Ranunculus dahlgreniae (section Batrachium, Ranunculaceae), a new species from Crete, Greece, with remarks on taxonomy and phylogenetic relations within the section

A new species, Ranunculus dahlgreniae, is described from a seasonal lake at Omalos Plateau, Lefka Ori Mountains, western Crete, Greece. The heterophyllous species resembles R. saniculifolius, R. peltatus, and the Mediterranean forms of R. baudotii. It differs from the aforementioned species by a combination of characters not found in any of them, i.e., 5–6 mm long petals, up to 2.2 mm long, glabrous achenes with a partly persistent style, a densely pubescent, in fruit slightly elongating receptacle, and intermediate leaves with rigid filiform apical segments, being divided into two or three cuneate, shortly petiolate leaflets. A key to all similar East Mediterranean taxa is presented. DNA analyses based on the sequencing of nuclear, ribosomal Internal Transcribed Spacer (ITS), and two chloroplast noncoding regions (rpl32-trnL and psbE-petL), complemented by the analysis of genome-wide polymorphism using double digest RAD Sequencing (ddRADseq) supported that Ranunculus dahlgreniae is a distinct lineage, clearly separated from R. peltatus, R. baudotii, and R. saniculifolius. The phylogeny based on ddRADseq resembles the topologies obtained from chloroplast and nrITS data but with increasing resolution and support of fine-scale relationships. Extensive sampling, including taxa from temperate Europe and the West Mediterranean area, as well as the application of reduced-representation sequencing, allowed to better understand the pattern of diversity in the section Batrachium.