The genus Ruppia L. (Ruppiaceae) in the Mediterranean region: An overview

• Revision of knowledge on the diversity and distribution of Mediterranean Ruppia species.
• An evolutionary history of the genus Ruppia shows polyploidization and hybridization.
• Ecological parameters have a key role in Ruppia presence and growth.
• The western Mediterranean basin appears a center of Ruppia diversity.
• An identification key of the Ruppia species is provided.

This paper reviews the current knowledge on the diversity, distribution and ecology of the genus Ruppia L. in the Mediterranean region. The genus Ruppia, a cosmopolitan aquatic plant complex, is generally restricted to shallow waters such as coastal lagoons and brackish habitats characterized by fine sediments and high salinity fluctuations. In these habitats Ruppia meadows play an important structural and functional role. Molecular analyses revealed the presence of 16 haplotypes in the Mediterranean region, one corresponding to Ruppia maritima L., and the others to various morphological forms of Ruppia cirrhosa (Petagna) Grande, all together referred to as the “R. cirrhosa s.l. complex”, which also includes Ruppia drepanensis Tineo. Populations of hybrid origin between R. maritima and R. cirrhosa and polyploidy have been detected.