Supplementary Data - Master's Thesis Vincent Rankl

The Gobioidei are a highly diverse suborder of the teleost fishes, with worldwide ecological success in marine, freshwater and brackish environments. The majority of their diversity is concentrated within the sister families Gobiidae and Oxudercidae (“gobies” hereafter), which despite their diversity exhibit an unexpectedly narrow range of phenotypic variation. This may be explained by repeated convergent evolution driven by similar ecological pressures, leading to similar phenotypes. Convergent evolution has been demonstrated in gobioid fishes, but most work has focused on external body and head morphology rather than osteology. This thesis tests whether ecological adaptations are also reflected in the vertebral column of European gobies. To this end, vertebrae of selected species from the Gobius, Aphia and Pomatoschistus lineages were imaged using micro-CT techniques and analyzed through comparative anatomy, cluster analysis and geometric morphometrics. Our results indicate that freshwater species tend to exhibit a notch in the apex of the neural arch of the atlas and shorter centra than marine species, which we attributed to possible adaptations to flow-variable environments or paedomorphosis resulting from the generally highly variable conditions of freshwater habitats. Moreover, we found that the nektonic and hyperbenthic species in our sample exhibited longer centra than the epibenthic species, which we interpreted as an adaptation to increase swimming performance. Finally, we detected possible phylogenetic signals. Specifically, most Gobiidae exhibit two ventral ridges on the centra in the vertebrae of the abdominal-caudal transition while Oxudercidae show only one. Neural arch width may further allow differentiation between the European lineages of the Gobiidae and Oxudercidae. These results indicate that vertebral morphology is shaped by both ecological adaptations and evolutionary history. Ultimately, our findings highlight the investigation of postcranial osteology in gobies as a promising field of research.