Salvatore Brullo, Gianpietro Giusso del Galdo & Edwin Lanfranco A new species of Zannichellia L. (Zannichelliaceae) from Malta Abstract Brullo S., Giusso del Galdo G. & Lanfranco E.: A new species of Zannichellia L. (Zannichelliaceae) from Malta. Zannichellia melitensis a new species from the Maltese Archipelago is described and illustrated. It occurs in the small pools of the calcareous plateaux, where it grows together with other hydrophytes. Its relationships with the other known species of the genus Zannichellia are also examined. Introduction Zannichellia L. is a widely distributed genus centred in the Northern Hemisphere with the highest concentration of species in the Mediterranean basin. On the basis of morphological features, regarding the habit, stamens, stigmas and achenes, several species were previously described within this genus (Desfontaines 1798, Willdenow 1805, Reichenbach 1830, Wallmann 1840, Reuter 1854, Clavaud 1888, etc.). On the contrary, other authors regard that many of the described taxa have to be referred to a single variable species (see Dandy 1980). More recently, Talavera & al. (1986), in their revision of the genus Zannichellia, recognise six species, well differentiated from the morphological, caryological and anatomical point of view; they are Z. obtusifolia Talavera, Garcia Muríllo & Smit, Z. palustris L., Z. pedunculata Reichenb., Z. contorta (Desf.) Chamisso & Schlech., Z. peltata Bertol. and Z. major Boenn. ex Reichenb. During field work connected with the Maltese flora, a peculiar Zannichellia, occurring frequently in small pools on the calcareous plateaux of the islands of this archipelago, was found. Previously, Sommier & Caruana Gatto (1915), Borg (1927) and Haslam & al. (1977) referred these populations to Z. palustris and/or Z. pedunculata (as "Z. palustris var. pedicellata Fries"); but morphological and anatomical surveys have allowed to highlight that these populations are well differentiated from the other known species of the genus Zannichellia. Therefore, they are treated as a species new to science. Zannichellia melitensis Brullo, Giusso & Lanfranco sp. nova (Fig.1) Typus: Malta, Ghallis, 28.02.1999, Bartolo, Brullo, Lanfranco & Stevens (holotype CAT) Herba aquatica, annua, internodiis usque ad 2 mm longis, 7-8 aeriphorus canalibus in cortice, foliis 1.5-5 cm longis, 0.25-0.3 cm latis, obtusiusculis, 2 aeriphorus canalibus in mesophyllo, flores masculini et feminei in eodem nodo, filamento staminali 5-10 mm longo, anthera tetraloculari, 1.3-1.4 mm longa, flore femineo, 3-4 carpellato, stigmate linguiformi, lanceolato, superficie alveolata, achenio sessili vel subsessili, corpore 3-3.2 mm longo, plicato in margine convexo, rostro 1.2-1.5 mm longo. Hydrophyte submerged, annual, monoecious, rhizomatous. Stem elongated, slender, 615 cm high. Internodes up to 2 cm long, with 7-8 aeriferous canals in the cortex. Leaves linear, flat, 1.5-5 cm long, 0.25-0.3 mm wide, somewhat obtusely at apex, with 2 aeriferous canals in the mesophyll. Female and male flowers inserted in the same node. Stamen filament 5-10 mm long, and anther 4-locular, 1.3-1.4 mm long. Female flower shortly pedicelled, with membranous perianth, provided with 3-4 (5) free carpels. Stigma linguiform, lanceolate, entire at margin, with alveolate surface. Achenes sessile or subsessile, with corpus 3-3.2 mm long, laterally compressed, plicate at the convex margin, beak 1.2-1.5 mm long. Specimina visa. – Malta, in inundatis Wied S. Julian, 10.03.1874, Duthie (FI); ibid., secus diam a Notabile (Rabat) ad Imtahleb ducentim in rivo, 06.05.1907, Sommier (FI); ibid., inter Birchircara et S. Paulo a mare in rivo ad viam, 03.05.1907, Sommier (FI); ibid., in inundatis Wied at Zasel, 16.03.1874, Duthie (FI); ibid., 27.03.1967, Wied ilGhasel, Lanfranco (L); ibid., 26.10.1969, Ta' Zuta, in a rock pool, Lanfranco (L); ibid., Wied Harq Hamiem, 25.10.1970, Lanfranco (L); ibid., 10.02.1972, Verdala, Lanfranco (L); ibid., Wied il-Ghasel, 01.02.1978, Lanfranco (L); ibid., 04.03.1979, Wied Babu, specimen with galls, Lanfranco (L); ibid., Dingli, 27.02.1999, Bartolo, Brullo, Lanfranco & Stevens (CAT); ibid., Ras il Bajjada, 27.02.1999, Bartolo, Brullo, Lanfranco & Stevens (CAT); ibid., Fiddien near Rabat, 16.04.1987, Brullo, Pavone (CAT); ibid., Tal-Blata, 09.04.1984, Brullo, Pavone (CAT); Gozo, Cala Dueira, in una pozzanghera laghetto, 17.04.1906, Sommier (FI); ibid., in una pozzanghera, 17.04.1907, Sommier (FI); ibid., Cala Dweira, 13.04.1987, Brullo, Pavone (CAT); ibid., Xlendi Valley, 13.04.1987, Brullo, Pavone (CAT); ibid., Wied il Mielah, 13.04.1987, Brullo, Pavone (CAT); Comino, 07.05.1907, Sommier (FI); ibid., pozzanghera, 07.05.1907, Sommier (FI). Ecology and distribution. – Zannicchellia melitensis is linked to the small deep pools, temporary swamped by rainwater, which are quite frequent on the calcareous plateaux of the Archipelago Maltese islands. In particular it grows in the islands of Malta, Gozo and Comino, where is possible to see it from December to April. In these damp habitats, Z. melitensis is associated with other submerged hydrophytes, such as Damasonium bourgaei Cosson, Callitriche truncatula Guss., Elatine gussonei (Sommier) Brullo & al., Chara vulgaris L., Ranunculus saniculifolius Viv., etc. From the phytosociological point of view, this community can be assigned to the CallitrichoBatrachion, alliance of the Potametea class. Taxonomic relationships. – According to Talavera & al. (1986), within the genus Zannichellia L. two sections can be recognized: sect. Zannichellia and sect. Monopus Graebner. The first one is morphologically characterized by male and female flowers borne by the same node, stamen filament 0.7-10 mm long, and anthers generally 2locular (rr. 3- 4-locular); while the second one is differentiated by male and female flowers borne by different nodes, stamen filament 9-60 mm long, and anthers 4-locular. Due to the monoecious nodes and short stamen filaments, Z. melitensis belongs clearly to sect. Zannichellia; however, because of the constant occurrence of 4-locular anthers, it must be referred to the sect. Monopus. Therefore, it is possible to assert that the number of the anther loculi is not a good diacritic character to differentiate the sections, since Z. palustris, which is the species type of the sect. Zannichellia, shows anthers with 2-4 loculi. In its obtuse leaves, aeriferous canals in the cortex and 4-locular anthers, Z. melitensis would seem related to Z. obtusifolia, but they differ in many morphological characters. In particular, Z. obtusifolia shows leaves 1.5 mm wide, without aeriferous canals, stamen filament 12-60 mm long, anther 1.7-2.5 mm long, dioecious nodes, stigma infundibular, ovate, achene corpus 1.7-2.5 mm long, dentate at margin. Basing on the occurrence of aeriferous canals in the cortex, stamen filament up to 10 mm long, monoecious nodes, female flower with 3-5 carpels, stigma linguiform and lanceolate, Z. melitensis seems to be related to Z. major as well. However, the latter differs distinctly from Z. melitensis in having a more robust habit, leaves acute, up to 2 mm wide, achene corpus 3.2-4.5 mm long, dentate at margin. Moreover, Z. melitensis differs from all the other known species, apart from the many morphological features, also in its ecological requirements. In fact, this species occurs exclusively in the small deep pools hollowed out in the calcareous rock, while all the others, according to Van Vierssen (1982) and Talavera & al. (1986), grow on the muddy bottom of rivers, streams, lagoons, ponds, marshes with stagnant or slow moving waters (fresh or brackish). On the whole, Z. melitensis can be considered a species taxonomically quite differentiated, having an anient origin in consequence of its geographic isolation and ecological specialisation. Therefore, as with many other palaeo-endemisms occurring in the Maltese Archipelago (see Brullo & Pavone 1987, 1988; Lanfranco 1989, 1995), Z. melitensis is an ancestral species, with a remarkable phytogeographical significance. References Borg, J. 1927: Descriptive flora of the Maltese Islands including the ferns and flowering plants. – Malta. Brullo, S. & Pavone, P. 1987: Cremnophyton lanfrancoi: a new genus and species of Chenopodiaceae from Malta. – Candollea 42:621-625. – & – 1988: Hyoseris frutescens, a new species from Gozo (Malta). – Candollea 43:717-726. Clavaud, C. 1888: Sur les Zannichellia du Départament de la Gironde. – Acta Soc. Linn. Bordeaux 42:67-68. Dandy, J. E. 1980: Zannichellia L. In: Tutin & al. (eds.). Flora Europaea 5:13. – Cambridge. Desfontaines, R. L. 1798: Flora Atlantica, sive Historia Plantarum, quae in Atlante, Agro tunetano et algeriensi crescunt. – Parisiis. Haslam, S. M., Sell, P. D. & Wolseley, P. A. 1977: A flora of the Maltese Islands. – Malta. Lanfranco, E. 1989: The flora. in: Schembri P. J. & Sultana G. (eds.) Red Data Book for the Maltese Islands. Malta. – 1995: The Maltese flora and conservation. – Ecol. Medit. 21(1/2):165-168. Reichenbach, H. G. L. 1830: Flora Germanica excursoria 1. – Lipsiae. Reuter, P. 1854: Catalogue des Graines recueillies en 1854 et offertes en échange par le Jardin Botanique de Genève. - Genève. Sommier, S. & Caruana Gatto, A. 1915: Flora Melitensis Nova. – Firenze. Talavera, S., García Murillo, P. & Smit, H. 1986: Sobre el genero Zannichellia L. (Zannichelliaceae). – Lagascalia 14:241-271. Van Vierssen, W. 1982: The ecology of communities dominated by Zannichellia taxa in Western Europe. I. Characterization and ecology of the Zannichellia taxa. – Aquatic Bot. 12:103-155. Wallmann, J. 1840: En ny Zannichellia. – Bot. Not. 1840:42-46. Willdenow, C. L. 1805: Species Plantarum 4(1). – Berolini. Adresses of the authors: S. Brullo & G. Giusso del Galdo, Dipartimento di Botanica, via A. Longo, 19, I - 95125 Catania, Italy. E. Lanfranco, Department of Biology, University of Malta, , Msida MSD 06, Malta. Table 1 Differential morphological characters of the species of Zannichellia Character life form internodes [perhaps it is better to state "<x" or ">x" rather than long/short] no. aeriferous canals in the cortex leaf width (mm) leaf apex no. aeriferous canals in the leaf length of stamen filament (mm) anther length (mm) no. loculi of the anther flower sexuality in the nodes no. carpels of female flower stigma shape stigma surface stigma margin achene podocarp (mm) achene corpus (mm) achene beak (mm) ecology obtusifolia annual long contorta perennial short peltata annual long palustris annual long major perennial long pedunculata annual long melitensis annual long 9-11 1,5 obtuse 0 12-33(60) 1,7-2,5 4 dioecious 2 (3-5) infundibular, ovate alveolate entire or slightly dentate 0,6-1,5 0 0.7 acute 2 9-42 1-1.5 4 dioecious 4 (7) discoid, rounded 0 0.5 acute 2 10-30 1.2-1.8 4 dioecious 2 (3-5) infundibular, rounded alveolate irregularly dentate 0.2-0.5 0 1 acute 2 0.7-10 0.3-1.7 2-3-4 monoecious (2) 4 (8) infundibular, lanceolate alveolate irregularly dentate several 2 acute 2 2-10 1.2-1.8 2 monoecious (2) 3-5 linguiform, lanceolate alveolate entire 0 0.8 acute 2 1.5-4 (7) 0.3-0.8 2 monoecious 2-4 (6) linguiform, lanceolate alveolate entire 7-8 0.25-0.3 obtuse 2 5-10 1.3-1.4 4 monoecious 3-4 (5) linguiform, lanceolate alveolate entire 0.2-0.9 0.8-2 0-0.2 1,7-2,2 (2,5) 1-1,5 temporary lagoons with fresh waters 2.2-2.3 0.5-1 brooks and streams of calcareous mountains with fresh and oxygenated waters - absent or unknown? 3.2-4.5 1.5-1.7 salt-marshes with sandy soils 1.8-2.7 1.3-2 lakes or streams with fresh or brackish waters 3-3.2 1.2-1.5 temporary small pools on calcareous rocks with fresh waters crested irregular 0.3-0.7 2.5-3 0.9-2 lagoons with slow moving waters (fresh or brackish) 1.6-2.8 0.1-1.4 lakes or streams with fresh or brackish waters