Ontogenetic Variation in Skull Shape of Thrichomys apereoides (Rodentia: Echimyidae)

Monteiro, Leandro R.; Lessa, Leonardo Guimarães; Abe, Augusto Shinya

doi:10.2307/1383212

Cited by 29 publications

(23 citation statements)

References 22 publications

(6 reference statements)

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“…niloticus have longer zygomatic arches with a sharper-angled leading edge that may possibly allow for greater masseter muscle attachments (Satoh and Iwaku 2004). It has been argued that the shape of certain bony structures can be altered by the atrophy or hypertrophy of attached muscles (Monteiro et al 1999). Nevertheless, other studies reported on associations between sexual differences and competition between males (Darwin 1874), food resources (Schoener 1967), diet selection and intake rates (Yamada and Kimmel 1991), habitat use (Clutton-Brock et al 1987), growth rates, and strategies (Zelditch et al 1992), in addition to variation in individual reproductive success (Weckerly 1998).…”

Section: Discussion Sexual Dimorphismmentioning

confidence: 99%

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Geometric craniometric analysis of sexual dimorphism and ontogenetic variation: A case study based on two geographically disparate species, Aethomys ineptus from southern Africa and Arvicanthis niloticus from Sudan (Rodentia: Muridae)

Abdel-Rahman

Taylor²,

Contrafatto

et al. 2009

Mammalian Biology

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Non-geographic morphometric variation, particularly at the level of sexual dimorphism and ontogenetic (agerelated) variation, has been documented in rodents, and useful for establishing whether to analyse sexes separately or together, and for selecting adult specimens for subsequent data recording and analysis. However, such studies have largely been based on traditional morphometric analyses of linear measurements that mainly focus on overall size, rather than shape-related morphometric variation. Unit-free, landmark/outline-based geometric morphometric analyses are considered to offer a more appropriate tool for assessing shape-related morphometric variation. In this study, we used geometric cranial morphometric analysis to assess the nature and extent of sexual dimorphism and age variation within the Tete veld rat, Aethomys ineptus (Thomas and Wroughton, 1908) from southern Africa and the African Nile rat, Arvicanthis niloticus (Desmarest, 1822) from Sudan. The results obtained were in turn compared with previously published results based on independent geometric and traditional cranial morphometric data from the same sampled populations examined in the present study. While our geometric morphometric results detected statistically significant sexual dimorphism in cranial shape within Ar. niloticus only, previously published results based on traditional morphometric data failed to detect significant sexual dimorphism within this species. However, similar to previously published traditional morphometric data, our geometric morphometric results detected statistically significant age-related variation in cranial shape and size within both Ae. ineptus and Ar. niloticus, with individuals of age classes 5 and 6 being considered to represent adult specimens. Our results highlight the importance of carefully evaluating both size-and shape-related non-geographic morphometric variation prior to the analysis of geographic variation and the delineation of species. Erroneous conclusions of non-geographic variation may have implications in the interpretation of geographic and evolutionary processes that may be responsible for morphological differences at both the inter-and intra-specific levels.

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Section: Discussion Sexual Dimorphismmentioning

confidence: 99%

“…In addition, shape variation occurring during ontogeny was estimated by multivariate regression analysis (Zar 1996;Monteiro et al 1999) of partial warps (i.e., total shape matrix) on centroid size and age categories. Since our results (see later) revealed the absence of sexual dimorphism in size (i.e., centroid size) in Ar.…”

Section: Age Classesmentioning

confidence: 99%

Geometric craniometric analysis of sexual dimorphism and ontogenetic variation: A case study based on two geographically disparate species, Aethomys ineptus from southern Africa and Arvicanthis niloticus from Sudan (Rodentia: Muridae)

Abdel-Rahman

Taylor²,

Contrafatto

et al. 2009

Mammalian Biology

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“…Morphological integration can be signiWcantly modiWable within a single pattern of development (Zelditch Fig. 4 Post-metamorphic ontogenetic transformations in cranial shape of each species, calculated by multivariate regression of shape on size, and illustrated as a thin plate spline deformation grid 1988; Zelditch and Carmichael 1989;Cane 1993;Monteiro et al 1999) so further inspection of the forces producing a speciWc pattern of covariation between and among skull parts, including developmental, functional and biomechanical factors, will be needed to provide more information on the common factors shaping the newt skull during postmetamorphic growth.…”

Section: Post-metamorphic Modeling Of the Triturus Skullmentioning

confidence: 99%

Ontogeny of skull size and shape changes within a framework of biphasic lifestyle: a case study in six Triturus species (Amphibia, Salamandridae)

et al. 2007

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As with many other amphibians, Triturus species are characterized by a biphasic life cycle with abrupt changes in the cranial skeleton during metamorphosis. The post-metamorphic shape changes of the cranial skeleton were investigated using geometric morphometric techniques in six species: Triturus alpestris, T. vulgaris, T. dobrogicus, T. cristatus, T. carnifex, and T. karelinii. The comparative analysis of ontogenetic trajectories revealed that these species have a conserved developmental rate with divergent ontogenetic trajectories of the ventral skull shape that mainly reXect phylogenetic relatedness. A striking exception in the ontogenetic pattern was possibly found in T. dobrogicus, characterized by a marked increase in the developmental rate compared to the other newt species. The size-related shape changes explained a large proportion of shape change during postmetamorphic growth within each species, with marked positive allometric growth of skull elements related to foraging.

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“…We chose skull morphology (size and shape) as a surrogate of overall morphological diversity as it is associated with the main sensory systems related to environmental perception and reflects changes in the dietary and ecological interactions across populations (Klaczko, Sherratt, & Setz, 2016;Monteiro, Lessa, & Are, 1999;Nogueira, Peracchi, & Monteiro, 2009). First, we analyzed nine species (shrews, moles, and rodents) distributed over a wide altitudinal range and with distinct ecological attributes to assess whether phenotypic divergence is a common phenomenon in small mammals and whether it shows consistent parallel patterns.…”

Section: Introductionmentioning

confidence: 99%

Divergent selection along elevational gradients promotes genetic and phenotypic disparities among small mammal populations

Feijó

Wen

Cheng

et al. 2019

Ecology and Evolution

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Species distributed along mountain slopes, facing contrasting habitats in short geographic scale, are of particular interest to test how ecologically based divergent selection promotes phenotypic and genetic disparities as well as to assess isolation‐by‐environment mechanisms. Here, we conduct the first broad comparative study of phenotypic variation along elevational gradients, integrating a large array of ecological predictors and disentangling population genetic driver processes. The skull form of nine ecologically distinct species distributed over a large altitudinal range (100–4200 m) was compared to assess whether phenotypic divergence is a common phenomenon in small mammals and whether it shows parallel patterns. We also investigated the relative contribution of biotic (competition and predation) and abiotic parameters on phenotypic divergence via mixed models. Finally, we assessed the population genetic structure of a rodent species (Niviventer confucianus) via analysis of molecular variance and FST along three mountain slopes and tested the isolation‐by‐environment hypothesis using Mantel test and redundancy analysis. We found a consistent phenotypic divergence and marked genetic structure along elevational gradients; however, the species showed mixed patterns of size and skull shape trends across mountain zones. Individuals living at lower altitudes differed greatly in both phenotype and genotype from those living at high elevations, while middle‐elevation individuals showed more intermediate forms. The ecological parameters associated with phenotypic divergence along elevation gradients are partly related to species' ecological and evolutionary constraints. Fossorial and solitary animals are mainly affected by climatic factors, while terrestrial and more gregarious species are influenced by biotic and abiotic parameters. A novel finding of our study is that predator richness emerged as an important factor associated with the intraspecific diversification of the mammalian skull along elevational gradients, a previously overlooked parameter. Population genetic structure was mainly driven by environmental heterogeneity along mountain slopes, with no or a week spatial effect, fitting the isolation‐by‐environment scenario. Our study highlights the strong and multifaceted effects of heterogeneous steep habitats and ecologically based divergent selective forces in small mammal populations.

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Ontogenetic Variation in Skull Shape of Thrichomys apereoides (Rodentia: Echimyidae)

Cited by 29 publications

References 22 publications

Geometric craniometric analysis of sexual dimorphism and ontogenetic variation: A case study based on two geographically disparate species, Aethomys ineptus from southern Africa and Arvicanthis niloticus from Sudan (Rodentia: Muridae)

Geometric craniometric analysis of sexual dimorphism and ontogenetic variation: A case study based on two geographically disparate species, Aethomys ineptus from southern Africa and Arvicanthis niloticus from Sudan (Rodentia: Muridae)

Ontogeny of skull size and shape changes within a framework of biphasic lifestyle: a case study in six Triturus species (Amphibia, Salamandridae)

Divergent selection along elevational gradients promotes genetic and phenotypic disparities among small mammal populations

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