Pterygopappus

Sage cushion plant
Pterygopappus lawrencii
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Asterales
Family:	Asteraceae
Tribe:	Gnaphalieae
Genus:	Pterygopappus Hook.f.
Binomial name
Pterygopappus lawrencii Hook.f.
Synonyms
Gnaphalium sect. Pterygopappus (Hook.f.) Baill. Pterygopappus lawrencei Hook.f., alternate spelling

Pterygopappus is a genus of flowering plants in the Gnaphalieae tribe within the daisy family.^[1][2] There is only one known species Pterygopappus lawrencii (Sage cushion plant) which is endemic to alpine Tasmania. It forms thick, light blue/green mats with densely packed leaves. It is most common in the mountains of the northeastern part of the island. It is a slow grower and prefers cool, moist environments.^[3][4][5][6]

Description[]

P. lawrencei has a noticeably tufted habit and is easily identified by its sage-green leaves^[7] which are no more than 5 mm long. These leaves are tightly congested^[8] and can be said to resemble a small cabbage or rose. They are covered in very fine, small and white hairs.^[9] Beneath the tightly grouped sets of leaves, stems elongate at a rate which is equal to the rate at which new leaves are produced.^[8] It is therefore difficult to identify which leaves are connected to which stem.^[8] This is the main method for how this species spreads across the alpine landscape.^[8] From the centre of the small ‘rosette’ emerges a white, small daisy like flower between December- March.^[8] The fruit of this species is an achene.^[9]

Habitat and distribution[]

P. lawrencei is found in montane heathlands, alpine vegetation areas and wet screes.^[9] It is distributed mostly across the east of Tasmania especially in the Central Plateau areas^[9] of Mount Field National Park and Cradle Mountain National Park. The habitat of the species displays the hardiness of the plant. It is ideally found in areas with a thin and peaty soil, the product of heavily eroded dolerite and siliceous bedrock, where most of the soil has been removed by glacial processes.^[10] It is also constantly exposed to high winds, snow and low temperatures^[10] It is unusual to find an area of P. lawrencei growing as a monoculture as they most often occur within a mosaic of other cushion plant species such as Donatia novae-zelandiae, Dracophyllum minimum, Abrotanella forsteroides and Schizacme archeri.^[7] This ability to grow extremely close and integrate with other cushion plant species is part of the reason for their success in these trying conditions. The tightly packed leaves enable a reasonably constant temperature to be maintained at the core of the plant,^[8] and their low and spreading nature enables them to miss the worst of the wind sweep.

Ecological importance[]

The species can be described as an engineering or foundation species, due to its ability to create tarns and small rivers in alpine areas.^[10] Collectively, cushion plants promote species richness. They have been found to attract a greater diversity of species in alpine areas compared to non-cushion plants, provide both refuge for arthropods as well as a pollination resource for insects.^[11]

Threats[]

One of the major threats to alpine vegetation is fire, although this is a species which is able to recover from fire reasonably well.^[10] However, foot traffic from bushwalkers greatly damages these plants, especially in very wet or waterlogged areas.^[12] Damaged plants may take up to 10 years to fully recover, in which time erosion is increased due to lack of soil stability created by these plants.^[13] Insects and arthropods which depend upon these species for food and refuge may also decrease in these areas.

References[]