Helenium virginicum
Encyclopedia
Helenium virginicum is a rare species of flowering plant in the aster family
known by the common name Virginia sneezeweed. It occurs in the United States, where it has a disjunct distribution
; it is known only from Virginia
and Missouri
. It is limited to a specific type of habitat and it is threatened by modification of this habitat. It was federally listed as a threatened species of the United States in 1998.
At the time the plant received federal protection it was known from 28 populations in two Virginia counties. Soon after, a population of similar plants was found in Missouri and by genetic analysis
were confirmed to be of the same species. Searches turned up a total of 44 occurrences in six counties in the Ozark Highlands
of Missouri. This disjunct distribution
was probably caused by the cleaving of the species' geographical range during Pleistocene
glaciation, leaving two relict
ranges.
This plant is similar to and often mistaken for Helenium autumnale
, the common sneezeweed. It is a perennial herb generally growing to a maximum height between 70 centimeters and 1.1 meters, but it is known to reach 1.7 meters at times. There is a basal rosette of leaves and an erect, winged stem lined with lance-shaped leaves that become smaller toward the top of the stem. The inflorescence
has several flower heads
, each with a spherical disc covered with disc florets and lined with yellow ray florets just over a centimeter long. Blooming occurs in July through October. The plant is self-incompatible
.
This species only grows near sinkhole
ponds in the Ozark Highlands of Missouri and the western margin of the Blue Ridge Mountains
in Virginia. These ponds are lined with clay or bedrock
and are filled with water from about January to June or July each year. They may take the form of actual holes or they may be more like very wet meadow
s. The ponds are often actively grazed
by cattle and can tolerate disturbance. The hydrology
of the sinkholes varies seasonally and year to year, causing a similar fluctuation in the population and recruitment
of the sneezeweed.
The greatest threat to this species is habitat modification. Destruction of the sinkhole habitat could lead to the extinction
of the species.
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 name Virginia sneezeweed. It occurs in the United States, where it has a disjunct distribution
Disjunct distribution
In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but widely separated from each other geographically...
; it is known only from Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
and 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...
. It is limited to a specific type of habitat and it is threatened by modification of this habitat. It was federally listed as a threatened species of the United States in 1998.
At the time the plant received federal protection it was known from 28 populations in two Virginia counties. Soon after, a population of similar plants was found in Missouri and by 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....
were confirmed to be of the same species. Searches turned up a total of 44 occurrences in six counties in the Ozark Highlands
The Ozarks
The Ozarks are a physiographic and geologic highland region of the central United States. It covers much of the southern half of Missouri and an extensive portion of northwestern and north central Arkansas...
of Missouri. This disjunct distribution
Disjunct distribution
In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but widely separated from each other geographically...
was probably caused by the cleaving of the species' geographical range during Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
glaciation, leaving two relict
Relict
A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....
ranges.
This plant is similar to and often mistaken for Helenium autumnale
Helenium autumnale
Helenium autumnale is a flowering plant native to North America. Common names include common sneezeweed and large-flowered sneezeweed.-Natural habitat and distribution:...
, the common sneezeweed. It is a perennial herb generally growing to a maximum height between 70 centimeters and 1.1 meters, but it is known to reach 1.7 meters at times. There is a basal rosette of leaves and an erect, winged stem lined with lance-shaped leaves that become smaller toward the top of the stem. 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...
has several flower heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
, each with a spherical disc covered with disc florets and lined with yellow ray florets just over a centimeter long. Blooming occurs in July through October. The plant is self-incompatible
Self-incompatibility in plants
Self-incompatibility is a general name for several genetic mechanisms in angiosperms, which prevent self-fertilization and thus encourage outcrossing...
.
This species only grows near sinkhole
Sinkhole
A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks or suffosion processes for example in sandstone...
ponds in the Ozark Highlands of Missouri and the western margin of the Blue Ridge Mountains
Blue Ridge Mountains
The Blue Ridge Mountains are a physiographic province of the larger Appalachian Mountains range. This province consists of northern and southern physiographic regions, which divide near the Roanoke River gap. The mountain range is located in the eastern United States, starting at its southern-most...
in Virginia. These ponds are lined with clay or bedrock
Bedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
and are filled with water from about January to June or July each year. They may take the form of actual holes or they may be more like very wet meadow
Meadow
A meadow is a field vegetated primarily by grass and other non-woody plants . The term is from Old English mædwe. In agriculture a meadow is grassland which is not grazed by domestic livestock but rather allowed to grow unchecked in order to make hay...
s. The ponds are often actively grazed
Grazing
Grazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...
by cattle and can tolerate disturbance. The hydrology
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
of the sinkholes varies seasonally and year to year, causing a similar fluctuation in the population and recruitment
Recruitment (biology)
In biology, recruitment occurs when juvenile organisms survive to be added to a population. The term is generally used to refer to a stage whereby the organisms are settled and able to be detected by an observer....
of the sneezeweed.
The greatest threat to this species is habitat modification. Destruction of the sinkhole habitat could lead to the extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
of the species.