Callitriche antarctica Engelm. ex Hegelmaier 1867

1. Callitriche antarctica Engelm. ex Hegelmaier (1867: 20)

Type: — FRANCE. ÎLES KERGUELEN: 1839–1843, J.D. Hooker s.n. (lectotype [designated by Lansdown and Hassemer 2021: 88] MEL 2409648! [Figure 2]; isolectotype W 0122126!). Epitype (designated Lansdown and Hassemer 2021: 88): FRANCE. ÎLES KERGUELEN: Grande Terre, Port-aux-Français, elephant seal wallows next to greenhouses, 5 m, 30 December 2011, R.C. Winkworth & F. Hennion 42 (P 02432590! [Figure 3]).

Description (from Lansdown and Hassemer 2021):—Stem and leaf scales present, at least in some populations. Leaf bases broadly connate, forming a cup. Lower leaves reduced to scarious, spathulate, evanescent scales. Lingulate leaves unknown; expanded submerged or floating leaves somewhat fleshy, 2.3–10.0(–18.0) mm long × 1.3–4.8 mm wide, irregularly 3-veined and sometimes additional free veins from the midrib and side nerves, apical leaves may form a floating rosette; terrestrial leaves somewhat fleshy, similar to expanded leaves but generally smaller. Flowers solitary; upper flowers ♂, lower ♀. Bracts lacking. Styles erect, persistent, 1.4–3.2 mm long. Filament short and stout before dehiscence, lengthening to 14 mm long and becoming more delicate after dehiscence; anthers 0.6–0.7 mm long × 0.7–0.8 mm wide, quadrilocular; pollen yellow. Fruit not strumose, subsessile, as wide as or wider than high, dull brown or blackish when mature, 0.7–1.3 mm long × 0.7–1.5 mm wide, unwinged.

Illustrations: —Plates 1169(11) and 1171(9) in Fassett (1951); Figures 6 (a–b) and 6A(a–e) in Mason (1959); Figure 6 in Bacigalupo (1979); Figure 1 (b) in Lansdown and Hassemer 2021. Fig. 1a.

Recognition: — C. antarctica can be distinguished from all other Callitriche species except C. aucklandica by the fleshy leaves with connate bases. C. aucklandica differs from C. antarctica in the narrow wing on the fruit, however this can be difficult to discern, particularly on herbarium specimens, which is why doubt remains as to the occurrence of C. antarctica on the Auckland Islands.

Distribution: —Native. Within the region, this species has been confirmed only from islands south of mainland New Zealand, including Antipodes Island (Godley 1989), Chatham Island, Macquarie Island and The Snares (Hay et al. 2004) (Fig. 2). Elsewhere, it occurs on islands from 40º south to Antarctica (Fassett 1951, Mason 1959, Bacigalupo 1979, Pisano & Schlatter 1981) and has been recorded from Argentina: Tierra del Fuego; Chile: Patagonia (Domínguez & Aravena 2012); France: Crozet Islands and Possession Island, Kerguelen; South Africa: Prince Edward Islands. UK: Falkland Islands, South Georgia (van Mieghem & van Oye 1965). See map on page 167 in Fassett (1951). Records of C. antarctica from the Auckland Islands are discussed by Mason (1959). However, whilst she states that “that C. antarctica does occur on the Auckland Islands is established beyond doubt by a specimen of Hooker’s at Kew, which according to Dr. R. Melville (personal communication) is conspecific with the Campbell Island syntype ”, there is no specimen in Kew collected by Hooker which can be unambiguously be identified as C. antarctica and which was unequivocally collected on Auckland Island. The condition of Hooker’s collections of Callitriche antarctica is discussed by Lansdown and Hassemer (2021) but it is considered prudent to dismiss records of C. antarctica from the Auckland Islands unless this can be confirmed with good fruiting material.

Habitats and Ecology: — Callitriche antarctica occurs as a terrestrial (Schotsman 1961), marginal, or less often aquatic plant to a depth of 2.5 m (Whinam 1989, Scott 1990, Dominguez and Aravena 2012) on bare peat, sand, gravel or rocks. Throughout much of its range, it is strongly associated with wet areas which are enriched with dung from marine mammals such as seal wallows (Hughes 1986, Selkirk, Seppelt and Selkirk 1990, Mukhadi 2011, M. Fountain pers. comm.). It is also found in pool complex vegetation subject to low intensity use by moulting seals (Scott 1990) and wandering albatross (Diomedia exulans von Linné1758: 132) (Warham 1996), as well as petrel nests (Gressit and Clagg 1970) and abandoned penguin colonies (Hay, Warham and Fineran 2004, Ewans and Lake 2011). It often occurs where areas that are kept wet by seepages around the base of Poa cookii (Hook.f.) Hook.f. (1879: 14), P. foliosa (Hook.f.) Hook.f. (1864: 338) or P. flabellata (Lam.) Raspail (1829: 76) tussocks are damaged by animals (Pisano and Schlatter 1981, Scott 1990, Selkirk, Seppelt and Selkirk 1990). It occurs in and on the margins of still or slow-flowing water of seepages, streams, lakes, ponds and pools. It will occur in wetlands associated with raised beaches (Whinam 1989) and coastal rocks with species such as Plantago barbata G.Forst (1789: 25) or Ranunculus crassipes Hook. f. (1844: 224), in bog pools with Azorella selago Hook. f. (1844: 284), Colobanthus kerguelensis Hook. f. (1844: 249), Poa cookii and Pringlea antiscorbutica R.Br. ex Hook. f. (1844: 239), wet Deschampsia antarctica É.Desv. in Gay (1854: 338) swards and flushes, bogs characterized by Juncus scheuchzerioides Gaudich. (1825: 100) and Rostkovia Desv. (1809: 324) sp. (Whinam 1989, Upson 2012), on seepages over rocks with Poa litorosa Cheeseman (1906: 902, 1156), Bulbinella rossii (Hook.f.) Cheeseman (1906: 717) and Polystichum vestitum (G.Forst.) C. Presl (1836: 83) and on disturbed ground such as roadsides. 0–620 m elevation.

Conservation Status: — C. antarctica is classed as Least Concern as it is widespread with stable populations and does not face any major threats (IUCN 2012). It is classed as Naturally Uncommon, Range Restricted, Secure Overseas in New Zealand (de Lange et al. 2018).

Additional material studied:—For a list of confirmed specimens, see Lansdown and Hassemer (2021).