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Peraxilla colensoi
Herbarium specimen
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Order:	Santalales
Family:	Loranthaceae
Genus:	Peraxilla
Species:	P. colensoi
Binomial name
Peraxilla colensoi William Colenso

Peraxilla colensoi, the scarlet mistletoe, is a shrubby parasitic plant composed of broad, leathery leaves that grow up to 8 cm long and have a red edge. The common name is derived from the scarlet petals of the plant that bloom every October to January. These mistletoes are parasitic plants whose seeds attach themselves to host plants. The most common host for these plants is the silver beech. The plant can grow up to 3 meters tall and are often located in low altitudes throughout the North and South Islands of New Zealand.

Description

This is a parasitic plant and relies on its host to grow and survive on. Individuals of this species are shrubs up to 3m long and will further out to branches on its host. It has glossy green paired leaves and red tubular flowers. The fruit produced is a small, round yellow color and the leathery leaves of the shrub will fall and cover the forest floor.

Distribution

Peraxilla colensoi naturally occurs to grow on other trees in New Zealand. It is native to the North and South Island of New Zealand. Specifically it can be found on the South Island beech forests. This is a parasitic plant therefore it grows on other trees, plants, and flowers from October to January. The abundance of Peraxilla colensoi appears to follow a structural gradient in forests. Forests that contain open-canopied, all-aged forests had higher densities of peraxilla colensoi, while a dense-canopied, even-aged forest contained little to no Peraxilla. The position of this mistletoe is likely dependent on the opportunities available for seed dispersing birds to excrete and regurgitate seeds. This indicates that different forest structures can present different opportunities for birds which impacts mistletoe establishment. Peraxilla is likely to be most common in areas that observe frequent bird appearances. Several studies have observed larger host trees had a higher rate of peraxilla in comparison to smaller host trees. Larger host trees are capable of supporting a higher mistletoe volume than smaller host trees. The correlation between tree size and mistletoe abundance is that larger trees are able to receive a higher number of mistletoe seeds since they are better perches for birds, resulting in the positive relationship between tree size and mistletoe abundance.

Habitat and ecology

The species is an annual short-lived plant that flowers between the months October through January. Temperatures during this time could be as low as 68 degrees fahrenheit to a high of 86 degrees fahrenheit. This is a parasitic plant, so it latches onto other species to grow, therefore interacting with other species. It relies on its host species for nutrients and water. It can be found in the mid elevation points on trees.

Flowers and fruit

Flowers of Peraxilla colensoi are red and orange in color. They usually flower in the months of October to January. The flowers grow in groups, and are usually found in clumps of 3 to 10. The flower heads usually grow up to 60 mm long. The buds of the flower are not able to open up by themselves. They require assistance from birds that try to extract the nectar from the flower. They twist on the top of the flower that allows it to open up and this helps the birds get nectar while also allowing the flower fertilize as well. The flowers are able to fall and litter the entire floor below them.

Peraxilla colensoi also has fruits that grow to be small and oval shaped and are a yellowish golden color when they ripen. These fruits are eaten by the birds in the area and the seeds of the fruit are excreted by the bird. This allows the plant to spread to new locations. In order for the seed to develop it must land on a branch so it can attach with its haustoria, which are sucker like roots. The preferred host species for this parasitic species is Lophozonia menziesii but there are 16 other species that are known to be host species for Peraxilla colensoi.

Predators and seed dispersers

Peraxilla colensoi is browsed by the common brushtail possum, an invasive species in New Zealand. The increase in browsing by this animal has caused a great depletion in the plant species, leading to it possibly being endangered.

The caterpillar of the endemic moth Zelleria maculata mines the leaves as well as feeds on the inside flower buds of P. colensi and as a result can affect the production of seeds of this plant.

Since Peraxilla colensoi is a parasitic plant its seeds attach itself to its preferred host as a source of food, with its most common host being silver beeches. The fruit of the plant when ripe is eaten by birds. These birds excrete these seeds which hopefully will land on a branch and attach through its adaptive sucker roots known as haustoria.

References

1. ^ "Peraxilla colensoi". New Zealand Plant Conservation Network. Retrieved 2020-11-02.
2. ^ Norton, David A.; Ladley, Jenny J.; Owen, Hamish J. (September 1997). "Distribution and population structure of the loranthaceous mistletoes Alepis flavida, Peraxilla colensoi , and Peraxilla tetrapetala within two New Zealand Nothofagus forests". New Zealand Journal of Botany. 35 (3): 323–336. doi:10.1080/0028825X.1997.10410158. ISSN 0028-825X.
3. Sessions, L. A.; Kelly, D. (2001). "Methods for monitoring herbivory and growth of New Zealand mistletoes (Loranthaceae)". New Zealand Journal of Ecology. 25 (2): 19–26. JSTOR 24055294.
4. Dave Kelly; Jenny J. Ladley; Alastair W. Robertson; Lisa Crowfoot (8 October 2008). "Flower predation by Zelleria maculata (Lepidoptera) on Peraxilla mistletoes: effects of latitude and fragmentation, and impact on fruit set" (PDF). New Zealand Journal of Ecology. 32 (2). Retrieved 15 January 2017.
5. Dave Kelly; Jenny J. Ladley; Alastair W. Robertson; David A. Norton (2000). "Limited forest fragmentation improves reproduction in the declining New Zealand mistletoe Peraxilla tetrapetala (Loranthaceae)". In Andrew G. Young; Geoffrey M. Clarke (eds.). Genetics, Demography and Viability of Fragmented Populations. Cambridge University Press. p. 241–252. doi:10.1017/CBO9780511623448.018. ISBN 0521794218.
6. Peter de Lange; David Norton, eds. (June 1997), New Zealand’s loranthaceous mistletoes (PDF), pp. 1–225, Wikidata Q124157540, archived from the original (PDF) on 6 January 2024
7. J. de Lange, Peter (20 July 1995). "Historical Distributions of the New Zealand's loranthaceous mistletoes". Department of Conservation: 17–20.
8. "Peraxilla colensoi Scarlet Mistletoe". Art and Science of Horticulture. Retrieved 2020-11-02.

• Loranthaceae
• Flora of New Zealand
• Taxa named by William Colenso