''Bidens amplectens'', the Waiʻanae kokoʻolau, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

. It belongs to the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

Bidens ''Bidens'' is a genus of flowering plants in the aster family, Asteraceae.''Bidens''.
Flo ...

, collectively called kokoʻolau or koʻokoʻolau in the Hawaiian language. It is found in coastal and dry lowland habitats in the Waiʻanae Range on Oʻahu. It is threatened by

habitat loss Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

due to the spread of

invasive weed An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

s and

brush fire A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identif ...

s. The species is also threatened by

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

and

habitat degradation Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

, and

herbivory A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

. ''Bidens amplectens'' is currently listed as

endangered 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 in ...

under the Endangered Species Act.

General description

''Bidens amplectens'' is a member of the sunflower family (

). It is an herb with branched stems, from 1.5 to 3 m (5 to 10 ft) tall. It has sparsely

pubescent The adjective pubescent may describe: * people or animals undergoing puberty * plants that are hairy, covered in trichomes * insects that are covered in setae In biology, setae (singular seta ; from the Latin word for "bristle") are any of a ...

leaves that are pinnately compound, 9 to 15 cm (14 to 22 in) long with 3 to 5 leaflets. Cymes with lateral branches have 10 to 30 flower heads. Ray florets are yellow, 7 to 9 per head, and disk florets are 40 to 60 per head with yellow corollas. Achenes (dry fruit) are gray, straight, wingless, 5 to 8 mm (0.2 to 0.3 in) long and 1 mm (0.04 in) wide, sparsely setose (bristly) on margins and faces.

Life history

''Bidens amplectens'' is a short-lived annual or

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wid ...

dicot The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, t ...

herb. This species' lifespan is between 1 to 10 years. Little is known about the life history of ''Bidens amplectens''. Flowering was observed in April, May, October, and November. ''Bidens amplectens

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, a ...

vectors,

seed dispersal In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors ...

agents, specific environmental requirements, and limiting factors are unknown. ''Bidens amplectens'' is known to

hybridize Hybridization (or hybridisation) may refer to: *Hybridization (biology), the process of combining different varieties of organisms to create a hybrid *Orbital hybridization, in chemistry, the mixing of atomic orbitals into new hybrid orbitals *Nu ...

with Bidens ''torta'', another flower native to O'ahu.

Ecology

Diet

''Bidens amplectens'' is a photosynthetic

autotroph An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Wo ...

Pollinators

Features of the Bidens genus’ flowers indicate pollination by birds, however, this has not been observed in nature.

Habitat

The habitat for ''Bidens amplectens'' includes cliffs and talus slopes in lowland dry shrubland on the

windward Windward () and leeward () are terms used to describe the direction of the wind. Windward is ''upwind'' from the point of reference, i.e. towards the direction from which the wind is coming; leeward is ''downwind'' from the point of reference ...

side of the Waiʻanae mountains. This species was noted as present in 2012 in coastal and lowland dry habitats. The coastal ecosystem on O'ahu includes mixed herblands, shrublands, and grasslands, from sea level to 980 ft (300 m) in elevation. It is generally within a zone above the influence of waves to within 330 ft (100 m) inland. The coastal vegetation zone is typically dry, with annual rainfall of less than 20 in (50 cm). Windward rainfall may be higher.

Biological diversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity'') ...

is low to moderate in this ecosystem. It may include some specialized plants and animals. The lowland dry ecosystem includes shrublands and forests generally below 3,300 ft (1,000 m) elevation. This system receives less than 50 in (130 cm) annual rainfall, with mostly dry substrate. On O'ahu, this ecosystem is typically found on the leeward side of the Wai'anae Mountains, and the leeward southern coast, including Diamond Head Crater. Biological diversity is low to moderate in this ecosystem.

Range

''Bidens amplectens'' is native to O'ahu. Plant growth occurs on windward cliffs and crests along the northern portion of the Waianae Mountains on the island. The species is present in the coastal and lowland dry ecosystems, at elevations between 300 and 1,400 ft (90 and 430 m). ''Bidens amplectens'' is involved in

hybrid swarm A hybrid swarm is a population of hybrids that has survived beyond the initial hybrid generation, with interbreeding between hybrid individuals and backcrossing with its parent types. Such population are highly variable, with the genetic and phe ...

s near

Kaena Point Kaena or Kaena Point is the westernmost tip of land on the island of Oahu. In Hawaiian, ''kaena'' means 'the heat'. The area was named after a brother or cousin of Pele. The point is designated as a Natural Area Reserve. Some ancient Hawaii ...

to Makua Valley with ''Bidens torta''. The entirety of the species is restricted to the island of O'ahu.

Conservation

Population size

There are currently 10 populations of ''Bidens amplectens'' totaling fewer than 500 individuals. Historically, this species was fairly common. In 2003, the widespread population was estimated to total fewer than 1,000 individuals. Last recorded, there are about 10 populations of ''Bidens amplectens''. Seven of these populations in similar locations have numbers ranging from 10 individuals to more than 100 individuals. Three populations were observed elsewhere, numbered between 25 and 56 individuals.

Past and current geographical distribution

Historically ''Bidens amplectens'' ranged from Puʻupueo to Makaleha along the northwestern side of the Waiʻanae mountains on Oʻahu. Currently, there are about 10 populations at slightly higher elevations on the windward slopes. ''Bidens amplectens'' hybridizes and intergrades with ''Bidens torta'' from near Kaʻena Point to the head of Mākua Valley on the summit ridges of the Waiʻanae mountains. Pure ''Bidens amplectens'' is restricted to the windward cliffs and crests.

Major threats

Habitat modification and destruction by invasive introduced plants negatively affects ''Bidens amplectens'' at all locations in the Waiʻanae mountains. Fire is noted as a threat to ''Bidens amplectens'', as well as its vulnerability to

. Predation and herbivory by feral pigs, goats, and rodents were reported to be a threat to ''Bidens amplectens''. The additional threat hybridization with ''Bidens torta'' can result in loss of species diversity, local adaptations, and genetic representation.

Fire

Fire kills ''Bidens amplectens'' plants and seeds. Fires also have the potential to allow nonnative species to become established. The nonnative species that invade after fires tend to be ideal fuel for further fires. Additionally, these nonnative species can outcompete native species like ''Bidens amplectens''.

Hurricanes

Due to the low number and small range of ''Bidens amplectens'', hurricanes are a big threat. Hurricanes can cause destruction of plants and habitats. Extreme weather, like hurricanes, can damage or destroy ''Bidens amplectens'' plants and seeds. Hurricanes also destroy other vegetation, creating new gaps in forest canopies. The change in sunlight is a disturbance that can allow nonnative species to invade.

Invasive species

Since their introduction by humans to Hawaii, feral pigs and goats have become major threats to native plants. Feral pigs and livestock goats may eat ''Bidens amplectens''. Additionally, they can damage or kill ''Bidens amplectens'' through rooting or trampling. When pigs root in the dirt, they disturb soil, and when they defecate, they fertilize soil. Pigs often carry nonnative plants on their hooves and coats, as well as in their feces. This creates opportunities for nonnative plants to invade. Nonnative feral goats pressure these native plants through foraging and movement through vegetation.

Listing under the Endangered Species Act

''Bidens amplectens'' was first listed as a candidate for protection under the Endangered Species Act as threatened in 2004. The final rule for the species listed it as endangered under the ESA in September 2012, along with 22 other species on O'ahu. At listing, critical habitat was established for the plant in two habitat types (1,508 ac, 607 ha). The species' status has not been revised since listing.

5-Year review

The first 5-year review for ''Bidens amplectens'' was initiated in October 2018. The plant was originally listed as endangered with a priority number 2. The recovery priority number is based on the high degree of threat and a high potential for recovery with threats that are well understood and can be alleviated. ''Bidens amplectens'' remains in danger of extinction throughout its range. The Hawaii Division of Forestry and Wildlife (DOFAW) monitors ''Bidens amplectens''. Previously, outplanting has been attempted with more than 400 individuals, and efforts are ongoing. Currently there is a lack of information on the success of outplanted populations. There are seeds and propagules in collections for this species available for continued research and outplanting attempts. The reviewing party suggests additional management actions are needed to conserve this species in the future.Recovery Outline for the Island of Oahu.https://ecos.fws.gov/docs/recovery_plan Retrieved 2022-04-26.

Species Status Assessment

Not available for this species.

Recovery plan

The draft recovery plan for ''Bidens amplectens'' is in preparation. Even without a recovery plan, critical habitat has been established. Four units of coastal habitat and 5 units of lowland dry habitat are listed as critical habitat for ''Bidens amplectens''. The Hawaiʻi and Pacific Plants Recovery Coordinating Committee (HPPRCC) has outlined actions and goals for stages leading towards recovery. The first step in recovering the species is to prevent extinction. To do this, the plant must be managed to control threats, such as fencing. It must also have 50 individuals from each of three populations secured off-site, such as a nursery or seed bank collection. In addition, at least three populations should be documented on Oʻahu where ''Bidens amplectens'' now occur or occurred historically. Each of these populations must be naturally reproducing and increasing in number. There must be at least 100 mature, reproducing individuals per population. This recovery objective has not been met. The following recovery stages’ (Interim, Downlisting, and Delisting) objectives have not been met.https://ecos.fws.gov/docs/tess/species_nonpublish/2781.pdf

Recommendations for future actions

There are recommended actions for each threat against ''Bidens amplectens''. Authorities should continue to survey for ''Bidens amplectens'' in historical locations and potentially suitable habitats. Suitable habitat may be affected in the future by climate change which must be accounted for. There is a need for control of harmful nonnative invasive plants that compete with ''Bidens amplectens''. As fire is a major threat, conservationists must develop and put in place fire prevention management plans. As herbivory is another major threat, exclosures or strategic fencing at all populations of ''Bidens amplectens'' should be constructed. Similarly, implementation of effective control methods for rats is necessary. For preservation of this species, collection of seeds for storage and propagation efforts is highly important. These seeds can be used for maintenance and reintroduction. There is a high need to start planning and contribute to enacting ecosystem-level restoration and management for this species. There is an interim recovery outline for the island of O'ahu that includes ''Bidens amplectens'' and all other

endemic species Endemism is the state of a species being found 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 found elsew ...

. The outline is provided by the US Fish and Wildlife Service. The recovery outline suggests many of the actions listed by the HPPRCC plan. It lists many recovery efforts in place on the island, though most are small or underfunded. The Final Recovery Plan for O'ahu and Multi-Island listing is intended to be in place in 2026.

References

{{Taxonbar, from=Q2901714 amplectens Endemic flora of Hawaii Biota of Oahu Waianae Range Taxonomy articles created by Polbot