Cranial Phenotype Research Articles

The value of axillary, facial, occipital, subclavian and common carotid arteries ultrasound in the diagnosis of giant cell arteritis

Abstract Objective To assess the diagnostic value for GCA in adding the axillary arteries (AX) to the temporal artery (TA) ultrasound, particularly in patients with a cranial phenotype of the disease; and to investigate the utility of facial (FA), occipital (OC), subclavian (SC) and common carotid (CC) ultrasound in patients with suspected GCA. Methods Patients with new-onset GCA and a positive ultrasound of the TA, AX, FA, OC, SC or CC, followed at the rheumatology departments of two academic centres, were retrospectively included. Results Two hundred and thirty patients were assessed. TA halo sign was identified in 206/230 (89.6%) cases, FA in 40/82 (48.8%), OC in 17/69 (24.6%), AX in 56/230 (24.3%), SC in 31/57 (54.4%) and CC in 14/68 (20.6%). Negative TA ultrasound was found in 24/230 (10.4%) patients: 22 had AX involvement, one exclusive OC involvement and one exclusive SC involvement. Adding AX evaluation to the TA ultrasound increased the diagnostic yield for GCA by 9.6%, whereas adding OC or SCs to the TA and AX ultrasound increased it by 1.4% and 1.8%, respectively. No value was found in adding the FA or CCs. Notably, 13 patients with cranial symptoms and four with exclusively cranial symptoms showed negative TA ultrasound but positive AX ultrasound. Conclusion Adding the evaluation of AXs to the TA ultrasound increased the number of patients diagnosed with GCA, even in cases of predominantly cranial symptoms. In the subset of patients where these arteries were assessed, no substantial benefit was found in adding the FA, OC, SC or CC arteries to the TA and AX ultrasonographic assessment.

Giant cell arteritis: incidence and phenotypic distribution in Western Norway 2013-2020.

There is an increasing awareness of the spectrum of phenotypes in giant cell arteritis (GCA). However, there is sparse evidence concerning the phenotypic distribution which may be influenced by both genetic background and the environment. We established a cohort of all GCA-patients in the Bergen Health Area (Western Norway), to describe the phenotypic distribution and whether phenotypes differ with regards to incidence and clinical features. This is a retrospective cohort study including all GCA-patients in the Bergen Health Area from 2013-2020. Data were collected by reviewing patient records, and patients considered clinically likely GCA were included if they fulfilled at least one set of classification criteria. Temporal artery biopsy (TAB) and imaging results were used to classify the patients according to phenotype. The phenotype "cranial GCA" was used for patients with a positive TAB or halo sign on temporal artery ultrasound. "Non-cranial GCA" was used for patients with positive findings on FDG-PET/CT, MRI-, or CT angiography, or wall thickening indicative of vasculitis on ultrasound of axillary arteries. Patients with features of both these phenotypes were labeled "mixed." Patients that could not be classified due to negative or absent examination results were labeled "unclassifiable". 257 patients were included. The overall incidence of GCA was 20.7 per 100,000 persons aged 50 years or older. Overall, the cranial phenotype was dominant, although more than half of the patients under 60 years of age had the non-cranial phenotype. The diagnostic delay was twice as long for patients of non-cranial and mixed phenotype compared to those of cranial phenotype. Headache was the most common clinical feature (78% of patients). Characteristic clinic features occurred less frequently in patients of non-cranial phenotype compared to cranial phenotype. The overall incidence for GCA was comparable to earlier reports from this region. The cranial phenotype dominated although the non-cranial phenotype was more common in patients under 60 years of age. The diagnostic delay was longer in patients with the non-cranial versus cranial phenotype, indicating a need for examination of non-cranial arteries when suspecting GCA.

Prevalence and characteristics of subclinical giant cell arteritis in polymyalgia rheumatica.

The main objective of this study was to analyse the prevalence and characteristics of subclinical GCA in patients with PMR. This was a cross-sectional multicentre international study of consecutive patients with newly diagnosed PMR without symptoms or signs suggestive of GCA. All patients underwent US of the temporal superficial, common carotid, subclavian and axillary arteries. Patients with halo signs in at least one examined artery were considered to have subclinical GCA. The clinical, demographic and laboratory characteristics of the PMR group without subclinical vasculitis were compared with subclinical GCA, and the pattern of vessel involvement was compared with that of a classical single-centre GCA cohort. We included 346 PMR patients, 267 (77.2%) without subclinical GCA and 79 (22.8%) with subclinical GCA. The PMR patients with subclinical GCA were significantly older, had a longer duration of morning stiffness and more frequently reported hip pain than PMR without subclinical GCA. PMR with subclinical GCA showed a predominant extracranial large vessel pattern of vasculitic involvement compared with classical GCA, where the cranial phenotype predominated. The patients with PMR in the classical GCA group showed a pattern of vessel involvement similar to classical GCA without PMR but different from PMR with subclinical involvement. More than a fifth of the pure PMR patients had US findings consistent with subclinical GCA. This specific subset of patients showed a predilection for extracranial artery involvement. The optimal screening strategy to assess the presence of vasculitis in PMR remains to be determined.

Phenotypical Variability of the Internal Acoustic Canal in the Middle Cranial Fossa Surgery.

Introduction The wide range of anatomical variability of the structures of the middle cranial fossa (MCF) and the lack of reliable surgical landmarks contribute to a high level of complications in the surgical treatment of vestibular schwannomas. We hypothesized that the cranial phenotype influences the shape of the MCF, the orientation of the pyramid of the temporal bone, and the relative topography of the internal acoustic canal (IAC). Methods The skull base structures were studied on 54 embalmed cadavers and 60 magnetic resonance images of the head and neck by photo modeling, dissection, and three-dimensional analysis techniques. By the value of the cranial index, all specimens were subdivided into dolichocephalic, mesocephalic, and brachycephalic groups for comparison of variables. Results The length of the superior border of the temporal pyramid (SB), the apex to squama distance, and the width of the MCF all peaked in the brachycephalic group. The value of the angle between the SB and the axis of the acoustic canal varied from 33 to 58 degrees; it peaked in the dolichocephalic group and showed its smaller value in the brachycephalic one. The pyramid to squama angle had reversed distribution and dominated in the brachycephalic group. Conclusion The cranial phenotype influences the shape of the MCF, temporal pyramid, and IAC. Presented in this article data help specialists operating on the vestibular schwannoma to localize the IAC based on the individual shape of a skull.

Phenotypical variability of the sigmoid sinus in translabyrinthine and retrosigmoid surgeries

IntroductionWe hypothesized that the cranial phenotype influences the shape of the posterior cranial fossa and the relative position of the sigmoid sinus.Materials and methodsThe topography of the sigmoid sinus was studied on 26 magnetic resonance venograms and 35 embalmed cadavers by morphometric analysis, dissection, and photo modeling techniques.ResultsThe data show that the transverse diameter of the posterior cranial fossa correlates positively with the laterolateral diameter of the skull. The majority of cases with the low-anterior position of the sigmoid sinus were recorded in the brachycephalic group (82%), while the high-posterior localization of the sigmoid sinus was typical for the dolichocephalic patients (63%). The results of the ANOVA test confirm the significance of differences.ConclusionsThe shape of the skull reflects the morphology of the posterior cranial fossa and influences the topographic characteristics of the sigmoid sinus that must be considered in the selection of surgical approach to the inner ear and pontocerebellar angle.

P292 Follow up of giant cell arteritis patients with ultrasound: can cranial giant cell arteritis phenotype evolve towards large vessel vasculitis?

Abstract Background/Aims Ultrasound (US) is well-established in diagnosis of giant cell arteritis (GCA) but its value in follow-up is not yet adequately defined. The large vessel vasculitis (LVV) phenotype of GCA has less favourable outcomes and more often requires steroid-sparing treatment compared to the cranial phenotype. Evolution towards LVV might account for first-line treatment failure and impact on further therapeutic decisions. Here we review follow-up data from the NHS Lanarkshire GCA service and describe several relevant cases. Methods We performed a retrospective review of routine clinical and ad hoc US data from the NHS Lanarkshire GCA service between November 2018 and October 2021. Patients with cranial GCA at baseline and no involvement of large vessels were identified; demographic and clinical data of those who later developed US signs of LVV were reviewed. US positivity was defined by temporal artery intima media thickness (IMT) ≥0.5mm or LV IMT >1.0mm. Results 53 patients were diagnosed with GCA during the study period. At initial visit, 35 had cranial GCA on US, 12 had LVV, 6 were US negative. Five patients with cranial GCA developed US signs of LVV during follow-up. One of these was in remission clinically and had borderline IMT of 1.0mm. The other four had clinical relapse with mean LV IMT of 1.8mm (range 1.6-2.2); relapses occurred at mean 40 weeks (range 29-53), on prednisolone doses 0-15mg; all were subsequently commenced on steroid-sparing treatment (Table). Conclusion Cranial and LVV phenotypes of GCA may represent different stages of disease. US can be used to confirm evolution to LVV; identification of LVV US signs may explain clinical relapse and support the introduction of steroid sparing treatment. Disclosure A. Ciechomska: Other; Speaker, travel and registration fee sponsorship from Novartis, Abbvie, Chugai Pharma, Colgene, Roche and Lilly. A.R. Melville: Other; Dr Melville is a Medical Research Council (MRC) and GlaxoSmithKline (GSK) Experimental Medicine Initiative to Explore New Therapies clinical training fellow.

Genetic evidence for facial variation being a composite phenotype of cranial variation and facial soft tissue thickness

Facial and cranial variation represent a multidimensional set of highly correlated and heritable phenotypes. Little is known about the genetic basis explaining this correlation. We develop a software package ALoSFL for simultaneous localization of facial and cranial landmarks from head computed tomography (CT) images, apply it in the analysis of head CT images of 777 Han Chinese women, and obtain a set of phenotypes representing variation in face, skull and facial soft tissue thickness (FSTT). Association analysis of 301 single nucleotide polymorphisms (SNPs) from 191 distinct genomic loci previously associated with facial variation reveals an unexpected larger number of loci showing significant associations (P < 1e–3) with cranial phenotypes than expected under the null (O/E = 3.39), suggesting facial and cranial phenotypes share a substantial proportion of genetic components. Adding FSTT to a SNP-only model shows a large impact in explaining facial variance. A gene ontology analysis reveals that bone morphogenesis and osteoblast differentiation likely underlie our cranial-significant findings. Overall, this study simultaneously investigates the genetic effects on both facial and cranial variation of the same sample, supporting that facial variation is a composite phenotype of cranial variation and FSTT.

Deletion of ERF and CIC causes abnormal skull morphology and global developmental delay.

The ETS2 repressor factor (ERF) is a transcription factor in the RAS-MEK-ERK signal transduction cascade that regulates cell proliferation and differentiation, and pathogenic sequence variants in the ERF gene cause variable craniosynostosis inherited in an autosomal dominant pattern. The reported ERF variants are largely loss-of-function, implying haploinsufficiency as a primary disease mechanism; however, ERF gene deletions have not been reported previously. Here we describe three probands with macrocephaly, craniofacial dysmorphology, and global developmental delay. Clinical genetic testing for fragile X and other relevant sequencing panels were negative; however, chromosomal microarray identified heterozygous deletions (63.7–583.2 kb) on Chromosome 19q13.2 in each proband that together included five genes associated with Mendelian diseases (ATP1A3, ERF, CIC, MEGF8, and LIPE). Parental testing indicated that the aberrations were apparently de novo in two of the probands and were inherited in the one proband with the smallest deletion. Deletion of ERF is consistent with the reported loss-of-function ERF variants, prompting clinical copy-number-variant classifications of likely pathogenic. Moreover, the recent characterization of heterozygous loss-of-function CIC sequence variants as a cause of intellectual disability and neurodevelopmental disorders inherited in an autosomal dominant pattern is also consistent with the developmental delays and intellectual disabilities identified among the two probands with CIC deletions. Taken together, this case series adds to the previously reported patients with ERF and/or CIC sequence variants and supports haploinsufficiency of both genes as a mechanism for a variable syndromic cranial phenotype with developmental delays and intellectual disability inherited in an autosomal dominant pattern.

Postnatal Cranial Characterization in a Mouse Model of Cortex‐Specific Overexpression of BAF170

The BRG1/BRM-associated factor (BAF) chromatin remodeling complexes are composed of the mutually exclusive brahma or brahma-related gene 1 ATPases, along with several other structural subunits and their isoforms. BAF complexes serve specific functions in widely different cell types and developmental processes. Mammalian BAF170, a subunit of chromatin remodeling complex mSWI/SNF, is an intrinsic factor controlling cortical size. It was previously reported that conditional deletion of BAF170 promotes indirect neurogenesis by increasing the pool of intermediate progenitors and results in an enlarged cortex, whereas cortex specific BAF170 overexpression results in a smaller cortex. However, the influence of cortex specific BAF170 overexpression on size and shape of the craniofacial complex, specifically the skull, is not well understood. We hypothesized that the skull phenotype of mice with cortex specific BAF170 overexpression may include indirect effects of the reduced cortex including reduced intracranial volume and linear distance measures of the skull relative to unaffected littermates. To further understand the influence of cortex-specific conditional overexpression of BAF170 on the cranial phenotype of young mice, we examined two postnatal ages of the cortex specific BAF170 overexpression mouse model. Here, we combine measures of gross observation (body weight, body length, brain weight) and of 3D micro-computed tomography imaging of the head (overall skull length, cranial length, cranial height, cranial width, intracranial volume) at 28 (P28; N=6) and 42 (P42; N=12) days of age to assess the influence of BAF170 overexpression on skull morphology as compared to unaffected littermates. In our small sample, gross examination of the brain indicated an obviously distinctive brain morphological phenotype at both ages, including a visibly smaller cortex, in mice with overexpression of BAF170. Results showed few other differences at P28, although brain weight and skull width were reduced in mice with cortex specific BAF170 overexpression as compared to unaffected littermates. By P42, brain weight was no longer different between the genotypes, but cranial length, width, and height were all smaller. Additionally, intracranial volume was reduced in mice overexpressing BAF170 at P42. These results suggest that BAF170 overexpression in mice, which specifically supervises development of a smaller cortex, affects their skull phenotype in terms of size and possibly shape at P28 and P42, with potentially increased differences occurring with age. Further morphometric exploration is necessary to determine whether additional craniofacial differences exist at other ages.

Anatomy-based diagnostic criteria for complex body wall anomalies (CBWA).

BackgroundPrecise diagnosis and classification of CBWA cases can be challenging. BSA are considered when there is a body wall anomaly, skeletal abnormalities, and the umbilical cord is anomalous, absent or rudimentary, and LBWC when there is a body wall and structural limb anomalies with or without craniofacial abnormalities.MethodsPubMed was searched for body stalk anomalies, limb body wall complex, body stalk anomalies and amniotic band syndrome, and limb body wall complex and amniotic band syndrome. Sixty nine articles were selected and reviewed. This article systematically classifies the variants of CBWA in 218 cases, the study is based on the embryological and anatomical criteria established by Martín‐Alguacil and Avedillo to study BSA in the pig.ResultsEight different BSA presentation were defined. One hundred and eighty nine cases were classified as BSA, from which five were Type I, nine Type II, 20 Type III, 57 Type IV, 11Type V, 24 Type VI, 11 Type VII, and 52 Type VIII. Twenty six cases presented cranial phenotype, 114 abdominal phenotype, 42 cranio/abdominal overlapping phenotype, and five without defined phenotype. In addition, 52 BSA cases presented some kind of spinal dysraphism (SPDYS) and were classified as BSA/SPDYS, most of these cases did not show structural limb anomalies, except for three cases and were classified as LBWC/SPDYS.ConclusionThis morphology‐based classification represents a useful tool for clinical diagnosis, it helps to quantify and to evaluate CBWA in a precise, objective manner.

From Phenotype to Genotype And Back Again

Traditionally, anthropologists study evolutionary change throughmorphological analysis of fossils and comparative primate data. For the analysis of the genotypephenotype continuum, the current emphasis on genes is misplaced because genes don’t make structure. Developmental processes make structure through the activity of cells that use instructions specified by genes. A critical mechanism underlying any phenotypic trait is the genetically guided change in developmental events that produce the trait. But even when a developmental mechanism is identified, the links between genetically guided instructions and phenotypic outcome are lengthy, complicated, flexible, and sensitive to physical forces of functioning organs. We use the study of craniofacial phenotypes of craniosynostosis (premature closure of sutures) to demonstrate how patterns produced by the covariation of cranial traits cannot always reveal mechanism. Next we turn toencephalization, a critical feature of human evolution that covaries with cranial phenotypes, and show how experimental approaches can be used to analyze mechanism underlying this well-documented pattern in human evolution. With the realization that no single line of evidence can explain the dramatic changes in cranial morphology that characterize human evolution come fundamental changes in the way we conduct anthropological inquiry - collaborative efforts from scientists with diverse expertise will continue to push the field forward.

Scleraxis genes are required for normal musculoskeletal development and for rib growth and mineralization in zebrafish.

Tendons are an essential part of the musculoskeletal system, connecting muscle and skeletal elements to enable force generation. The transcription factor scleraxis marks vertebrate tendons from early specification. Scleraxis-null mice are viable and have a range of tendon and bone defects in the trunk and limbs but no described cranial phenotype. We report the expression of zebrafish scleraxis orthologs: scleraxis homolog (scx)-a and scxb in cranial and intramuscular tendons and in other skeletal elements. Single mutants for either scxa or scxb, generated by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9), are viable and fertile as adult fish. Although scxb mutants show no obvious phenotype, scxa mutant embryos have defects in cranial tendon maturation and muscle misalignment. Mutation of both scleraxis genes results in more severe defects in cranial tendon differentiation, muscle and cartilage dysmorphogenesis and paralysis, and lethality by 2–5 wk, which indicates an essential function of scleraxis for craniofacial development. At juvenile and adult stages, ribs in scxa mutants fail to mineralize and/or are small and heavily fractured. Scxa mutants also have smaller muscle volume, abnormal swim movement, and defects in bone growth and composition. Scleraxis function is therefore essential for normal craniofacial form and function and vital for fish development.—Kague, E., Hughes, S. M., Lawrence, E. A., Cross, S., Martin-Silverstone, E., Hammond, C. L., Hinits, Y. Scleraxis genes are required for normal musculoskeletal development and for rib growth and mineralization in zebrafish.

Whole-exome sequencing identified four loci influencing craniofacial morphology in northern Han Chinese

Facial shape differences are one of the most significant phenotypes in humans. It is affected largely by skull shape. However, research into the genetic basis of the craniofacial morphology has rarely been reported. The present study aimed to identify genetic variants influencing craniofacial morphology in northern Han Chinese through whole-exome sequencing (WES). Phenotypic data of the volunteers’ faces and skulls were obtained through three-dimensional CT scan of the skull. A total of 48 phenotypes (35 facial and 13 cranial phenotypes) were used for the bioinformatics analysis. Four genetic loci were identified affecting the craniofacial shapes. The four candidate genes are RGPD3, IGSF3, SLC28A3, and USP40. Four single-nucleotide polymorphism (SNP) site mutations in RGPD3, IGSF3, and USP40 were significantly associated with the skull shape (p < 1×10−6), and three SNP site mutations in RGPD3, IGSF3, and SLC28A3 were significantly associated with the facial shape (p < 1×10−6). The rs62152530 site mutation in the RGPD3 gene may be closely associated with the nasal length, ear length, and alar width. The rs647711 site mutation in the IGSF3 gene may be closely associated with the nasal length, mandibular width, and width between the mental foramina. The rs10868138 site mutation in the SLC28A3 gene may be associated with the nasal length, alar width, width between tragus, and width between the mental foramina. The rs1048603 and rs838543 site mutations in the USP40 gene may be closely associated with the pyriform aperture width. Our findings provide useful genetic information for the determination of face morphology.

Dietary niche and the evolution of cranial morphology in birds.

Cranial morphology in birds is thought to be shaped by adaptive evolution for foraging performance. This understanding of ecomorphological evolution is supported by observations of avian island radiations, such as Darwin's finches, which display rapid evolution of skull shape in response to food resource availability and a strong fit between cranial phenotype and trophic ecology. However, a recent analysis of larger clades has suggested that diet is not necessarily a primary driver of cranial shape and that phylogeny and allometry are more significant factors in skull evolution. We use phenome-scale morphometric data across the breadth of extant bird diversity to test the influence of diet and foraging behaviour in shaping cranial evolution. We demonstrate that these trophic characters are significant but very weak predictors of cranial form at this scale. However, dietary groups exhibit significantly different rates of morphological evolution across multiple cranial regions. Granivores and nectarivores exhibit the highest rates of evolution in the face and cranial vault, whereas terrestrial carnivores evolve the slowest. The basisphenoid, occipital, and jaw joint regions have less extreme differences among dietary groups. These patterns demonstrate that dietary niche shapes the tempo and mode of phenotypic evolution in deep time, despite a weaker than expected form–function relationship across large clades.

Changes in ontogenetic patterns facilitate diversification in skull shape of Australian agamid lizards

BackgroundMorphological diversity among closely related animals can be the result of differing growth patterns. The Australian radiation of agamid lizards (Amphibolurinae) exhibits great ecological and morphological diversity, which they have achieved on a continent-wide scale, in a relatively short period of time (30 million years). Amphibolurines therefore make an ideal study group for examining ontogenetic allometry. We used two-dimensional landmark-based geometric morphometric methods to characterise the postnatal growth patterns in cranial shape of 18 species of amphibolurine lizards and investigate the associations between cranial morphology, and life habit and phylogeny.ResultsFor most amphibolurine species, juveniles share a similar cranial phenotype, but by adulthood crania are more disparate in shape and occupy different sub-spaces of the total shape space. To achieve this disparity, crania do not follow a common post-natal growth pattern; there are differences among species in both the direction and magnitude of change in morphospace. We found that these growth patterns among the amphibolurines are significantly associated with ecological life habits. The clade Ctenophorus includes species that undergo small magnitudes of shape change during growth. They have dorsoventrally deep, blunt-snouted skulls (associated with terrestrial lifestyles), and also dorsoventrally shallow skulls (associated with saxicolous lifestyles). The sister clade to Ctenophorus, which includes the bearded dragon (Pogona), frill-neck lizard (Chlamydosaurus), and long-nosed dragon (Gowidon), exhibit broad and robust post-orbital regions and differing snout lengths (mainly associated with scansorial lifestyles).ConclusionsAustralian agamids show great variability in the timing of development and divergence of growth trajectories which results in a diversity of adult cranial shapes. Phylogenetic signal in cranial morphology appears to be largely overwritten by signals that reflect life habit. This knowledge about growth patterns and skull shape diversity in agamid lizards will be valuable for placing phylogenetic, functional and ecological studies in a morphological context.

Geographic variation in a South American clade of mormoopid bats, Pteronotus (Phyllodia), with description of a new species

The subgenus Phyllodia (genus Pteronotus) comprises 9 species ranging from the western coast of Mexico to central Brazil, including Greater and Lesser Antilles. Two of them, Pteronotus rubiginosus and Pteronotus sp. 1, form an endemic South American clade within Phyllodia and are reported in sympatry for several localities in Guyana, Suriname, French Guiana, and northern Brazil. We herein performed a comprehensive investigation to fully characterize the cranial variation and genetic intraspecific structuring within this clade. We also integrated genetic, morphological, and acoustic evidence to formally describe the species previously reported as Pteronotus sp. 1. Specimens of P. rubiginosus occurring in sympatry with the new species have a more distinctive cranial phenotype than those from allopatric areas, suggesting character displacement as a potential force promoting divergence by decreasing resource competition or reproductive interactions between them. Although the 2 species are sympatric in several localities, the divergence in their echolocation calls also may be promoting resource partitioning at the microhabitat level, with P. rubiginosus foraging in less cluttered areas and the new species restricted to more cluttered areas.

Skulls That Speak

Antoine Balzeau critically reviews a recent paper by Hugo Reyes-Centeno, Katerina Harvati, and Gerhard Jäger, “Tracking Modern Human Population History from Linguistic and Cranial Phenotype” that argues for a link between the development of human language and the evolving shape of the human skull.

A test for paedomorphism in domestic pig cranial morphology.

Domestic animals are often described as paedomorphic, meaning that they retain juvenile characteristics into adulthood. Through a three-dimensional landmark-based geometric morphometric analysis of cranial morphology at three growth stages, we demonstrate that wild boar (n = 138) and domestic pigs (n = 106) (Sus scrofa) follow distinct ontogenetic trajectories. With the exception of the size ratio between facial and neurocranial regions, paedomorphism does not appear to be the primary pattern describing the observed differences between wild and domestic pig cranial morphologies. The cranial phenotype of domestic pigs instead involves developmental innovation during domestication. This result questions the long-standing assumption that domestic animal phenotypes are paedomorphic forms of their wild counterparts.

Tracking modern human population history from linguistic and cranial phenotype.

Languages and genes arguably follow parallel evolutionary trajectories, descending from a common source and subsequently differentiating. However, although common ancestry is established within language families, it remains controversial whether language preserves a deep historical signal. To address this question, we evaluate the association between linguistic and geographic distances across 265 language families, as well as between linguistic, geographic, and cranial distances among eleven populations from Africa, Asia, and Australia. We take advantage of differential population history signals reflected by human cranial anatomy, where temporal bone shape reliably tracks deep population history and neutral genetic changes, while facial shape is more strongly associated with recent environmental effects. We show that linguistic distances are strongly geographically patterned, even within widely dispersed groups. However, they are correlated predominantly with facial, rather than temporal bone, morphology, suggesting that variation in vocabulary likely tracks relatively recent events and possibly population contact.

Characterizing phenotypic divergence using three-dimensional geometric morphometrics in four populations of threespine stickleback (Gasterosteus aculeatus; Pisces: Gasterosteidae) in Katmai National Park and Preserve, Alaska

The threespine stickleback (Gasterosteus aculeatus L., 1758) is a vertebrate model for the study of the relationship between phenotype and environment in facilitating rapid evolutionary change. Using four populations from a system of lakes in Katmai National Park and Preserve, Alaska, and microcomputed tomography and three-dimensional geometric morphometrics, we test the hypothesis that stickleback populations inhabiting freshwater environments display cranial phenotypes that are intermediate between the putative ancestral form and the low-plated freshwater populations that demonstrate substantial divergence toward new phenotypic optima. We further test the hypothesis that phenotypic covariance structure is disrupted in the context of such putatively recent adaptive events. We report significant phenotypic differences among all four populations that includes a component of sexual dimorphism. Furthermore, we show evidence of disrupted phenotypic covariance structure among these populations. Taken together, these findings indicate the importance of phenotypic quantification as a key step in elucidating both the ecological processes responsible for rapid adaptive radiations and the role of developmental mechanisms in biasing evolutionary change.