Class
Order
Family
Genus
Classification
Nomenclature
Scientific Name:
Isoetes alpina Kirk, Trans. & Proc. New Zealand Inst. 7: 377, t. 25 (1875)
Synonymy:
Lectotype (selected by Brownsey et al. 2018): Lake Guyon, W.T.L. Travers s.n., WELT P003771!
Etymology:
Vernacular Name(s):
alpine quillwort
Description
Aquatic, growing submerged, evergreen. Stem short, erect, 1–10 mm tall, 2–10 mm wide. Leaves in tufts of up to 35, 25–450 mm long, 0.5–2.5 mm diameter, erect, linear, terete, with conspicuous air chamber; apices long acuminate; margins entire, bases swollen, 3.5–10.5 mm wide, broadly winged. Sporangia ovoid, 2–9 mm long, 2–5 mm wide. Megaspores grey to white, surfaces smooth. Microspores echinate.
Recognition
Isoetes alpina is difficult to distinguish from I. kirkii, most characters overlapping in their range of variation. However, I. alpina is generally a more robust plant, producing tufts of up to 35 leaves, which can grow much longer and wider than in I. kirkii. The sporangia are also generally longer and wider than in I. kirkii. Isoetes alpina is best distinguished by the megaspores, which are grey to white in colour with a smooth surface, in contrast to those of I. kirkii, which are white and distinctly tuberculate on their surfaces (Large & Braggins 1991).
Distribution
South Island: Western Nelson, Marlborough, Westland, Canterbury, Otago, Southland, Fiordland.
Altitudinal range: 20–1700 m.
Isoetes alpina is circumscribed here as confined to the South Island, occurring in lakes and tarns from north-west Nelson to Fiordland. It is mostly found in a zone from 450–1700 m, but in Westland, Fiordland and Southland descends almost to sea level. Plants with smooth macrospores also occur at L. Taupō and L. Rotoiti (e.g. AK 259222) in the North Island, but these may be apomictic, tetraploid plants (Hofstra et al. 2006), possibly belonging to a different taxon.
Habitat
Isoetes alpina usually occurs in montane lakes and tarns, growing submerged on mud, sand or rock substrates. Occasionally it is found in mud on lake margins, and rarely in streams. It has been recorded growing in water up to 5.5 m deep in L. Pōteriteri (CHR 502298) and up to 8.5 m deep in L. Wakatipu (CHR 478370). The NIWA Aquatic Plant Database has maximum depth records of 10 m in L. Tennyson, 12 m in L. Wānaka and 12.5 m in L. Coleridge (Paul Champion, pers. comm., July 2018).
Biostatus
Indigenous (Endemic)
Cytology
2n = 22 (Marsden 1979)
Notes
Isoetes alpina was first collected by F.W. Hutton and W.T.L. Travers from Lake Guyon in 1872, and then by Sven Berggren from Lake Pearson in 1874. It was subsequently described by Kirk (1875) from material sent to him by Travers. The principal point of difference noted by Kirk was the smooth surface of the macrospores, in contrast to the tuberculate macrospores of I. kirkii.
Images
Bibliography
Brownsey, P.J.; Given, D.R.; Lovis, J.D. 1985: A revised classification of New Zealand pteridophytes with a synonymic checklist of species. New Zealand Journal of Botany 23(3): 431–489.
Brownsey, P.J.; Perrie, L.R. 2018: Isoetaceae. In: Breitwieser, I.; Wilton, A.D. (ed.) Flora of New Zealand — Ferns and Lycophytes. Fascicle 25. Manaaki Whenua Press, Lincoln.
Brownsey, P.J.; Perrie, L.R.; Field, A.R. 2018: Taxonomic notes on the New Zealand flora: lectotypes in Isoetaceae and Lycopodiaceae. New Zealand Journal of Botany 56(4): 396–405.
de Lange, P.J.; Rolfe, J.R.; Barkla J.W.; Courtney, S.P.; Champion, P.D.; Perrie, L.R.; Beadel, S.N.; 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. No. 22. [Not Threatened]
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. [Not Threatened]
Hofstra, D.E.; Gemmill, C.E.C.; de Winton, M.D. 2006: Preliminary genetic assessment of New Zealand Isoetes and Nitella, using DNA sequencing and RAPDs. Science for Conservation 266: 1–30.
Kirk, T. 1875: Description of a new species of Isoëtes. Transactions and Proceedings of the New Zealand Institute 7: 377.
Large, M.F.; Braggins, J.E. 1991: Spore atlas of New Zealand ferns and fern allies. SIR Publishing, Wellington.
Marsden, C.R. 1979: Morphology and taxonomy of Isoetes in Australasia, India, north-east and south-east Asia, China and Japan. Unpublished PhD thesis, University of Adelaide, Australia.
