scholarly journals Cranial shape variation in mink: Separating two highly similar species

2021 ◽  
Author(s):  
Eloy Gálvez‐López ◽  
Brandon Kilbourne ◽  
Philip G. Cox
Keyword(s):  
Similar Species ◽  
Shape Variation ◽  
Cranial Shape

scholarly journals Heterochronic Shifts Mediate Ecomorphological Convergence in Skull Shape of Microcephalic Sea Snakes

2019 ◽  
Vol 59 (3) ◽  
pp. 616-624 ◽  
Author(s):  
Emma Sherratt ◽  
Kate L Sanders ◽  
Amy Watson ◽  
Mark N Hutchinson ◽  
Michael S Y Lee ◽  
...  
Keyword(s):  
Morphological Changes ◽  
Shape Variation ◽  
Micro Computed Tomography ◽  
Trophic Specialization ◽  
Evolutionary Patterns ◽  
Dietary Specialization ◽  
Geometric Morphometric ◽  
Sea Snakes ◽  
Morphometric Methods ◽  
Cranial Shape

Abstract Morphological variation among the viviparous sea snakes (Hydrophiinae), a clade of fully aquatic elapid snakes, includes an extreme “microcephalic” ecomorph that has a very small head atop a narrow forebody, while the hind body is much thicker (up to three times the forebody girth). Previous research has demonstrated that this morphology has evolved at least nine times as a consequence of dietary specialization on burrowing eels, and has also examined morphological changes to the vertebral column underlying this body shape. The question addressed in this study is what happens to the skull during this extreme evolutionary change? Here we use X-ray micro-computed tomography and geometric morphometric methods to characterize cranial shape variation in 30 species of sea snakes. We investigate ontogenetic and evolutionary patterns of cranial shape diversity to understand whether cranial shape is predicted by dietary specialization, and examine whether cranial shape of microcephalic species may be a result of heterochronic processes. We show that the diminutive cranial size of microcephalic species has a convergent shape that is correlated with trophic specialization to burrowing prey. Furthermore, their cranial shape is predictable for their size and very similar to that of juvenile individuals of closely related but non-microcephalic sea snakes. Our findings suggest that heterochronic changes (resulting in pedomorphosis) have driven cranial shape convergence in response to dietary specializations in sea snakes.

scholarly journals Evolutionary morphology of the rabbit skull

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2453 ◽  
Author(s):  
Brian Kraatz ◽  
Emma Sherratt
Keyword(s):  
Small Proportion ◽  
Phylogenetic Signal ◽  
Morphological Data ◽  
Shape Variation ◽  
Evolutionary Morphology ◽  
Crown Group ◽  
Size Change ◽  
Generalist Species ◽  
Facial Region ◽  
Cranial Shape

The skull of leporids (rabbits and hares) is highly transformed, typified by pronounced arching of the dorsal skull and ventral flexion of the facial region (i.e., facial tilt). Previous studies show that locomotor behavior influences aspects of cranial shape in leporids, and here we use an extensive 3D geometric morphometrics dataset to further explore what influences leporid cranial diversity. Facial tilt angle, a trait that strongly correlates with locomotor mode, significantly predicts the cranial shape variation captured by the primary axis of cranial shape space, and describes a small proportion (13.2%) of overall cranial shape variation in the clade. However, locomotor mode does not correlate with overall cranial shape variation in the clade, because there are two district morphologies of generalist species, and saltators and cursorial species have similar morphologies. Cranial shape changes due to phyletic size change (evolutionary allometry) also describes a small proportion (12.5%) of cranial shape variation in the clade, but this is largely driven by the smallest living leporid, the pygmy rabbit (Brachylagus idahoensis). By integrating phylogenetic history with our geometric morphometric data, we show that the leporid cranium exhibits weak phylogenetic signal and substantial homoplasy. Though these results make it difficult to reconstruct what the ‘ancestral’ leporid skull looked like, the fossil records suggest that dorsal arching and facial tilt could have occurred before the origin of the crown group. Lastly, our study highlights the diversity of cranial variation in crown leporids, and highlights a need for additional phylogenetic work that includes stem (fossil) leporids and includes morphological data that captures the transformed morphology of rabbits and hares.

Use of Continuous Cranial Shape Variation in the Identification of Divergent Crocodile Species of the Genus Mecistops

2021 ◽  
Author(s):  
Amanda N. Carr ◽  
Jennifer H. Nestler ◽  
Kent A. Vliet ◽  
Christopher A. Brochu ◽  
Christopher M. Murray ◽  
...  
Keyword(s):  
Shape Variation ◽  
Cranial Shape

scholarly journals Cranial shape variation and molecular phylogenetic structure of crested newts (Triturus cristatus superspecies: Caudata, Salamandridae) in the Balkans

2008 ◽  
Vol 95 (2) ◽  
pp. 348-360 ◽  
Author(s):  
ANA IVANOVIĆ ◽  
KONSTANTINOS SOTIROPOULOS ◽  
TANJA D. VUKOV ◽  
KAROLOS ELEFTHERAKOS ◽  
GEORG DŽUKIĆ ◽  
...  
Keyword(s):  
Shape Variation ◽  
Triturus Cristatus ◽  
Phylogenetic Structure ◽  
The Balkans ◽  
Molecular Phylogenetic ◽  
Cranial Shape

scholarly journals Hominoid intraspecific cranial variation mirrors neutral genetic diversity

2018 ◽  
Vol 115 (45) ◽  
pp. 11501-11506 ◽  
Author(s):  
Julia M. Zichello ◽  
Karen L. Baab ◽  
Kieran P. McNulty ◽  
Christopher J. Raxworthy ◽  
Michael E. Steiper
Keyword(s):  
Genetic Diversity ◽  
Homo Sapiens ◽  
Population History ◽  
Cranial Morphology ◽  
Shape Variation ◽  
Evolutionary Processes ◽  
Cranial Variation ◽  
History Of ◽  
Fossil Hominin ◽  
Cranial Shape

Natural selection, developmental constraint, and plasticity have all been invoked as explanations for intraspecific cranial variation in humans and apes. However, global patterns of human cranial variation are congruent with patterns of genetic variation, demonstrating that population history has influenced cranial variation in humans. Here we show that this finding is not unique toHomo sapiensbut is also broadly evident across extant ape species. Specifically, taxa that exhibit greater intraspecific cranial shape variation also exhibit greater genetic diversity at neutral autosomal loci. Thus, cranial shape variation within hominoid taxa reflects the population history of each species. Our results suggest that neutral evolutionary processes such as mutation, gene flow, and genetic drift have played an important role in generating cranial variation within species. These findings are consistent with previous work on human cranial morphology and improve our understanding of the evolutionary processes that generate intraspecific cranial shape diversity within hominoids. This work has implications for the analysis of selective and developmental pressures on the cranium and for interpreting shape variation in fossil hominin crania.

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