Callitriche mathezii Schotsman (1976: 199)

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 : 59-62

5. Callitriche mathezii Schotsman (1976: 199)

Type: — MAROC: Plateau Central , Massif du Mtourzgane – Akzou, vasques dans les quartzites, 2 May 1970, J. Mathez 55078 (holotype MPU 310674; isotype RAB 085553 ) .

Distribution: — Callitriche mathezii is endemic to Morocco, where it has been confirmed from a total of seven main areas: three on the Central Plateau (Oulmès, Aguelmous-Mante, and Aguelmous-Akzou) and four in the Middle Atlas (Aguelmam Afennourir and sites between Jbel Hebri and Timahdite), as well as two records from the Rif Mountains in the north ( Fig. 2A ). The distribution of these records suggests that it may be under-recorded, however it appears to be dependent on a fairly limited habitat type and it is therefore unlikely to be abundant anywhere in its range.

Habitat and ecology: — Callitriche mathezii occurs in seasonally-inundated standing water bodies. In the Central Plateau, it was recorded from two distinct habitat-types: cupular pools in quartzite, including the type locality, and a shallow valley wetland complex, surrounded by arable land. At the type locality, hill tops are composed of horizontal quartzite exposures (J. Mathez in Schotsman 1976) between 1400–1500 m elevation, with scattered trees grading into Quercus ilex von Linné (1753: 995) woodland on the lower slopes. In a few locations, hollows in the bedrock accumulate water, which persists for more than a few months. These hollows range in size from a few centimetres to 2– 3 m in diameter. When holding water, they typically support few species, such as Callitriche mathezii , C. brutia subsp. naftolskyi , and Isoetes velata A.Braun in Bory & Durieu (1849: fig. 1), with filamentous green algae. As they dry out, these are replaced by species more typical of very shallow or dried out pools, such as Crassula vaillantii ( Willdenow 1798: 720) Roth (1827: 992) , Lythrum thymifolia , Plantago coronopus von Linné (1753: 115) , and Spergularia rubra ( von Linné 1753: 423) Presl & Presl (1819: 94) . Callitriche mathezii was recorded from a second series of cupular pools in arable land near Mante. In this area, low granite bedrock exposures are scattered in a large area of open ground. These exposures contained a very small number of seasonal pools supporting a similar range of species, with C. mathezii in two. In the valley wetland complex, C. mathezii was abundant as terrestrial plants on bare mud in a band around the remaining water, with species such as Elatine hydropiper and Ranunculus peltatus , as well as on the margin of a stream were it was mixed with a wide range of species such as Callitriche stagnalis , Pilularia minuta , and Lythrum borysthenicum .

In the Middle Atlas, Callitriche mathezii was found in large seasonal lakes and pools on basalt on the plateau south of Timahdite. Most of these are in an area heavily grazed by sheep and consequently characterised by bare, very rocky ground. However, Aguelmam Afennourir is a Ramsar site and subject to much lower grazing pressure. It may represent the character that all of these high-altitude lakes would have if grazing pressure was reduced. In these sites, C. mathezii occurred throughout the water and margins up to about 0.5 m depth, with a range of species dominated by true aquatics, such as C. truncata subsp. truncata , Eleocharis palustris , Ranunculus batrachioides Pomel (1874: 249) , and R. peltatus . At Aguelmam Afennourir, C. mathezii occurred in a very species-rich assemblage with multiple canopies of submerged, floating and aquatic plants, such as Damasonium bourgaei Cosson (1849: 47) , Elatine macropoda Gussone (1826: 475) , Eleocharis acicularis Roemer & Schultes (1817: 154) , Groenlandia densa Fourreau (1869: 169) , Helosciadium repens Schultz (1854: 237) , Juncus heterophyllus Dufour (1825: 88) , Rorippa hayanica Maire (1927: 4) , and Zannichellia palustris von Linné (1753: 969) .

Notes: —Existing information on the morphology of Callitriche mathezii is based on the type description,which was derived from herbarium specimens. As is typical with reference to Callitriche species, study of fresh material has enabled development of a more informed description as follows:

Stem and leaf scales present. Leaf bases connate. Lingulate leaves unknown, expanded submerged or floating leaves typically with long petiole terminated by a small blade which can be very broad relative to its length, 1.2–3.3 × 0.5–2.2 mm, venation simple or complex with numerous loops and anastomosing veins, petiole 0.6–5.1 mm, apical leaves forming a floating rosette, leaves of terrestrial plants narrowly elliptic 1.6–2.5 × 0.2–0.9 mm. Flowers solitary, usually predominantly one gender on a shoot or even entire plant. Bracts falcate, persistent 0.5–0.9 mm. Styles erect, becoming recurved in fruit, ≤ 4.1 mm. Filaments erect ≤ 3.5 mm; anthers reniform, 0.4–0.6 mm diam.; pollen yellow. Fruit not strumose, subsessile or pedicellate to 10.8 mm, ± as wide as high, blackish when mature, contrasting with pale wing, 0.8–1.3 × 0.8–1.4 mm, wing throughout.

It is of note that Callitriche mathezii was found flowering and developing fertilised fruit submerged ( Fig. 2B ), which is not typical of the Callitriche species with yellow pollen of which few are known to flower underwater. Pollination must involve transport of pollen in the water column, as this species is more or less dioecious in the location where this behaviour was observed. It is also of note that C. mathezii is clearly adapted to survive as a terrestrial form on damp mud, a capacity that was considered unlikely by Schotsman (1976).

Schotsman (1976) studied herbarium material from Akzou and temporary pools on schist near Oulmès. She noted differences between these two populations, particularly that the fruit of the population at Oulmès were smaller, with a narrower wing than those from Akzou. Comparison of fresh material from Akzou, Oulmès, and Jbel Hebri shows that while the fruit of the material from Oulmès are slightly smaller than those from Akzou, those from Jbel Hebri are smaller still ( Fig. 3A ), showing almost no overlap with those from the other two sites. Photographs of fruit from these three sites show the difference in wing width noted by Schotsman (1976), as well as quite striking differences in the shape of the fruit ( Fig. 3B ).

Schotsman (1976) also noted that some rosettes of Callitriche mathezii only held female flowers, while others held only male flowers. Examination of abundant fresh material from Akzou, Oulmès, and Jbel Hebri showed that plants from Oulmès ( Fig. 2C ) and Akzou were almost entirely dioecious with hundreds of flowers of a single gender on one plant, but only one or two of the other gender. In contrast, those from the Jbel Hebri - Timahdite area had ♀ flowers toward the base, with ♂ toward the apex, suggesting that ♀ flowers develop first, followed by ♂. The differences between populations in these three areas are greater than differences that have been considered sufficient to treat populations as different varieties, subspecies or even species in other regions (e.g. Lansdown & Hassemer 2021, Lansdown 2022). In a global revision of the genus (see Lansdown 2022) no such morphological variation has been found within any other species except C. palustris and C. hermaphroditica , both of which considered to include a number of sub-specific taxa (e.g. Lansdown 2006b). These apparent differences in morphology and reproductive strategy between populations occurring over a relatively small area suggest that C. mathezii has a very low dispersal capacity, such that each population may be considered largely genetically isolated. Without more information, it would be premature to describe sub-specific taxa within C. mathezii or to describe any of the populations as different species. However, it is clear that there would be great merit in more detailed research into variation in the taxon recognised as C. mathezii , particularly if supported by genetic analysis.

Recognition: — Callitriche mathezii can be distinguished from other Callitriche species recorded from Morocco, except C. deflexa , by the combination of the small fruit that are blackish when mature. It can be distinguished from C. deflexa by the fruit that are subsessile and longer than wide, and the solitary flowers.

Illustrations: —Figures in Schotsman (1976: 200, 202, 204), and this paper ( Figs 2B, 2D and 3B ).

Specimens examined: — MOROCCO: Daias à Ouelmès (schistes) 1200 m, s.d., Emberger s.n. ( RAB 13821) (mixed with C. brutia ) . Plateau Central ( Haut Pays ) - Zaïan, Aguelmous, petites mares temporaires sur dalles horizontals de quartizites, 1627 m, s.d., J. Mathez 5508 ( RAB 085553 , MPU 310674 ) . Inundated flat pasture near Chefchaouene , 16 April 2019, G. Pils s.n. (herb. G. Pils). Large seasonal pool near Oulmès, 1170 m, 28 April 2019, R.V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks s.n. ( RAB) . Cupular pools in granite near Mante, 1163 m altitude, 30 April 2019, R.V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks ( RAB) . Akzou , 1486 m, 1 May 2019, R.V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks s.n. ( RAB) . 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 ( RAB) . 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) . Seasonal lakes between Azrou and Timahdite (Jbel Hebri), 1912 m altitude, 2 May 2019, R.V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks s.n. ( RAB) .

Field records: —Seasonal stream near Oulmès, 1170 m alt, 28 th April 2019, R.V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks. Pools in granite outcrops near the Hotel des Thermes à Tarmilate (Oulmès), 29 April 2019, R.V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks. Akzou, 1487 m, 1 May 2019, R.V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks. Akzou, 1433 m, 1 May 2019, R.V. Lansdown, L. Rhazi, P. Grillas, M. El Madihi, J. Snoeks. Lac Afennourir, 1801 m altitude, 10 June 2019, R.V. Lansdown, N. Fetnassi, I. Mostakim.

Figures

FIGURE 2. Callitriche mathezii. A. Known distribution in Morocco. B. Growing submerged in a pool south of Timahdite in April 2019, with well-developed, long-pedicellate fruit and yellow pollen. C. Almost entirely female plant from Oulmès. Photographs: © R.V. Lansdown.

FIGURE 3. A. Fruit biometrics of C. mathezii at three sites (Akzou, Oulmès, and Jbel Hebri). B. Fruit from three sites: left—Akzou; middle—Oulmès; right—Jbel Hebri. Photographs: © R.V. Lansdown.