Effects of phylogeny and locomotor style on the allometry of body mass and pelvic dimensions in birds

Abstract

The pelvic girdle provides physical support and attachment for the hind limb musculature. In birds there is variability in pelvic morphology across different orders and this has been used as evidence for various types of locomotion. However, the morphological variation of pelvic bones has yet to be studied systematically in birds. Therefore, we investigated basic allometric relationships among female body mass (as a size proxy) and various pelvic measurements in a phylogenetic context. We also examined in detail the inter-relationships among various pelvic measurements. Also considered were the effects of broader taxonomic relationships at the level of order, with further examination of the influence of style of terrestrial locomotion on the allometric relationships. Positive relationships were initially found among all pelvic linear measurements and female body mass (FBM). The relationships among measures of pelvic width and FBM were isometric, whereas those between pelvic length and FBM showed positive allometry. Also, FBM explained more of the variance in pelvic length than in width. Similarly, the angle of the pelvis had a significant negative relationship, but FBM only explained a very low proportion of the variation in pelvic angles. In general terms, ancova showed that the effect of FBM was smaller than the effect of locomotor style in this species set. Both the synsacrum and pelvic girdle play roles in weight support and therefore scale in proportion to body weight accordingly. All three parts of the pelvis (ilium, ischium and pubis) are attached around the acetabulum and also provide muscle attachment points, so it might be expected for them to scale in a similar manner. Increased angulation of the pelvis is linked to orders which employ their hind limbs in feeding, perching and running, although FBM also explains a very low proportion of the variation in pelvic angle. Muscle attachment and the confines on morphology presented by locomotion explain much of the variation exhibited by the relationships among pelvic measurements.

Size and shape correlation of birds' pelvis and egg: Impact of developmental mode, habitat, and phylogeny

“…Given that egg is formed in the caudal part of bird's body, it can be assumed that topographically it will be located more caudal than the center of gravity, which, apparently, also contributes to adaptation to swimming. Taking into account these examples, we confirm the assumption of Anten‐Houston et al () and Deeming () that the shape of eggs is more associated with the style of terrestrial locomotion than with reproduction, although it mainly concerns on the degree of egg elongation.…”

“…It should be noted that pelvis shape is affected by bird habitat and functioning of the terrestrial locomotor module (Anten‐Houston et al, ; Bogdanovich, ; Stoessel et al, ). In raptorial birds, the relatively wide pelvis with the shortened postacetabular region was formed due to specific foraging, in which pelvic limbs are used for an active attack on prey (Usenko, ), and arboreal habitat that, probably, was initial for these birds (Sushkin, ).…”

“…However, an egg is formed in the abdominal cavity and its shape may be determined by pelvis morphology. Such possible relationship between the shape of pelvis and egg of birds was suggested by Rensch (1947), Warham (1990), Stoddard et al (2017), Anten-Houston, Ruta, and Deeming (2017) and Deeming (2017), but this hypothesis was not explicitly tested. However, a possible relationship between pelvis shape and egg shape may be obscured by the fact that the pelvis of extant birds is open ventrally, and therefore, does not strongly restrain the size of eggs, especially diameter; in contrast to Jurassic and Cretaceous fossil birds, whose pelvis had pubic fusion (symphysis), because of what they laid diminutive eggs (Deeming & Mayr, 2018;Dyke & Kaiser, 2010).…”

What is bred in the bone: Ecomorphological associations of pelvic girdle form in greater Antillean Anolis lizards

“…When placed into context of their consequences for muscle force and muscle vectors that act on the pelvic girdle (Anten‐Houston et al, ), the particular configuration that characterizes three of the examined anoline ecomorphs (twig; crown giant; trunk‐crown) is consistent with the biomechanical demands of their particular microhabitat. Further information regarding differences in locomotor style and relative positioning (origins) and distribution of muscle masses (Toro et al, ) is needed to explore these ideas further, as is more information about distinct patterns of stance, gait, and locomotion in these ecomorphs.…”

Nesting environment may drive variation in eggshell structure and egg characteristics in the Testudinata

“…Any species absent from this base tree were inserted using Phylowidget (http://www.phylowidget.org) at an appropriate position based on specific phylogenetic relationships for families (Fritz et al., ; Georges & Adams, ; Georges, Adams, & McCord, ; McCord, Joseph‐Ouni, & Lamar, ; Spinks, Thomson, Gidiş, & Shaffer, ). Most analyses involved pglm run in R (R Core Team, ) using code previous used by Anten‐Houston, Ruta, and Deeming () and Deeming () and supplied by Carl Soulsbury (personal communication, 2017). The models tested for the effect of shell type as a fixed factor together with various other continuous variables as covariates.…”