Callitriche truncata Gussone (1826: 4)

Lansdown, Richard V., Rhazi, Laila, Saber, Er-Riyahi, Madihi, Mohammed El & Grillas, Patrick, 2022, The genus Callitriche (Plantaginaceae, Callitricheae) in Morocco, Phytotaxa 555 (1), pp. 53-72 : 65-66

9. Callitriche truncata Gussone (1826: 4)

Type: —In stagnis Caabriae orientale prope Cotrone, April, Martio (without location).

9a. Callitriche truncata subsp. occidentalis ( Rouy 1910: 186) Schotsman (1986: 153)

Type: — FRANCE. Manche. Vallée de la Taute à Carentan , fossé d’eau saumâtre, sur le fond de sable (dépôt marin), 31 May 1863. E. Lebel s.n. (P 03961335) .

Distribution: Callitriche truncata subsp. occidentalis occurs in coastal areas in Malta and from northern Syria along the north coast of the Mediterranean and Atlantic coast of the Iberian Peninsula, France, and Belgium to the Netherlands, where it appears to be spreading northwards ( Lansdown 2008). In Morocco it has been confirmed from two coastal sites near Rabat, which represent the only two confirmed records of this subspecies from North Africa ( Fig. 4D ). It is also possible that it is spreading in the south of its range and that these represent recent colonisation.

Habitat and ecology: —This subspecies typically occurs in seasonal coastal wetlands in the Mediterranean, but in ditches, lakes, and occasionally rivers further north. In Morocco it has been collected from a eutrophic drainage dyke in coastal cattle-grazed scrub with Chara von Linné (1753: 1156) sp. , Lemna gibba , and Hydrodictyon reticulatum ( von Linné 1753: 1165) Bory (1824: 506) (RNG 27366).

Recognition: — Callitriche truncata subsp. occidentalis can be distinguished from all other Callitriche taxa recorded from Morocco by the combination of translucent leaves that are not connate at the base, and unwinged fruit with divergent mericarps.

Illustrations: —Figures in Lansdown [2008: 24 (3b), 67].

Specimens examined: — MOROCCO: In eutrophic drainage dyke in coastal cattle-grazed scrub with Chara sp. , Lemna gibba , and Hydrodictyon , 42 km from Rabat along coast road to Mohammedia, Bouznika to Mohammedia, 10 m, 2 June 2002, S.L. Jury, M. Ait Lafikh, M.A. Carine and F.J. Rumsey 19506 (RNG 27366).

9b. Callitriche truncata subsp. truncata

Distribution: —The distribution of Callitriche truncata subsp. truncata is very poorly-known, due to the difficulty of confirming the identity of dried material ( Lansdown et al. 2017). Good numbers of specimens have been confirmed from Sicily and Syria and it appears likely that it occurs on islands in the Mediterranean from the Levant throughout much of the region to Morocco. However, it is certainly under-recorded and more information is needed to confirm its distribution and conservation status ( Fig. 4E ).

Habitat and ecology: —Most confirmed records of Callitriche truncata subsp. truncata are from seasonal pools, including cupular pools in limestone in Sicily. In Morocco it has been recorded from dayas, cupular pools on basalt, and the large seasonal pools of the Middle Atlas. It is generally considered to be an obligate submerged aquatic (e.g. Schotsman 1967) and in Morocco was mainly recorded with species that can be considered truly aquatic (48%). However, as the wetlands in which it occurs are seasonal it also occurred with species that may be considered typical of marginal or seasonal wetlands (48%) and a small number of terrestrial species (4%), and was found in a terrestrial form (see below). Typical associates were Alisma lanceolatum Withering (1796: 362) , Callitriche mathezii , Chara sp. , Drepanocladus aduncus ( Hedwig 1801: 295) Warnstorf (1903: 400) , Elatine macropoda , Eleocharis acicularis , E. palustris , Glyceria spicata , Groenlandia densa , Helosciadium repens , Juncus articulatus von Linné (1753: 327) , J. heterophyllus , Lythrum portula , Myriophyllum spicatum von Linné (1753: 992) , Nitella Agardh (1824 : xxvii) sp., Potamogeton pusillus von Linné (1753: 127) , P. trichoides Chamisso & Schlechtendal (1827: 175) , Ranunculus batrachoides , R. peltatus , Rorippa hayanica , Stuckenia pectinata ( von Linné 1753: 127) Börner (1912: 713) , and Zannichellia palustris . Elevation in Morocco: 1200—2000 m.

Notes: — Callitriche truncata includes three subspecies: C. truncata subsp. fimbriata Schotsman (1967: 39) is distinguished by the wing of the fruit that degrades while still on the plant to leave a fine fringe of fibrils, the only other Callitriche showing this fimbriate fruit margin is the recently described C. ciliata Lansdown & Hassemer (2021: 94) . Callitriche truncata subsp. occidentalis is distinguished by the unwinged fruit and in C. truncata subsp. truncata the fruit are winged, but the wing remains entire while on the plant. Callitriche truncata subspp. occidentalis and truncata are easily distinguished from each other when fresh by the presence or absence of a wing on the fruit. However, confirmation of dried material of C. truncata subsp. truncata can be very difficult, because distortion of immature fruit during pressing can give the impression of a wing on the fruit of C. truncata subsp. occidentalis . Critical confirmation is dependent upon inspection of the internal structure of the wing cells, requiring destructive examination, which is not always possible or appropriate with herbarium specimens. Callitriche truncata subspp. fimbriata and truncata are very poorly known, with most information derived from a small number of herbarium specimens. Callitriche truncata subsp. fimbriata is known only from a small number of limans (large, seasonal steppic lakes) in the Astrakhan region of southern Russia ( Lansdown 2008).

Examination of material recorded as C. truncata subsp. truncata from the Jbel Hebri - Timahdite area in the Middle Atlas showed that the wing of some fruit remaining on the plant degraded, leaving a fringe of fibrils. It is not clear whether:

• Callitriche truncata subspp. fimbriata and truncata are good taxa, but C. truncata subsp. fimbriata has a disjunct distribution with populations in southern Russia and in Morocco, similar to the distribution of other species, such as Marsilea strigosa and Damasonium alisma Miller (1768) .

• This character occurs in other populations identified as C. truncata subsp. truncata , bringing the validity of C. truncata subsp. fimbriata into question.

This issue can only adequately be resolved by a combined morphological and molecular study of both C. truncata subsp. fimbriata and truncata from throughout their known range, including more detailed research into populations in the Middle Atlas. The plants recorded from the Middle Atlas are treated here as C. truncata subsp. truncata until their true identity can be confirmed.

In contrast to statements made by Schotsman (1967), but as has been demonstrated to be the case with C. truncata subsp. occidentalis , plants of C. truncata subsp. truncata at Aguelmam Afennourir were found developing a stable terrestrial form, in which broad, opaque leaves with abundant stomata were developed by plants creeping over mats of filamentous algae.

Recognition: — Callitriche truncata subsp. truncata can be distinguished from all other Callitriche taxa recorded from Morocco by the combination of leaves that are not connate at the base, and the fruit that are very narrowly winged.

Illustrations: —Figures in Lansdown [2008: 24 (3a), 67].

Specimens examined: — MOROCCO: Oulmès , daia, 1200 m, 8 May 1926, [Emberger?] s.n. ( RAB 13816) . Moyen Atlas , Daya sur basalte, 1500 m, 16 June 1936 [Emberger?] s.n. ( RAB9665 ) . Moyen Atlas , Petite daya près d’Ito, 16 June 1936 [Emberger?] s.n. ( RAB 9635 ) . Vasques et berges de l’Ighzan Ain-Biod près Sidi Otsmane, 25 June 1974, J. Mathez 7311 ( RAB 47217) . Seasonal lakes between Azrou and Timahdite (Jbel Hebri), 1928 m altitude, 2 May 2019, R.V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks s.n. ( RAB) . Lac Afennourir , 1801 m altitude, 10 June 2019, R.V. Lansdown, N. Fetnassi, I. Mostakim s.n. ( RAB) .

Figures

FIGURE 4. Known distribution of Callitriche species in Morocco. A. C. obtusangula. B. C. regis-jubae. C. C. stagnalis. D. C. truncata subsp. occidentalis. E. C. truncata subsp. truncata. F. All records of all Callitriche species in Morocco.