Age-dependent variation of aedeagal morphology in Agabusuliginosus and the status of A.lotti (Coleoptera, Dytiscidae).

A doubt has arisen about the taxonomic status of Agabuslotti within the Agabusuliginosus species group due to morphological similarities and lack of molecular data. In this study, a comprehensive morphological and molecular analysis of specimens from Central Europe was conducted, focusing on the Hungarian population. Morphological comparisons of genital structures revealed age-dependent variations, suggesting a gradual transition from A.lotti to A.uliginosus. Molecular analysis of COI sequences further supported this hypothesis, showing minimal genetic differences among most specimens, with only one individual exhibiting distinctiveness. Therefore, A.lotti syn. nov. must be regarded as a junior synonym of A.uliginosus. Our findings also highlight the need for additional multi-marker studies covering a broader geographic range and including both molecular and morphological approaches to elucidate the taxonomic and phylogenetic relationships within this species group. The inclusion of Hungarian samples notably enriched the diversity of haplotypes, emphasizing the importance of expanding sampling efforts in future research.