Callitriche lusitanica Schotsman (1961: 112)

Lansdown, Richard V., Bazos, Ioannis, Caria, Maria Carmela, Troia, Angelo & Wieringa, Jan J., 2017, New distribution and taxonomic information on Callitriche (Plantaginaceae) in the Mediterranean region, Phytotaxa 313 (1), pp. 91-104 : 93-94

Callitriche lusitanica Schotsman (1961: 112)

In 2003, a Callitriche specimen was sent to RVL by IB from between Parakila and Agra on Lesvos. It was tentatively identified as C. lusitanica but could not be confirmed as some critical elements were lacking. Further material was collected from the same site by IB and S. Zervou on 10 May 2014 and confirmed as C. lusitanica by RVL in January 2015. Subsequently, in the course of fieldwork, C. lusitanica was found at four sites scattered through the mountainous central and eastern parts of Sardinia. In all of the Sardinian sites it was associated with the main channel of medium-sized to large rivers, either in the channel itself, where it formed large stands, in backwaters, on the margins or growing over boulders. In deeper water, it occurred with Callitriche obtusangula Le Gall (1852: 202) , filamentous green algae, Lemna gibba Linnaeus (1753: 970) , Myriophyllum spicatum Linnaeus (1753: 992) , Nasturtium officinale Brown (1812: 110) , Potamogeton crispus Linnaeus (1753: 126) , P. schweinfurthii Bennett (1901: 220) , Ranunculus peltatus , R. penicillatus ( Dumortier 1863: 216) Babington subsp. pseudofluitans ( Syme 1863: 20) Webster (1988: 20) var. vertumnus Cook (1966: 160) , R. trichophyllus Chaix ex Villars (1786: 335) , Sparganium erectum Linnaeus (1753: 971) , and Stuckenia pectinata ( Linnaeus 1753: 127) Börner (1912: 713) . On the margins and in backwaters, it was recorded with Apium nodiflorum ( Linnaeus 1753: 251) Lagasca (1821: 101) , Corrigiola littoralis , Cyperus fuscus Linnaeus (1753: 46) , C. longus Linnaeus (1753: 45) , Fontinalis hypnoides Hartman (1843: 434) , Scirpoides holoschoenus ( Linnaeus 1753: 49) Soják (1972: 127) , Juncus articulatus Linnaeus (1753: 327) , J. pygmaeus , Mentha × villosa-nervata Opiz (1831: 60) , M. pulegium , Montia fontana Linnaeus (1753: 87) var. chondrosperma (Fenzl in Ledebour 1843: 152) Walters (1956: 4), Oenanthe crocata Linnaeus (1753: 254) , Parentucellia viscosa Caruel (1885: 482) , Ranunculus muricatus , R. ophioglossifolius , R. peltatus , Rumex conglomeratus Murray (1770: 52) , Schoenoplectus lacustris ( Linnaeus 1753: 48) Palla (1888: 299) , Typha angustifolia Linnaeus (1753: 971) and Veronica anagallis-aquatica Linnaeus (1753: 12) . A notable feature of populations in Sardinia not recorded in populations in the Iberian Peninsula is the development of extensive, evidently persistent terrestrial plants, both on the margins where water-levels had dropped but particularly growing over boulders in the channel where they may remain humid for months.

Callitriche lusitanica is fairly widespread in the western half of the Iberian Peninsula, it has been recorded from Algeria, Morocco, Tunisia and there is a specimen collected by the late Avinoam Danin from Golan in Israel (BR). A plant found in Siracusa Province, Sicily by AT was identified as this species from a photograph. It is clearly much more widespread than previously thought and likely to have been under-recorded throughout much of the region. The range of C. lusitanica can now be seen to extend from the Iberian Peninsula and Morocco east through Sardinia and Lesvos to Israel, suggesting that this species should be sought elsewhere in North Africa, as well as possibly in the Balearic Islands.

In 2010, an assessment of the extinction risk of European populations of C. lusitanica classed it as Near Threatened ( Bilz et al. 2011) on the basis that “This species is classed as Near Threatened as it has a restricted distribution area and its freshwater habitat is degrading. Expected future demand of water in the southern European regions, will worsen the situation for this species and it could quickly fall into a threatened category”. The discovery of additional populations extending from Sardinia and Sicily east to Syria and Israel means that its distribution is no longer restricted and although its habitat is threatened throughout its range, the likelihood of extinction must now be considered remote. Callitriche lusitanica should therefore be classed as Least Concern ( IUCN 2012).