Aegialitis
Encyclopedia
Aegialitis is a genus
of two shrubby mangrove
species, with one native to Southeast Asia
and the other native to Australia
and Papua New Guinea
.
species have leafy stems with leathery leaves arranged alternately or spirally. The leaf margins are entire and have parallel veins.
The hermaphroditic
flowers are pollinated by Hymenoptera
, Lepidoptera
, and Diptera
. Flowers are arranged in terminal cymose racemous
inflorescence
s. Individual flowers have five sepal
s arranged in a fused tube around the white gamopetalous corolla that has five petals fused into a short tube. The androecium consists of five stamen
s that are attached near the base of the corolla tube. The superior gynoecium
has five carpels, each with a 1-celled pistil and unilocular
ovaries
. Fruit are dehiscent
and have a spongy mesocarp.
Unlike other mangrove species, the members of Aegialitis generally do not have aerial root
s.
through the Northern Territory
and into Queensland
and along the coastline of Papua New Guinea. A. rotundifolia is found on the shorelines of the Andaman Sea
and the Bay of Bengal
from Orissa
to Mergui
and on the Andaman Islands
.
The distribution of these two species with respect to the other members of the Plumbaginaceae is suggestive of the evolutionary history and phylogenetic
placement of Aegialitis. Several authors have discovered evidence for three distinct southern migrations of this mostly Northern Hemisphere
family, the first of which remained isolated and evolved into the existing members of this genus. This hypothesized migration and evolutionary history explains the more primitive breeding system characteristics and morphology in this genus in relation to the rest of the family.
As with other mangrove species, the habitat preferred by the members of this genus are sandy or rocky soils in the more saline environment of the mangroves toward the sea. The species are thus halophytic
.
in his 1810 work Prodromus Florae Novae Hollandiae et Insulae Van Diemen
when he described the single species A. annulata. The second species was described by William Roxburgh
in the 1830s. A genus of grass
es was given the same genus name in 1820 by Carl Bernhard von Trinius
and later renamed Rostraria
.
There have been several opinions on the proper placement of the genus in relation to the rest of the Plumbaginaceae, though most authors have noted its distinct characteristics make it difficult to place properly. In 1968 Igorj Alexandrovich Linczevski suggested that the genus be included in its own monotypic
family, the Aegialitidaceae. The Plumbaginaceae has historically been divided into either two subfamilies or two tribes and each approach has offered a different perspective of the proper taxonomic relationship in the family. Through cladistic analysis
using both genetic and morphological characteristics, studies have concluded that Aegialitis is the sister taxon
to the rest of its subfamily (Staticoideae) and thus has been assigned to the monotypic tribe Aegialitideae, which is sister to the tribe Staticeae (including the genera Acantholimon
, Armeria
, Goniolimon, Limoniastrum, and Limonium).
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 two shrubby mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
species, with one native to Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
and the other native to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
.
Description
The two species of the genus are woody mangrove shrubs or small trees that grow up to 2 to 3 m tall. The deciduousDeciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
species have leafy stems with leathery leaves arranged alternately or spirally. The leaf margins are entire and have parallel veins.
The hermaphroditic
Plant sexuality
Plant sexuality covers the wide variety of sexual reproduction systems found across the plant kingdom. This article describes morphological aspects of sexual reproduction of plants....
flowers are pollinated by Hymenoptera
Hymenoptera
Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...
, Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
, and Diptera
Diptera
Diptera , or true flies, is the order of insects possessing only a single pair of wings on the mesothorax; the metathorax bears a pair of drumstick like structures called the halteres, the remnants of the hind wings. It is a large order, containing an estimated 240,000 species, although under half...
. Flowers are arranged in terminal cymose racemous
Raceme
A raceme is a type of inflorescence that is unbranched and indeterminate and bears pedicellate flowers — flowers having short floral stalks called pedicels — along the axis. In botany, axis means a shoot, in this case one bearing the flowers. In a raceme, the oldest flowers are borne...
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...
s. Individual flowers have five sepal
Sepal
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...
s arranged in a fused tube around the white gamopetalous corolla that has five petals fused into a short tube. The androecium consists of five stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
s that are attached near the base of the corolla tube. The superior gynoecium
Gynoecium
Gynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
has five carpels, each with a 1-celled pistil and unilocular
Locule
A locule is a small cavity or compartment within an organ or part of an organism ....
ovaries
Ovary (plants)
In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...
. Fruit are dehiscent
Dehiscence (botany)
Dehiscence is the opening, at maturity, in a pre-defined way, of a plant structure, such as a fruit, anther, or sporangium, to release its contents. Sometimes this involves the complete detachment of a part. Structures that open in this way are said to be dehiscent...
and have a spongy mesocarp.
Unlike other mangrove species, the members of Aegialitis generally do not have aerial root
Aerial root
Aerial roots are roots above the ground. They are almost always adventitious. They are found in diverse plant species, including epiphytes such as orchids, tropical coastal swamp trees such as mangroves, the resourceful banyan trees, the warm-temperate rainforest rātā and pōhutukawa Aerial roots...
s.
Distribution and habitat
The two species of the genus are native to Southeast Asia and Australia, but their distribution ranges do not overlap. A. annulata is found along the northern coasts of Australia from Western AustraliaWestern Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
through the Northern Territory
Northern Territory
The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...
and into Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
and along the coastline of Papua New Guinea. A. rotundifolia is found on the shorelines of the Andaman Sea
Andaman Sea
The Andaman Sea or Burma Sea is a body of water to the southeast of the Bay of Bengal, south of Burma, west of Thailand and east of the Andaman Islands, India; it is part of the Indian Ocean....
and the Bay of Bengal
Bay of Bengal
The Bay of Bengal , the largest bay in the world, forms the northeastern part of the Indian Ocean. It resembles a triangle in shape, and is bordered mostly by the Eastern Coast of India, southern coast of Bangladesh and Sri Lanka to the west and Burma and the Andaman and Nicobar Islands to the...
from Orissa
Orissa
Orissa , officially Odisha since Nov 2011, is a state of India, located on the east coast of India, by the Bay of Bengal. It is the modern name of the ancient nation of Kalinga, which was invaded by the Maurya Emperor Ashoka in 261 BC. The modern state of Orissa was established on 1 April...
to Mergui
Mergui
Myeik is a city in Tanintharyi Division in Myanmar , located in the extreme south of the country on the coast of an island on the Andaman Sea. the estimated population was over 209,000. The area inland from the city is a major smuggling corridor into Thailand.-History:Myeik was the southernmost...
and on the Andaman Islands
Andaman Islands
The Andaman Islands are a group of Indian Ocean archipelagic islands in the Bay of Bengal between India to the west, and Burma , to the north and east...
.
The distribution of these two species with respect to the other members of the Plumbaginaceae is suggestive of the evolutionary history and phylogenetic
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
placement of Aegialitis. Several authors have discovered evidence for three distinct southern migrations of this mostly Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...
family, the first of which remained isolated and evolved into the existing members of this genus. This hypothesized migration and evolutionary history explains the more primitive breeding system characteristics and morphology in this genus in relation to the rest of the family.
As with other mangrove species, the habitat preferred by the members of this genus are sandy or rocky soils in the more saline environment of the mangroves toward the sea. The species are thus halophytic
Halophyte
A halophyte is a plant that grows where it is affected by salinity in the root area or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs, and seashores. An example of a halophyte is the salt marsh grass Spartina alterniflora . Relatively few plant species are...
.
Botanical history and taxonomy
The genus Aegialitis was described by Robert BrownRobert Brown (botanist)
Robert Brown was a Scottish botanist and palaeobotanist who made important contributions to botany largely through his pioneering use of the microscope...
in his 1810 work Prodromus Florae Novae Hollandiae et Insulae Van Diemen
Prodromus Florae Novae Hollandiae et Insulae Van Diemen
Prodromus Florae Novae Hollandiae et Insulae Van Diemen is an 1810 flora of Australia by botanist Robert Brown. Often referred to as Prodromus Flora Novae Hollandiae, or by its standard botanical abbreviation Prodr. Fl. Nov. Holland., it was the first attempt at a survey of the Australian flora...
when he described the single species A. annulata. The second species was described by William Roxburgh
William Roxburgh
William Roxburgh was a Scottish surgeon and botanist. He has been called the Father of Indian Botany.-Early life:Roxburgh was born at Underwood in the parish of Craigie, Ayrshire. He studied medicine in Edinburgh...
in the 1830s. A genus of grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
es was given the same genus name in 1820 by Carl Bernhard von Trinius
Carl Bernhard von Trinius
Carl Bernhard von Trinius was a German-born botanist.Trinius was a specialist in grasses and described many species in his career including Agrostis pallens, Cenchrus agrimonioides and Festuca subulata....
and later renamed Rostraria
Rostraria
Rostraria is a genus of annual grasses, which are native to Eurasia and North Africa and widely naturalised elsewhere.There are around 10 currently recognised species, including:*Rostraria clarkeana Holub...
.
There have been several opinions on the proper placement of the genus in relation to the rest of the Plumbaginaceae, though most authors have noted its distinct characteristics make it difficult to place properly. In 1968 Igorj Alexandrovich Linczevski suggested that the genus be included in its own monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
family, the Aegialitidaceae. The Plumbaginaceae has historically been divided into either two subfamilies or two tribes and each approach has offered a different perspective of the proper taxonomic relationship in the family. Through cladistic analysis
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
using both genetic and morphological characteristics, studies have concluded that Aegialitis is the sister taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
to the rest of its subfamily (Staticoideae) and thus has been assigned to the monotypic tribe Aegialitideae, which is sister to the tribe Staticeae (including the genera Acantholimon
Acantholimon
Acantholimon is a genus of small flowering plants within the plumbago or leadwort family, Plumbaginaceae. They are distributed from southeastern Europe to central Asia and also in South America, but also cultivated elsewhere in rock gardens.-Species:Species of Acantholimon include:*Acantholimon...
, Armeria
Armeria
Armeria is the botanical name for a genus of flowering plants. These plants are sometimes known as "thrift" or as the "sea pinks" as they are often found on coastlines...
, Goniolimon, Limoniastrum, and Limonium).