Comparative ecogeographical variation in skull size and shape of two species of woolly opossums (genus Caluromys)

Magnus, Luíza Z.; Machado, Renata; Cáceres, Nilton C.

doi:10.1016/j.jcz.2017.03.003

Cited by 27 publications

(11 citation statements)

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“…Suggestions of a constraint on marsupial skull shape through static allometry are at odds with several geometric morphometric studies that show only low or moderate levels of static allometry in marsupial crania [15,[20][21][22]. Two recent studies on kangaroos even suggested that allometry plays a lesser role in shaping cranial variation in this group, instead positing fast adaptation or individual developmental plasticity of the masticatory apparatus as the main driver [23,24].…”

Section: Introductionmentioning

confidence: 99%

Individual variation of the masticatory system dominates 3D skull shape in the herbivory-adapted marsupial wombats

et al. 2019

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Background: Within-species skull shape variation of marsupial mammals is widely considered low and strongly size-dependent (allometric), possibly due to developmental constraints arising from the altricial birth of marsupials. However, species whose skulls are impacted by strong muscular stressesparticularly those produced through mastication of tough food itemsmay not display such intrinsic patterns very clearly because of the known plastic response of bone to muscle activity of the individual. In such cases, allometry may not dominate within-species shape variation, even if it is a driver of evolutionary shape divergence; ordination of shape in a geometric morphometric context through principal component analysis (PCA) should reveal main variation in areas under masticatory stress (incisor region/zygomatic arches/mandibular ramus); but this main variation should emerge from high individual variability and thus have low eigenvalues. Results: We assessed the evidence for high individual variation through 3D geometric morphometric shape analysis of crania and mandibles of three species of grazing-specialized wombats, whose diet of tough grasses puts considerable strain on their masticatory system. As expected, we found little allometry and low Principal Component 1 (PC1) eigenvalues within crania and mandibles of all three species. Also as expected, the main variation was in the muzzle, zygomatic arches, and masticatory muscle attachments of the mandibular ramus. We then implemented a new test to ask if the landmark variation reflected on PC1 was reflected in individuals with opposite PC1 scores and with opposite shapes in Procrustes space. This showed that correspondence between individual and ordinated shape variation was limited, indicating high levels of individual variability in the masticatory apparatus. Discussion: Our results are inconsistent with hypotheses that skull shape variation within marsupial species reflects a constraint pattern. Rather, they support suggestions that individual plasticity can be an important determinant of within-species shape variation in marsupials (and possibly other mammals) with high masticatory stresses, making it difficult to understand the degree to which intrinsic constraints act on shape variation at the within-species level. We conclude that studies that link micro-and macroevolutionary patterns of shape variation might benefit from a focus on species with low-impact mastication, such as carnivorous or frugivorous species.

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Section: Introductionmentioning

confidence: 99%

Individual variation of the masticatory system dominates 3D skull shape in the herbivory-adapted marsupial wombats

et al. 2019

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“…CREA-like shape variation is also found in other kangaroo species, and is allometric in tammar wallabies [60] and quokkas [20], but only partially so among the rock wallabies [15]. By contrast, geometric morphometric analyses of two marsupial species with a comparatively soft dietthe insectivorous Dromiciops gliroides and two species of the omnivorous Caluromys -show little cranial variation of zygomatic arch or rostrum shape, but strong-species allometry [21,22]. The variable association of the CREA shape variation with allometry may therefore be related to varying biomechanical stresses on individual skulls depending on a species' feeding ecology (but note that CREA has been shown within mongooses and fruit bats, which both do not feed on hard items [59]).…”

Section: Discussionmentioning

confidence: 96%

“…Partitions not expected to vary were the rest of the cranium (501 landmarks) or mandible (400 22 landmarks) (Additional File 10). To account for different landmark numbers per partition, we also rarefied each partition to the minimum landmark number (66/cranium and 35/mandible).…”

Section: Partition Selectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Individual variation of the masticatory system dominates 3D skull shape in the herbivory-adapted marsupial wombats

Weisbecker

Guillerme

Speck

et al. 2019

Preprint

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Background: Within-species skull shape variation of marsupial mammals is widely considered low and strongly size-dependent (allometric), possibly due to developmental constraints arising from the altricial birth of marsupials. However, species whose skulls are impacted by strong muscular stresses -particularly those produced through mastication of tough food items -may not display such intrinsic patterns very clearly because of the known plastic response of bone to muscle activity of the individual. In such cases, shape variation should not be dominated by allometry; ordination of shape in a geometric morphometric context through principal component analysis (PCA) should reveal main variation in areas under masticatory stress (incisor region/zygomatic arches/mandibular ramus); but this main variation should emerge from high individual variability and thus have low eigenvalues. Results:We assessed the evidence for high individual variation through 3D geometric morphometric shape analysis of crania and mandibles of thre species of grazing-specialized wombats, whose diet of tough grasses puts considerable strain on their masticatory system. As expected, we found little allometry and low Principal Component 1 (PC1) eigenvalues within crania and mandibles of all three species. Also as expected, the main variation was in the muzzle, zygomatic arches, and masticatory muscle attachments of the mandibular ramus. We then implemented a new test to ask if the landmark variation reflected on PC1 was reflected in individuals with opposite PC1 scores and with opposite shapes in Procrustes space. This showed that correspondence between individual and ordinated shape variation was limited, indicating high levels of individual variability in the masticatory apparatus. Discussion:Our results are inconsistent with hypotheses that skull shape variation within marsupial species reflects a constraint pattern. Rather, they support suggestions that individual plasticity can be an important determinant of within-species shape variation in marsupials (and possibly other mammals) with high masticatory stresses, making it difficult to understand the degree to which intrinsic constraint act on shape variation at the within-species level. We conclude that studies that link micro-and macroevolutionary patterns of shape variation might benefit from a focus on species with low-impact mastication, such as carnivorous or frugivorous species.3

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“…The utility of interpreting SDMs outcomes in the light of relevant, but independently conducted, phylogenetic analyses is widely recognized and often practiced; but lacking a methodological framework to fully integrate the two, comparison is usually undertaken in a qualitative manner after separate and sequential model building (e.g. Graham et al, 2004;Rivera et al, 2011;Martínez and Di Cola, 2011;Brown and Knowles, 2012;Bornholdt et al, 2013;Paz et al, 2015;Dianat et al, 2016;Liu et al, 2016;Magnus et al, 2017;Camacho et al, 2017). Although phylogenies have yet to become nested components of SDMs, they have been routinely applied during linear regression as tools to account for species non−independence when evaluating the relationship between species traits and between traits and environmental variables.…”

Section: Introductionmentioning

confidence: 99%

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Supplemental Information 1: Code and Data to Construct Models

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There is an acknowledged need to combine species distribution and macro-ecological models with phylogenetic information, particularly when biogeographic research incorporates multiple species, explores phenotypic traits, or is spatially dynamic. Our aim is to present a new approach to multi-species joint modeling that applies spatially explicit phylogenetic regression to simultaneously predict species occurrence probability and the geographic distribution of interspecific continuous morphological traits. We developed a multi-tiered Bayesian geostatistical model that incorporates a species phylogeny, morphometric traits, and environmental variables to jointly estimate traits and geographic distributions for six species of South American leaf-eared mice (genus: Phyllotis). Covariates are included with the model to control for genetic relatedness, specimen age, specimen sex, and repeated measures errors. To help gauge model performance, we compared our approach to predictions made using several other species distribution modeling applications. Our integrated modeling framework demonstrated improved accuracy over alternative species distribution modeling techniques as judged by model sensitivity, specificity, and the true skill statistic. The inclusion of trait-based covariates and model terms to account for genetic relatedness, repeated measures, and spatial error were determined important as judged by credible intervals and parsimony metrics. Species distribution models and trait-based approaches that do not account for spatial dependencies, phylogenetic relationships, or repeated measures sampling errors may produce parameter estimates with smaller uncertainty than is warranted and produce predictions with significant error. Our study offers tools to address spatially and phylogenetically structured species data and presents an approach to integrating biological comparative methods in biogeographic research.

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Comparative ecogeographical variation in skull size and shape of two species of woolly opossums (genus Caluromys)

Cited by 27 publications

References 60 publications

Individual variation of the masticatory system dominates 3D skull shape in the herbivory-adapted marsupial wombats

Individual variation of the masticatory system dominates 3D skull shape in the herbivory-adapted marsupial wombats

Individual variation of the masticatory system dominates 3D skull shape in the herbivory-adapted marsupial wombats

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