Shape Covariation (or the Lack Thereof) Between Vertebrae and Other Skeletal Traits in Felids: The Whole is Not Always Greater than the Sum of Parts

Abstract

Within carnivorans, cats show comparatively little disparity in overall morphology, with species differing mainly in body size. However, detailed shape analyses of individual osteological structures, such as limbs or skulls, have shown that felids display significant morphological differences that correlate with their observed ecological and behavioural ranges. Recently, these shape analyses have been extended to the felid axial skeleton. Results demonstrate a functionally-partitioned vertebral column, with regions varying greatly in level of correlation between shape and ecology. Moreover, a clear distinction is evident between a phylogenetically-constrained neck region and a selection-responsive posterior spine. Here, we test whether this regionalisation of function reflected in vertebral column shape is also translated into varying levels of phenotypic integration between this structure and most other skeletal elements. We accomplish this comparison by performing pairwise tests of integration between vertebral and other osteological units, quantified with 3D geometric morphometric data and analysed both with and without phylogenetic correction. To our knowledge, this is the first study to test for integration across a comprehensive sample of whole-skeleton elements. Our results show that, prior to corrections, strong covariation is present between vertebrae across the vertebral column and all other elements, with the exception of the femur. However, most of these significant correlations disappear after correcting for phylogeny, which is a significant influence on cranial and limb morphology of felids and other carnivorans. Our results thus suggest that the vertebral column of cats displays relative independence from other skeletal elements and may represent several distinct evolutionary morphological modules.Electronic supplementary materialThe online version of this article (10.1007/s11692-017-9443-6) contains supplementary material, which is available to authorized users.

A fly in a tube: Macroevolutionary expectations for integrated phenotypes

“…Studies of full skeletal integration are at present limited to cats, demonstrating that the presacral vertebral column is composed of five discrete modules that don't map simply onto standard anatomical regions (cervical, thoracic, lumbar; Randau and Goswami ), but do reflect the developmental origins of vertebral structures (Randau and Goswami ). Moreover, these studies demonstrate that the vertebral column as a whole is relatively independent of the cranial and appendicular skeletons (Randau and Goswami ). At present, this observed variation across extant mammals does not allow for determination of the polarity of shifts in the pattern of modularity in either the cranial or postcranial skeleton of mammals; specifically, it is unclear whether the changes in trait relationships observed across the major mammalian clades represent an increase or a decrease in integration, if either, without data outside of crown Mammalia.…”

A first glimpse at the influence of body mass in the morphological integration of the limb long bones: an investigation in modern rhinoceroses

“…In this context, we chose to present and discuss both uncorrected and corrected analyses for multiple comparisons, especially for the analyses at the intraspecific level, where the correction had a higher impact (see Results). We applied a Benjamini-Hochberg correction to our data (Benjamini and Hochberg, 1995) as described by Randau and Goswami (2018)…”

“…Conversely, other works have proposed that body mass may still have an impact on the shape covariation of the limb long bones (Hanot et al, 2017;Randau and Goswami, 2018), possibly more pronounced for heavier species (Schmidt and Fischer, 2009). Drawing on this, we chose to explore the integration patterns among modern rhinoceroses, which constitute the second heaviest terrestrial group after elephants among modern mammals (Alexander and Pond, 1992).…”

Occipital hemi‐bun development and shape covariation in a longitudinal extant human growth sample

“…Also, unlike some other analyses, 2B‐PLS does not necessitate the naming of independent and dependent variables and can successfully assess patterns of covariation when the two sets of data contain an unequal number of variables (Rohlf & Corti, ; Zelditch et al, ). This analysis has been shown to be useful for evaluating morphological integration between divergent structures (Adams, ; Randau & Goswami, ). Not only can 2B‐PLS be used to assess covariation between two sets of shape variables, but it can also assess covariation between shape and nonshape variables (Rohlf & Corti, ; Zelditch et al, ).…”