Vertebral shape in Delphinidae within a phylogenetic frame

MARCHESI, MARÍA CONSTANZA; SECULI, E; COSCARELLA, MARIANO A.; GONZALEZ JOSÉ, R

Congreso; 25th Biennial Conference on the Biology of Marine Mammals; 2024

Introduction: Differences in vertebral morphology in cetaceans would be related to various functional abilities, promoting ecological diversity and adaptive radiation. Current morphological traits reflect both evolutionary adaptations and phylogenetic history. Several studies have used shape analysis to elucidate evolutionary, but few have explored the presence of phylogenetic signal in cetacean vertebral morphology.Objective:To study the relevance of phylogenetic signal in vertebral morphology in dolphinsTo what extent vertebral shape is constrained by phylogeny? To what extent is it associated with size or particular habitats?M&M: 3D landmarks five regions 524 vertebrae 128 specimens24 species of dolphins Skeleton of the hourglass dolphin (Lagenorhynchus cruciger) depicting both traditional and functional regions and the position of the five different vertebrae selected for the study. Cv: cervical region; Th: anterior thorax; ThTo: limit between thorax and torso, Tm: mid torso; SP: synclinal point; TS: tailstock; F: fluke. Scale = 5 cm.Phylogeny pruned from “Tree of Life” (McGowen et al., 2020). Different colors and symbols according to habitat and subfamily, respectively. Vertical bars denote subfamilies: Delphinidae (D), Globicephalinae (G), and Lissodelphininae (L). Análisis: R v4.4.1 (R Core Team, 2023) Packages: Geomorph v4.0., RRPP v2.0.0, “ape” v5.7-1 and “phytools” v2.1-1-GPA -Phylo PCA (PhyPCA) and Phylogenetically aligned component analysis (PACA): graphical comparisons, angles.-Kmult : expected under Brownian motion model Kmult = 1.-FiloANOVA on habitat and size (on selected PhyPcs and PACs that accounted 95% of variation in shape)ResultsPlot of the first two axis for the phyloPCA (PhyPCA) and the phylogenetically aligned component analysis (PACA). Th: anterior thorax; ThTo: limit between thorax and torso; Tm: mid torso; SP: synclinal point; TS: tailstock. Different symbols correspond to different subfamilies and clades. Different colors correspond to different habitats. Shapes for extreme species are shown in each region. Results on: a) the angles comparison (â); b) Test for phylogenetic signal (Kmult); and z values for a PhyloANOVA with habitat (H) and centroid size (CS) as factors. * p  0.05, ** p  0.01, *** p  0.001.a)PhyPC1 vs PAC1b) n PhyPCsc) n PACsd)PhyloANOVA nPhyPCsâKmultKmultCSHTh146.280.524**0.569**-0.5040.9232ThTo148.400.4580.483*2.786**3.241***Tm8.99***0.794**0.822**0.7113.511***SP114.940.607***0.629**2.194*3.284**TS16.56***0.878**0.940***1.11780.7184Differences between the angles: greater amount of variation not related to phylogeny in three regions, the anterior thorax (Th), the posterior thorax (ThTo), and the synclinal point (SP). Similarities between the angles, and RV scores in the mid-torso (Tm) and tail stock (TS) suggest as greater effect of phylogeny on vertebral morphology. Species with particular habitat requirements within subfamilies, diverging greatly from their closest relatives and showing features beneficial from a biomechanical point of view.Through Phylogenetic ANOVAS and Kmults suggest both ecology and phylogeny have effect on vertebral morphology. CONCLUSION:-Multiple signals affecting vertebral shape, at various phylogenetic levels and on numerous dimensions of shape, differentially depending on the region along the skeleton-At family level: vertebral morphology in the thorax (Th), limit thorax-torso (ThTo), and the synclinal point (SP) partially constrained by phylogeny and partially by other several factors such as ecology and size. -Vertebral morphology of the mid torso (Tm) and the tail stock (TS) had the highest phylogenetic signals. Ecological signal also detected for the most biomechanically relevant region in fast swimming oceanic species (Tm), with species with similar biomechanical requirements located close disregarding phylogeny and suggesting a great influence of ecological factors at subfamily levels, and.