''Marsilea villosa'', the ihiihi ( Hawaiian) or villous waterclover ( English), is a species of

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

that is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the islands of

Oahu Oahu (, , sometimes written Oahu) is the third-largest and most populated island of the Hawaiian Islands and of the U.S. state of Hawaii. The state capital, Honolulu, is on Oahu's southeast coast. The island of Oahu and the uninhabited Northwe ...

Molokai Molokai or Molokai ( or ; Molokaʻi dialect: Morotaʻi ) is the fifth most populated of the eight major islands that make up the Hawaiian Islands archipelago in the middle of the Pacific Ocean. It is 38 by 10 miles (61 by 16 km) at its g ...

and

Niihau Niihau (Hawaiian language, Hawaiian: ), anglicized as Niihau ( ), is the seventh largest island in Hawaii and the westernmost of the main islands. It is southwest of Kauai, Kauai across the Channels of the Hawaiian Islands#Kaulakahi Channel, Ka ...

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

. It is found exclusively in areas that experience periodic

flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

ing and become ephemeral pools within low elevation

dry forests The tropical and subtropical dry broadleaf forest is a habitat type defined by the World Wide Fund for Nature and is located at tropical and subtropical latitudes. Though these forests occur in climates that are warm year-round, and may receive ...

and

shrublands Spring Park is a small area in London, England. It is within the London Borough of Bromley and the London Borough of Croydon, straddling the traditional Kent-Surrey border along The Beck. Spring Park is located north of Addington, London, Adding ...

. Standing water allows the sporocarp to open and release

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

s. It also enables the resulting

sperm Sperm (: sperm or sperms) is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm ...

to swim toward and

fertilize Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or off ...

female

ova , abbreviated as OVA and sometimes as OAV (original animation video), are Japanese animated films and special episodes of a series made specially for release in home video formats without prior showings on television or in theaters, though the ...

. For new plants to become established, the waters must subside. Sporocarps only form once the soil has dried to a certain level. Like other species in its genus, the leaves of ''M. villosa'' resemble those of a

four-leaf clover The four-leaf clover is a rare mutation of the common three-leaf clover that has four Leaflet (botany), leaflets instead of three. According to traditional sayings, such clovers bring good luck, a belief that dates back to at least the 17th cent ...

Conservation

Fewer than 2,000 individual plants exist in four remaining

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

s. The plant 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, inv ...

in 1992.

References

External links

villosa ''Villosa'' is a genus of freshwater mussels, aquatic bivalve molluscs in the family Unionidae. Species Species within the genus ''Villosa'': * '' Villosa amygdala'' * '' Villosa arkansasensis'' - Ouachita creekshell * '' Villosa choctawensi ...

Endemic flora of Hawaii Native ferns of Hawaii {{Polypodiidae-stub