Ecological determinants of clinal morphological variation in the cranium of the North American gray wolf

O’Keefe, F. Robin; Meachen, Julie; Fet, Elizabeth V.; Brannick, Alexandria L.

doi:10.1644/13-mamm-a-069

Cited by 36 publications

(48 citation statements)

References 37 publications

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“…Shape change due to static allometry comprises the first principal component of the ordination. As described in the results, the increase in molar size, movement down the static allometry axis, and reorientation of the masseter line of action characterize the female morphotype, just as in the gray wolf (O'Keefe et al, 2013). The presence of a prominent axis of sexual dimorphism in these data is reassuring, because it indicates that we are FIGURE 8.…”

Section: Sexual Dimorphismsupporting

confidence: 57%

“…Lastly, there is clear evidence of static allometry on this axis, with the basicranium relatively large and the viscerocranium relatively small in animals with large molars. Taken together, this axis shows a clear pattern of sexual dimorphism, because it carries the hallmark dimorphism in molar size identified in Canis lupus (O'Keefe et al, 2013). The other shape changes seen on this axis are also plausibly attributable to dimorphism, because they resemble the static allometry observed in C. lupus.…”

Section: Landmark Datamentioning

confidence: 61%

“…Knowledge of the covariance structure of extant gray wolf crania has recently improved (O' Keefe et al, 2013) and is a good source of testable hypotheses. The first axis of covariation in the C. lupus data set is strongly correlated with size, and sexual dimorphism is the single most powerful factor underlying this axis (O'Keefe et al, 2013). Sexual dimorphism should also be a relatively strong factor in the covariance structure of dire wolves at La Brea, an inference supported by the fact that sexual dimorphism in C. dirus was of similar magnitude to that observed in modern canines (VanValkenburgh and Sacco, 2002).…”

Section: Experimental Designmentioning

confidence: 83%

“…Gray wolves clearly follow Bergmann's Rule, with body size increasing with latitude and hence decreasing temperature (O'Keefe et al, 2013).…”

Section: Experimental Designmentioning

confidence: 90%

“…This late-stage somatic allometry is identifiable as the second axis of covariation in the gray wolf (O'Keefe et al, 2013). On it, the teeth remain constant while the non-dental (somatic) parts of the skull grow up around them.…”

Section: Experimental Designmentioning

confidence: 99%

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Cranial morphometrics of the dire wolf, Canis dirus, at Rancho La Brea: temporal variability and its links to nutrient stress and climate

O’Keefe

Binder

Frost³

et al. 2014

Palaeontologia Electronica

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The tar pits of Rancho La Brea are a unique window onto the biology and ecology of the terminal Pleistocene in southern California. In this study we capitalize on recent advances in understanding of La Brea tar pit chronology to perform the first morphometric study of crania of the dire wolf, Canis dirus, over time. We first present new data on tooth fracture and wear from pits dated older than heretofore analyzed, and demonstrate that fracture and wear events, and the increased competition and heightened carcass utilization they are thought to represent, were of varying intensity across the sampled time intervals. Skull size, and by extension body size, is shown to differ significantly among pits at La Brea, with the strongest single observation being reduction in body size at the last glacial maximum. Skull size variation is shown to be a result of both ontogenetic and evolutionary factors, neither of which is congruent with a temporal version of Bergmann's rule. Skull shape difference among the pits is also significant, with shape variability attributable to both neotenic effects in populations with high breakage and wear, and evolutionary changes possibly due to climate change. Testing of this hypothesis requires better accuracy and precision in La Brea carbon data, a program that is within the reach of current AMS dating technology.

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Section: Sexual Dimorphismsupporting

confidence: 57%

Section: Landmark Datamentioning

confidence: 61%

Section: Experimental Designmentioning

confidence: 83%

“…Gray wolves clearly follow Bergmann's Rule, with body size increasing with latitude and hence decreasing temperature (O'Keefe et al, 2013).…”

Section: Experimental Designmentioning

confidence: 90%

Section: Experimental Designmentioning

confidence: 99%

See 3 more Smart Citations

Cranial morphometrics of the dire wolf, Canis dirus, at Rancho La Brea: temporal variability and its links to nutrient stress and climate

O’Keefe

Binder

Frost³

et al. 2014

Palaeontologia Electronica

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Morphology‐based diagnostics of “protodogs.” A commentary to Galeta et al., 2021, Anatomical Record, 304, 42–62, doi: 10.1002/ar.24500

Janssens

Boudadi‐Maligne

Lawler

et al. 2021

The Anatomical Record

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In a recent article in this journal, Galeta et al., (2020) discussed eight Pleistocene "protodogs" and seven Pleistocene wolves. Those "protodogs" had been diagnosed in earlier publications, based on skull morphology. We re-examined the Galeta et al. paper to offer comments on their observed outcomes, and the conclusion of presumed domestication. Of seven metrics that the authors used, five differed statistically between their two groups. However, from more elaborate studies, some of those same metrics had been rejected previously as not valid species-distinguishing traits. In this respect, we do accept cranium size and wider palate as species-distinguishing metrics. The physical size of their specimens was much larger than other archaeological specimens that have been accepted as dogs. Additionally, their sample size was small, compared to the number of available specimens, as shown from previous publications by the same group. Thus, we considered statistical differences that were found between groups in their study, and assessed whether the outcomes could have resulted from natural morphological variation. We examined a group of 73 dire wolves ((Aenocyon [Canis] dirus;, using the same methods as used by Galeta et al., (2020). We could segregate two distinct morphological groups in our study, one having outcomes that were identical to the "protodogs" in Galeta et al. (2020). For the specimens of extinct dire wolves to segregate in the same way as the subjects from Galeta et al. indicates that natural variation probably was the driver of their observed outcomes, domestication being an unlikely assumption.

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Morphological differences between putative Paleolithic dogs and wolves: A commentary to Janssens et al. (2021)

Galeta

Lázničková‐Galetová

Sablin

et al. 2022

The Anatomical Record

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regarding the morphological differences between putative Paleolithic dog and Pleistocene wolf crania. The authors argued that these differences reflect the normal population variation of wolves, that some of the cranial measurements used do not reflect morphological changes during domestication, and that our canid dataset was small because we inexplicably omitted several specimens we analyzed in our previous publications. In this commentary, we briefly address the issue of within and between morpho-population variability. The results based on our canid sample suggest that the magnitude of morphological differences between distinct morpho-populations (i.e., recent northern dogs and wolves) is at least twice as large as that observed within morpho-populations (between two groups of recent northern wolves segregated by cluster analysis). The morphological differences between putative Paleolithic dogs and Pleistocene wolves are relatively large, which may indicate that they did not likely represent a single Late Pleistocene morpho-population. Finally, we clarified the rationale behind the composition of our 2021 dataset to show that we did not adjust the list of the analyzed specimens. Although the sample size was small, the randomization analysis published in 2021 confirmed that the unbalanced composition of the reference sample did not affect the reliability of the morphological segregation of putative Paleolithic dogs and Pleistocene wolves.

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Ecological determinants of clinal morphological variation in the cranium of the North American gray wolf

Cited by 36 publications

References 37 publications

Cranial morphometrics of the dire wolf, Canis dirus, at Rancho La Brea: temporal variability and its links to nutrient stress and climate

Cranial morphometrics of the dire wolf, Canis dirus, at Rancho La Brea: temporal variability and its links to nutrient stress and climate

Morphology‐based diagnostics of “protodogs.” A commentary to Galeta et al., 2021, Anatomical Record, 304, 42–62, doi: 10.1002/ar.24500

Morphological differences between putative Paleolithic dogs and wolves: A commentary to Janssens et al. (2021)

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