Polygala lewtonii
Encyclopedia
Polygala lewtonii is a rare species of flowering plant in the milkwort family
known by the common name Lewton's polygala, or Lewton's milkwort. It is endemic to Florida
in the United States, where it is limited to the central ridge of the peninsula. There are about 49 occurrences of the plant remaining. Most occurrences contain very few plants. The species is threatened by the loss and degradation of its habitat. This is a federally listed endangered species
of the United States.
The plant is a short-lived perennial herb producing erect, fleshy stems from the top of its taproot
. The stems grow up to 20 centimeters tall. The leaves are alternately arranged and overlapping, with a number of small leaves in the axil of one larger leaf. They are linear to spatula
-shaped and about a centimeter long. The top of each stem is occupied by a short inflorescence
of flowers. There are three types of flowers on this plant. The most obvious is the chasmogamous type borne in the inflorescence on the stem. These are each half a centimeter long with pink winglike sepal
s and three smaller tufted pink petals at the center. The second type of flower is cleistogamous
and borne at the base of the plant. These do not open, but self-pollinate
. These flowers, which occur at the leaf axils, are rare. The third type of flower is a cleistogamous, unopening type that remains underground. These are borne on a stalk up to 40 centimeters long which is located just below the surface of the soil. They are white in color, and also self-pollinate. The very uncommon mode of reproduction characterized by aboveground chasmogamous flowers and belowground cleistogamous flowers is called amphicarpy and it is known from fewer than 100 plant species. The different types of flowers may occur at different times of the year. The aboveground flowers depend on insect pollinator
s for successful reproduction, as evidenced by the low fruit production of flowers in a pollinator-exclusion experiment. Pollinators include bee-flies
, flower flies, and leaf-cutter bees
. The fruit is a capsule containing cylindrical seeds each about 0.3 centimeters long. The seeds have hairs which attract ants, which then collect and disperse
them. The most common type of seed-collecting ant is Pheidole morrissii and others include Paratrichina arenavaga and P. phantasma.
This plant grows on the sandhill
s of Central Florida
and the transition between sandhill and Florida scrub
. The land is dominated by longleaf pine, turkey oak, and other oak
s. It can also be found in recently cleared areas such as the dry, open clearings around power line
s. The substrate is yellow sand. Other endangered plant species in the habitat include Warea amplexifolia
, Ziziphus celata
, Prunus geniculata
, and Nolina brittoniana
.
The habitat occupied by this plant is maintained by a natural fire regime
. Fire helps the plant by removing competing plants and the buildup of ground litter and lichen
s. Though the plant is burned in fires, its seedlings sprout in large numbers in the seasons after a large fire, in one case increasing the population by 800%. It is thought that smoke may trigger or foster germination
of seeds in the soil seed bank
. Fire also benefits the plant by increasing its survival, lowering its age of reproductive maturity, and increasing the density of the plants.
Because fire is beneficial and necessary for the plant, the common practice of fire suppression is a major threat to its survival. The plant declines the longer its habitat goes without a fire. Another major threat to the species is the outright loss of its habitat to development. The yellow-sand sandhill regions are desirable for conversion to citrus groves. Land has also been consumed in rapidly expanding development of residential areas. The destruction of the habitat has resulted in habitat fragmentation
. Remaining fragments are popular terrain for off-road vehicle
enthusiasts.
Many occurrences of the plant are located on land that is now protected. Prescribed burns help to bring the habitat back to its normal state.
Polygalaceae
The Polygalaceae or Milkwort family is a family of flowering plants in the order Fabales. They have a near-cosmopolitan range, with about 17 genera and 900–1,000 species of herbs, shrubs and trees...
known by the common name Lewton's polygala, or Lewton's milkwort. It is endemic to Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
in the United States, where it is limited to the central ridge of the peninsula. There are about 49 occurrences of the plant remaining. Most occurrences contain very few plants. The species is threatened by the loss and degradation of its habitat. This is a federally listed endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
of the United States.
The plant is a short-lived perennial herb producing erect, fleshy stems from the top of its taproot
Taproot
A taproot is an enlarged, somewhat straight to tapering plant root that grows vertically downward. It forms a center from which other roots sprout laterally.Plants with taproots are difficult to transplant...
. The stems grow up to 20 centimeters tall. The leaves are alternately arranged and overlapping, with a number of small leaves in the axil of one larger leaf. They are linear to spatula
Spatula
The term spatula is used to refer to various small implements with a broad, flat, flexible blade used to mix, spread and lift materials including foods, drugs, plaster and paints...
-shaped and about a centimeter long. The top of each stem is occupied by a short inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
of flowers. There are three types of flowers on this plant. The most obvious is the chasmogamous type borne in the inflorescence on the stem. These are each half a centimeter long with pink winglike sepal
Sepal
A sepal is a part of the flower of angiosperms . Collectively the sepals form the calyx, which is the outermost whorl of parts that form a flower. Usually green, sepals have the typical function of protecting the petals when the flower is in bud...
s and three smaller tufted pink petals at the center. The second type of flower is cleistogamous
Cleistogamy
Cleistogamy or automatic self-pollination describes the trait of certain plants to propagate by using non-opening, self-pollinating flowers...
and borne at the base of the plant. These do not open, but self-pollinate
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
. These flowers, which occur at the leaf axils, are rare. The third type of flower is a cleistogamous, unopening type that remains underground. These are borne on a stalk up to 40 centimeters long which is located just below the surface of the soil. They are white in color, and also self-pollinate. The very uncommon mode of reproduction characterized by aboveground chasmogamous flowers and belowground cleistogamous flowers is called amphicarpy and it is known from fewer than 100 plant species. The different types of flowers may occur at different times of the year. The aboveground flowers depend on insect pollinator
Pollinator
A pollinator is the biotic agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain...
s for successful reproduction, as evidenced by the low fruit production of flowers in a pollinator-exclusion experiment. Pollinators include bee-flies
Bombyliidae
Bombyliidae is a large family of flies with hundreds of genera, although their life cycles are not well known. Adults generally feed on nectar and pollen, thus are pollinators of flowers. They superficially resemble bees, thus are commonly called bee flies, and this may offer the adults some...
, flower flies, and leaf-cutter bees
Megachilidae
The Megachilidae are a cosmopolitan family of solitary bees whose pollen-carrying structure is restricted to the ventral surface of the abdomen...
. The fruit is a capsule containing cylindrical seeds each about 0.3 centimeters long. The seeds have hairs which attract ants, which then collect and disperse
Seed dispersal
Seed dispersal is the movement or transport of seeds away from the parent plant. Plants have limited mobility and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic and biotic vectors. Seeds can be dispersed away from the parent plant...
them. The most common type of seed-collecting ant is Pheidole morrissii and others include Paratrichina arenavaga and P. phantasma.
This plant grows on the sandhill
Sandhill
A sandhill is a type of ecological community or xeric wildfire-maintained ecosystem. It is not the same as a sand dune. It features very short fire return intervals, one to five years. Without fire, sandhills undergo ecological succession and become more oak dominated.Entisols are the typical...
s of Central Florida
Central Florida
Central Florida is a regional designation for the area surrounding Orlando in east central Florida, United States. The area represents the third largest population concentration in Florida, after the South Florida and Tampa Bay regions, respectively....
and the transition between sandhill and Florida scrub
Florida scrub
Florida scrub is an endangered temperate coniferous forest ecoregion of the state of Florida in the United States. It is found on coastal and inland sand ridges and is characterized by a xeromorphic plant community dominated by shrubs and dwarf oaks. Scrub soils, a type of entisol, are derived...
. The land is dominated by longleaf pine, turkey oak, and other oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
s. It can also be found in recently cleared areas such as the dry, open clearings around power line
Power Line
Power Line is an American political blog, providing news and commentary from a conservative point-of-view. It was originally written by three lawyers who attended Dartmouth College together: John H. Hinderaker, Scott W. Johnson, and Paul Mirengoff...
s. The substrate is yellow sand. Other endangered plant species in the habitat include Warea amplexifolia
Warea amplexifolia
Warea amplexifolia is a rare species of flowering plant in the mustard family known by the common names wideleaf pinelandcress, wideleaf warea, and clasping warea. It is endemic to Florida in the United States, where it is limited to a few counties in the central part of the peninsula. It is...
, Ziziphus celata
Ziziphus celata
Ziziphus celata, commonly known as the Florida ziziphus, is a terrestrial flowering plant endemic to central Florida. Ziziphus celata is very nearly extinct.-Description:It is a small spiny shrub that is usually less than 2 meters tall...
, Prunus geniculata
Prunus geniculata
Prunus geniculata is a rare species of plum known by the common name scrub plum. It is endemic to Florida in the United States, where it occurs on the Lake Wales Ridge in the central ridges of the peninsula...
, and Nolina brittoniana
Nolina brittoniana
Nolina brittoniana is a rare species of flowering plant in the asparagus family known by the common name Britton's beargrass. It is endemic to Florida, where there are 72 known populations, only a few of which are large enough to be considered viable. It is federally listed as an endangered species...
.
The habitat occupied by this plant is maintained by a natural fire regime
Fire regime
A fire regime is the pattern, frequency and intensity of the bushfires and wildfires that prevails in an area. It is an integral part of fire ecology, and renewal for certain types of ecosystems. If fires are too frequent, plants may be killed before they have matured, or before they have set...
. Fire helps the plant by removing competing plants and the buildup of ground litter and lichen
Lichen
Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
s. Though the plant is burned in fires, its seedlings sprout in large numbers in the seasons after a large fire, in one case increasing the population by 800%. It is thought that smoke may trigger or foster germination
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...
of seeds in the soil seed bank
Soil Seed Bank
The soil seed bank refers to the natural storage of seeds, often dormant, within the soil of most ecosystems. The study of soil seed banks started in 1859 when Charles Darwin observed the emergence of seedlings using soil samples from the bottom of a lake. The first scientific paper on the subject...
. Fire also benefits the plant by increasing its survival, lowering its age of reproductive maturity, and increasing the density of the plants.
Because fire is beneficial and necessary for the plant, the common practice of fire suppression is a major threat to its survival. The plant declines the longer its habitat goes without a fire. Another major threat to the species is the outright loss of its habitat to development. The yellow-sand sandhill regions are desirable for conversion to citrus groves. Land has also been consumed in rapidly expanding development of residential areas. The destruction of the habitat has resulted in habitat fragmentation
Habitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population fragmentation...
. Remaining fragments are popular terrain for off-road vehicle
Off-road vehicle
An off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks...
enthusiasts.
Many occurrences of the plant are located on land that is now protected. Prescribed burns help to bring the habitat back to its normal state.