Cephalopod beaks are important chitinous hard structures, used for preying upon and fragmenting prey. Thus, it is expected that ecological pressures drive cephalopod beak shape. These structures, which are used in species identification, may exhibit a certain association with phylogenetic relationships among cephalopod species. Here, we investigated the relative importance of ecological pressures and phylogenetic relatedness for determining beak shape of Mediterranean cephalopods. Phylogenetic analyses based on complete mitogenomes and nuclear ribosomal genes allowed the evolutionary relationships among 19 selected cephalopods to be clarified. Geometric morphometric techniques were implemented to describe beak shape variation across these cephalopods. Stable isotopic values of δ13C and δ15N were used as proxies of their trophic niche. Phylogenetic signal was detected in the shape of both lower and upper beaks. However, the lower beak exhibited higher interspecific variation in closely related species, which may explain why lower beak morphology has been traditionally used as a taxonomic identification tool in cephalopods. In addition, integration tests revealed an evolutionary covariation between the upper and lower beak shape. However, the link between beak shape and trophic niche could not be established. These results suggest that beak shape is more strongly associated with species phylogenetic relationships than with ecological pressures related to feeding habits

Cephalopod Intenational Advisory Council (CIAC) Symposium, 4-8 April 2022, Sesimbra, Portugal

Peer reviewed