Isolepis basilaris
Common names
pygmy clubrush
Biostatus
Native – Endemic taxon
Category
Vascular
Structural class
Sedges
Detailed description
Minute, moss-like, densely tufted plant forming circular patches 10–100 mm diameter and up to 60 mm tall, bright green above, reddish brown below. Rhizome < 1 mm. diameter, much branched; sheathing bract at each node loose, membranous, with red nerves. Culms < 1.5 rarely up to 30 mm long, < 0.5 mm diameter. Leaves 1–2 on each branch, much > culms, 5–60 mm long, < 0.5 mm wide, setaceous, plano-convex; sheath membranous, red-nerved. Inflorescence an apparently lateral, single spikelet, or rarely 2, hidden among the leaves, pale green, occasionally with red markings; subtending bract leaf-like, channelled, very much > culm from which it arises and almost = leaves. Spikelets 2.5–3.5 × 1.5–2.0 mm, elliptical or oblong. Glumes 1–2 mm. long, ovate, elliptical, obtuse, white and membranous, or with patches of red on the sides; keel thick, green, occasionally slightly excurrent. Hypogynous bristles 0. Stamens 2–3. Style-branches 2–3. Nut c. 0.5 × 0.5 mm, c. ⅔ length of glume, obovoid to suborbicular, plano-convex, dorsally rounded, noticeably apiculate, red-brown to dark brown, almost black, surface often shining but distinctly reticulate.
Similar taxa
Isolepis caligenis. Isolepis basilaris has 1–2 leaves per tuft, very short flower stems with spikelets hidden amongst leaves and very dark brown nuts, flat on one side. Isolepis caligenis has 2–5 leaves per tuft, longer flower stems and pearly grey nuts, rounded on both sides. Occasionally Isolepis basilaris with elongated flower stems is difficult to distinguish from I. caligenis if fruit is immature.
Distribution
Endemic. North Island and South Island from Hawke’s Bay to Southland.
Habitat
Coastal, lowland to upland habitats, up to 700 m a.s.l. On damp, sandy or silty margins of lagoons, tarns, ephemeral lakes and rivers, freshwater or brackish.
Current conservation status
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2023 | At Risk – Naturally Uncommon | Qualifiers: EF, RR, Sp
Threats
Domestic and feral cattle, sheep, horses and pigs are the serious threats throughout this species range, mainly through browse, trampling, and facilitating the spread of weeds. Competition from taller vegetation is significant at many sites. Coastal development (e.g., road widening) and erosion are further common threats to most populations. In some locations plants are threatened by 4-wheel drive vehicles.
Detailed taxonomy
Family
Synonyms
Scirpus basilaris (Hook.f.) C.B.Clarke, Isolepis novae-zelandiae Colenso
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Flowering
September–November
Fruiting
December–April (but seedheads long persistent)
Life cycle and dispersal
Nuts are dispersed by water and possibly granivory and attachment (Thorsen et al., 2009).
Propagation technique
Easily grown from fresh seed and division of whole plants.
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland). If you have suggestions for the Wetland Indicator Status Rating, please contact: [Enable JavaScript to view protected content]
OBL: Obligate Wetland
Almost always is a hydrophyte, rarely in uplands (non-wetlands).
Other information
Cultivation
Not commercially available but plants are held by several Botanic Gardens and specialist growers.
Etymology
isolepis: From the Greek isos (equal) and lepis (scale)
basilaris: From Latin ‘basis’ borrowed originally from Greek, meaning basal
NVS code
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
ISOBAS
Previous conservation statuses
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2017 | At Risk – Declining | Qualifiers: EF, RR, Sp
2012 | Threatened – Nationally Vulnerable | Qualifiers: EF, RR, Sp
2009 | Threatened – Nationally Endangered | Qualifiers: De
2004 | Serious Decline
Regional conservation statuses
The regional threat classification system leverages off the national assessments in the NZTCS, providing information relevant for the regional context. Otago conservation status information is sourced from the “Regional conservation status of indigenous vascular plants in Otago” Jarvie S et al. (2024) report.
Otago: 2024 | Threatened – Regionally Endangered | Qualifiers: DPR, NStr, PF, RR
Referencing and citations
References and further reading
Johnson AT, Smith HA. 1986. Plant Names Simplified: Their pronunciation, derivation and meaning. Landsman Bookshop Ltd, Buckenhill, UK.
Moore LB, Edgar E. 1970. Flora of New Zealand, Volume II. Indigenous Tracheophyta: Monocotyledones except Gramineae. Government Printer, Wellington, NZ. 354 p.
Thorsen MJ, Dickinson KJM, Seddon PJ. 2009. Seed dispersal systems in the New Zealand flora. Perspectives in Plant Ecology, Evolution and Systematics 11: 285–309. https://doi.org/10.1016/j.ppees.2009.06.001.
Attribution
Description adapted from Moore and Edgar (1970).
Some of this factsheet information is derived from Flora of New Zealand Online and is used under a Creative Commons Attribution 3.0 New Zealand licence.