Dysphania pusilla
Common name
Small fathen
Synonyms
Chenopodium pusillum Hook.f.; Dysphania pusilla (Hook.f.) Paul G.Wilson et K.A.Sheph. nom., superf.
Family
Amaranthaceae
Flora category
Vascular – Native
Endemic taxon
Indeterminate
Endemic genus
No
Endemic family
No
Structural class
Dicotyledonous Herbs other than Composites
Current conservation status
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2017 using the New Zealand Threat Classification System (NZTCS). This report includes a statistical summary and brief notes on changes since 2012 and replaces all previous NZTCS lists for vascular plants. Authors: By Peter J. de Lange, Jeremy R. Rolfe, John W. Barkla, Shannel P. Courtney, Paul D. Champion, Leon R. Perrie, Sarah M. Beadel, Kerry A. Ford, Ilse Breitwieser, Ines Schönberger, Rowan Hindmarsh-Walls, Peter B. Heenan and Kate Ladley.
2018 | Threatened – Nationally Endangered
Previous conservation statuses
2017 | Threatened – Nationally Endangered
2009 | Extinct
2004 | Data Deficient
Distribution
Endemic. Formerly recorded in the North Island (Lake Taupo, Wairarapa). Recently (2015) rediscovered in the Eastern South Island
Habitat
Open or sparsely-vegetated ground such as clay and salt plans, dried out river and lake beds. Also collected from cultivated land and railway yards.
Features
Annual, cushion-forming, yellow-green, prostrate herb with all parts finely glandular hairy. Leaves suborbicular (nearly circular in profile), broadly ovate to ovate-oblong, margins entire, or sinuate (wavy) sometimes deeply lobed. Flowers minute, greenish-yellow, in dense axillary clusters (glomerules), perianth (united floral envelopes) divided into (3-)4(-5) segments. Stamen, 1(-2). Seed 0.5-0.8 mm diameter, dark red brown, aligned vertical in perianth.
Similar taxa
Dysphania pusilla is very similar to some of the small forms of the introduced Australian D. pumilio. The key differences are that D. pumilio usually has (4-)5 perianth segments, slightly larger seeds, and more deeply divided leaves.
Flowering
November - March
Flower colours
Green, Yellow
Fruiting
December - May
Propagation technique
Easily grown from seed. A short-lived annual that self-establishes in sites where it has been grown.
Threats
Formerly assessed as ‘Taxonomically Indeterminate / Extinct’ (de Lange et al. 2013) following its rediscovery some 65 years after it was last seen (Clayton-Greene et al. 2015), the species is now listed as ‘Threatened / Nationally Endangered’ (de Lange et al. 2018). For more information see below.
Etymology
pusilla: Small
Further Notes
On the basis of molecular phylogenetic evidence the genus Dysphania R.Br. has been reinstated (see Mosyakin & Clemants 2002; Shepherd & Wilson 2008, 2009). the genus is distinguished from Chenopodium s.s. by their minute flowers which occur in compact, cymose clusters and by the presence of subsessile glands or simple and acuminate, multicellular, glandular hairs as well as DNA evidence (see summary by Shepherd & Wilson 2008).
Dysphania pusilla presents somewhat of an enigma in the New Zealand Flora. Herbarium records suggest it was never common in the North Island, where it was collected as a ‘weed’ in Maori gardens. Historical South Island records tend to correlate to old sheep runs with one 1950s record from a railway yard in Christchurch. The species was not then seen again until the summer of 2014-2015 when it was discovered in a remote portion of the upper Clarence River, and in parts of the McKenzie Basin (Clayton-Greene 2015). No one is sure why it vanished for some 65 years, only to reappear in several locations, sometimes as 1000’s of plants. The habitats occupied are not singular but rather widespread, mostly weedy, often heavily grazed, though one is within a fenced wetland system set up for threatened wading birds (where water levels are artifically controlled). Although many plants were seen in 2015 / 2016 the area of occupancy is small, and the species is potentially threatened from competition by weeds if grazing pressure is reduced. For this reason Dysphania pusilla, once regarded as ‘Extinct’ has been assessed as ‘Nationally Endangered’ (de Lange et al. 2018).
One pressing issue remains. Is Dysphania pusilla truly indigenous / endemic? Preliminary DNA data based on one marker (nrDNA ITS) places this species with D. pumilio. Further study of the relationship of Dysphania pusilla with D. pumilio - a very variable species in Australia is needed. It may well be that Dysphania pusilla is also in Australia, and that it may even be an early introduction to New Zealand.
Attribution
Fact Sheet prepared and updated for NZPCN by P.J. de Lange (30 August 2018)
References and further reading
Clayton-Greene, J.; Courtney, S.; Rebergen, A.; Head, N. 2016: The rediscovery of the presumed extinct Dysphania pusilla. Trilepidea 139: 1-3.
de Lange, P.J.; Rolfe, J.R.; Champion, P.D.; Courtney, S.P.; Heenan, P.B.; Barkla, J.W.; Cameron, E.K.; Norton, D.A.; Hitchmough, R.A. 2013: Conservation status of New Zealand indigenous vascular plants, 2012. New Zealand Threat Classification Series 3. Department of Conservation, Wellington. 70pp.
de Lange, P.J.; Rolfe, J.R.; Barkla, J.W.; Courtney, S.P.; Champion, P.D.; Perrie, L.R.; Beadel, S.M.; Ford, K.A.; Breitwieser, I.; Schönberger, I.; Hindmarsh-Walls, R.; Heenan, P.B.; Ladley, K. 2018: Conservation status of New Zealand indigenous vascular plants. 2017. New Zealand Threat Classification Series 22: 82pp.
Mosyakin, S.L. Clemants, S.E. 2002: New nomenclatural combinations in Dysphania R.Br. (Chenopodiaceae): taxa occurring in North America. Ukrayins’kyi Botanicnyi Zhurnal 59: 380–385.
Shepherd, K.A.; Wilson, P.G. 2008: New combinations in the genus Dysphania (Chenopodiaceae). Nuytsia 18: 267-272.
Shepherd, K.A.and Wilson, P.G. 2009: Clarification of recent combinations in the genus Dysphania (Chenopodiaceae) Nuytsia 19: 198-199,
Citation
Please cite as: de Lange, P.J. (Year at time of access): Dysphania pusilla Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/dysphania-pusilla/ (Date website was queried)