Callitriche stagnalis

Callitriche stagnalis is a perennial aquatic vascular plant species. Also known as pond water-starwort, C. stagnalis, may thrive in a variety of aquatic and subaquatic habitats, specially those exhibiting slowly moving to non-moving water. Although C. stagnalis does not pose a threat to humans, its reproductive rate may pose a threat to native vegetation in areas where it has been introduced, as the resulting dense vegetative mats frequently out-compete native species.

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Description (after Lansdown 2008): — Stem and leaf scales present. Leaf bases connate. Lingulate leaves very rare, usually lacking, expanded submerged or floating leaves variable, from broadly parallel-sided, through obovatespathulate to almost circular, 2.7 – 21.7 mm long × 1.4 – 8.3 mm wide; venation simple or complex with numerous loops and anastomosing veins, petiole 0.7 – 6.5 (– 7.5) mm long; the apical leaves forming a floating rosette; leaves of terrestrial plants narrowly elliptic 2.6 – 4.4 mm long × 1.6 – 3.3 mm wide, petiole 0.8 – 2.1 mm long. Flowers usually solitary. Bracts falcate, persistent 0.6 – 2.69 mm long. Styles erect, becoming recurved in fruit, ≤ 6 mm long. Filament erect, becoming recurved and continuing to grow after dehiscence, ≤ 16.2 mm long; anthers quadrilocular, 0.3 – 0.9 mm diameter; pollen yellow. Fruit not strumose, subsessile or occasionally very shortly-pedicellate, ± as wide as high, greyish when mature, 1.1 – 1.8 mm long × 1.1 – 2.0 mm wide, winged throughout. Illustrations: — Figures 10 (a – b) and 10 A (a – e) in Mason (1959); Figures 1 D – F in Orchard (1980); Figures on pages 81 and 83 in Lansdown (2008). Fig. 10 j. Recognition: — C. stagnalis can be distinguished from all other Callitriche species in the region except C. platycarpa by the large, pale, broadly-winged fruit which are greyish or pale brownish-grey when mature. It can only reliably be distinguished from C. platycarpa by the pollen which is ellipsoid, compared to the bluntly triangular pollen of C. platycarpa. C. stagnalis also rarely produces linear leaves, has a broader wing to the fruit and is typically more greyish than that of C. platycarpa, however these differences are not diagnostic.

standing waters

mesotrophic

shortlived

cuddly

mobile

Distribution: — Callitriche stagnalis is a predominantly European species, occurring east from Norway into Russia and south to Greece and Turkey, but rare in the east and has not been confirmed from the Levant or North Africa east of Morocco. The limits of its distribution have been obscured by frequent and widespread mis-identification. It is widespread and abundant throughout the Iberian Peninsula, but in Morocco is known only from the Central Plateau and the Rif, where it is frequent (Fig. 4 C). Habitat and ecology: — Callitriche stagnalis occurs in a wide range of habitats, most often on wet tracks in woodland, in pools in pasture, lake and river margins, and the margins of ditches. In Morocco it has been recorded from reservoirs and ponds, as well as cupular pools in granite, wet flushes, and streams. It occurs with a wide range of species and records from Moroccan populations include 23 % that may be considered truly aquatic, 38 % typical of marginal habitats or seasonal wetlands, and 39 % terrestrial, reflecting its occurrence in both seasonal and permanent wetlands. Typical associates in Morocco include Anthoxanthum odoratum von Linné (1753: 28), Callitriche brutia subsp. naftolskyi, C. mathezii, C. regis-jubae, Eleocharis palustris, Fontinalis Hedwig (1801: 298) sp., Helosciadium nodiflorum, Hordeum murinum von Linné (1753: 85), Juncus bufonius, Lemna gibba, Lythrum hyssopifolia, Mentha pulegium von Linné (1753: 577), Mentha suaveolens Ehrhart (1792: 149), Nasturtium officinale, Nerium oleander von Linné (1753: 209), Plantago coronopus, Poa annua von Linné (1753: 68), Polypogon monspeliensis Desfontaines (1798: 67), Potamogeton nodosus, Pulicaria arabica, Ranunculus ophioglossifolius, R. peltatus, Scrophularia auriculata, and Veronica catenata. Elevation in Morocco: 0 – 1560 m. Recognition: — Callitriche stagnalis can be distinguished from other Callitriche species recorded from Morocco except C. cribrosa, by the combination of the large fruit that are greyish-brown when mature, and large anthers with yellow pollen. It can only reliably be distinguished from C. cribrosa by the looped testa of the fruit, however most healthy plants of C. cribrosa will have leaves with more than seven parallel veins, whereas the leaves of C. stagnalis have fewer veins. Illustrations: — Figures in Lansdown [2008: 24 (6 – 6 x), 81, 83] and in Lansdown (2022: Fig. 10 j). Specimens examined: — MOROCCO: Stream, Asmismis, s. d., N. D. Simpson 36.378 (BM). Al-Hoceima. Izdad, 1 July 1993, J. A. Mejias, S. Silvestre s. n. (RNG). Barrage Smir, Tetouan. M’diq, 4 April 1994, J. M. Montserrat, B. Vales s. n. (RNG). Souk el Arba de Beni Hassim, 6 June 1994, M. A. Mateos, J. M. Montserrat s. n. (RNG). Larache, Ksor-el-Kebir, Orillas del rio Loukkos Arcillas, 30 m, 17 March 1995, M. A. Mateos, M. C. Reina, G. Sangalli, Sardóa, B. Valdés, 4783 / 95 (RNG). Wet flush on open west-facing slope, NE of Chefchaouen, track to Jbel Tassaout just above Talembote village, 21.4 km from main Tetouan to Chefchaouen, 595 m, 27 May 2002, S. L. Jury, M. Ait Lafikh, R. Brown, M. A. Carine & F. J. Rumsey 19371 (RAB 65458, RNG 27229). Wet flush with Salix, just below spring, track down E of Mirador de Perdicaris, Prov. Tanger above Tanger, 26 May 2002, S. L. Jury, M. Ait Lafkih, R. Brown, M. A. Carine, F. J. Rumsey s. n. (RAB 65491, RNG 27154). In village pond, turning off Oued Laou Valley along road by Oued Tassikeste and up track at Hamada Village, 7 June 2005, S. L. Jury, M. Ait Lafkih, R. Brown, M. A. Carine, F. J. Rumsey 199 (RNG 44276). Stream upstream of the Akalii dam, 28 April 2019, R. V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks s. n. (RAB). Field records: — Seasonal stream near Oulmès, 1170 m, 28 April 2019, R. V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks. River near Oulmès, 30 April 2019, R. V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks. Cupular pools in granite near Mante (Aguelmous), 1163 m altitude, 30 April 2019, R. V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks. Sidi Mrahe stream, 1043 m, 30 April 2019, R. V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks. Stream near Hotel des Thermes à Tarmilate (Oulmès), 28 April 2019, R. V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks. Stream Tna Ounahal, 1129 m altitude, 30 April 2019, R. V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks.

Distribution: — Non-native. Within the region Callitriche stagnalis is widespread and abundant throughout much of Victoria and coastal areas into central Queensland, as well as in the west around Perth (Fig. 17). In New Zealand it has been recorded more or less throughout on the mainland, as well as on the Chatham Islands (de Lange et al. 2011). It is native to Europe, where it occurs from the Azores to Iceland and east to the western side of the Ural Mountains in Russia. It also occurs as an alien in North America and South America, including the Falkland Islands (Lansdown and Hassemer 2021). Habitats and Ecology: — In the region, Callitriche stagnalis is the Callitriche species most frequently found growing in permanent water bodies, including rivers, streams, lakes and ponds. It has been described as the most common aquatic species of the genus in wet areas modified by human activity, such as ponds, lakes, ditches and drains (Mason 1959, Stanley and Ross 1986, Webb et al. 1988, Jeanes 1999, Bean 2007). Within its native range, it occurs in poached ephemeral pools on woodland rides, heathland, wet corners of pasture, seepages, flushes, lake and river margins, and the margins of ditches. 0 – 1600 m elevation in its native range. There is no information available on elevation in the region. Conservation Status: — Least Concern (Lansdown 2014 b).