Ontogenetic Trajectories Research Articles

Heterochronic origin of spherical fusulinid foraminifera in the late Paleozoic

AbstractHeterochrony describes acceleration, displacement, and/or retardation of descendants’ development events compared with ancestral states and has often been cited as an important process to bring about morphological novelty. It was coined one-and-a-half centuries ago and has been discussed by both paleobiologists and biologists frequently ever since. Many types of fossil organisms preserve aspects of their development histories in their bones or shells that have been used for heterochrony analyses, with body size being used as a developmental age indicator, despite questions being raised regarding this practice. For organisms whose hard structures consist of multiple chambers, or that contain growth lines, age information suggested by these structures independently can facilitate ontogenetic modeling. In this way, relations among size, shape, and age can be established to document patterns of morphological development.Morphological analysis of pseudoschwagerine fusulinids, a fossil foraminifera group that developed a morphologically novel spherical shell, along with their presumptive triticitid ancestors illustrates this approach to heterochrony analysis. Ontogenetic trajectory comparisons of four major pseudoschwagerine genera, as well as those of triticitids, document relations between their shapes, sizes, and developmental ages. A complex of heterochronic patterns, including peramorphic predisplacement, hypermorphosis, and acceleration, characterize pseudoschwagerine development and appear to be responsible for the novel appearance of large, inflated fusiform and spherical tests in these late Paleozoic benthic foraminifera. The morphometric approach employed in this investigation could be applied widely in the quantitative morphological studies of development histories in a variety of other fossil groups.

The Network Ontogeny of the Parrot: Altriciality, Dynamic Skeletal Assemblages, and the Avian Body Plan

We analyze the connectivity patterns and fusion events among bones leading to the adult skeletal organization during the development of the superaltricial monk parakeet (Myiopsitta monachus, Psittaciformes), providing insights about the functional and evolutionary significance in the avian structural design. By using whole mount specimens stained for cartilage and bone, we apply anatomical network analysis (AnNA) to study the ontogenetic trajectory of the entire skeleton from embryonic stage 34 to adult. As bones condense, connect, and fuse to each other, we follow skeletal assemblages forming networks that change dynamically as the monk parakeet grows. Our results show that the pelvic girdle connects with the vertebral column prior to the pectoral girdle and that the pelvic girdle and hindlimbs connection begins and ends before that of the pectoral girdle and the forelimbs. We hypothesize that connections of the girdles and limbs could be linked to the altriciality of the species due to requirements for active movement in the use of the hindlimbs inside the nest, but not the need to use forelimbs to fly until much later. Further, as bones of the skull and pelvis fuse during development they form the largest and more connected assemblages, acting as attractors to connect to other bones, showing congruence between the connectivity pattern at each ontogenetic stage and the characteristic avian body plan.

Developmental morphology of the cervical vertebrae and the emergence of sexual dimorphism in size and shape: A computed tomography study.

Cervical vertebral bodies undergo substantial morphological development during the first two decades of life that are used clinically to visually determine skeletal maturation with the cervical vertebral maturation index (CVMI). CVMI defines six stages that capture the morphological transformations from 6 years to 18 years. However, CVMI has poor reproducibility given its qualitative nature and does not account for sexual dimorphism. This study aims to quantify the morphological development of the cervical vertebral bodies C2-C7 in size (height and depth) and shape and examine the emergence of sexual dimorphism. Using 115 (70 M;45F) computed tomography studies from typically developing individuals ages 6months to 20 years, landmarks were placed at the margins of the C2-C7 cervical vertebral bodies in the midsagittal plane for size and shape analysis. Findings revealed a dichotomy in the growth trends of height versus depth. The C2-C7 growth in depth gained the majority of the adult size by age 5 years, while the C3-C7 growth in height displayed two periods of accelerated growth during early childhood and puberty. Significant sex differences were found in height and depth growth trends and the form-space ontogenetic trajectories during puberty, with minor but evident differences emerging at age 3 years. Female C2-C7 depth measures were smaller than males at all ages. However, sex differences in height became evident due to males continuing to grow after females reach maturity. Findings quantify the morphological developmental stages of CVMI and emphasize the need to account for sex differences when assessing skeletal maturation.

Allometry and Ontogeny in the Vertebral Column of Southern Hemisphere Dolphins: a 3D Morphofunctional Approach

Commerson’s dolphin (Cephalorhynchus commersonii), Peale’s dolphin (Lagenorhynchus australis), dusky dolphin (Lagenorhynchus obscurus), and hourglass dolphin (Lagenorhynchus cruciger) are closely related species occurring in the Southern Hemisphere. Even though they are partially sympatric, they have evolved towards diverse foraging strategies, prey, and habitat preferences. Size variation occurs both among and within species. Our goal was to study the allometric patterns and ontogenetic trajectories in the vertebral column of these dolphins related to their ecology. We choose nine functionally homologous vertebrae in each column and digitized five different tridimensional configurations, containing 28 to 41 landmarks depending on the functional region under analysis. We explored different levels of allometry (static, ontogenetic, and evolutionary) using multivariate regressions of shape vs. log-transformed centroid size. We compared ontogenetic allometry regression vectors to evidence differences in growth patterns. Finally, we calculated Procrustes distances of shape configurations to determine the timing of shape shifts. Of the studied species, When compared to the Lagenorhynchus species, Commerson’s dolphin showed the highest degrees of allometry, both static and ontogenetic. The macroevolutive trends indicate a high degree of evolutionary morphological change, which could be associated with the rapid evolutionary radiation proposed for the group. This is the first time that allometric changes are studied in small cetaceans by means of 3D geometric morphometrics.

Population Density Effects on Carapace Growth in Clam Shrimp: Implications for Palaeontological Studies.

Fossil morphological data are time-averaged and generally reflect an overlap of different sources of carapace variability. To examine whether a proposed relationship between size and population density in fossil spinicaudatans is biologically meaningful, we set up rearing experiments involving two extant species: Eulimnadia texana and Eocyzicus argillaquus. Three and five days after hydration, clam shrimp were transferred into cups of various population densities that ranged between 1 and 15 inds/400 ml. Size and shape were measured 14 and 16 days after hydration, respectively. Every second day, we recorded length and sex of E. texana, which matured faster in lower-density cups. According to our growth model, population density and maximal carapace length follow a logarithmic relationship. At maturity, hermaphrodites yielded similar lengths across all population densities (~4.7 mm at 24°C), independent of age. Hence, clam shrimp can put off reproductive maturity as a response to decreased growth under higher density conditions. Growth rate generally decreases at maturity, but that effect is more pronounced in clam shrimp of high population densities, while low-density adults keep growing. For both species, multivariate analyses reveal that carapace size of low-density individuals is significantly larger than carapace size of higher-density individuals, while size values of intermediate densities cannot be distinguished. Shape distinction is strong in hermaphrodites of E. texana: 39.8% of the density-dependent shape variation is associated with relative umbo height, which is generally higher in individuals of smaller population densities. The H/L ratio, which is often used as a simple shape indicator, does not contribute to the main variation in shape, but it forms one of several ratios significant for 18.3% of the shape variability. In turn, the H/L ratio drives 30% of the shape variation in E. argillaquus. In addition, higher densities triggered shifts in ontogenetic growth trajectories in one third of the individuals, which led to aberrant morphologies. The present rearing experiment shows that some of the morphological variability on fossil bedding planes can be explained by population density. Also, it implies a considerable amount of ecophenotypic variability in Spinicaudata that affects our understanding of fossil taxonomy and palaeoecology.

Epigenetic Molecular Mechanisms in Insects.

Insects are the largest animal group on Earth both in biomass and diversity. Their outstanding success has inspired genetics and developmental research, allowing the discovery of dynamic process explaining extreme phenotypic plasticity and canalization. Epigenetic molecular mechanisms (EMMs) are vital for several housekeeping functions in multicellular organisms, regulating developmental, ontogenetic trajectories and environmental adaptations. In Insecta, EMMs are involved in the development of extreme phenotypic divergences such as polyphenisms and eusocial castes. Here, we review the history of this research field and how the main EMMs found in insects help to understand their biological processes and diversity. EMMs in insects confer them rapid response capacity allowing insect either to change with plastic divergence or to keep constant when facing different stressors or stimuli. EMMs function both at intra as well as transgenerational scales, playing important roles in insect ecology and evolution. We discuss on how EMMs pervasive influences in Insecta require not only the control of gene expression but also the dynamic interplay of EMMs with further regulatory levels, including genetic, physiological, behavioral, and environmental among others, as was earlier proposed by the Probabilistic Epigenesis model and Developmental System Theory.

Ontogenetic analysis of Anisian (Middle Triassic) ptychitid ammonoids from Nevada, USA

AbstractPtychitesis among the most widely distributed ammonoid genera of the Triassic and is namesake of a family and superfamily. However, representatives of the genus mostly show low-level phenotypic disparity. Furthermore, a large number of taxa are based on only a few poorly preserved specimens, creating challenges to determine ptychitid taxonomy. Consequently, a novel approach is needed to improve ptychitid diversity studies. Here, we investigatePtychitesspp. from the middle and late Anisian of Nevada. The species recorded includePtychites embreein. sp., which is distinguished by an average conch diameter that is much smaller and shows a more evolute coiling than most of its relatives. The new species ranges from theGymnotoceras mimetusto theGymnotoceras rotelliformiszones, which makes it the longest-ranging species of the genus. For the first time, the ontogenetic development ofPtychiteswas obtained from cross sections where possible. Cross-sectioning highlights unique ontogenetic trajectories in ptychitids. This demonstrates that, despite showing little phenotypic disparity,Ptychiteswas highly ontogenetically differentiated, and thus the high taxonomic diversity at the species level is justified for the species investigated.UUID:http://zoobank.org/5abe2487-8a00-4b48-adc7-ec7db7a097f7

Growing up aspen: ontogeny and trade-offs shape growth, defence and reproduction in a foundation species.

Intraspecific variation in foundation species of forest ecosystems can shape community and ecosystem properties, particularly when that variation has a genetic basis. Traits mediating interactions with other species are predicted by simple allocation models to follow ontogenetic patterns that are rarely studied in trees. The aim of this research was to identify the roles of genotype, ontogeny and genotypic trade-offs shaping growth, defence and reproduction in aspen. We established a common garden replicating >500 aspen genets in Wisconsin, USA. Trees were measured through the juvenile period into the onset of reproduction, for growth, defence chemistry (phenolic glycosides and condensed tannins), nitrogen, extrafloral nectaries, leaf morphology (specific leaf area), flower production and foliar herbivory and disease. We also assayed the TOZ19 sex marker and heterozygosity at ten microsatellite loci. We found high levels of genotypic variation for all traits, and high heritabilities for both the traits and their ontogenetic trajectories. Ontogeny strongly shaped intraspecific variation, and trade-offs among growth, defence and reproduction supported some predictions while contradicting others. Both direct resistance (chemical defence) and indirect defence (extrafloral nectaries) declined during the juvenile stage, prior to the onset of reproduction. Reproduction was higher in trees that were larger, male and had higher individual heterozygosity. Growth was diminished by genotypic allocation to both direct and indirect defence as well as to reproduction, but we found no evidence of trade-offs between defence and reproduction. Key traits affecting the ecological communities of aspen have high levels of genotypic variation and heritability, strong patterns of ontogeny and clear trade-offs among growth, defence and reproduction. The architecture of aspen's community genetics - its ontogeny, trade-offs and especially its great variability - is shaped by both its broad range and the diverse community of associates, and in turn further fosters that diversity.

Modern human changes in regulatory regions implicated in cortical development

BackgroundRecent paleogenomic studies have highlighted a very small set of proteins carrying modern human-specific missense changes in comparison to our closest extinct relatives. Despite being frequently alluded to as highly relevant, species-specific differences in regulatory regions remain understudied. Here, we integrate data from paleogenomics, chromatin modification and physical interaction, and single-cell gene expression of neural progenitor cells to identify derived regulatory changes in the modern human lineage in comparison to Neanderthals/Denisovans. We report a set of genes whose enhancers and/or promoters harbor modern human single nucleotide changes and are active at early stages of cortical development.ResultsWe identified 212 genes controlled by regulatory regions harboring modern human changes where Neanderthals/Denisovans carry the ancestral allele. These regulatory regions significantly overlap with putative modern human positively-selected regions and schizophrenia-related genetic loci. Among the 212 genes, we identified a substantial proportion of genes related to transcriptional regulation and, specifically, an enrichment for the SETD1A histone methyltransferase complex, known to regulate WNT signaling for the generation and proliferation of intermediate progenitor cells.ConclusionsThis study complements previous research focused on protein-coding changes distinguishing our species from Neanderthals/Denisovans and highlights chromatin regulation as a functional category so far overlooked in modern human evolution studies. We present a set of candidates that will help to illuminate the investigation of modern human-specific ontogenetic trajectories.

Ontogenetic trajectories of septal spacing in modern cuttlefishes are phylogenetically dependent

In this study, the ontogenetic trajectories of septal spacing between succeeding chambers of five modern cuttlefishes, Sepia esculenta, S. lycidas, S. latimanus, S. pharaonic and Sepiella japonica, which were all wild-caught around Japan, were analysed. The ontogenetic trajectories of septal spacing of all examined cuttlefishes demonstrate a decrease in septal spacing followed by an increase during the earliest ontogenetic stage. This trend is assumed to be related to hatching. After the rapid decrease and increase in septal spacing, species-dependent trends occur irrespective of sex and locality. Based on cluster analyses of general trends recognized in each species, the five examined species can be categorized into two groups: (1) a group by S. pharaonis, S. esculenta and Sepiella japonica; and (2) S. latimanus and S. lycidas as more distant branching groups within the five examined species. This classification is concordant with some phylogenetic clades determined from DNA analyses. Therefore, we hypothesized that the ontogenetic trajectories of septal spacing among modern cuttlefishes are phylogenetically dependent. If this hypothesis holds in fossil cuttlefishes, the examination of ontogenetic trajectories of septal spacing would give new insight into the recognition not only of the life history but also of the phylogeny of fossil cuttlefishes.

Plant ontogeny determines strength and associated plant fitness consequences of plant-mediated interactions between herbivores and flower visitors.

Plants show ontogenetic variation in growth–defence strategies to maximize reproductive output within a community context. Most work on plant ontogenetic variation in growth–defence trade‐offs has focussed on interactions with antagonistic insect herbivores. Plants respond to herbivore attack with phenotypic changes. Despite the knowledge that plant responses to herbivory affect plant mutualistic interactions with pollinators required for reproduction, indirect interactions between herbivores and pollinators have not been included in the evaluation of how ontogenetic growth–defence trajectories affect plant fitness.In a common garden experiment with the annual Brassica nigra, we investigated whether exposure to various herbivore species on different plant ontogenetic stages (vegetative, bud or flowering stage) affects plant flowering traits, interactions with flower visitors and results in fitness consequences for the plant.Effects of herbivory on flowering plant traits and interactions with flower visitors depended on plant ontogeny. Plant exposure in the vegetative stage to the caterpillar Pieris brassicae and aphid Brevicoryne brassicae led to reduced flowering time and flower production, and resulted in reduced pollinator attraction, pollen beetle colonization, total seed production and seed weight. When plants had buds, infestation by most herbivore species tested reduced flower production and pollen beetle colonization. Pollinator attraction was either increased or reduced. Plants infested in the flowering stage with P. brassicae or Lipaphis erysimi flowered longer, while infestation by any of the herbivore species tested increased the number of flower visits by pollinators.Our results show that the outcome of herbivore–flower visitor interactions in B. nigra is specific for the combination of herbivore species and plant ontogenetic stage. Consequences of herbivory for flowering traits and reproductive output were strongest when plants were attacked early in life. Such differences in selection pressures imposed by herbivores to specific plant ontogenetic stages may drive the evolution of distinct ontogenetic trajectories in growth–defence–reproduction strategies and include indirect interactions between herbivores and flower visitors. Synthesis. Plant ontogeny can define the direct and indirect consequences of herbivory. Our study shows that the ontogenetic stage of plant individuals determined the effects of herbivory on plant flowering traits, interactions with flower visitors and plant fitness.

How many ontogenetic points are needed to accurately describe the ontogeny of a cephalopod conch? A case study of the modern nautilid Nautilus pompilius.

Recent advancements in tomographic techniques allow for detailed morphological analysis of various organisms, which has proved difficult in the past. However, the time and cost required for the post-processing of highly resolved tomographic data are considerable. Cephalopods are an ideal group to study ontogeny using tomography as the entire life history is preserved within a conch. Although an increasing number of studies apply tomography to cephalopod conchs, the number of conch measurements needed to adequately characterize ontogeny remains unknown. Therefore, the effect of different ontogenetic sampling densities on the accuracy of the resultant growth trajectories needs to be investigated. Here, we reconstruct ontogenetic trajectories of a single conch of Nautilus pompilius using different numbers of ontogenetic points to assess the resulting accuracies. To this end, conch parameters were measured every 10°, 30°, 45°, 90°, and 180°. Results reveal that the overall patterns of reconstructed growth trajectories are nearly identical. Relatively large errors appear to occur where growth changes occur, such as the points of hatching and the onset of morphogenetic countdown before the attainment of maturity. In addition, a previously undocumented growth change before hatching was detected when measurements were taken every 10°, 30°, and 45°, though this growth change was obscured when fewer measurements were used (90° and 180°). The lower number of measurements also masks the subtle fluctuating patterns of conch parameters in middle ontogeny. We conclude that the measurements of a conch every 30° and 45° permit a reasonably precise description of conch ontogeny in nautilids. Since ammonoids were likely more responsive to external stimuli than to nautilids, a much denser sampling may be required for ammonoids.

Chamber volume development, metabolic rates, and selective extinction in cephalopods

Reconstructing the physiology of extinct organisms is key to understanding mechanisms of selective extinction during biotic crises. Soft tissues of extinct organisms are rarely preserved and, therefore, a proxy for physiological aspects is needed. Here, we examine whether cephalopod conchs yield information about their physiology by assessing how the formation of chambers respond to external stimuli such as environmental changes. We measured chamber volume through ontogeny to detect differences in the pattern of chamber volume development in nautilids, coleoids, and ammonoids. Results reveal that the differences between ontogenetic trajectories of these cephalopods involve the presence or absence of abrupt decreases of chamber volume. Accepting the link between metabolic rate and growth, we assume that this difference is rooted in metabolic rates that differ between cephalopod clades. High metabolic rates combined with small hatching size in ammonoids as opposed to lower metabolic rates and much larger hatchlings in most nautilids may explain the selective extinction of ammonoids as a consequence of low food availability at the end of the Cretaceous.

Stabilities of Infant Behaviors and Maternal Responses to Them.

Consistency in the order of individuals in a group across substantial lengths of time-stability-is a central concept in developmental science for several reasons. Stability underscores the meaningfulness of individual differences in psychological phenomena; stability informs about the origins, nature, and overall developmental course of psychological phenomena; stability signals individual status and so affects the environment, experience, and development; stability has both theoretical and clinical implications for individual functioning; and stability helps to establish that a measure constitutes a consequential individual-differences metric. In this three-wave prospective longitudinal study (Ns = 40 infants and mothers), we examined stabilities of individual variation in multiple infant behaviors and maternal responses to them across infant ages 10, 14, and 21 months. Medium to large effect size stabilities in infant behaviors and maternal responses emerged, but both betray substantial amounts of unshared variance. Documenting the ontogenetic trajectories of infant behaviors and maternal responses helps to elucidate the nature and structure of early human development.

Decoupled ontogeny of in vivo bite force and mandible morphology reveals effects of weaning and sexual maturation in mice

Abstract The link between performance, morphology and their sources of variation is a major target of evolutionary functional biology. In vertebrates, many studies have linked in vivo bite force to skull morphology, mostly at the interspecific level. Within species, however, the ontogeny of bite force, in relation to the development of the mandible, remains poorly known, despite its relevance for life history and for the co-evolution of form and function. Here, ontogenetic trajectories of bite force, correlated with mandible size and shape, are reported for the first time in a wild-derived colony of laboratory mice. Bite forces were measured in vivo and mandible morphology was assessed using geometric morphometrics. Most coordinated changes in morphology and in vivo bite force occur during the first stages of growth, prior to weaning. Mandible shape stabilizes after day 23. The increases in mandible size and body mass slow down around day 40, but still increase during adulthood. Despite slowing down after weaning, bite force increases through a second phase during sexual maturation (days 30–40). This may be linked to the progressive tempering of weaning stress, continued growth and synchronization of the muscular and osteological systems, together with hormonal changes, as we observed a concomitant appearance of sexual dimorphism.

What factors influence our reconstructions of Morrison Formation sauropod diversity?

The Upper Jurassic Morrison Formation classically represents the “Golden Age” of sauropods, and the Morrison Formation is reported to have yielded 13 genera and 24 species of sauropods. This incredible diversity has produced numerous theories attempting to reconcile the co-occurrence of such large, and similar taxa. Previously, a comparably high diversity has been proposed for the Late Cretaceous Hell Creek Formation of North America – possibly comprising nearly three dozen species from over 20 genera of ankylosaura, caenagnathids, ceratopsians, dromaeosaurids, hadrosaurs, ornithomimids, pachycephalosaurs, thescelosaurs, and tyrannosaurs. However, much of the morphologic variation previously ascribed to taxonomic differences has recently been shown to be a result of stratigraphy and/or ontogeny – resulting in this rich assemblage being downsized to 13 genera and 16 species. Whereas still rich in diversity, such factors have an immediate effect towards our reconstruction of true richness.Following the example of the Hell Creek Formation, we can investigate the ontogenetic and strati-graphic origin of possible diversity inflation in other formations, and within this study, apply it to the Morrison Formation. New dating techniques are resulting in finer temporal resolution, and are changing the temporal position of well-known quarries. Differences in body size and ontogenetic stages can also affect diversity estimates. Plotting body size stratigraphically, it initially appears that larger specimens (interpreted as different species) occur higher in the section. An increase in average body size may be a legitimate trend, but there are several specimens that counter this “rule” for many genera. Likewise, dramatic allometric ontogenetic trajectories have led to the erection of at least three diplodocid genera – Amphicoelias, Seismosaurus, and Suuwassea – and it is suspected that many more Morrison Formation “species” could alternatively be explained as ontogimorphs. We have a long way to go towards revealing the true nature of Morrison Formation sauropod diversity. Although dietary partitioning undoubtedly occurred at the level of both the species (e.g., Brachiosaurus vs. Diplodocus) and between ontogenetic stages, a base of 24 levels of co-occurring divisions seems unlikely. The Morrison Formation may have exhibited a sauropod-rich assemblage unlike any other in North America, and the implications of stratigraphy, ontogeny, and variation may be minor, yet these factors alter perceived “diversity.” True diversity will not be fully understood unless these factors are considered.

The polyphasic ontogeny of the discoidal Late Devonian ammonoid Acrimeroceras

The Late Devonian ammonoid species Acrimeroceras falcisulcatum and A. stella have similar-shaped discoidal adult conchs. Their conch morphology and its ontogenetic development are described and analysed. Despite great similarities in their adult conch morphology, they can be clearly distinguished by differences in the shape of their juvenile whorl profile and by the growth trajectories of their cardinal conch parameters: conch width index, umbilical width index and whorl expansion rate. Quantification of ontogenetic change in the two species demonstrates that the stratigraphically younger species A. falcisulcatum possesses the less complex ontogeny compared to the stratigraphically older A. stella. The closely related genus Paratornoceras (early Famennian) and the unrelated Late Visean Calygirtyoceras show juvenile conch morphology and ontogenetic trajectories very similar to Acrimeroceras stella. This similarity can be seen as iterative independent unfolding of homoplastic characters, possibly linked to size-dependence of the functional morphology of the conchs.

Genetic and morphological divergence in the warm-water planktonic foraminifera genus Globigerinoides.

The planktonic foraminifera genus Globigerinoides provides a prime example of a species-rich genus in which genetic and morphological divergence are uncorrelated. To shed light on the evolutionary processes that lead to the present-day diversity of Globigerinoides, we investigated the genetic, ecological and morphological divergence of its constituent species. We assembled a global collection of single-cell barcode sequences and show that the genus consists of eight distinct genetic types organized in five extant morphospecies. Based on morphological evidence, we reassign the species Globoturborotalita tenella to Globigerinoides and amend Globigerinoides ruber by formally proposing two new subspecies, G. ruber albus n.subsp. and G. ruber ruber in order to express their subspecies level distinction and to replace the informal G. ruber "white" and G. ruber "pink", respectively. The genetic types within G. ruber and Globigerinoides elongatus show a combination of endemism and coexistence, with little evidence for ecological differentiation. CT-scanning and ontogeny analysis reveal that the diagnostic differences in adult morphologies could be explained by alterations of the ontogenetic trajectories towards final (reproductive) size. This indicates that heterochrony may have caused the observed decoupling between genetic and morphological diversification within the genus. We find little evidence for environmental forcing of either the genetic or the morphological diversification, which allude to biotic interactions such as symbiosis, as the driver of speciation in Globigerinoides.

Ontogeny of the facial phenotypic variability in Mexican patients with 22q11.2 deletion syndrome

Background22q11.2 deletion syndrome is a medical condition that results from genomic loss at chromosome 22. Affected patients exhibit large variability that ranges from a severe condition to mild symptoms. In addition, the spectrum of clinical features differs among populations and even within family members. The facial features related to this syndrome are not an exception, and although part of its variation arises through development, few studies address this topic in order to understand the intra and inter-population heterogeneities. Here, we analyze the ontogenetic dynamics of facial morphology of Mexican patients with del22q11.2 syndrome.MethodsFrontal facial photographs of 37 patients (mean age = 7.65 ± 4.21 SE) with del22q11.2DS and 200 control subjects (mean age = 7.69 ± 4.26 SE) were analyzed using geometric morphometric methods. Overall mean shape and size differences between patients and controls were analyzed, as well as differences in ontogenetic trajectories (i.e. development, growth, and allometry).ResultsWe found that Mexican patients show typical traits that have been reported for the Caucasian population. Additionally, there were significant differences between groups in the facial shape and size when all the ontogenetic stages were considered together and, along ontogeny. The developmental and allometric trajectories of patients and controls were similar, but they differed in allometric scaling. Finally, patients and controls showed different growth trajectories.ConclusionThe results suggest that the typical face of patients with del22q11.2DS is established prenatally; nonetheless, the postnatal ontogeny could influence the dysmorphology and its variability through size-related changes.

Skull ontogeny of the pronghorn (Antilocapraamericana) in the comparative context of native North American ungulates

The pronghorn (Antilocapra americana (Ord, 1815)) is the single survivor of a largely extinct, isolated pecoran lineage (Antilocapridae) native to North America. We describe postnatal ontogeny of its skull in a comparative framework inclusive of representatives of other typical North American ungulate linages, all of which partially overlap in geographic distribution and share habitat with A. americana. To describe allometric growth, we took 23 linear cranial measurements in 30 specimens of A. americana and applied bi- and multi-variate statistics. The skull of A. americana generally grew with negative rates in width and height dimensions, and with positive rates in length, including an elongation of rostrum, particularly the nasals, and a relative narrowing of the braincase. We compared skull development in A. americana with development in two cervids (white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)) and wapiti (Cervus canadensis Erxleben, 1777)) and two bovids (bighorn sheep (Ovis canadensis Shaw, 1804) and American bison (Bison bison (Linnaeus, 1758))). The multivariate ontogenetic trajectory of A. americana overlapped greatly with that of Odocoileus virginianus, and differed from the other species in varying degrees. These results indicated an essentially convergent pattern of skull growth with species showing important functional similarities, such as cervids of comparable size and feeding habits.