''Ottelia'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of an

aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...

family Hydrocharitaceae described as a genus in 1805. The genus is native to tropical and subtropical regions of

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

, and

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

.Cook, C.D.K. and Urmi- Konig, K. (1984
A revision of the genus ''Ottelia'' (Hydrocharitaceae). 2. The species of Eurasia, Australasia and America
''Aquatic Botany'' 20: 131–177

Description

The genus is highly variable, with a variety of features. It contains aquatic herbs with crowded leaves. Some of the leaves are held on short stems. Others float on long stems. The rooting stem is long. The flowers are held in a herbaceous bract that is many nerved and has two to six clear ribs. The tubular spathe is shortly divided into two. Each flower has two rows of a trimerous perianth held above the beak of the ovary. The rigid outer layer is oblong or linear. The larger inner layer is petal-like with a fleshy appendage at the base. There are six or more stamens, often with flattened filaments. The ovary is oblong and beaked with strongly developed placentas dividing it into six chambers that contain many ovules. There are six linear styles that are partially split in two. The tapering oblong fruits are included in the floral bract and have three to six wings. They contain numerous small, oblong seeds. It has been suggested that this genus should be divided into two subgenera and four sections: * Subgenus Ottelia has bisexual flowers. ** Section Ottelia: The spathes have a single flower and six to nine carpels in the ovary. ** Section Oligolobos: The spathes have many flowers and an ovary with three carpels. * Subgenus Boottia has unisexual flowers. The male spathes have one to many flowers while the female spathes always have many flowers. ** Section Boottia: The males spathes have one flower and the ovaries of the female flowers have nine to fifteen carpels. ** Section Xystrolobos: The female spathes have two to many flowers and an ovary with three or nine carpels.

Distribution

This genus is found throughout the

Paleotropics The Paleotropical Kingdom (Paleotropis) is a floristic kingdom comprising tropical areas of Africa, Asia and Oceania (excluding Australia and New Zealand), as proposed by Ronald Good and Armen Takhtajan. Part of its flora, inherited from the ancient ...

, from

and

New Caledonia ) , anthem = "" , image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg , map_alt = Location of New Caledonia , map_caption = Location of New Caledonia , mapsize = 290px , subdivision_type = Sovereign st ...

and to

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

. The areas with the highest diversity occur in central Africa (about 13 species) and south east Asia (about 8 species).They are mostly found growing in lakes, slow flowing creeks and rivers.

Phylogenomics and evolution

Originating in the mid

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

, this genus now consists of two major clades that correspond to the two major centers of diversity - Africa and Asia. Morphological evidence suggests that this genus originated in Africa. It then spread to South America and Australasia via the ocean, and then from Australasia to Asia. Global cooling, the development of the East Asian monsoon climate and tectonic movement likely aided diversification in China. The movement of the Yunnan-Guizhou Plateau Pin the liocenehas been suggested to explain the high endemism of Chinese species of ''Ottelia''.

Species

This genus is the second largest in its family (Hydrocharitaceae). The following species are accepted:

Conservation

The species belonging to this genus are being increasingly negatively impacted by the use and pollution of their water bodies. They have also been declining as a result of climate change. This will continue to occur as climate change accelerates habitat fragmentation and habitat loss due to changing conditions, including increasing water temperatures.

Gallery

Ottelia alismoides - flower view.jpg, Flower of ''Ottelia alismoides''

References

Hydrocharitaceae genera {{monocot-stub