Abrodictyum caudatum
Synonyms
Trichomanes caudatum Brack.; Cephalomanes caudatum (brack.) Bostock; Macroglena caudata (Brack.) Copel.
Family
Hymenophyllaceae
Flora category
Vascular – Native
Endemic taxon
No
Endemic genus
No
Endemic family
No
Structural class
Ferns
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) – more information about this can be found on the NZTCS website. This report includes a statistical summary and brief notes on changes since 2012 and replaces all previous NZTCS lists for vascular plants.
Please note, threat classifications are often suggested by authors when publications fall between NZTCS assessment periods – an interim threat classification status has not been assessed by the NZTCS panel.
- Conservation status of New Zealand indigenous vascular plants, 2017 . 2018. 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. Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2017 | Threatened – Nationally Critical | Qualifiers: DP, SO
Previous conservation statuses
2012 | At Risk – Naturally Uncommon | Qualifiers: DP, OL, SO
2009 | Threatened – Nationally Critical
Distribution
Indigenous. New Zealand: Kermadec Islands (Raoul Island), North Island (Kerikeri, Auckland). Also the wider Pacific, eastern Australia (Queensland to Victoria), New Guinea, Malesia, New Caledonia, Fiji, Samoa, Tahiti and Rarotonga.
Habitat
Epiphytic on the trunks of wheki (Dicksonia squarrosa) in lowland, riparian forest.
Detailed description
Diminutive, epiphytic fern. Rhizome long creeping 1–1.5 mm diameter, densely clothed with spreading bristle-like dark red-brown multicellular hairs. Fronds crowded toward rhizome apex, 10–20 mm long. Stipes 3–5 mm long, bearing two faint longitudinal ridges. Frond lamina deeply 1–2(–3) pinnatifid, broadly deltoid to narrowly ovate, 8–10(–12) mm wide, membranous, ± pale green; apex erect, ultimate segments linear, 1–3 mm long, 0.3–0.4 mm wide, ± glabrous. Sori inconspicuous, immersed in the apices of basal segments of secondary pinnae, involucre funneliform, 0.2–0.5(–1.0) mm long, 0.3–0.6 mm wide at apex, narrowly winged for most of length, ± narrowly triangular, mouth lobed 4×, lobes entire, spreading; receptacle exserted.
Similar taxa
The mainland New Zealand form of Abrodictyum caudatum is superficially similar to Polyphlebium endlicherianum and P. venosum. From Polyphlebium endlicherianum it differs by its deltoid frond and by the lobed involucre of the fruiting receptacle. Further it differs by its ecology as P. endlicherianum is rarely found in this country as an epiphyte, while Abrodictyum caudatum in New Zealand, as elsewhere in the world, is strictly epiphytic. From Polyphlebium venosum, Abrodictyum caudatum differs by having a deltoid frond, and especially by the obvious lack of distinct veins within the fronds.
New Zealand plants of Abrodictyum caudatum may yet warrant formal recognition as a separate species or subspecies (B.S. Parris pers. comm.). In particular they are much smaller than this species usually is overseas, they have a less well defined creeping rhizomatous habit, and the fronds are much smaller and less divided than is usual for this species, furthermore the involucre is distinctly divided into 4 entire lobes (it is usually entire in A. caudatum). However, Abrodictyum caudatum is a highly variable species and sequences of the New Zealand plant are the same as samples of A. caudatum from Fiji so it seems best for now to place our plant there. Raoul Island Abrodictyum caudatum are different again and they would repay further study.
Flower colours
No flowers
Life cycle
Fruiting material appears to be present in the New Zealand population throughout the year.
Propagation technique
Difficult—should not be removed from the wild.
Threats
Currently this species is known from two sites in mainland New Zealand, the Kerikeri population is present on < 10 wheki (Dicksonia squarrosa) in a small are of riparian forest. The host trees are at risk from flooding, weeds and, as they grow alongside a popular walking track, vandalism. The population has declined since it was first discovered in the late 1990s as some host trees have died. The population is being carefully monitored by the Department of Conservation. An Auckland population has recently been dicovered, here it is found on one wheki tree, growing with Hymenodon pilifer, Tmesipteris tannensis,Lepraria ulrikii and other bryophytes (Ford, 2023). Both these populations were found by chance and it is very easily overlooked it is quite likely that further populations exist elsewhere in New Zealand. On Raoul Island (Kermadec Islands group) it is known from a single site near the summit of that island.
Etymology
abrodictyum: From the Greek habros ‘delicate’, ‘pretty’ and diktyon ‘net’, literally “delicate net”
caudatum: With a tail
Where To Buy
Not commercially available
Taxonomic Notes
NZPCN now follows Ebihara et al. (2006) in recognising Abrodictyum as distinct from Trichomanes—although Brownsey & Perrie (2016) rejected this idea, the generic segregation was adopted by the PPG I (2016) and is now widely followed throughout the world.
Attribution
Fact sheet prepared for NZPCN by P.J. de Lange 10 March 2011 with modification to threats made by M. Ford (4/12/23). Description modified from Bostock & Spokes (1998) using measurements taken from the limited New Zealand herbarium material available. Notes on variability of A. caudatum in New Zealand from B.S. Parris (pers. comm.)
References and further reading
Bostock PD, Spokes TM. 1998. Hymenophyllaceae. Flora of Australia 48, Ferns Gymnosperms and allied groups: 116–148. ABRS/CSIRO Victoria, Australia.
Brownsey PJ, Perrie LR. 2016. Hymenophyllaceae. In: Breitwieser I, Heenan PB, Wilton AD. Flora of New Zealand - Ferns and Lycophytes. Fascicle 15. Manaaki Whenua Press, Lincoln, NZ. https://doi.org/10.7931/B1QP4Z.
Ebihara A, Dubuisson, J-Y, Iwatsuki K, Hennequin S, Ito M. 2006. A taxonomic revision of the Hymenophyllaceae. Blumea 51: 2–57. https://doi.org/10.3767/000651906X622210.
Ford M. 2023. Under our nose, a second record of the bristle fern Abrodictyum caudatum for mainland New Zealand. Trilepidea 231: 3–5.
PPG 1: The Pteridophyte Phylogeny Group 2016. A community-derived classification for extant lycophytes and ferns. Journal of Systematics and Evolution 54: 563–603. https://doi.org/10.1111/jse.12229.
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Abrodictyum caudatum Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/abrodictyum-caudatum/ (Date website was queried)