LAUSR

Divergence in acoustic traits between closely related species can be explained by phylogenetic history. In gobies, phylogenies reconstructed with acoustic signals primarily overlap with studies based on morphological or molecular data. Here, sound production of the two Ponto-Caspian gobies, Neogobius melanostomus and Ponticola kessleri, was recorded in controlled conditions and compared to determine the degree of interspecific acoustic variation across benthophilin gobies. Both species produced tonal-like sounds characterized by unique temporal and spectral properties during agonistic and reproductive intraspecific interactions, while the acoustic comparison revealed that the vocalizations of these two species differ in almost every acoustic property. N. melanostomus vocal structure was characterised by short (c. 100 ms), low-frequency (< 100 Hz) tonal sounds repeated at a relatively faster rate, while P. kessleri sounds appeared as a broadband, downward frequency modulated longer calls (c. 450 ms). Some acoustic features (sound rate and duration) proved to be stereotyped and could be considered a species-specific trait that could potentially be utilized to discriminate males or used by females for mate assessment. The tonal sounds appear to have a deeper origin within the Benthophilinae subfamily, as all acoustically investigated species to date have been able to produce this sound type. The recorded vocal repertoire represents a baseline for future comparative acoustic studies among the benthophilin gobies, aiming to gain additional information on the evolution of acoustic communication within Ponto-Caspian gobies and highlighting their importance in reconstructing phylogenetic relationships.