Comparative genetics of Scyphozoan species reveals the geological history and contemporary processes of the Mediterranean Sea

Jellyfish are attractive biological indicators of shifts in the marine environment, as they have limited mobility and they are highly exposed to the physics and chemistry of the water column. For this study, we focused on three Mediterranean macro-jellyfish - Rhizostoma pulmo, Aurelia sp. and Phyllorhiza punctata. We used comparative genomics and molecular clock (timetree) approaches to estimate occurrences of past geological events and contemporary anthropogenic effects in the Mediterranean Sea. Our results proved that these events have left their mark on the genomes of marine jellyfish. Genomic data of R. pulmo revealed a divergence point between the East and West MS populations that occurred 4.59 Ma, after the Zanclean flood, suggesting that at this time these regions had formed the two distinct ecological environments we know today. We propose that before that time (4.59 Ma), the highly mixed Atlantic and Mediterranean waters led to the wide dispersal of different species in the MS,...