Ripogonum scandens

Ripogonum scandens (commonly known as supplejack, Māori: kareao, pirita, translated as "twisted rope") is a common rainforest vine endemic to New Zealand. The species was described by Johann Reinhold Forster, and Georg Forster in 1776. It has a conservation status of Not Threatened.

Taxonomy
Supplejack is in the plant family Ripogonaceae. In 1769, during explorer Lieutenant James Cook's first voyage of discovery, botanists Joseph Banks and Daniel Solander collected specimens of "supplejack" (Ripogonum scandens) in New Zealand. The species was described in Solander's unpublished manuscript Primitiae Florae Novae Zelandiae and was illustrated by Sydney Parkinson.

While anchored at Dusky Bay (now Dusky Sound) in the South Island of New Zealand during his second voyage in 1773, Cook remarked in his journal:

"In many parts the woods are so over-run with supplejacks, that it is scarcely possible to force one's way amongst them. I have seen several which were fifty or sixty fathoms long."

During this voyage, naturalist Johann Reinhold Forster, and his son Georg Forster collected specimens of supplejack, as noted by the elder Forster in his journal:

"A kind of climbing plant called the supple Jack by our Sailors, on account of its pliancy, bears red berries, something similar to cherries, & runs up the highest trees, climbs over to another, & after having made its way over many of them, it often comes again down & strikes fresh roots."

In 1776, the Forsters published the genus Ripogonum in the second edition of their Characteres Generum Plantarum with Ripogonum scandens as the type species.

Description
The supplejack vine is an evergreen climbing vine or liana. It climbs by coiling its hard but flexible stems around tree trunks and branches. When there are no supporting trees for the vines to climb up, the vines form a dense knotted tangle on the forest floor. It starts its life as a sappy stem searching for a support, and in the first few years of growth, the supplejack resembles a small shrub, but in its later seasons the stems start to spiral around the supporting trees.

In summer, when the conditions are right, the tips of the vines can grow up to 5 cm per day, allowing the vines to climb high into the canopy. When the vines reach the sunlight at the top of the canopy, they begin to produce green leafy stems (as opposed to the brown woody stems below). The leaves are opposite, ovate and shiny. The fruits are small (1 cm diameter), red berries.

Traditional Māori uses
Traditionally supplejack was used by Māori to bind and pull objects. For example, the vine was used to tie firewood together and for towing small canoes.

Medicinally the supplejack root was boiled to make a drink to help a variety of conditions including rheumatism, fever, disability, bowel problems and skin diseases. The soft, fresh shoots of the vine can also be eaten raw or cooked as a vegetable.

Distribution and habitat
This species is found in the North and South Islands of New Zealand as well as a few offshore islands including Stewart and Chatham Islands.

Throughout the North Island, R. scandens is mainly present is lowland and mountainous forests dominated by hardwood and podocarp. It occurs infrequently in the Hawke’s Bay only in old coastal forests. It is found at altitudes in the North Island of up to 900m in the Kapamahunga range.

In the South Island, Ripogonum scandens is abundant on the western coast, but does not tend to seep into the forests, instead staying on the seaward facing ranges. Throughout Marlborough, Canterbury and Otago, the occurrence of  R. scandens is found sparingly in relics of old forests and mainly found on peninsulas such as Kaikoura, Banks and Otago.

Ripogonum scandens is not found on the Three Kings Islands and on the Poor Knights Islands.

Habitat preferences
Ripogonum scandens will inhabit a wide range of soil types such as red-brown loams, pumice, yellow brown and alluvial. It has also been known to be able to withstand swampy forests where the soil may be flooded periodically throughout the year and hooping of the roots above ground was observed in such soil conditions.

Phenology
Shoots of differing lengths can be seen at all times during the year however they are most common during the springtime.

Flowering takes place from October until May when the stem is in full light at the top of the canopy. Anthers become visible in December and through January. Male and female flowers are separate, female flowers produce the larger berries.

Fruiting takes place throughout the year. Once pollination has occurred, either by either an insect or by the wind, the fruit takes approximately 12–15 months to fully ripen. The seed germinates easily as long as it doesn’t dry out.

Fossils
Miocene fossil leaves of Ripogonum from the Manuherikia Group are indistinguishable from the extant species, R. scandens.

Pathogens and predators
Kererū (Hemiphaga novaeseelandiae) and blackbirds (Turdus merula) are two bird species that consume supplejack fruit. Kaka (Nestor meridionalis) have also been known to eat supplejack berries.

Another climber species, Geitonoplesium cymosum, has been introduced to New Zealand. This species is similar to the native supplejack but may out-compete supplejack.

Wild pigs also have a negative impact on juvenile supplejack as they forage through the forest floor. While they are disturb and consume other plants, they also uproot growing supplejack. Deer and cattle also have the same negative impact on supplejack. These mammals graze on the seedlings and growing juvenile plants. Possums (Trichosurus vulpecula) also feed on supplejack berries. Supplejack was included in a seed predation study with ten other woody forest species, where overall, seed predation be vertebrates was very low.

Sooty mould (Trichopeltheca asiatica) is common across New Zealand and smothers the supplejack leaves and stems, affecting the plant's photosynthetic capability.

Larvae of the moth Ctenopseustis obliquana are found in ripe fruit and will consume the stems, leaves and flowers of the supplejack.

Conservation status
The species is listed as "Not Threatened" on the most recent assessment (2017-2018) under the New Zealand Threatened Classification system for plants.