)
William Hudson FRS was a British botanist and apothecary based in London. His main work was Flora Anglica, published in 1762. He was elected a fellow of the Royal Society in 1761.- Life and work :...
in 1778. It has frequently been confused with the other circumpolar long-leaf Drosera, D. intermedia. This confusion was fueled by the resurfacing of an older name, D. longifolia (described by Carl Linnaeus in 1753), which was regarded as being too ambiguous in description and had been applied to specimens of both D. anglica and D. intermedia. Herbarium specimens were also a mix of the two species. These points led Martin Cheek
Martin Cheek
Dr. Martin Roy Cheek is a taxonomist and botanist specialising in the carnivorous plant genus Nepenthes.-Research:Cheek has described several new Nepenthes species, mostly with Matthew Jebb, including: N. argentii, N. aristolochioides, N. danseri, N. diatas,...
to propose D. longifolia for rejection as a species name in 1998. The proposal was accepted and the taxon listed as rejected in 1999.
Hybrids
Several naturally occurring hybrids involving D. anglica exist. These include:| D. anglica × capillaris | = D. × anpil |
| D. anglica × filiformis Drosera filiformis Drosera filiformis, commonly known as the Thread-leaved sundew, is a small, insectivorous, rosette forming species of perennial herb. A species of sundew, it is unusual within its genus in that the long, erect, filiform leaves of this plant unroll in spirals - an arrangement similar to the... |
= D. × anfil |
| D. anglica × linearis Drosera linearis Drosera linearis, commonly called the slenderleaf sundew, is a sundew found in the Great Lakes region of North America, in Canada and the United States, such as in Michigan.... |
|
| D. anglica × intermedia Drosera intermedia Drosera intermedia, commonly known as the oblong-leaved sundew or spoonleaf sundew, is an insectivorous plant species belonging to the sundew genus. It is a temperate or tropical species native to Europe, southeastern Canada, the eastern half of the United States, Cuba and northern South America.-... |
= D. × anterm |
| D. anglica × spatulata Drosera spatulata Drosera spatulata, the spoon-leaved sundew, is a variable, rosette-forming sundew with spoon-shaped leaves. The specific epithet is Latin for "spatula shaped," a reference to the form of the leaves... |
= D. × nagamoto |
| D. linearis Drosera linearis Drosera linearis, commonly called the slenderleaf sundew, is a sundew found in the Great Lakes region of North America, in Canada and the United States, such as in Michigan.... × anglica |
= D. × linglica |
| D. rotundifolia Drosera rotundifolia Drosera rotundifolia is a species of sundew, a carnivorous plant often found in bogs, marshes and fens... × anglica |
= D. × obovata |
These are all sterile. In addition, several man-made hybrids
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...
have been made.
External links
- Jepson Manual Treatment
- Species account, photographs, and Wisconsin distribution from Wisconsin State Herbarium (UW-Madison)
- GRIN taxonomy page, including global distribution info
- USDA plant profile
- Key to North American Drosera species
- Cultivation Information
- International Carnivorous Plant Society
- Insectivorous Plants (1875) by Charles Darwin