Rhizophoraceae

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Rhizophoraceae
Rhizophora yngtree.jpg
Young Rhizophora mangle, a mangrove
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Malpighiales
Family: Rhizophoraceae
R.Br. in Flinders
Genera

See text

Rhizophoraceae Distribution.svg
The range of Rhizophoraceae
  •   Tropical trees
  •   Mangroves

The Rhizophoraceae is a family of tropical or subtropical flowering plants. [1] It includes around 147 species distributed in 15 genera. [2] Under the family, there are three tribes, Rhizophoreae, Gynotrocheae, and Macarisieae. [2] Even though Rhizophoraceae is known for its mangrove members, only the genera under Rhizophoreae grow in the mangrove habitats and the remaining members live in inland forests. [2]

Contents

Taxonomy

This family is now placed in the order Malpighiales, though under the Cronquist system, they formed an order in themselves (Rhizophorales). [3] It is sister group to Erythroxylaceae. [2] The sister group to the tribe Rhizophoreae is Gynotrocheae. [2] The generic relationships within the Macarisiae are not fully resolved. [2]

Within the mangrove tribe Rhizophoreae, there are four genera: Rhizophora, Kandelia, Ceriops, and Bruguiera. [2] Bruguiera is the basal genus and Rhizophora the most derived genus in the tribe. [2] Rhizophora is the only pan-tropical genus that is distributed along the intertidal zones of both the Indo-West Pacific (IWP) and Atlantic-East Pacific (AEP) regions. [4] The remaining mangrove genera are restricted to the IWP region. [4]

Genera

Morphological Characteristics

The tribe Macarisieae is characterized by a few plesiomorphies unknown in the rest of the family, such as superior ovary position, the presence of a seed appendage, and the absence of aerial roots. [5]

Within Gynotrocheae, Crossostylis is morphologically distinct from other Gynotrocheae in having capsular fruits that split open at maturity and an appendage on a mature seed. [5] In addition, Crossostylis possesses a multi-celled archesporium in ovules just like members in Macarisieae, while the archesporium is one-celled in the other Gynotrocheae. [5]

Among Rhizophoreae, there are three distinctive characters known as the adaptive features to the mangrove habitats: viviparous embryogenesis, high salt tolerance and aerial roots. [6]

Vivipary: The embryo of Rhizophoreae starts germination without dormancy. [6] It grows out of the seed coat and the fruit while still remain attached to the parent plant. [6] Although vivipary is found in other unrelated mangrove taxa such as Avicennia (Acanthaceae), Nypa (Arecaceae), and Pelliciera (Tetrameristaceae), they only break the seed coat but not the fruit wall before they split open. [6] Vivipary in Rhizophoreae include several embryological characteristics: [6] (1) the active growth of a hypocotyl meristem in the cotyledonary body, with endosperm overflow from the embryo sac. The growth of an endosperm can force open the micropyle, so that the embryo develops out of the integument. 2) The development of cotyledons as a cylindrical body. (3) The development of just one embryo, with other ovules being aborted after anthesis.

Wood anatomy: Rhizophoreae possess narrow and dense vessels. [7] These wood structures keep the xylem sap in high tension to absorb water, resulting in a high sodium chloride concentration and high osmatic potential. [7] Terrestrial species in Rhizophoreae could not survive in the intertidal zone because the osmatic potential in the sea water would be much higher than that in the xylem sap of the tree, resulting in water loss and disruption of cellular functions. [7]

Aerial roots: Instead of having tap roots deep underground, Rhizophoreae develop roots that branch out from the stem some distance above the soil surface. [8] Underground roots, like all plant tissues, require oxygen for respiration. [8] In underground soils of terrestrial habitats, gas exchanges take place at the interstitial pores among the soil particles. [8] In waterlogged soils, the diffusion rate of oxygen is extremely low. Rhizophoreae adapts to the anaerobic soils by having extensive roots above the ground which increases the surface area for gas exchanges. [8] The surface of aerial roots carry numerous gas exchange pores called lenticels, through which oxygen could diffuse into the underground tissues with air-filled spaces. [8]

Evolutionary history

The ancestor of Rhizophoraceae experienced two whole genome duplication events. [8] The first duplication event corresponds to the triplication shared among angiosperms. [8] The second duplication event was dated to ~74.6 million years ago (mya). [8] Around 66 mya, the planet underwent the Cretaceous–Tertiary mass extinction. [8] Then around 56.4 mya, the mangrove lineage diverged from its terrestrial relatives. [8] The divergence happened to occur in the time frame with in the extreme global warming event, the Paleocene-Eocene Thermal Maximum (PETM). [8] During this time period, there is a shift from a terrestrial to a marine, potentially anoxic, sedimentary depositional environment, suggesting a sea level rise. [8] After the dramatic global warming period, the mangrove species within Rhizophoraceae diversified within 10 mya, [8] which is relatively short in evolutionary sense. Although the sequence of the events does not suggest an absolute causal relationships between the former and the latter, a reasonable hypothesis for the diversification of Rhizophoraceae could be formulated: The second event of whole genome duplication increased the adaptability of the ancestor of Rhizophoraceae and chances of survival during the Cretaceous-Tertiary mass extinction by generating novel genetic materials for evolution to work on. [8] During the PETM global warming period, the terrestrial ancestors of Rhizophoraceae living close to the shore were forced into the intertidal zone because of a large-scale sea-level rise. [8] This sea level change exerted some selective pressure on the ancestors of Rhizophoraceae and those that were successfully adapted to the intertidal zone diverged from their terrestrial relatives and colonized this new habitat. [8] Eventually, differential habitats within the intertidal zone resulted in the speciation within the mangrove lineage of Rhizophoraceae. [8]

Related Research Articles

<span class="mw-page-title-main">Mangrove</span> Shrub growing in brackish water

A mangrove is a shrub or tree that grows mainly in coastal saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have special adaptations to take in extra oxygen and to remove salt, which allow them to tolerate conditions that would kill most plants. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in several plant families. They occur worldwide in the tropics and subtropics and even some temperate coastal areas, mainly between latitudes 30° N and 30° S, with the greatest mangrove area within 5° of the equator. Mangrove plant families first appeared during the Late Cretaceous to Paleocene epochs, and became widely distributed in part due to the movement of tectonic plates. The oldest known fossils of mangrove palm date to 75 million years ago.

<span class="mw-page-title-main">Coringa Wildlife Sanctuary</span> Sanctuary in Andhra Pradesh, India

Coringa Wildlife Sanctuary is an estuary situated near Kakinada in Andhra Pradesh, India. It is the third largest stretch of mangrove forests in India with 24 mangrove tree species and more than 120 bird species. It is home to the critically endangered white-backed vulture and the long billed vulture. Mangroves are a group of trees and shrubs that live in the coastal intertidal zone, with a dense tangle of prop roots that make the trees appear to be standing on stilts above the water. This tangle of roots allows the trees to handle the daily rise and fall of tides; hence, the mangrove forest gets flooded at least twice per day. The roots also slow the movement of tidal waters, causing sediments to settle out of the water and build up the muddy bottom.

<i>Rhizophora mangle</i> Species of flowering plant in the mangrove family Rhizophoraceae

Rhizophora mangle, the red mangrove, is distributed in estuarine ecosystems throughout the tropics. Its viviparous "seeds", in actuality called propagules, become fully mature plants before dropping off the parent tree. These are dispersed by water until eventually embedding in the shallows.

<i>Rhizophora</i> Genus of trees

Rhizophora is a genus of tropical mangrove trees, sometimes collectively called true mangroves. The most notable species is the red mangrove but some other species and a few natural hybrids are known. Rhizophora species generally live in intertidal zones which are inundated daily by the ocean. They exhibit a number of adaptations to this environment, including pneutomatophores that elevate the plants above the water and allow them to respire oxygen even while their lower roots are submerged and a cytological molecular "pump" mechanism that allows them to remove excess salts from their cells. The generic name is derived from the Greek words ριζα (rhiza), meaning "root," and φορος (phoros), meaning "bearing," referring to the stilt-roots.

<i>Avicennia germinans</i> Species of tree

Avicennia germinans, the black mangrove, is a shrub or small tree growing up to 12 meters in the acanthus family, Acanthaceae. It grows in tropical and subtropical regions of the Americas, on both the Atlantic and Pacific Coasts, and on the Atlantic Coast of tropical Africa, where it thrives on the sandy and muddy shores where seawater reaches. It is common throughout coastal areas of Texas and Florida, and ranges as far north as southern Louisiana and coastal Georgia in the United States.

<i>Rhizophora apiculata</i> Species of tree

The tall-stilt mangrove belongs to the Plantae kingdom under the Rhizophoraceae family. R. apiculata is distributed throughout Australia, Guam, India, Indonesia, Malaysia, Micronesia, New Caledonia, Papua New Guinea, the Philippines, Singapore, the Solomon Islands, Sri Lanka, Taiwan, the Maldives, Thailand, Vanuatu, and Vietnam. Rhizophora apiculata is called ‘bakhaw lalaki,’ in the Philippines, "Thakafathi ތަކަފަތި" in the Maldives, 'Đước' in Vietnam, Garjan in India, as well as other vernacular names.

<i>Bruguiera gymnorhiza</i> Species of tree

Bruguiera gymnorhiza, the large-leafed orange mangrove or oriental mangrove,) is a mangrove tree that grows usually to 7–20 metres (23–66 ft) high, but sometimes up to 35m, that belongs to the family Rhizophoraceae. It is found on the seaward side of mangrove swamps, often in the company of Rhizophora. It grows from the Western Pacific across Indian Ocean coasts to Cape Province, South Africa.

<span class="mw-page-title-main">New Guinea mangroves</span> Mangrove ecoregion that covers extensive areas of the coastline New Guinea

The New Guinea mangroves is a mangrove ecoregion that covers extensive areas of the coastline New Guinea, the large island in the western Pacific Ocean north of Australia.

<i>Avicennia alba</i> Species of plant

Avicennia alba is a species of tropical mangrove in the family Acanthaceae. It is found growing in coastal and estuarine locations in India, Southeast Asia, Australia, and Oceania.

<i>Kandelia obovata</i> Species of flowering plant

Kandelia obovata is a species of plant in the Rhizophoraceae family, i.e. a kind of mangrove. It is found in Vietnam, Natuna Islands of Indonesia, Southern China, Hong Kong, Taiwan, and Japan. Its presence in the Philippines is possible but not confirmed.

<span class="mw-page-title-main">Madagascar mangroves</span> Coastal ecoregion in the mangrove forest biome found on the west coast of Madagascar

Madagascar mangroves are a coastal ecoregion in the mangrove forest biome found on the west coast of Madagascar. They are included in the WWF's Global 200 list of most outstanding ecoregions.

<span class="mw-page-title-main">Southern Africa mangroves</span> Ecoregion of mangrove swamps in rivers and estuaries on the eastern coast of South Africa

The Southern Africa mangroves are mangrove ecoregion on the Mozambique's southernmost coast and the eastern coast of South Africa.

<span class="mw-page-title-main">Ord River Floodplain</span> Floodplain in Australia

The Ord River floodplain is the floodplain of the lower Ord River in the Shire of Wyndham-East Kimberley, in the Kimberley region of northern Western Australia. It lies within the Victoria Bonaparte IBRA bioregion and contains river, seasonal creek, tidal mudflat and floodplain wetlands, with extensive stands of mangroves, that support saltwater crocodiles and many waterbirds. It is recognised as an internationally important wetland area, with 1,384 square kilometres (534 sq mi) of it designated on 7 June 1990 as Ramsar Site 477 under the Ramsar Convention on Wetlands.

<span class="mw-page-title-main">Sunda Shelf mangroves</span> Mangrove ecoregion in Southeast Asia

The Sunda Shelf mangroves ecoregion, in the mangrove biome, are on the coasts of the islands of Borneo and eastern Sumatra in Malaysia and Indonesia. They are home to the proboscis monkey.

<i>Bruguiera</i> Genus of flowering plants

Bruguiera is a plant genus in the family Rhizophoraceae. It is a small genus of five mangrove species and three hybrids of the Indian and west Pacific Ocean region, its range extending from East Africa and Madagascar through coastal India, Sri Lanka and Southeast Asia to northern Australia, Melanesia and Polynesia. It is characterised by calyces with 8-16 lanceolate, pointed lobes, 16-32 stamens, explosive release of pollen, and viviparous propagules. It is named in honour of French explorer and biologist Jean Guillaume Bruguière (1750–1798). Recently, the eighth taxa of Bruguiera, B. × dungarra was recognised as occurring in northern Australia.

<i>Bruguiera cylindrica</i> Species of flowering plant

Bruguiera cylindrica is a mangrove in the family Rhizophoraceae. It grows in mangrove swamps in tropical Asia.

<i>Ceriops tagal</i> Species of tree

Ceriops tagal, commonly known as spurred mangrove or Indian mangrove, is a mangrove tree species in the family Rhizophoraceae. It is a protected tree in South Africa. The specific epithet tagal is a plant name from the Tagalog language.

<i>Ceriops australis</i> Species of flowering plant

Ceriops australis, the yellow mangrove or smooth-fruited yellow mangrove, is a species of mangrove in the family Rhizophoraceae, native to tropical northern Australia and southern New Guinea. It is a common species in the region and although mangroves are threatened by habitat destruction and climate change, the International Union for Conservation of Nature has assessed its conservation status as being of "least concern".

<i>Rhizophora racemosa</i> Species of tree

Rhizophora racemosa is a species of mangrove tree in the family Rhizophoraceae. It has a patchy distribution on the Pacific coast of Central and South America, occurs in places on the Atlantic coast of that continent, and has a more widespread range on the Atlantic coast of West Africa.

References

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