''Diplazium molokaiense'' is a rare species of fern known by the common name Molokai twinsorus fern. It is endemic to Hawaii, where it is one of the rarest ferns.Wood, K. R. (2006)
Conservation status of the Hawaiian endemic fern ''Diplazium molokaiense'' (Athyriaceae) in Honomanu, East Maui, Hawai'i.
''Endangered Species Research'' 5 1-5. It has historically been found on the islands of

Kauai Kauai, () anglicized as Kauai ( ), is geologically the second-oldest of the main Hawaiian Islands (after Niʻihau). With an area of 562.3 square miles (1,456.4 km2), it is the fourth-largest of these islands and the 21st largest island ...

, Oahu,

Lanai Lanai ( haw, Lānai, , , also ,) is the sixth-largest of the Hawaiian Islands and the smallest publicly accessible inhabited island in the chain. It is colloquially known as the Pineapple Island because of its past as an island-wide pineapple pl ...

Molokai Molokai , or Molokai (), is the fifth most populated of the eight major islands that make up the Hawaiian Islands, Hawaiian Islands archipelago in the middle of the Pacific Ocean. It is 38 by 10 miles (61 by 16 km) at its greatest length an ...

, and

Maui The island of Maui (; Hawaiian: ) is the second-largest of the islands of the state of Hawaii at 727.2 square miles (1,883 km2) and is the 17th largest island in the United States. Maui is the largest of Maui County's four islands, which ...

, but it is thought to have been extirpated from four of them and today can be found only on Maui where fewer than 70 individual plants remain. The fern was federally listed as an

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

of the United States in 1994.

Characteristics

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

rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...

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

Habitat

This fern grows in the moist riparian forests on the slopes of two mountains on Maui, one of which is the volcano Haleakalā. It can be found next to streams lined with basalt boulders and near waterfalls and plunge pools. The forest in the area has a mostly open canopy and is dominated by ʻōlapa (''Cheirodendron trigynum'') and ʻōhiʻa lehua (''Metrosideros polymorpha''). Other plants of the understory include Ākala (''Rubus hawaiensis''), Kanawao (''Broussaisia arguta'') and '' Coprosma'' species. The fern grows from walls of

moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...

y rocks alongside other ferns such as ''

Pteris cretica ''Pteris cretica'', the Cretan brake, ribbon fern, or Cretan brake fern, is a species of evergreen fern in the family Pteridaceae, native to Europe, Asia and Africa. Description The fern grows to tall by broad. It has arching pinnate fronds ...

'', '' Polystichum haleakalense'', ''

Pneumatopteris sandwicensis ''Pneumatopteris'' is a genus of about 80 species of terrestrial ferns in the family Thelypteridaceae. The range of the genus extends from tropical Africa, through Asia, Malesia and Australia to the Pacific islands, including Hawaii an ...

'' and ''

Diplazium sandwichianum ''Diplazium'' is a genus of ferns that specifically includes the approximately 400 known species of twinsorus ferns. The Greek root is ''diplazein'' meaning ''double'': the indusia in this genus lie on both sides of the vein. These ferns were ...

''.

Endangered status

Threats to this rare fern include habitat destruction and degradation due to the action of feral pigs,

flash flood A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice or snow flowing o ...

ing, and invasive plant species such as Australian blackwood (''Acacia melanoxylon''), sticky snakeroot (''Ageratina adenophora''), sweet vernal grass (''Anthoxanthum odoratum''), fringed willowherb (''Epilobium ciliatum''), velvet grass (''Holcus lanatus''), and

cat's ear Cat's ear is the common name for several species of flowering plants: *''Hypochaeris'' species, especially ''Hypochaeris radicata ''Hypochaeris radicata'' (sometimes spelled ''Hypochoeris radicata'') – also known as catsear, flatweed, cat's- ...

(''Hypochoeris radicata'').

References

External links

USDA Plants Profile
{{Taxonbar, from=Q5279805 molokaiense Native ferns of Hawaii Endemic flora of Hawaii Biota of Maui Biota of Molokai Plants described in 1913