Previous genotype:phenotype mapping of the mouse and primate dentition revealed the presence of pre- and post-canine modules in mice and anthropoid primates, as well as molar and premolar submodules in anthropoid primates. We estimated phenotypic correlation matrices for species that sample broadly across Mammalia to test the hypothesis that these modules exist across a broader range of taxa and thereby represent a conserved mammalian trait. We calculated phenotypic correlation matrices from linear dental measurements of 419 individual specimens representing 5 species from 4 mammalian orders: Artiodactyla (Odocoileus hemionus), Carnivora (Canis latrans and Ursus americanus), Didelphimorphia (Didelphis virginiana), and Primates (Colobus guereza). Our results based on hierarchical clustering indicate a generally higher correlation within incisors and among post-canine teeth. However, the post-canine phenotypic correlation matrices do not consistently exhibit the premolar and molar submodularity observed in anthropoid primates. Additionally, we find evidence of sex differences in the Odocoileus phenotypic correlation matrices: Males of this species exhibit overall higher inter-trait correlations compared to females. Our overall findings support the interpretation that incisors and post-canine dentition represent different phenotypic modules, and that this architecture may be a conserved trait for mammals.
Previous work on the mandibular canal, mental foramen, and mandibular foramen has focused on humans and some other non‐primate mammals (with small sample sizes), but little work has investigated the mandibular canal and inferior alveolar nerve (IAN) across primates. However, it is important to understand the relationship between the IAN and mandibular canal due to the IAN's close relationship to the teeth and mastication, and thus dietary adaptations. While it is assumed that most bony canals within the skull grow around and form to pre‐existing nervous structures, this relationship has never been validated for the IAN and mandibular canal. MicroCT scans of 273 individuals (131 females, 134 males, and 8 unknown sex) from 68 primate species and three mammalian outgroups, and diceCT scans of 66 individuals (35 females, 23 males, and 8 unknown sex) from 33 primate species and the same mammalian outgroups were used to create 3D models of the IAN and mandibular canal from which cross‐sectional areas were taken at various points on the structures. Using qualitative descriptions, phylogenetic generalized least squares analysis, and phylogenetic ANOVAs, we were able to establish three main conclusions: (1) the mandibular canal is most often not a defined canal within the mandible of primates, (2) when the canal can be identified, the IAN does not comprise most of the space within, and (3) there are significant relationships between the IAN and the corresponding canals, with most showing isometry and the mental foramen/nerve showing negative allometry.
more » « less- PAR ID:
- 10419229
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- The Anatomical Record
- Volume:
- 307
- Issue:
- 1
- ISSN:
- 1932-8486
- Format(s):
- Medium: X Size: p. 97-117
- Size(s):
- p. 97-117
- Sponsoring Org:
- National Science Foundation
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Abstract Objectives Previous studies associate females who died in young adulthood with narrower obstetric pelvic dimensions, presumably in association with obstetric insufficiency (though this causal relationship is unresolved). In this study, we examine whether females within groups living at higher latitudes present this pattern, as high‐latitude groups have larger pelvic dimensions than groups previously examined. These patterns are compared with males. We assess whether there is evidence for younger ages‐at‐death in females to have been in response to natural selection against narrower true pelvis dimensions.
Methods We measured 14 pelvic dimensions in 327 adults (188 females, 139 males), representing archaeological sites from mid‐latitude and high‐latitude North America. Individuals were placed into a “young” or “not young” age‐at‐death category. Latitude, sex, and age‐at‐death groups were compared using ANOVAs and scaled variance, and evidence for selection was examined with
F ‐tests.Results Pelvic dimensions were larger in high‐latitude females and males. Females but not males who died at younger ages had smaller pelvic canals than older individuals, especially in the mediolateral inlet and anteroposterior outlet dimensions. Variance in all pelvic dimensions is equal between the two female age‐at‐death groups.
Conclusions We found narrower obstetrical dimensions in the female pelvis among individuals who died at younger ages. However, statistically equivalent variances in the two female age‐at‐death groups does not support natural selection on pelvic dimensions as leading to younger ages at death. We instead argue that this difference is result of continued growth due to remodeling in the pelvis occurring in females, but not males, after early adulthood.
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Abstract The nutrient artery provides ~50%–70% of the total blood volume to long bones in mammals. Studying the functional characteristics of this artery in vivo can be difficult and expensive, so most researchers have measured the nutrient foramen, an opening on the outer surface of the bone that served as the entry point for the nutrient artery during development and bone ossification. Others have measured the nutrient canal (i.e., the passage which the nutrient artery once occupied), given that the external dimensions of the foramen do not necessarily remain uniform from the periosteal surface to the medullary cavity. The nutrient canal, as an indicator of blood flow to long bones, has been proposed to provide a link to studying organismal activity (e.g., locomotor behavior) from skeletal morphology. However, although external loading from movement and activity causes skeletal remodeling, it is unclear whether it affects the size or configuration of nutrient canals. To investigate whether nutrient canals can exhibit phenotypic plasticity in response to physical activity, we studied a mouse model in which four replicate high runner (HR) lines have been selectively bred for high voluntary wheel‐running behavior. The selection criterion is the average number of wheel revolutions on days 5 and 6 of a 6‐day period of wheel access as young adults (~6–8 weeks old). An additional four lines are bred without selection to serve as controls (C). For this study, 100 female mice (half HR, half C) from generation 57 were split into an active group housed with wheels and a sedentary group housed without wheels for 12 weeks starting at ~24 days of age. Femurs were collected, soft tissues were removed, and femora were micro‐computed tomography scanned at a resolution of 12 μm. We then imported these scans into AMIRA and created 3D models of femoral nutrient canals. We tested for evolved differences in various nutrient canal traits between HR and C mice, plastic changes resulting from chronic exercise, and the selection history‐by‐exercise interaction. We found few differences between the nutrient canals of HR versus C mice, or between the active and sedentary groups. We did find an interaction between selection history and voluntary exercise for the total number of nutrient canals per femur, in which wheel access increased the number of canals in C mice but decreased it in HR mice. Our results do not match those from an earlier study, conducted at generation 11, which was prior to the HR lines reaching selection limits for wheel running. The previous study found that mice from the HR lines had significantly larger total canal cross‐sectional areas compared to those from C lines. However, this discrepancy is consistent with studies of other skeletal traits, which have found differences between HR and C mice to be somewhat inconsistent across generations, including the loss of some apparent adaptations with continued selective breeding after reaching a selection limit for wheel‐running behavior.
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