Abstract
Pallavicinia lyellii (Hook.) Carruth. (Pallaviciniaceae) is a globally widespread species recorded in Asia from Turkey to Oceania (Grolle and Piipo 1984, 1986; Mamontov et al. 2015; Kürschner and Frey 2020), in Africa (see below), in North America and the Caribbean (Schuster 1992), and in South America (Hässel de Ménendez and Rubies 2009). Concerns have been voiced about the taxonomic identity of several records (see for instance Mamontov et al. 2015) such that the Asian mentions (and possibly others) should be revised. Pallavicinia lyellii has a southern-temperate suboceanic distribution in Europe. It has been recorded from the Atlantic coasts of continental Europe to Ukraine, and from Greece and Spain to Denmark, Lithuania and Macaronesia (Hodgetts and Lockhart 2020). It has vanished from Austria, the Czech Republic, Slovakia and Sweden. Its rarity and vulnerability are such that it is listed as 'Vulnerable' on the European Red List (Hodgetts and Lockhart 2020). Although widespread at the world scale, the species is uncommon in Africa: it is localised in East Africa (Wigginton and Grolle 1996), recorded in West Africa only in Cameroon, Nigeria and Sao Tomé (Wigginton 2004), and mentioned on Reunion Island (Grolle 1995). In North Africa, the species was only known in Tunisia (Ros et al. 2007), where its current status is uncertain. Given the species' apparent rarity and considerable phytogeographical interest, we undertook field and herbarium studies to relocate it in nature based on our knowledge of its local ecological requirements and to assess the possibility of implementing conservation measures. We examined all North African specimens of Pallavicinia lyellii stored in PC and in MHLCLF (which corresponds to a part of Jelenc herbarium). For each herbarium specimen, after checking the taxonomic identity, we estimated the surface size of thalli in cm², recorded the details of location and ecology, and deliberately searched for sexual individuals. Thalli were noted as male, female, or sterile. We compiled all bibliographical records of the species from publications dealing with North Africa (Labbe 1953; Jovet-Ast and Bischler 1971; Ros et al. 1999, 2007). From April 1-13, 2019, we conducted field surveys in Kroumiria, North Tunisia, in major peatlands and Alnus glutinosa swamps. We revisited localities where the species was previously mentioned. We evaluated the surface occupied by patches of Pallavicinia lyellii and recorded sexual individuals. We confirmed the identification of all specimens stored under the name Pallavicinia lyellii (Table 1), except PC0762698 (s.d, Aïn Draham) that only contained Pellia sp. All five North African specimens of Pallavicinia lyellii come from North Tunisia. Three main localities in Aïn Draham delegation are mentioned: