Karyotypes of european species of radix (Gastropoda: Pulmonata: Lymnaeidae) and their relevance to species distinction in the genus

Karyotypes of Radix auricularia (Linnaeus, 1758) and three disputable taxa considered by
different authors as distinct species or assigned as forms of Radix peregra (Muller, 1774),
sensu lato - R. labiata (Rossmassler, 1835), R. balthica (Linnaeus, 1758), and R. ampla
(Hartmann, 1821) - were studied with preparations obtained from gonad tissues by the airdrying
method. The studied taxa have the same diploid number (2n = 34), but are characterized
by different morphology of some chromosome pairs. In particular, R. labiata (traditionally
identified as R. peregra, s. s.) and R. balthica (= R. ovata in traditional understanding) differ
in the number of subtelocentric chromosomes (1 and 5, respectively), species status of
these taxa being also supported by pronounced differences in centomeric indexes of chromosome
pairs 4 and 16. Species distinctness of R. ampla is supported by differences in
three chromosome pairs, and karyological similarity between this taxon and R. balthica is
also noted. FN values varied among the studied taxa from 56 in R. ampla to 66 in R. labiata.
The known karyological characters are traced on phylogenetic trees suggested by recent
molecular reconstructions. This study demonstrates that karyology can be an effective tool
for aiding taxonomic distinctions of historically problematic groups of molluscs.