Boltonia decurrens
Encyclopedia
Boltonia decurrens is a rare species of flowering plant in the aster family
known by the common names decurrent false aster and claspingleaf doll's daisy. It is native to the floodplain
s along the Illinois
and Mississippi River
s in the United States
, where the habitat has been drastically altered, leading to its decline. The plant was once distributed across 400 kilometers of riverside forest from LaSalle, Illinois, to St. Louis, Missouri
. As the rivers and riparian
habitat alongside them have been developed, the plant's distribution has been fragmented into about 20 separate populations, mostly in Illinois
. At one point it was thought to have been extirpated
from Missouri
, but a few populations have been located near St. Louis since the mid-1980s. Despite having declined over time, several populations of the plant contain many thousands of individuals. Populations vary depending on the amount and duration of flood
ing that occurs in the area each year. The plant is a federally listed threatened species
.
This plant was long treated as a variety of Boltonia asteroides
until 1985, when it was elevated to species status, a status it had held once before. It is a bushy perennial herb sprawling to 1.5 meters in height, often exceeding two meters. The leaves are decurrent
, their bases extending down the stem at their attachment. The blades are up to 15 centimeters long and linear or lance-shaped. The inflorescence
is a large panicle
of leafy branches and many flower heads
with white or pale purple ray florets measuring 1 to 2 centimeters long. The center contains many yellow disc florets. Flowering occurs in August through October. The plant reproduces vegetatively
by growing new shoots and sexually
by making seed. The species produces a large amount of seeds, averaging 50,000 per plant. The seeds are dispersed
on the water, particularly during floods. In general the plant is adapted
to floods; it has been noted to grow underwater, produce an inflorescence above the surface, bloom and produce seeds in flooded conditions. The seeds germinate
when they fall on wet substrate, or sometimes while they are still floating about on the water.
Today the land next to the rivers is protected with many flood control
methods, and natural floodplain activity occurs in few places. The riverside landscape has been modified into cropland
, with marsh
es and prairie
s drained, walled off, and plowed. The rivers are contained with levee
s, controlled by locks
, and accessed via marina
s. While the plant is adapted to periodic flooding, its seedlings can only germinate and grow in clear water that allows sunlight in; flooding that occurs now is more likely to be turbid
with silt
, a condition the plant cannot tolerate. Recent large floods have been noted to deposit thick layers of silt, destroying plants. Also, the disturbance of flooding is rare enough now that riversides become overgrown with brush, shading out the plants in a similar way. In fact, in some areas the plant now depends on periodic human disturbance, such as mowing, to clear away the brush the way severe natural flooding once did.
Population sizes vary depending on the amount of disturbance, such as flooding, occurring in the area. Populations have been noted to contain anywhere between one plant and one million plants or more, and some populations disappear for a time. Several populations of the plant were noted to increase after the Great Flood of 1993
, with the most severely swamped populations growing most. Genetic analysis
reveals the species is genetically diverse
.
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
known by the common names decurrent false aster and claspingleaf doll's daisy. It is native to the floodplain
Floodplain
A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge...
s along the Illinois
Illinois River
The Illinois River is a principal tributary of the Mississippi River, approximately long, in the State of Illinois. The river drains a large section of central Illinois, with a drainage basin of . This river was important among Native Americans and early French traders as the principal water route...
and Mississippi River
Mississippi River
The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
s in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, where the habitat has been drastically altered, leading to its decline. The plant was once distributed across 400 kilometers of riverside forest from LaSalle, Illinois, to St. Louis, Missouri
St. Louis, Missouri
St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...
. As the rivers and riparian
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
habitat alongside them have been developed, the plant's distribution has been fragmented into about 20 separate populations, mostly in Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
. At one point it was thought to have been extirpated
Local extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...
from Missouri
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...
, but a few populations have been located near St. Louis since the mid-1980s. Despite having declined over time, several populations of the plant contain many thousands of individuals. Populations vary depending on the amount and duration of flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
ing that occurs in the area each year. The plant is a federally listed threatened 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...
.
This plant was long treated as a variety of Boltonia asteroides
Boltonia asteroides
False aster or White doll's daisy is a species of ornamental plant.-External links:* University of Southern Indiana* United States Department of Agriculture...
until 1985, when it was elevated to species status, a status it had held once before. It is a bushy perennial herb sprawling to 1.5 meters in height, often exceeding two meters. The leaves are decurrent
Decurrent
Decurrent is a term used in botany and mycology to describe plant or fungal parts that extend downward.In botany, the term is most often applied to leaf blades that partly wrap or have wings around the stem or petiole and extend down along the stem...
, their bases extending down the stem at their attachment. The blades are up to 15 centimeters long and linear or lance-shaped. The 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...
is a large panicle
Panicle
A panicle is a compound raceme, a loose, much-branched indeterminate inflorescence with pedicellate flowers attached along the secondary branches; in other words, a branched cluster of flowers in which the branches are racemes....
of leafy branches and many flower heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
with white or pale purple ray florets measuring 1 to 2 centimeters long. The center contains many yellow disc florets. Flowering occurs in August through October. The plant reproduces vegetatively
Vegetative reproduction
Vegetative reproduction is a form of asexual reproduction in plants. It is a process by which new individuals arise without production of seeds or spores...
by growing new shoots and sexually
Sexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...
by making seed. The species produces a large amount of seeds, averaging 50,000 per plant. The seeds are dispersed
Biological dispersal
Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...
on the water, particularly during floods. In general the plant is adapted
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
to floods; it has been noted to grow underwater, produce an inflorescence above the surface, bloom and produce seeds in flooded conditions. The seeds germinate
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...
when they fall on wet substrate, or sometimes while they are still floating about on the water.
Today the land next to the rivers is protected with many flood control
Flood control
In communications, flood control is a feature of many communication protocols designed to prevent overwhelming of a destination receiver. Such controls can be implemented either in software or in hardware, and will often request that the message be resent after the receiver has finished...
methods, and natural floodplain activity occurs in few places. The riverside landscape has been modified into cropland
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
, with marsh
Marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
es and prairie
Prairie
Prairies are considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and grasses, herbs, and shrubs, rather than trees, as the dominant vegetation type...
s drained, walled off, and plowed. The rivers are contained with levee
Levee
A levee, levée, dike , embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels...
s, controlled by locks
Lock (water transport)
A lock is a device for raising and lowering boats between stretches of water of different levels on river and canal waterways. The distinguishing feature of a lock is a fixed chamber in which the water level can be varied; whereas in a caisson lock, a boat lift, or on a canal inclined plane, it is...
, and accessed via marina
Marina
A marina is a dock or basin with moorings and supplies for yachts and small boats.A marina differs from a port in that a marina does not handle large passenger ships or cargo from freighters....
s. While the plant is adapted to periodic flooding, its seedlings can only germinate and grow in clear water that allows sunlight in; flooding that occurs now is more likely to be turbid
Turbidity
Turbidity is the cloudiness or haziness of a fluid caused by individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality....
with silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
, a condition the plant cannot tolerate. Recent large floods have been noted to deposit thick layers of silt, destroying plants. Also, the disturbance of flooding is rare enough now that riversides become overgrown with brush, shading out the plants in a similar way. In fact, in some areas the plant now depends on periodic human disturbance, such as mowing, to clear away the brush the way severe natural flooding once did.
Population sizes vary depending on the amount of disturbance, such as flooding, occurring in the area. Populations have been noted to contain anywhere between one plant and one million plants or more, and some populations disappear for a time. Several populations of the plant were noted to increase after the Great Flood of 1993
Great Flood of 1993
The Great Mississippi and Missouri Rivers Flood of 1993 occurred in the American Midwest, along the Mississippi and Missouri rivers and their tributaries, from April to October 1993. The flood was among the most costly and devastating to ever occur in the United States, with $15 billion in damages...
, with the most severely swamped populations growing most. Genetic analysis
Genetic analysis
Genetic analysis can be used generally to describe methods both used in and resulting from the sciences of genetics and molecular biology, or to applications resulting from this research....
reveals the species is genetically diverse
Genetic diversity
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....
.
External links
- Boltonia decurrens Research Station. Southern Illinois University.
- USDA Plants Profile