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

Abstract

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. Graphical abstract

Geometric morphometrics casts light on phylogenetic relevance of cephalopod beak morphological

“…However, the phenogram of beak shape in this study could still indicate the classification relationship of cephalopods at the family level, as demonstrated by molecular phylogenetic trees and phylogenetic signal results (Figure , the left side of Figures 5, 6, 9; Tables 3, 4). Previous studies have also suggested a strong relationship between beak shape and phylogeny (Neige & Dommergues, 2002; Roscian et al, 2022; Sánchez‐Márquez et al, 2023; Tanabe et al, 2015). Above all, we found that Lepidoteuthidae and Octopodoteutidae have very different body morphology in adults but similar beaks and are closely phylogenetically related (Fernández‐Álvarez et al, 2022; Jereb & Roper, 2005b; Jereb et al, 2014).…”

“…The phylogenetic signals of beak shape were assessed by using a phylogenetic tree in combination with geometric morphometric approaches. This assessment is a cutting‐edge approach for studying cephalopods and can be used as an analytical framework (Adams & Collyer, 2018; Baken et al, 2021; Díaz‐Santana‐Iturrios et al, 2022; Roscian et al, 2022; Sánchez‐Márquez et al, 2023). In this study, beak shapes showed a strong phylogenetic signal (K = 1.420 and 0.912 for upper and lower beaks, respectively, p = .001), which is consistent with Sánchez‐Márquez et al (2023), indicating that the information contained in the lateral shape of the beaks is a useful material for cephalopod phylogeny studies.…”

“…This assessment is a cutting‐edge approach for studying cephalopods and can be used as an analytical framework (Adams & Collyer, 2018; Baken et al, 2021; Díaz‐Santana‐Iturrios et al, 2022; Roscian et al, 2022; Sánchez‐Márquez et al, 2023). In this study, beak shapes showed a strong phylogenetic signal (K = 1.420 and 0.912 for upper and lower beaks, respectively, p = .001), which is consistent with Sánchez‐Márquez et al (2023), indicating that the information contained in the lateral shape of the beaks is a useful material for cephalopod phylogeny studies. In addition, The SDA and HCA result (the left side of Figures 5 and 6; Tables 3, 4) also confirms the validity of beak shape identification at family and genus levels because the lateral profile also contained a great deal of shape information (Rostrum length, Jaw angle, etc.).…”

“…The beak of a cephalopod is the most important feeding organ and has been used for identification at the species and population levels (Fang et al, 2018; Fang et al, 2021; Pacheco‐Ovando et al, 2021; Xavier et al, 2011). Sánchez‐Márquez et al (2022) demonstrated that phylogenetic relatedness showed a significant impact on the beak shape of 18 cephalopods sampled from the western Mediterranean Sea. Therefore, crucial information could be stored in beak shape that could eventually become a useful material for investigating the stock assessment, taxonomic, and evolutionary systems biology studies of cephalopods.…”

Early prey intake of a short‐finned pilot whale (Globicephala macrorhynchus Gray, 1846, Cetacea: Delphinidae) in the Canary Islands

“…In addition, the authors would like to thank the veterinary team of the IUSA‐ULPGC for providing the samples for study and the BIOECOMAC research group of the University of La Laguna for their support during the campaign. We are very grateful for the cession of the reference collection of cephalopod beaks AFOC (ICM‐CSIC, Barcelona; Sánchez‐Márquez et al., 2023 ). Alejandro Escánez has been funded by the Action funded by the Ministry of Universities under the application 33.50.460A.752 and by the European Union NextGeneration EU/PRTR through a Margarita Salas contract of the University of Vigo, as well as by the Ministry of Science and Innovation project DeepCom CTM2017‐88686‐P.…”