Callitriche cycloptera Schotsman (1985d: 116)

Lansdown, Richard V., 2022, The genus Callitriche (Plantaginaceae, Callitricheae) in Australasia and Oceania, Phytotaxa 547 (3), pp. 243-284 : 257-258

8. Callitriche cycloptera Schotsman (1985d: 116) .

Type: — NEW GUINEA. OROBE PROVINCE. Goropu Mountains (Mt. Suckling), Pumpunipon grassplain, in shade of forest edge in boggy paces; 2065. m, ca. 9º40’ S- 148º56’ E, 14 June 1972, J.F. Veldkamp & P.F. Stevens 5594 (Holotype: L 249923) .

Description: —Stem and leaf scales present. Leaf bases connate. Lingulate leaves unknown; expanded submerged or floating leaves unknown; leaves of terrestrial plants spathulate, up to 6.0 mm long × 2.8 mm wide; secondary veins do not rejoin the central vein, toward the centre of the blade small veins may arise from the primary vein, these may be free or join the secondary veins, petiole 0.4–0.7 mm long. Flowers pedunculate, ♂ and ♀ in the same axil. Bracts probably lacking. Styles divergent or erect, 0.4–0.5 µm long. Filament arising from peduncle, slightly curved, 0.5–0.6 mm long; anthers quadrilocular, 0.1–0.27 mm long × 0.2–0.3 mm wide; pollen yellow. Fruit subsessile, wider than high, maroon or chestnut when mature, 0.8–1.0 mm long × 1.2 mm wide, broadly winged throughout except for a very narrow part where mericarps are connected.

Illustrations: —Plates 2(M) and 3(3–4) in Schotsman (1985c), plate 1 in Schotsman (1985d), Fig. 1h .

Recognition: — C. cycloptera can be distinguished from all other Callitriche species in the region by the wing of the fruit which is very broad (approximately ½ the width of fruit) and extends completely around each mericarp except for the narrow point where the mericarps are attached. The maroon/chestnut colour of the fruit also helps to distinguish it from many species. It is most similar to C. muelleri but that species has leaves with a single tooth on each margin which is lacking in C. cycloptera .

Distribution: — C. cycloptera is endemic to New Guinea, where it is known from two areas: Mount Suckling (Goropi), the highest peak in the Goropu Mountains in the south east, and Mount Salawaket on the Huon Peninsula ( Fig. 9 ).

Habitats and Ecology: — C. cycloptera forms lawns between mosses and liverworts on peaty soils under the overhanging branches of Dacrycarpus expansus de Laub. (1969: 334) trees on the edge of high-elevation peat bogs dominated by Deschampsia klossii Ridl. (1913: 268) tussocks in a region which air temperatures may vary from –5 ºC (or even –8 ºC) at night to 22 ºC during the day (J.F.Veldkamp in litt. to H.D.Schotsman) ( Schotsman 1985d: 119–102). It has also been found growing among liverworts and mosses in the bed of a dried-out oxbow (ibid.). 1660–2065 m elevation.

Conservation Status: —This species is known from a small number of collections from two areas in Papua New Guinea. It is not known to face any particular threats but it has an estimated Extent of Occurrence (EOO) of 14,539 km 2 and AOO of 12 km 2 ( IUCN 2012). The Pumpunipon Plain is considered to be a single wetland complex on the floodplain of the Pumpinawa River and is therefore treated here as a single location, with the Huon Peninsula as a second location. This species is likely to be vulnerable to climate change as it is restricted to high altitude, while areas where it has been recorded around Mount Suckling are threatened by forest clearance, it is therefore assessed as Vulnerable: B1ab(iii)+2ab(iii); D2 ( IUCN 2012).

Selected specimens examined: —Mount Salawaket, Oro Province. s.d., T.G. Hartley 11099 (GH!); Mt. Suckling, 1660 m, 21 July 1972, P.F. Stevens and J.F. Veldcamp LAE 55723 (CANB! 247539).

Figures

FIGURE 1. Fruits of Callitriche in Oceania and Australasia: a—C. antarctica, b—C. aucklandica, c—C. brachycarpa, d—C. brutia, e—C. capricorni, f—C. chathamensis, g—C. cyclocarpa i face on and ii end on, h—C. cycloptera, i—C. deflexa, j—C. fuliginea.

FIGURE 9. The distribution of confirmed specimens of C. cycloptera