Abstract
The scapula is one of the morphologically more variable bones in the carnivore postcranial skeleton, but the causes of such variation are unclear. The aim of this study is to assess which factors are related to the shape variation in the carnivore scapula, since the order Carnivora presents not only a high degree of variability in scapular morphology, but also in body size, locomotor behaviour,
and habitat.
A total of 28 landmarks were digitized on a sample of 156 specimens belonging to 71 species using a 3D digitizer (Immersion MicroScribe 3D). After aligning the specimens by means of a Procrustes superimposition, a principal components
analysis was carried out to study shape variation using MorphoJ software. The six first principal components (PCs) explained almost 80% of shape variation. PC1, which accounts for 34.54% of shape variation, is characterized by a decrease in the surface area of both fossa supraspinata and fossa infraspinata and clearly separates seals and sea lions from the rest of the carnivores (Fig. 1).
In the rest of PCs no such clear separation exists, but several trends related to locomotor behaviour are observed. PC2 implies a reduction of fossa supraspinata and the acromion process (Fig. 1) and PC2 scores increase from aquatic species to scansorial ones, reaching a maximum in terrestrial species. PC3 is characterized by an enlargement of the caudal part of margo vertebralis scapulae (mvs) and a reduction of the cranial part of mvs, which causes an increase in the curvature of the scapular spine, and also by a wider acromion process and neck of the scapula, and a more convex margo cranialis. In PC4 the scapula gets longer and proportionally narrower, with a more convex mvs, and from arboreal species to scansorial ones to aquatic and semifossorial species PC4 scores increase, reaching highest values for terrestrial species. In PC5 aquatic species have the lowest values and semifossorial species, the highest,
seemingly related to a broader margo caudalis, a reduction of fossa infraspinata and a more cranially oriented glenoid cavity. Finally, PC6 implies a concave margo caudalis and a caudally projected glenoid cavity and separated Phoca vitulina from the rest of species.
A regression of the PC scores on log-transformed centroid size (ln CS) revealed that size accounts for 14.80% of shape variation in the carnivore scapula, though its contribution to individual factors varies from 0 to 35%. Finally, MANOVA tests were carried out on the PC scores to assess the effect of phylogeny, locomotor
behaviour and habitat on shape variation. Results show that morphological variation in the carnivore scapula is related both to phylogeny and habitat, but not to locomotor behaviour. Nevertheless, the effect of habitat proved to be non-significant once the effect of size was removed (using the residuals of the regressions on ln CS). Thus, in spite of the high variability in locomotor behaviour and habitat of the carnivores, it seems that scapular shape is mainly determined by phylogeny.
and habitat.
A total of 28 landmarks were digitized on a sample of 156 specimens belonging to 71 species using a 3D digitizer (Immersion MicroScribe 3D). After aligning the specimens by means of a Procrustes superimposition, a principal components
analysis was carried out to study shape variation using MorphoJ software. The six first principal components (PCs) explained almost 80% of shape variation. PC1, which accounts for 34.54% of shape variation, is characterized by a decrease in the surface area of both fossa supraspinata and fossa infraspinata and clearly separates seals and sea lions from the rest of the carnivores (Fig. 1).
In the rest of PCs no such clear separation exists, but several trends related to locomotor behaviour are observed. PC2 implies a reduction of fossa supraspinata and the acromion process (Fig. 1) and PC2 scores increase from aquatic species to scansorial ones, reaching a maximum in terrestrial species. PC3 is characterized by an enlargement of the caudal part of margo vertebralis scapulae (mvs) and a reduction of the cranial part of mvs, which causes an increase in the curvature of the scapular spine, and also by a wider acromion process and neck of the scapula, and a more convex margo cranialis. In PC4 the scapula gets longer and proportionally narrower, with a more convex mvs, and from arboreal species to scansorial ones to aquatic and semifossorial species PC4 scores increase, reaching highest values for terrestrial species. In PC5 aquatic species have the lowest values and semifossorial species, the highest,
seemingly related to a broader margo caudalis, a reduction of fossa infraspinata and a more cranially oriented glenoid cavity. Finally, PC6 implies a concave margo caudalis and a caudally projected glenoid cavity and separated Phoca vitulina from the rest of species.
A regression of the PC scores on log-transformed centroid size (ln CS) revealed that size accounts for 14.80% of shape variation in the carnivore scapula, though its contribution to individual factors varies from 0 to 35%. Finally, MANOVA tests were carried out on the PC scores to assess the effect of phylogeny, locomotor
behaviour and habitat on shape variation. Results show that morphological variation in the carnivore scapula is related both to phylogeny and habitat, but not to locomotor behaviour. Nevertheless, the effect of habitat proved to be non-significant once the effect of size was removed (using the residuals of the regressions on ln CS). Thus, in spite of the high variability in locomotor behaviour and habitat of the carnivores, it seems that scapular shape is mainly determined by phylogeny.
| Original language | English |
|---|---|
| Title of host publication | Comparative Biochemistry and Physiology |
| Subtitle of host publication | Part A: Molecular & Integrative Physiology |
| Pages | 63-64 |
| Volume | 150 |
| ISBN (Electronic) | 1095-6433 |
| DOIs | |
| Publication status | Published - 8 Jul 2008 |
| Event | Society for Experimental Biology: Annual Main Meeting - Marseille, France Duration: 6 Jul 2008 → 10 Jul 2008 |
Conference
| Conference | Society for Experimental Biology |
|---|---|
| Abbreviated title | SEB @Marseille |
| Country/Territory | France |
| City | Marseille |
| Period | 6/07/08 → 10/07/08 |