Differentiation of skull morphology and cranial kinesis in common toads

Abstract

AbstractWe examined the cranial morphology and cranial kinesis of the common toadsBufo bufoandB. spinosuswith micro-computed tomography and geometric morphometrics and compared the results with published data for related species in a phylogenetic context. The species significantly diverge in skull shape. The skull ofB. spinosusis shorter and higher, with a ventral arm of the squamosal bone and the jaw articulation point positioned perpendicular to the braincase, in comparison with a more lateral position inB. bufo. In either species, females have a shorter snout and a higher and wider skull at the jaw articulation point that is positioned more posteriorly, in comparison with conspecific males. High variation in the amount of bone ossification was recorded in both species, ranging from scarcely ossified and loosely connected bones to highly ossified and firmly connected bones. We also found that skull shape and inferred kinetic properties of the skull are highly variable across the Bufonini tribe. However, sample sizes are mostly small and intraspecific variation is high, which might compromise the analyses. Overall, the results suggest that developmental plasticity produces high variation in ossification and cranial kinesis, affecting individuals’ feeding performances. At the population level, this variation supports an efficient exploitation of the habitat and may promote morphological adaptation in a changing environment.