| Riccia atlantica | |
|---|---|
Scientific classification  | |
| Kingdom: | Plantae |
| Division: | Marchantiophyta |
| Class: | Marchantiopsida |
| Order: | Marchantiales |
| Family: | Ricciaceae |
| Genus: | Riccia |
| Species: | R. atlantica |
| Binomial name | |
| Riccia atlantica Sérgio & Perold | |
Riccia atlantica is a rare species of liverwort in the family Ricciaceae. It is endemic to the Madeira archipelago and the Savage Islands in Portugal. Its natural habitat is rocky shores.
Riccia atlantica was first scientifically described in 1992 by Cécilia Loff Pereira Sérgio Costa Gomes and Sarie Magdalena Perold. The type specimen (holotype: LISU; isotype: MADJ) was collected at Ponta de S. Lourenço, Nossa Senhora de Piedade, Madeira, at an elevation of 50–60 m. The species is classified within subgenus Riccia, section Riccia. [2]
Riccia atlantica is a small, annual liverwort that forms rosettes up to 10 mm wide. When fresh, the plant appears pale green with a distinctive shiny, crystalline surface texture due to its specialised surface (epithelial) cells. These cells are distinctly large, globe-shaped, and arranged in one or two layers. [2]
The individual branches of the plant are 3–6 mm long, 0.5–1.0 mm wide, and 0.3–0.5 mm thick. They fork once or twice symmetrically to form a Y-shape. In cross-section, each branch is flat on the bottom and rounded on top, being about 2 to 2.5 times wider than thick. The edges are rounded and blunt. When dry, the plant's edges curl slightly inward. [2]
The reproductive structures are separated by gender (dioicous), with male and female organs occurring on different plants. The male structures (antheridia) appear in groups of 4–6 along the plant's midline, with their necks projecting about 450 micrometres. Each branch typically contains 2–3 spore-producing capsules (sporangia). The spores are triangular-globular in shape, measuring 70–80 micrometres in diameter, and have a distinctive pattern of hexagonal compartments on their surface. [2]
The species is distinguished from its relatives by several features: its lack of protective hairs (cilia), its very small, transparent scales on the underside that do not reach the plant's edges, and its unique spore ornamentation pattern. [2]
Riccia atlantica is known from the Madeira archipelago (Madeira island, Porto Santo, and Deserta Grande) and the Selvagens archipelago, where it was first discovered in 2005. Its total extent of occurrence is about 11,260 km², with an area of occupancy of 32 km². [1]
The species grows on volcanic deposits, typically found near cliffs or on exposed slopes. [1] It specifically grows in rock cracks and under rocks in coastal exposed areas, [3] including on exposed coastal cliffs and eroded soil in rock hollows, at elevations between 50–250 metres. The species has low dispersal capacity, with its large spores typically remaining near the parent colonies. [1]
On Madeira island, it is found in the eastern part, specifically the Ponta de S. Lourenço area. This region is characterized by its xerothermic (hot and dry) conditions, receiving less than 500 mm of annual rainfall, which falls primarily in winter. [2] Under the influence of northeasterly trade winds but protected from cloud condensation by the low altitude, [3] it occurs alongside other short-lived bryophytes (mosses and liverworts) adapted to these harsh conditions, including Acaulon muticum , Fissidens algarvicus , Exormotheca pustulosa , Riccia nigrella , and Desmatodon convolutus . [2] The population is naturally restricted due to its specialised habitat requirements, and complete extinction has been predicted by 2070 in some climate change scenarios. [1]
Riccia atlantica is classified as Critically Endangered (CR) by the International Union for Conservation of Nature. The total population is estimated at fewer than 250 mature individuals, with each subpopulation containing fewer than 50 plants. [1]
Multiple threats endanger this species' survival. In Madeira and Porto Santo, tourism development and recreational activities pose the primary risks. On Deserta Island, climate change threatens the species by potentially reducing the shrub cover it depends on. In the Selvagens population, increasing soil salinity is causing a decline in suitable habitat. The species faces additional challenges from the spread of coarse grasses, which can prevent colonisation of new areas by limiting available bare surfaces. Changes in local agricultural practices may also reduce or alter suitable substrates. Wildfires pose a further threat to existing populations. [1] Modeling studies predict severe climate-driven habitat loss for R. atlantica over coming decades. Under moderate climate change scenarios, only about 1% of currently suitable habitat is expected to remain by 2070, while under more severe scenarios the species is predicted to face complete extinction in its native range due to loss of climatically suitable areas. [4]
Some protective measures are in place. The species is protected under regional legislation in Madeira, and its populations in Madeira, Deserta Grande, and Selvagem overlap with Natura 2000 sites. Conservation experts recommend careful protection of existing sites from tourism and agricultural impacts, along with regular monitoring of population status and habitat conditions. They also suggest considering ex situ conservation measures for this rare species. [1]
Madeira, officially the Autonomous Region of Madeira, is an autonomous region of Portugal. It is an archipelago situated in the North Atlantic Ocean, in the region of Macaronesia, just under 400 kilometres (250 mi) north of the Canary Islands —Spain—, 520 kilometres (320 mi) west of the Kingdom of Morocco and 805 kilometres (500 mi) southwest of mainland Portugal. Madeira sits on the African Tectonic Plate, although it is culturally, politically and ethnically associated with Europe, with its population predominantly descended from Portuguese settlers. Its population was 251,060 in 2021. The capital of Madeira is Funchal, on the main island's south coast.
The Marchantiophyta are a division of non-vascular land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information. The division name was derived from the genus name Marchantia, named by French botanist Jean Marchant after his father.
The Savage Islands or Selvagens Islands are a small Portuguese archipelago in the North Atlantic Ocean, 280 kilometres (175 mi) south of Madeira and 165 kilometres (105 mi) north of the Canary Islands. The archipelago includes two major islands, Selvagem Grande and Selvagem Pequena, each surrounded by a cluster of islets and reefs, with the total area of 2.73 km2 (1.05 sq mi). The archipelago is administered as part of the Portuguese municipality of Funchal, belongs to the Madeiran civil parish of Sé, and is the southernmost point of Portugal.
Riccia is a genus of liverworts in the order Marchantiales.
Marsupella profunda, the western rustwort, is a liverwort native to Europe and known only from Portugal and Great Britain (Cornwall) and has been sighted in the Canary Islands. It is a small reddish liverwort and can be confused with Marsupella sprucei which has a more widespread distribution.
An elater is a cell that is hygroscopic, and therefore will change shape in response to changes in moisture in the environment. Elaters come in a variety of forms, but are always associated with plant spores. In many plants that do not have seeds, they function in dispersing the spores to a new location. Mosses do not have elaters, but peristomes which change shape with changes in humidity or moisture to allow for a gradual release of spores.
Frullania polysticta is a species of liverwort in the family Frullaniaceae. It is found only in Madeira and the Canary Islands and is considered a vulnerable species.
Fulfordianthus evansii is a species of liverwort in the family Lejeuneaceae. It is found in Belize, Costa Rica, Guatemala, and Panama. Its natural habitat is subtropical or tropical moist lowland forests.
Radula jonesii is a species of liverwort in the family Radulaceae, first described in 1988 from specimens collected in the Anaga Mountains of Tenerife. Endemic to Macaronesia, this dark to olive-green liverwort is known from five locations on Madeira Island and one location on Tenerife, where it grows as both an epiphyte on trees such as Laurus novocanariensis and as a lithophyte on shaded rocks in old growth laurel forest ecosystems between 800–1,000 m (2,600–3,300 ft) altitude. The species is distinguished by its procumbent growth habit, pinnately branched stems measuring 10–15 mm (0.4–0.6 in) in length, and distinctive cellular features including uniformly thin-walled leaf cells. Classified as Endangered due to its restricted range and small population size, R. jonesii faces threats from climate change, habitat degradation, and tourism pressure, though its habitat receives protection through various conservation designations including UNESCO World Heritage status.
Lejeunea drehwaldii, synonym Sphaerolejeunea umbilicata, is a species of liverwort in the family Lejeuneaceae. It is endemic to Colombia. Its natural habitat is subtropical or tropical moist lowland forests.
Spruceanthus theobromae is a species of liverwort in the family Lejeuneaceae. It is endemic to Ecuador, where it is the only liverwort species known to be endemic to the western foothills of the Ecuadorian Andes.
Jensenia is a bryophyte plant genus in the liverwort family Pallaviciniaceae. It has been treated as a subgenus of Pallavicinia by several authors, though a set of features seems to set it apart as a genus. The six or seven species of the genus belong to a southern, possibly Gondwana element.
Radulaceae is a family of liverworts, and the only family in the order Radulales. The family comprises three genera: Radula, Cladoradula, and Dactyloradula, recognised as distinct following a 2022 taxonomic revision. Distinguishing features include bilobed leaves arranged in two rows, with the smaller lobe folded under the larger one, and rhizoids uniquely emerging from leaves rather than stems. The family lacks underleaves, which are common in other liverwort families. Fossil evidence from Burmese amber indicates the family had diversified by the Cretaceous period, approximately 98 million years ago, with molecular studies suggesting its divergence from related groups occurred during the Permian period.
Lejeunea hodgsoniana is a species of liverwort in the family Lejeuneaceae. Endemic to New Zealand, it was first recognized in 1980 but not formally described until 2013. The plant forms bright green mats up to 7 cm (2.8 in) in diameter on tree bark and occasionally on rocks. The species is found from the Kermadec Islands in the north to the Chatham Islands in the south, primarily in coastal and lowland areas below 100 m (330 ft) elevation. It is distinguished from related species by its relatively large size, multi-celled tooth on the leaf lobule, and deeply divided underleaves with pointed tips. While showing a particular affinity for mahoe trees, it grows on various native and introduced trees and is considered "Not Threatened" under the New Zealand Threat Classification System due to its abundance within its range and ability to grow in both pristine and disturbed habitats.
Whittlesford - Thriplow Hummocky Fields is a 55.6-hectare (137-acre) biological Site of Special Scientific Interest between Whittlesford and Thriplow in Cambridgeshire. This site has two unusual species, the nationally rare grass-poly, which is only found in south Cambridgeshire on the British mainland, and the nationally uncommon fairy shrimp Chirocephalus diaphanus. They are found in shallow hollows in arable fields, which are the result of ice lenses melting at the end of the last ice age. There are also uncommon liverworts.
The Madeira evergreen forests is a laurissilva ecoregion of southwestern Europe. It covers the archipelago of Madeira and some nearby islands in the Atlantic Ocean. Laurel forest, known as Laurisilva of Madeira, once covered the islands. Over centuries the laurel forests were mostly cleared. Madeira's remaining forests are now protected.
Trichocolea tomentella is a species of liverwort belonging to the family Trichocoleaceae. It forms loose, pale green to yellowish-white mats and is characterised by its highly divided leaves that give it a feathery or fuzzy appearance. The species has a wide distribution across temperate regions of the Northern Hemisphere, particularly in oceanic and suboceanic areas, occurring in Europe, Asia, North Africa, and eastern North America. It typically grows in moist, shaded locations, especially near springs and streams in deciduous and coniferous forests. While capable of sexual reproduction, with male and female structures on separate plants, it reproduces predominantly through vegetative means via branching and fragmentation. The species shows considerable morphological variation between populations but maintains stable taxonomic characteristics in its cell structure. Though it can form extensive pure patches and effectively compete with other bryophytes in suitable habitats, T. tomentella faces threats from habitat destruction, particularly through logging and drainage of its preferred moist forest habitats.
Atlantica calathoides is a species of land snail belonging to the family Gastrodontidae.
Fissidens microstictus is an extinct species of moss in the family Fissidentaceae. It was endemic to Madeira, Portugal. Last seen in 1982, it was assessed as extinct in 1992 due to the destruction of its natural habitat.
