Bulbinella rossii

Bulbinella rossii, commonly known as the Ross lily, is a species of flowering plant in the family Asphodelaceae. It is an endemic megaherb of New Zealand's subantarctic Auckland Islands and Campbell Island. It was first described in 1845 by Joseph Dalton Hooker in the Flora Antarctica, from material collected on Campbell Island, as Chrysobactron rossii.

Bulbinella rossii
Bulbinella rossii on Campbell Island
Conservation status
Naturally Uncommon (NZ TCS)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Monocots
Order:	Asparagales
Family:	Asphodelaceae
Subfamily:	Asphodeloideae
Genus:	Bulbinella
Species:	B. rossii
Binomial name
Bulbinella rossii (Hook.f.) Cheeseman
Synonyms
Chrysobactron rossii Hook.f. Anthericum rossii (Hook.f.) Hook.f.

B.rossii reaches a height of up to 1 metre (3 feet 3 inches). Its leaves are strap-like, dark green in colour and are up to 0.6–1 metre (2 feet 0 inches – 3 feet 3 inches) long. The inflorescence is a cylindrical raceme up to 600 mm long, with densely crowded golden-yellow flowers. The roots of B. rossii are often eaten by introduced pigs, but the species is avoided by cattle, goats and sheep. B. rossii occurs from sea level to high-altitude areas and prefers colder habitats with high water content. B. rossii was evaluated in the 2024 assessment by the New Zealand Threat Classification System as "At Risk — Naturally Uncommon".

Description

Bulbinella rossii is a large and dioecious megaherb in the family Asphodelaceae and the subfamily Asphodeloideae, it reaches a height of up to 1 metre (3 feet 3 inches) in height with a basal diameter of 40 mm. The dark green, fleshy, smooth, strap-like leaves are 0.6–1 m long and 15–60 mm wide. The inflorescence is a cylindrical raceme up to 600 mm long.^[1][2] The golden yellow flowers it produces are densely crowded, 10–14 mm in diameter. The ovoid seed capsules it produces are 10 mm long, containing narrowly winged, dark brown seeds. B. rossii flowers from October to January and fruits from December to March.^[2][3]

Its ovary is left undeveloped in male specimens; in female specimens, its tepals spread approximately 11–12 mm in diameter more erect and remaining, becoming more firm in texture as its fruit ripens; in female specimens; the capsules are broadly ovoid and the seeds are 6 mm long.^[4] B. rossii's younger flower buds and freshly opened blooms which are more closely packed compared to older flowers, which could contribute to greater heat retention in the areas. A 2016 study hypothesised that the warmth generated by inflorescences plays a role in attracting insects to its heated flowers, in the generally cold sub-Antarctic climate, where the average temperature is 6.88°C.^[5]

Phytochemistry

Species in the Bulbinella genus produce unique compounds called 'phenylanthraquinones', which are predominantly found in African species. However, Bulbinella species endemic to New Zealand also produce these compounds, especially B. rossii which contains unique sulphated phenylanthraquinones, including a glycoside-substituted compound (40-O-demethylknipholone-40-β-D-xylopyranosyl-300-sulphate). A high-performance liquid chromatography (HPLC) analysis of five New Zealand Bulbinella species revealed that all the species analysed contained phenylanthraquinones, with distinct profiles in leaves and roots. In the analysis, roots were found to be rich in both sulphated and free phenylanthraquinones, while leaves primarily contained free knipholone.^[6]

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Taxonomy

Classification

The Bulbinella genus was first established in 1843 by Carl Sigismund Kunth.^[4][7] Initially, six species from the Cape of Good Hope, in South Africa, were placed in the genus Bulbinella; three of them transferred from other genera and three of the species were described as new. In 1845, Joseph Dalton Hooker based his new genus Chrysobactron on B. rossii specimens collected from Campbell Island. The species was first published in the Flora Antarctica by him, noting that Chrysobactron was "very nearly allied" and had a similar appearance to the South African Bulbinella genus but he decided not to move the new genus into it.^[8][9]

In 1906, botanist Thomas Cheeseman had more than once expressed doubts about the generic status of the New Zealand species and placed them in Bulbinella rather than in Chrysobactron.^[10] In 1952, Lucy Cranwell studied the pollination of various New Zealand species, in her study, she mentioned the points of similarity between the grains of South African Bulbinella species and New Zealand Chrysobactron (now known as Bulbinella) species, but no other differences were mentioned by her.^[11][12]

There are twenty-three species in the genus Bulbinella; seventeen of which are located in South Africa, and six in New Zealand.^[13] A 2017 thesis by Collen Musara examined the genus Bulbinella and had hypothesised that B. rossii is the closest resemblance to the South African species because of B. rossii's fibrous leaf bases that other New Zealand Bulbinella species do not possess.^[14] B. rossii is closely related to B. gibbsii but differs due to its taller stature, broader leaves (up to 60 mm wide), and cylindric racemes supported on a stout axis that is hidden by dense flowers and fruits.^[2]

Etymology

The etymology of the genus, Bulbinella, translates to English as 'little bulb'. The specific epithet rossii is named after James Ross, the leader of Hooker's expedition. Hooker decided to name the specific epithet in honour of Ross because he brought many new species to him during their short stay on Campbell Island. The species is commonly known as the 'Ross lily'.^[2][9]

Distribution

B. rossii on Enderby Island

Bulbinella species are predominantly endemic to Africa, but six species are endemic to New Zealand, most of which are found predominantly in the South Island.^[6] B. rossii is endemic to New Zealand's subantarctic Auckland Islands and Campbell Islands.^[15] There, it is common and widespread from sea level to the highest parts of the island's mountains. Because it thrives where the ground has been disturbed, and because it is not particularly of interest to browsing animals, it is common near former human habitation sites and may form dense colonies in open herbfields and tussock grasslands.^[2]

In 1970, botanist R. H. Taylor studied the vegetation and wildlife of Enderby Island. In his study, he noted that B. rossii appeared to be more common on the north and west sides of the island and the south-east sides of the island appeared to be dominated by southern rātā (Metrosideros umbellata) forests.^[16]

Habitat

All New Zealand Bulbinella species are allopatric and prefer colder habitats with high water content.^[17][18] On the main Auckland Island, B. rossii occurs from sea level to high-altitude areas; but it is uncommon at lower-altitudes and is more common at higher-altitude areas where the ground is unfavourable for B. rossii to be rooted by introduced animals.^[19][20] On Campbell Island, B. rossii only becomes predominant above 250–300 m (820–980 ft) sea level.^[21]

Ecology

There is a weed which they call 'Bulbinella Rosi' [sic] growing on the island, which is spreading very rapidly, and appears to be going to over-run the country. The paddocks are simply a mass of it and where it is growing very thick, no other vegetation will thrive.

—M. McKay, 1910

The roots of B. rossii are often eaten by pigs, but the species is avoided by cattle and goats.^[20][19] B. rossii's bitter taste also makes it unattractive to sheep.^[4] On Campbell Island in 1910, M. McKay, a stock inspector who was on the island to inform New Zealand's Ministry of Agriculture concerning the cases of sheep scab on the island, mentioned B. rossii was so common on the island it resembled characteristics of an invasive species.^[22]

A 2013 research article by the New Zealand Journal of Botany reported on floral biology and pollination on Campbell Island. In it, the researchers observed many of Campbell Island wētā (Notoplectron campbellensis) individuals feeding on the pollen and nectar of B. rossii, with as many as eight individuals on an inflorescence.^[23][24] B. rossii was the most frequently visited species from their study. Other species noted in their study included: Melangyna novaezelandiae and Scoparia parmifera.^[25] B. rossii individuals are also known to be visited by hoverflies and other small flies.^[26][27]

A 2019 study conducted by Polar Research examinined the moths on New Zealand's subantarctic islands. Researchers noted that Graphania erebia, an endemic moth, was observed to visit the inflorescences of B. rossii and may be an important pollinator for the species. G. erebia moths either actively seek out B. rossii or are capable of travelling long distances at night and have more active foraging.^[28] The seeds of B. rossii are dispersed by the wind.^[2]

Conservation

B. rossii was evaluated in the most recent 2024 assessment by the New Zealand Threatened Classification System as "At Risk — Naturally Uncommon" because its distribution is confined to the Auckland and Campbell Islands groups.^[29] B. rossii appears to have no threats, and is listed because of its confined geographical area.^[30][2]

Recognition

As of 2025^[update], Bulbinella rossii is featured on the reverse of the New Zealand five-dollar note.^[31]