Passiflora mollissima HBK. Bailey (Passifloraceae)

Andean woody climber cultivated in tropical and warm-temperate zones for its edible fruit and attractive flowers. It has become a serious pest in the forests of Hawai'i.


Species characteristics

Life form, size and lifespan

Perennial woody vine reaching a length of 20 m and an age of 20 years. Usually climbing but in absence of support is either shrubby or trailing.

Taxonomy, variation and plasticity

In its native range P. mollissima is morphologically variable and frequently hybridizes with other species. In Hawai'i, at the exception of flowering and fruiting, the plant's phenology is variable. In East Africa two distinct forms occur.

Reproductive biology

The nectariferous flowers are large (5-10cm in diameter), pinkish, and borne singly at base of tendrils. They visited by a large number of insects and birds but are chiefly pollinated by honeybees and syrphids. Although mainly outcrossed, selfing occurs. Flowering and fruiting starts when the plant is one year old. The large yellowish fleshy fruits (5 cm) containing 180 seeds (? 6 mm) ripen in ca. 3 months and in Hawai'i are produced throughout the year with a peak during the wet season (December-March). Fruits are widely dispersed locally by native and alien birds and mammals but long distance dispersal also occurs. In New Zealand 50% of seeds survived burial for 66 weeks at 9 cm, and subsequently germinated. Seed germination is staggered with a peak within eight weeks following the breaking of dormancy.

Resilience and resistance

Has a high capacity for vegetative propagation, with the interconnected portions decaying. The plant is frost tolerant.

Environmental requirements and successional status

P. mollissima tolerates both high and low light levels. A seedling bank is commonly found under tree canopy although newly germinated seedlings do not tolerate dense shade. Optimal growth occurs in full sun light.

Products and uses

Species is widely cultivated in its native range and in many parts of the tropics and sub-tropics as an ornamental and for its fruits.


Status in native range

Range and abundance

Native to the tropical region of the Andes between 2000 and 3600 m a.s.l. Original distribution is unclear as the species has been widely cultivated. Natural populations are scattered and sparse.

Climate

Seasonal climate typically with a 2 months dry period and a mean annual temperature and rainfall of respectively ca. 13C and ca. 1300 mm. P. mollissima tolerates occasional frosts.

Site requirements

Not known

Weediness

Not reported.

Pests and diseases

Fungal pathogens and insects attack the fruits.


Status in invaded regions

History of introductions and intensity of invasions

Introduced to many tropical countries. First introduced to the island of Hawai'i around 1920. Subsequently introduced to several other sites on Hawai'i and two other nearby islands. P. mollissima occupies large areas on three Hawai'ian islands and may form continuous cover. Described as weedy in some parts of New Zealand and appears to have naturalised in some South African forests. In East Africa it is cultivated as an ornamental and often escaped, growing in forest edges and clearings.

Patterns of invasion and time-lag

Establishment and growth of P. mollissima increase with increasing light intensity. The densest infestations are found in openings and forest margins. In the forest environment a seedling bank exist and the seedlings are released as soon as a gap is formed in the canopy. In smaller gaps P. mollissima may fail to reach canopy height prior to gap closure. Once the vines have reached canopy height, they spread laterally. Increased disturbance increases the rate of the invasion particularly as a result of feral pig activity, logging or hurricanes. It appears that no time-lag occurred in Hawai'i between the timing of the various introductions and that of the plant's spread.

Site and climate

In Hawai'i, P. mollissima occurs between an elevation of 500 and 2500 m. It tolerates a wide variation in climate with a range of mean annual rainfall and temperatures of respectively 1250-2000 mm and 11-24 C. Short dry season occurs in June-July.

In New Zealand the vine is found in areas with a mean annual temperature of 11.4 to 15.0C and rainfall of 800 to 1200 mm.

Floristic region and vegetation types

The Hawai'ian islands are rich in endemic species but are prone to biological invasions by a wide array of plants and animals. P. mollissima is spreading into native forests, scrub vegetation, pastures, forestry plantations and lava flows.

Pests and diseases

Several fungal pathogens attack fruits but do not limit fruit production. In damper areas they suffer from slug herbivory.

Impact on ecosystem

In Hawai'i P. mollissima has a major impact on vegetation including suppression of tree regeneration, toppling of shallow-rooted trees, death of standing trees through shading and lowered species richness. Continuous prolific fruit production lead to an increase in population densities of exotic mammals, e.g. feral pigs.

Impact on humans and related activities

P. mollissima has no economic value in the tropics, while in New Zealand it is widely grown as a fruit and sold. It is a major problem in forestry, particularly following logging.

Control

Mechanical, chemical and biological means of control have been attempted with limited success in the tropics. In New Zealand cutting vines and wetting cuts with herbicide, particularly Tordon or Roundup, is effective although follow-up treatment may be required.


Ecological differences

Existence of ecological equivalent species and competitive interactions in invaded regions

There does not appear to be any ecological equivalent in Hawai'i.

Differences in status and ecology between invaded and native ranges

In Hawai'i, as opposed to South America, the species does not vary morphologically. Fruit set is greater in Hawai'i than in South America and this probably result from the lower insect herbivory suffered by flowers and fruits in the invaded range. Densities of P. mollissima in Hawai'i are far greater than those observed in the Andes.


Selected references

* LaRosa, A.M. (1984) The biology and ecology of Passiflora mollissima in Hawai'i. Univ. Hawaii Coop. Natl Park Resour. Stud. Tech. Rept 50, 1-168. Botany Dept, University of Hawaii, Honolulu.
** LaRosa, A.M. (1992) The status of banana poka in Hawai'i. In Stone, C.P., Smith, C.W. & Tunison, J.T. (Eds) Alien plant invasions in native ecosystems of Hawai'i: management and research, pp. 271-299. University of Hawaii Press, Honolulu.
* Markin, G.P., Lai, P.-Y. & Funasaki, G.Y. (1992) Status of biological control of weeds in Hawai'i and implications for managing native ecosystems. In Stone, C.P., Smith, C.W. & Tunison, J.T. (Eds) Alien plant invasions in native ecosystems of Hawai'i: management and research, pp. 466-482. University of Hawaii Press, Honolulu.
* Russell-Smith, J. & Bowman, D.M.J.S. (1992) Conservation of monsoon rainforest isolates in the Northern Territory, Australia. Biol. Conserv. 59, 51-63.
#* Wilde, W.J.J.O. de (1975) Passifloraceae. In Polhill, R.M. (Eds) Flora of tropical East Africa. Crown Agents for Oversea Governments and Administrations, London.
** Williams, P.A. & Buxton, R.P. (1995) Aspects of the ecology of two species of Passiflora (P. mollissima (Kunth) L. Bailey and P. pinnatistipula Cav.) as weeds in South Island, New Zealand. N.Z. J. Bot. 33, 315-323.

Pierre Binggeli

May 1997