DaphniolaRadoman, 1973 (Gastropoda: Hydrobiidae): shell biometry, mtDNA, and the Pliocene flooding

Shell biometry and cytochrome c oxidase subunit 1 (CO1) mtDNA were studied in Daphniola exigua (Schmidt, 1856), D. graeca Radoman, Citation1973, and D. louisi Falniowski and Szarowska, Citation2000 from Greece. Principal component analysis of shell morphometry confirmed the distinctness of D. louisi along the PC3 axis. Kimura 2‐parameter (K2P) genetic distances within D. graeca and D. exigua were 0.016 and 0.003–0.008, respectively, all D. louisi sequences were identical. The distance between D. exigua and D. graeca was 0.013–0.027. The distances between D. louisi and D. graeca, and D. louisi and D. exigua, were 0.098–0.110 and 0.091–0.096, respectively. The mean distance between D. louisi and the other Daphniola species was 0.098±0.007, while between the eight Daphniola specimens and the so far closest species Grossuana codreanui (Grossu, 1946) was 0.102–0.123. A maximum likelihood tree was constructed for all Daphniola, with Grossuana codreanui and Bythinella austriaca (Frauenfeld, 1856) as an outgroup. This confirmed that D. louisi is a distinct species, and must have diverged after the Pliocene marine transgression.