Extensive sampling sheds light on species-level diversity in Palearctic Placobdella (Annelida: Clitellata: Glossiphoniiformes)

The bloodfeeding leech genus Placobdella is dominated by North American diversity, with only a single nominal species known from Central America and one the Palearctic region. This likely due to considerable underestimation of biodiversity, but investigations into potential hidden diversity are lacking. To shed light on this, present study introduces new data for specimens initially identified as costata Ukraine (close type locality), Italy, Germany, Latvia, Montenegro, Bulgaria, Slovenia, Turkey, Azerbaijan, Tunisia, Algeria, uses both nuclear (Internal Transcribed Spacer [ITS] region) mitochondrial (cytochrome c oxidase subunit I [COI]) sequence in phylogenetic DNA barcoding frameworks, order better understand species-level diversity. Seven independent lineages trees, five which show adequate separation at COI locus suggest their unique status (COI distances between these clades range 4.86 8.10%). However, ITS that speciation recent or incipient clades, not enough time has passed clear this locus. We discuss evolutionary taxonomic implications our findings speculate dispersal events may have contributed shaping pattern geographic distribution.