Menodora
Encyclopedia
Menodora is a genus
of perennial plant
s and shrub
s in the olive family Oleaceae
. Its 23 species (as per Green 2003) are found in the temperate Americas
and in southern Africa
. These are uniformly species of deserts and arid grasslands or savannas.
with 5-10 lobes (rarely more), while the corolla is similarly united but with 4-6 lobes. The corolla is a pretty, bright yellow (except for M. spinescens, whose corollas are white), and is often scented. The fruit is a didymous, bilobed capsule with each globose locule or lobe containing 2-4 seeds. In the majority of species, each locule also features circumscissile dehiscence. Vegetatively, the plants are generally unremarkable, with a "green-stick" look that is common to many desert plants. In the dry seasons, plants may lose their generally small or reduced leaves altogether. Leaf shape within the genus is highly variable, ranging from short and linear to almost feathery and pinnatisect. Leaves are most commonly found arranged in opposite pairs, but in some individuals may be predominantly alternate.
and Bonpland
(1809) when they first encountered the genus in the present state of Hidalgo in Mexico.
Menodora longiflora has occasionally been treated as the monotypic genus Menodoropsis (Small, 1903) due to the extraordinary length of its corolla tube (to nearly 6 cm, as opposed to typical lengths of 0.3 to 0.7 cm in most other species), but based on both morphological and molecular data it plainly belongs within Menodora. Small took the name for the genus from one of the sections of the Menodora recognized by Asa Gray (1852). Neither the sectional classification of Gray (1852) nor Steyermark (1932) have been upheld by recent molecular studies.
One of the more distinctive things about this genus is the pattern of disjunction or non-continuous distribution. In the Americas
, the distribution jumps over the tropics, with only a few species whose individual distributions just cross into the tropics (e.g., north to central Bolivia
, and south to Oaxaca
in Mexico
). This is a common pattern found in many genera, but not many others with a similar amphitropical distribution also have connections across the Atlantic
with Africa
. This intercontinental distribution of Menodora was often cited as evidence of continental drift
or the breakup of the Pangaea
or Gondwana
n supercontinent
s, but more recently it has been judged to be the result of long distance dispersal.
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...
of perennial plant
Perennial 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...
s and shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
s in the olive family Oleaceae
Oleaceae
Oleaceae are a family containing 24 extant genera and around 600 species of mesophytic shrubs, trees and occasionally vines. As shrubs, members of this family may be twine climbers, or scramblers.-Leaves:...
. Its 23 species (as per Green 2003) are found in the temperate Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
and in southern Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. These are uniformly species of deserts and arid grasslands or savannas.
Description
The usually bisexual flowers have a united calyxSepal
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...
with 5-10 lobes (rarely more), while the corolla is similarly united but with 4-6 lobes. The corolla is a pretty, bright yellow (except for M. spinescens, whose corollas are white), and is often scented. The fruit is a didymous, bilobed capsule with each globose locule or lobe containing 2-4 seeds. In the majority of species, each locule also features circumscissile dehiscence. Vegetatively, the plants are generally unremarkable, with a "green-stick" look that is common to many desert plants. In the dry seasons, plants may lose their generally small or reduced leaves altogether. Leaf shape within the genus is highly variable, ranging from short and linear to almost feathery and pinnatisect. Leaves are most commonly found arranged in opposite pairs, but in some individuals may be predominantly alternate.
Etymology
Willis Jepson mistakenly suggested that the origin of the genus name was rather obscure, perhaps deriving from the Greek for "half-moon spear" for the appearance of the dehisced fruit on its pedicel. In reality, the name was specifically derived from the Greek μενος (menos), meaning "force," and Δορον (doron), meaning "gift," referring to the sustenance the plants provided to the horses of HumboldtAlexander von Humboldt
Friedrich Wilhelm Heinrich Alexander Freiherr von Humboldt was a German naturalist and explorer, and the younger brother of the Prussian minister, philosopher and linguist Wilhelm von Humboldt...
and Bonpland
Aimé Bonpland
Aimé Jacques Alexandre Bonpland was a French explorer and botanist.Bonpland's real name was Goujaud, and he was born in La Rochelle, a coastal city in France. After serving as a surgeon in the French army, and studying under J. N...
(1809) when they first encountered the genus in the present state of Hidalgo in Mexico.
Selected species
|
|
Menodora scabra Menodora scabra is a species of flowering plant in the olive family known by the common name rough menodora. It is native to the southwestern United States and northern Mexico, where it grows in varied mountain, plateau, and desert habitat. It is a small, multibranched subshrub producing several... A.Gray – Rough Menodora Menodora spinescens Menodora spinescens is a species of flowering plant in the olive family known by the common name spiny menodora. It is native to the southwestern United States, where it grows in varied mountain, canyon, and desert habitat. It is a shrub producing upright stems up to 90 centimeters tall, branching... A.Gray – Spiny Menodora |
Taxonomy
Some botanists have suggested based on molecular evidence that Menodora belongs within a broader circumscription of Jasminum. The two genera are closely related, but morphologically Menodora is quite distinct; it is not that Menodora may need to be placed within Jasminum, but that the alternate-leaved yellow-flowered jasmines may need to be removed from the circumscription of the larger genus.Menodora longiflora has occasionally been treated as the monotypic genus Menodoropsis (Small, 1903) due to the extraordinary length of its corolla tube (to nearly 6 cm, as opposed to typical lengths of 0.3 to 0.7 cm in most other species), but based on both morphological and molecular data it plainly belongs within Menodora. Small took the name for the genus from one of the sections of the Menodora recognized by Asa Gray (1852). Neither the sectional classification of Gray (1852) nor Steyermark (1932) have been upheld by recent molecular studies.
One of the more distinctive things about this genus is the pattern of disjunction or non-continuous distribution. In the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
, the distribution jumps over the tropics, with only a few species whose individual distributions just cross into the tropics (e.g., north to central Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
, and south to Oaxaca
Oaxaca
Oaxaca , , officially Estado Libre y Soberano de Oaxaca is one of the 31 states which, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided into 571 municipalities; of which 418 are governed by the system of customs and traditions...
in Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
). This is a common pattern found in many genera, but not many others with a similar amphitropical distribution also have connections across the Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
with Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. This intercontinental distribution of Menodora was often cited as evidence of continental drift
Continental drift
Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912...
or the breakup of the Pangaea
Pangaea
Pangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
or Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
n supercontinent
Supercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
s, but more recently it has been judged to be the result of long distance dispersal.