Riella mediterranea Segarra, Puche, Sabovlj., M.Infante & Heras

SPECIMEN EXAMINED. — Tunisia. Mogods, Bizerte Governorate, Delegation of Tinja: Ichkeul National Park, with sporophytes, 37°06’36.73”N, 09°40’55.83”E, 0 m a.s.l. (site 2019-102), 12.IV.2019, Ben Osman & Hugonnot (TUN[TUN2019-134]).

REMARKS

Riella mediterranea was collected under c. 20-30 cm of water in a temporary marsh located in the northern part of the Ichkeul National Park. In the slightly brackish water, the liverwort was growing on dense clay mixed with Chara galioides DC., C. oedophylla Feldm., Damasonium alisma Mill. subsp. bourgaei (Coss.) Maire and Ranunculus peltatus Schrank subsp. baudotii (Godr.) Ball. In other areas, this species occurs in arid or semi-arid environments submerged in temporary ponds of fresh or slightly brackish waters (Segarra-Moragues et al. 2014), which fully corresponds to the ecology in Tunisia.

Riella mediterranea is characterized by its helicoid thallus wing. Female involucres are acuminate, and generally have more than 10 low discontinuous, wings that reach neither the tip nor the base of the involucres. The wing cell margins are formed by 1-3 rows of hyaline cells, which are densely spinose and have distal spines that are longer than 8 µm with proximal acute spines. In a recent taxonomic review of Riella subg. trabutiella, R. mediterranea was described as a new species (Segarra-Moragues et al. 2014).Accordingly,the Tunisian records of R. cossoniana Trab. (Ros et al. 2007) should be checked.

Riella mediterranea is a Mediterranean species. In Europe, this liverwort is reported only on the Iberian Peninsula and in Malta (Segarra-Moragues et al. 2014). It is also present in North Africa and Southwestern Asia (Segarra-Moragues et al. 2014). Because of its recent taxonomic recognition, its distribution remains to be clarified.