Unravelling the phylogenetic and ecological drivers of beak shape variability in cephalopods

19 pages, 5 figures, 4 tables, supplementary Information https://doi.org/10.1007/s11160-022-09744-5.-- Data availability: Genetic data underlying this article are available in the GenBank Nucleotide Database at https://www.ncbi.nlm.nih.gov/genbank/ and can be accessed with the GenBank accession numbers OP151115-OP151122, OP161136-OP161143, OP235417-OP235424. The FastQ files can be accessed within the GenBank Nucleotide Database with the BioProject accession number PRJNA866317. Stable isotope and geometric morphometric data are available upon request from the corresponding author. Additional material is available in Supplementary files 1–3

Cephalopod beaks are essential for prey acquisition and fragmentation during feeding. Thus, it is expected that ecological pressures affect cephalopod beak shape. From a practical perspective, these structures are also used to identify gut contents of marine megafauna, such as toothed whales, sharks, seabirds, and large pelagic fishes. Here, we investigated the relative importance of ecological pressures and phylogenetic relatedness in the evolution of beak shape using a wide range of Mediterranean cephalopod species. Phylogenetic analyses based on complete mitogenomes and nuclear ribosomal genes provided a well-supported phylogeny among the 18 included cephalopods. Geometric morphometric and stable isotope methods were implemented to describe interspecific beak shape and trophic niche variability, respectively. Phylogenetic signal was detected in the shape of both parts of the beak (upper and lower). However, lower beak shape was more distinct among closely related species, in line with the empirical notion that lower beak morphology is more useful as an identification tool in cephalopods. Interestingly, no association between beak shape and trophic niche (stable isotope values) was found. These results suggest that the evolution of cephalopod beak shape as quantified here is mainly driven by phylogenetic relationships, while feeding habits play a minor role

We are thankful to the crew of the projects SAP (ARP029/18/00003, Departament d'Acció Climàtica, Alimentació i Agenda Rural, Generalitat de Catalunya), to BITER, OCTOSET and ECOPHYN (PID2020-114732RB-C31, RTI2018-097908-B-I00 and PID2021-126824NB-C32 respectively, Ministerio de Ciencia e Innovación, Gobierno de España) for granting the access to the samples and to Núria Lombarte Recasens for the illustrations provided of the beaks and major taxonomic groups. This study is part of the Master thesis of A.S.-M., who was supported by a JAE-Intro grant of CSIC (JAEIntro2020-ICM-2). F.Á.F.-Á. was supported by an Irish Research Council–Government of Ireland Postdoctoral Fellowship Award (ref. GOIPD/2019/460) and a JdC-I Postdoctoral Fellowship Grant (ref. IJC2020-043170-I) awarded by MCIN/AEI/10.13039/501100011033 and the European Union NextGenerationEU/PRTR. A.K. is supported by a Ramón y Cajal research grant co-funded by the Spanish State Research Agency and the European Social Fund (RYC2019-026688-I/AEI/10.13039/501100011033). M.T. was funded by a Ph.D. fellowship from the Irish Research Council (GOIPG/2017/1740) and was supported by the Dr. Tony Ryan Research Fund. This research was supported by the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S). [...] Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature

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