Diplazium molokaiense is a rare species of fern

Fern

A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

 known by the common name Molokai twinsorus fern. It is endemic to Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, where it is one of the rarest ferns. It has historically been found on the islands of Kauai

Kauai

Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...

, Oahu

Oahu

Oahu or Oahu , known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the U.S. state of Hawaii. The state capital Honolulu is located on the southeast coast...

, Lanai

Lanai

Lānai or Lanai is the sixth-largest of the Hawaiian Islands. It is also known as the Pineapple Island because of its past as an island-wide pineapple plantation. The only town is Lānai City, a small settlement....

, Molokai

Molokai

Molokai or Molokai is an island in the Hawaiian archipelago. It is 38 by 10 miles in size with a land area of , making it the fifth largest of the main Hawaiian Islands and the 27th largest island in the United States. It lies east of Oahu across the 25-mile wide Kaiwi Channel and north of...

, and Maui

Maui

The island of Maui is the second-largest of the Hawaiian Islands at and is the 17th largest island in the United States. Maui is part of the state of Hawaii and is the largest of Maui County's four islands, bigger than Lānai, Kahoolawe, and Molokai. In 2010, Maui had a population of 144,444,...

, but it is thought to have been extirpated

Local extinction

Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...

 from four of them and today it only exists on Maui. There are fewer than 70 individual plants remaining there. The fern was federally listed as an endangered species

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 of the United States in 1994.

Characteristics

This fern has leaves up to about 20 centimeters long growing from a twisted rhizome

Rhizome

In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...

. Each dark green, shiny leaf is made up of several pairs of leaflets, the largest of which is about 5 × 2 cm. They have pointed tips and slightly rippled edges. The sori

Sorus

A sorus is a cluster of sporangia .In fungi and lichens, the sorus is surrounded by an external layer. In some red algae it may take the form of a depression into the thallus....

 are up to a centimeter long and are narrow and somewhat curved in shape.

Habitat

This fern grows in the moist riparian

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 forests on the slopes of two mountains on Maui, one of which is the volcano

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 Haleakalā

Haleakala

Haleakalā , or the East Maui Volcano, is a massive shield volcano that forms more than 75% of the Hawaiian Island of Maui. The western 25% of the island is formed by the West Maui Mountains.- History :...

. It can be found next to streams lined with basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

 boulders and near waterfall

Waterfall

A waterfall is a place where flowing water rapidly drops in elevation as it flows over a steep region or a cliff.-Formation:Waterfalls are commonly formed when a river is young. At these times the channel is often narrow and deep. When the river courses over resistant bedrock, erosion happens...

s and plunge pool

Plunge pool

A plunge pool can be a natural hydrologic fluvial landform feature or a constructed recreational garden feature...

s. The forest in the area has a mostly open canopy and is dominated by ʻōlapa

Cheirodendron trigynum

Cheirodendron trigynum, also known as Ōlapa or Common Cheirodendron, is a species of flowering plant in the ginseng family, Araliaceae, that is endemic to Hawaii. It is a medium-sized tree, reaching a height of and a trunk diameter of...

 (Cheirodendron trigynum) and ʻōhiʻa lehua

Metrosideros polymorpha

The ōhia lehua is a species of flowering evergreen tree in the myrtle family, Myrtaceae, that is endemic to the six largest islands of Hawaii. It is a highly variable tree, being tall in favorable situations, and much smaller when growing in boggy soils or on basalt...

 (Metrosideros polymorpha). Other plants of the understory

Understory

Understory is the term for the area of a forest which grows at the lowest height level below the forest canopy. Plants in the understory consist of a mixture of seedlings and saplings of canopy trees together with understory shrubs and herbs...

 include Ākala

Rubus hawaiensis

Rubus hawaiensis, also called the Ākala, is a species of Rubus endemic to Hawaii. It is found on the islands of Kauai, Molokai, Maui, and Hawaii in mesic to wet forest at elevations of...

 (Rubus hawaiensis), Kanawao

Broussaisia

Kanawao is a species of perennial flowering plant in the Hydrangea family, Hydrangeaceae, that is endemic to Hawaii. It belongs to a monotypic genus....

 (Broussaisia arguta) and Coprosma

Coprosma

Coprosma is a genus of 108 species that are found in New Zealand , Hawaii , Borneo, Java, New Guinea, islands of the Pacific Ocean to Australia and the Juan Fernández Is. Many species are small shrubs with tiny evergreen leaves, but a few are small trees and have much larger leaves...

species. The fern grows from walls of moss

Moss

Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...

y rocks alongside other ferns such as Pteris cretica, Polystichum haleakalense, Pneumatopteris sandwicensis and Diplazium sandwichianum.

Endangered status

Threats to this rare fern include habitat destruction

Habitat destruction

Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...

 and degradation due to the action of feral pigs, flash flood

Flash flood

A flash flood is a rapid flooding of geomorphic low-lying areas—washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a storm, hurricane, or tropical storm or meltwater from ice or snow flowing over ice sheets or snowfields...

ing, and invasive plant species

Invasive species

"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

 such as Australian blackwood (Acacia melanoxylon), sticky snakeroot

Ageratina adenophora

Ageratina adenophora is a species of flowering plant in the daisy family known by many common names, including eupatory, sticky snakeroot, crofton weed, and Mexican devil.- Description :...

 (Ageratina adenophora), sweet vernal grass

Anthoxanthum odoratum

-Introduction:Anthoxanthum odoratum, known as sweet vernal grass, holy grass, vanilla grass or buffalo grass, is a short-lived grass found wild in acidic grassland in Eurasia. It is also grown as a lawn grass and a house plant, due to its sweet scent, and can also be found on unimproved pastures...

 (Anthoxanthum odoratum), fringed willowherb

Epilobium ciliatum

Epilobium ciliatum is a species of willowherb known by the common names Fringed Willowherb and American Willowherb. This plant is found in many parts of the world. It is native to much of North America and eastern Asia, and it is an introduced species in much of Eurasia and Australia...

 (Epilobium ciliatum), velvet grass

Yorkshire Fog

Yorkshire Fog or Velvet Grass, Holcus lanatus, is a perennial grass in the Poaceae Family. 'Lanatus' is latin for 'wooly' which describes the plant's hairy texture....

 (Holcus lanatus), and cat's ear

Catsear

Catsear , also known as flatweed, cat's ear or false dandelion, is a perennial, low-lying edible herb often found in lawns. The plant is native to Europe, but has also been introduced to the Americas, Japan, Australia and New Zealand where it can be an invasive weed...

(Hypochoeris radicata).