ABSTRACT
The symbiotic relationship between dinoflagellate algae in the family Symbiodiniaceae and scleractinian corals forms the base of the tropical reef ecosystem. In scleractinian corals, recruits acquire symbionts either "vertically" from the maternal colony or initially lack symbionts and acquire them "horizontally" from the environment. Regardless of the mode of acquisition, coral species and individual colonies harbor only a subset of the highly diverse complex of species/taxa within the Symbiodiniaceae. This suggests a genetic basis for specificity, but local environmental conditions and/or symbiont availability may also play a role in determining which symbionts within the Symbiodiniaceae are initially taken up by the host. To address the relative importance of genetic and environmental drivers of symbiont uptake/establishment, we examined the acquisition of these dinoflagellate symbionts in one to three-month-old recruits of Orbicella faveolata to compare symbiont types present in recruits to those of parental populations versus co-occurring adults in their destination reef. Variation in chloroplast 23S ribosomal DNA and in three polymorphic microsatellite loci was examined. We found that, in general, symbiont communities within adult colonies differed between reefs, suggesting that endemism is common among symbiont populations of O. faveolata on a local scale. Among recruits, initial symbiont acquisition was selective. O. faveolata recruits only acquired a subset of locally available symbionts, and these generally did not reflect symbiont populations in adults at either the parental or the outplant reef. Instead, symbiont communities within new recruits at a given outplant site and region tended to be similar to each other, regardless of parental source population. These results suggest temporal variation in the local symbiont source pool, although other possible drivers behind the distinct difference between symbionts within O. faveolata adults and new generations of recruits may include different ontogenetic requirements and/or reduced host selectivity in early ontogeny.
ABSTRACT
While type determination on bullets has been performed for over a century, type determination on cartridge cases is often overlooked. Presented here is an example of type determination of ejector marks on cartridge cases from Glock and Smith & Wesson Sigma series pistols using Naïve Bayes and Random Forest classification methods. The shapes of ejector marks were captured from images of test-fired cartridge cases and subjected to multivariate analysis. Naïve Bayes and Random Forest methods were used to assign the ejector shapes to the correct class of firearm with success rates as high as 98%. This method is easily implemented with equipment already available in crime laboratories and can serve as an investigative lead in the form of a list of firearms that could have fired the evidence. Paired with the FBI's General Rifling Characteristics (GRC) database, this could be an invaluable resource for firearm evidence at crime scenes.
ABSTRACT
Mass extinctions disrupt ecological communities. Although climate changes produce stress in ecological communities, few paleobiological studies have systematically addressed the impact of global climate changes on the fine details of community structure with a view to understanding how changes in community structure presage, or even cause, biodiversity decline during mass extinctions. Based on a novel Bayesian approach to biotope assessment, we present a study of changes in species abundance distribution patterns of macroplanktonic graptolite faunas (â¼447-444 Ma) leading into the Late Ordovician mass extinction. Communities at two contrasting sites exhibit significant decreases in complexity and evenness as a consequence of the preferential decline in abundance of dysaerobic zone specialist species. The observed changes in community complexity and evenness commenced well before the dramatic population depletions that mark the tipping point of the extinction event. Initially, community changes tracked changes in the oceanic water masses, but these relations broke down during the onset of mass extinction. Environmental isotope and biomarker data suggest that sea surface temperature and nutrient cycling in the paleotropical oceans changed sharply during the latest Katian time, with consequent changes in the extent of the oxygen minimum zone and phytoplankton community composition. Although many impacted species persisted in ephemeral populations, increased extinction risk selectively depleted the diversity of paleotropical graptolite species during the latest Katian and early Hirnantian. The effects of long-term climate change on habitats can thus degrade populations in ways that cascade through communities, with effects that culminate in mass extinction.
Subject(s)
Climate Change , Extinction, Biological , Fossils , Invertebrates/growth & development , Animals , Aquatic Organisms/classification , Aquatic Organisms/growth & development , Bayes Theorem , Biodiversity , Geologic Sediments , Invertebrates/classification , Models, Biological , Oceans and Seas , Time FactorsABSTRACT
Friction ridge impression appearance can be affected due to the type of surface touched and pressure exerted during deposition. Understanding the magnitude of alterations, regions affected, and systematic/detectable changes occurring would provide useful information. Geometric morphometric techniques were used to statistically characterize these changes. One hundred and fourteen prints were obtained from a single volunteer and impressed with heavy, normal, and light pressure on computer paper, soft gloss paper, 10-print card stock, and retabs. Six hundred prints from 10 volunteers were rolled with heavy, normal, and light pressure on soft gloss paper and 10-print card stock. Results indicate that while different substrates/pressure levels produced small systematic changes in fingerprints, the changes were small in magnitude: roughly the width of one ridge. There were no detectable changes in the degree of random variability of prints associated with either pressure or substrate. In conclusion, the prints transferred reliably regardless of pressure or substrate.
ABSTRACT
Presence of accidental characteristics on footwear strengthens the linkage of a given piece of footwear to a footwear impression left at a crime-scene. Thus an understanding of rate of appearance and disappearance of these characteristics is of importance. Artificial cut-marks, 1-3mm in depth, were cut into outsoles of 11 pairs of athletic shoes. Loss of these cut-marks and acquisition of new accidental characteristics/wear patterns were monitored over a seven-week time-span. Feature-vector methods were used to acquire multivariate data on wear/acquisition rates. A repeatability study indicated the feature vector method could detect small differences among shoes relative to measurement uncertainty. The shoes displayed a strong retention of artificial cut-marks over the study interval. Net rate of wear was 0.1% of the textured area of the shoe per week, predominantly in the heel and ball area. Results indicate accidental characteristics can reasonably be expected to persist over time.
ABSTRACT
Studies on human cadaver models have reported significant levels of distortion of bitemarks in skin, indicating that tooth characteristics are not reliably transferred and recorded in the bitten subject. Moreover, matches among the anterior biting dentition in open population studies have been found. This prompts the question as to what degree of difference in shape will distinguish one dentition from another as reflected in a bitemark. In order to understand how these variables appear on skin, 10 dental casts with systematic variations in tooth positions were produced. The height of the lateral incisors was systematically altered in 1mm increments up to 3mm and lateral incisor/canines were altered in facial/lingual displacement in 1mm increments up to 5mm. Each of the models was used to produce a series of 10 repeated bites, distributed over arms and legs of un-embalmed cadavers. Landmark-based geometric morphometrics were used for analysis of digital images of the bitemarks. Results indicate that alterations of height and displacement of particular teeth affected the position of impressions created by the adjacent teeth. Displacement of one lateral incisor/canine led to a relative shift in impressions of the central incisors and unaltered canines, while height alteration of the lateral incisors led to a shift in relative position of central incisors as recorded in the bitemark. The prominence of displacements was more pronounced in the bitemarks than in images of the dentition used to make the bites, thus the bitemarks tended to exaggerate the differences. It was found that a displacement of 5mm between teeth allowed for reliable distinction between bitemarks. No such threshold of distinction could be established for differences in height of teeth under these experimental conditions. The effect of distortion was more significant in the mandibular than maxillary arch, suggesting that the mandible exhibits higher variation than the maxilla, as impressed in skin. Numerous bitemarks also exhibited arch flattening, consistent with recent studies showing arch width as the principal variable in a bitemark.
Subject(s)
Bites, Human/pathology , Dentition , Cadaver , Forensic Dentistry , Humans , Image Processing, Computer-Assisted , Models, Dental , Photography, Dental , Principal Component AnalysisABSTRACT
An understanding of the variability of the anterior human dentition is essential in bitemark analysis. A collection of 1099 3D laser scans of paired maxillary and mandibular arches were studied using geometric morphometric methods. Analyses were performed without scale (shape only) and with scale (shape and size). Specimens differing by no more than experimentally obtained measurement error were counted as matches, or as indistinguishable. A total of 487 maxillary (396 size preserved), 131 mandibular (83 size preserved), and one paired dentition (two size preserved) matches were found. Principal component analysis and partial least squares revealed interpretable patterns of variation and covariation in dental shape, principally dominated by variation in dental arch width. The sensitivity of match rate to assumed degree of measurement error was also determined showing rapid increases in match rate as measurement error increased. In conclusion, the concept of dental uniqueness with regard to bitemark analysis should be approached with caution.
Subject(s)
Bites, Human , Dentition , Imaging, Three-Dimensional , Forensic Dentistry , Humans , Image Processing, Computer-Assisted , Least-Squares Analysis , Mandible , Maxilla , Models, Dental , Principal Component Analysis , Sample SizeABSTRACT
In bitemark analysis the extent of distortion of both maxillary and mandibular arches and how one affects the other has not been studied. A single dentition was used to create 49 bites on unembalmed cadavers. Landmarks were placed on digital images of the bitemarks and scanned images of the biting dentition. A sample of 297 randomly acquired dental models was used for comparison purposes. Geometric morphometric techniques were utilized to statistically describe size and shape change, as well as the correlation between the two arches. Results indicate that the predominant distortion seen was in arch width, at 7-28 times as large as measurement error in the biting dentition and roughly 50% of the variation seen in the random population of dentitions. The correlation of arch width distortion between arches was very low (â¼0.03). However, the principal patterns of all shape variation did co-vary in the bitemarks produced by the maxillary and mandibular dentition, an effect indicating independence of size and shape distortion. In conclusion, bitemark analysis should be approached with caution when the principal difference between suspects is arch width.
Subject(s)
Bites, Human/pathology , Dentition , Cadaver , Forensic Dentistry , Humans , Image Processing, Computer-Assisted , Mandible , Maxilla , Photography, DentalABSTRACT
The morphological study of extinct taxa allows for analysis of a diverse set of macroevolutionary hypotheses, including testing for change in the magnitude of morphological divergence, extinction selectivity on form, and the ecological context of radiations. Late Ordovician graptoloids experienced a phylogenetic bottleneck at the Hirnantian mass extinction (â¼445 Ma), when a major clade of graptoloids was driven to extinction while another clade simultaneously radiated. In this study, we developed a dataset of 49 ecologically relevant characters for 183 species with which we tested two main hypotheses: (i) could the biased survival of one graptoloid clade over another have resulted from morphological selectivity alone and (ii) are the temporal patterns of morphological disparity and innovation during the recovery consistent with an interpretation as an adaptive radiation resulting from ecological release? We find that a general model of morphological selectivity has a low probability of producing the observed pattern of taxonomic selectivity. Contrary to predictions from theory on adaptive radiations and ecological speciation, changes in disparity and species richness are uncoupled. We also find that the early recovery is unexpectedly characterized by relatively low morphological disparity and innovation, despite also being an interval of elevated speciation. Because it is necessary to invoke factors other than ecology to explain the graptoloid recovery, more complex models may be needed to explain recovery dynamics after mass extinctions.
Subject(s)
Biodiversity , Chordata, Nonvertebrate/physiology , Extinction, Biological , Fossils , Zooplankton/physiology , Animals , Chordata, Nonvertebrate/anatomy & histology , Chordata, Nonvertebrate/classification , Ecosystem , Genetic Speciation , Geologic Sediments , Models, Biological , Phylogeny , Species Specificity , Zooplankton/classificationABSTRACT
Criticisms of the forensic discipline of bitemark analysis state that the range of distortion in the shape of bitemark impressions in skin has not been scientifically established. No systematic statistical studies exist that explore this problem. As a preliminary investigation of this issue, a single dentition was mounted in a mechanical apparatus and used to create 89 bitemarks in human cadaver skin, both parallel and perpendicular to tension lines. Impressions of the same dentition were also created in wax. 2D scanned images of the biting dentition were obtained. Locations of incisal edges of all 6 anterior teeth as well as the midpoint of the canine were captured as landmarks in all specimens. This set of landmark data was then studied using established geometric morphometric methods. All specimen shapes were compared using Procrustes superimposition methods, and by a variation of Procrustes superimposition which preserves scale information. Match criteria were established by examining the range of variation produced by repeated measurements of the dentition for each class of specimen. The bitemarks were also compared to a population of 411 digitally scanned dentitions, again using the match criteria. Results showed that bitemarks in wax had lower measurement error than scanned images of the dentition, and both were substantially lower than measurement error as recorded in skin. None of the 89 bitemarks matched the measured shape of the biting dentition or bitemarks in wax, within the repeated measurements error level, despite the fact that all bitemarks were produced by this dentition. Comparison of the bitemarks to the collection of 411 dentitions showed that the closest match to the bitemarks was not always the same dentition that produced the bitemarks. Examination of Procrustes plots of matched shapes showed non-overlapping distributions of measurements of bitemarks in skin, wax, and the dentition. All had statistically significant differences in mean shape. Principal component analysis (PCA) and canonical variates analysis (CVA) both showed clear segregation of the three types of data. The patterns of variance revealed by PCA showed several distinct patterns produced by skin distortion; alteration of relative arch width, and varying displacement of non-aligned teeth in the dentition. These initial results indicate that when multiple suspects possess similar dentitions, bitemark analysis should be approached with caution.
Subject(s)
Bites, Human/pathology , Forensic Dentistry/methods , Dentition , Humans , Image Processing, Computer-Assisted , Inlay Casting Wax , Models, Dental , Principal Component AnalysisABSTRACT
Forensically identifying a suspect's dentition from a bitemark in an open population requires the supposition that every person's dental alignment is different. There have been few studies that have tested this claim. Four hundred and ten lower anterior dentitions from a selected population and 110 lower anterior dentitions from one that was orthodontically treated were measured using geometric morphometric analysis, allowing comparison of arch shape. Dental match rates of 1.46% and 42.7% of individuals were found in the respective populations, given an established measurement error. Orthodontic treatment had a strong effect on match rate suggesting that treated or naturally well-aligned dentitions may be indistinguishable. Sexual dimorphism was found to be only slightly significant. Principal shape variation in both populations was degree of arch curvature. Results of studying these populations show that dental matches can occur, and that statements of certainty concerning individualization in such populations should be approached with caution.
Subject(s)
Dentition, Permanent , Orthodontics, Corrective , Bites, Human/pathology , Female , Forensic Dentistry , Humans , Image Processing, Computer-Assisted , Male , Models, Dental , Models, Statistical , New York , Principal Component Analysis , Sex CharacteristicsABSTRACT
Uniqueness of the human dentition is a fundamental premise in bitemark analysis. Despite the importance of this key aspect of bitemark methodology, systematic studies of large populations have been limited. Furthermore, there have been no investigations of the significance of the third dimension with regard to dental uniqueness. One hundred digitally scanned mandibular models were analyzed in both 2D and three dimension (3D) using Landmark software. Additionally, 500 3D maxillary and mandibular sets were investigated for determining dental match rate. Statistical analysis was performed with geometric morphometric methods. Results show that measurements in 3D preserve more information about the dentition, reducing but not eliminating random matches in a sample population of 100 mandibular dentitions. Examination of pairs of maxillary and mandibular dentitions showed a substantial number of random matches (197 maxillary, 51 mandibular, one of both maxillary and mandibular). Conclusions indicate that a zero match rate cannot be claimed for the population studied.
Subject(s)
Bites, Human/pathology , Dentition , Forensic Dentistry/methods , Humans , Imaging, Three-Dimensional , Lasers , Mandible/anatomy & histology , Maxilla/anatomy & histologyABSTRACT
Skin is a less than ideal medium for recording bitemark impressions, and assessing the causes and magnitude of distortion has long been a question in forensic odontology. Affine methods have been suggested as a mathematical means to attempt to quantify the deformation typically seen with a bitemark. Thirty-six bites were created on unembalmed human cadavers with a single dentition. Three mathematical affine methods were evaluated to determine if the distortion could be described mathematically and effectively removed. A measure of mismatch of a dentition to a bitemark was developed based on landmark measurements establishing a numerical basis for comparisons of dentitions to bitemarks. Results indicate high levels of distortion in the bitemarks not attributable to affine deformations or measurement error, suggesting that non-uniform anisotropic properties of skin mostly contribute to the distortion seen, thus concluding that bitemark distortion cannot be corrected by using affine transformations.
Subject(s)
Bites, Human/pathology , Dentition , Models, Biological , Cadaver , Forensic Dentistry/methods , Humans , Image Processing, Computer-Assisted , Models, DentalABSTRACT
Recent scrutiny of forensic science has focused on unreliability of expert witness testimony when based on statements of individuality. In bitemark analysis, assumptions regarding uniqueness of the dentition have been based on use of the product rule while ignoring correlation and nonuniformity of dental arrangement. To examine the effect of these factors, two separate sets of scanned dental models (n=172 and n=344) were measured and statistically tested to determine match rates. Results were compared to those of a prior study. Seven and 16 matches of the six anterior lower teeth were found in the respective data sets. Correlations and nonuniform distributions of tooth positions were observed. Simulation tests were performed to verify results. Results indicate that given experimental measurement parameters, statements of dental uniqueness with respect to bitemark analysis in an open population are unsupportable and that use of the product rule is inappropriate.
Subject(s)
Dentition , Models, Biological , Monte Carlo Method , Bites, Human/pathology , Forensic Dentistry , Humans , Imaging, Three-Dimensional , Mandible , Models, DentalABSTRACT
BACKGROUND: Mixed breeding systems with extended clonal phases and weak sexual recruitment are widespread in nature but often thought to impede the formation of discrete evolutionary clusters. Thus, cyclic parthenogens, such as cladocerans and rotifers, could be predisposed to "species problems" and a lack of discrete species. However, species flocks have been proposed for one cladoceran group, Eubosmina, where putative species are sympatric, and there is a detailed paleolimnological record indicating a Holocene age. These factors make the Eubosmina system suitable for testing the hypotheses that extended clonal phases and weak sexual recruitment inhibit speciation. Although common garden experiments have revealed a genetic component to the morphotypic variation, the evolutionary significance of the morphotypes remains controversial. METHODOLOGY/PRINCIPAL FINDINGS: In the present study, we tested the hypothesis of a single polymorphic species (i.e., mixing occurs but selection maintains genes for morphology) in four northern European lakes where the morphotypes coexist. Our evidence is based on nuclear DNA sequence, mitochondrial DNA sequence, and morphometric analysis of coexisting morphotypes. We found significant genetic differentiation, genealogical exclusivity, and morphometric differentiation for coexisting morphotypes. CONCLUSIONS: We conclude that the studied morphotypes represent a group of young species undergoing speciation with apparent reproductive barriers despite coexistence in the freshwater pelagic zone.
Subject(s)
Crustacea/genetics , Animals , Breeding , Crustacea/classification , Crustacea/physiology , DNA, Mitochondrial/genetics , Europe , Fresh WaterABSTRACT
BACKGROUND: Geometric morphometric methods of capturing information about curves or outlines of organismal structures may be used in conjunction with canonical variates analysis (CVA) to assign specimens to groups or populations based on their shapes. This methodological paper examines approaches to optimizing the classification of specimens based on their outlines. This study examines the performance of four approaches to the mathematical representation of outlines and two different approaches to curve measurement as applied to a collection of feather outlines. A new approach to the dimension reduction necessary to carry out a CVA on this type of outline data with modest sample sizes is also presented, and its performance is compared to two other approaches to dimension reduction. RESULTS: Two semi-landmark-based methods, bending energy alignment and perpendicular projection, are shown to produce roughly equal rates of classification, as do elliptical Fourier methods and the extended eigenshape method of outline measurement. Rates of classification were not highly dependent on the number of points used to represent a curve or the manner in which those points were acquired. The new approach to dimensionality reduction, which utilizes a variable number of principal component (PC) axes, produced higher cross-validation assignment rates than either the standard approach of using a fixed number of PC axes or a partial least squares method. CONCLUSION: Classification of specimens based on feather shape was not highly dependent of the details of the method used to capture shape information. The choice of dimensionality reduction approach was more of a factor, and the cross validation rate of assignment may be optimized using the variable number of PC axes method presented herein.
ABSTRACT
Canalization may play a critical role in molding patterns of integration when variability is regulated by the balance between processes that generate and remove variation. Under these conditions, the interaction among those processes may produce a dynamic structure of integration even when the level of variability is constant. To determine whether the constancy of variance in skull shape throughout most of postnatal growth results from a balance between processes generating and removing variation, we compare covariance structures from age to age in two rodent species, cotton rats (Sigmodon fulviventer) and house mice (Mus musculus domesticus). We assess the overall similarity of covariance matrices by the matrix correlation, and compare the structures of covariance matrices using common subspace analysis, a method related to common principal components (PCs) analysis but suited to cases in which variation is so nearly spherical that PCs are ambiguous. We find significant differences from age to age in covariance structure and the more effectively canalized ones tend to be least stable in covariance structure. We find no evidence that canalization gradually and preferentially removes deviations arising early in development as we might expect if canalization results from compensatory differential growth. Our results suggest that (co)variation patterns are continually restructured by processes that equilibrate variance, and thus that canalization plays a critical role in molding patterns of integration.
Subject(s)
Sigmodontinae/growth & development , Skull/growth & development , Anatomy, Comparative , Animals , Mice , Morphogenesis , Principal Component Analysis , Skull/anatomy & histologyABSTRACT
Although it is well known that many mutations influence phenotypic variability as well as the mean, the underlying mechanisms for variability effects are very poorly understood. The brachymorph (bm) phenotype results from an autosomal recessive mutation in the phosphoadenosine-phosphosulfate synthetase 2 gene (Papps2). A major cranial manifestation is a dramatic reduction in the growth of the chondrocranium which results from undersulfation of glycosaminoglycans (GAGs) in the cartilage matrix. We found that this reduction in the growth of the chondrocranium is associated with an altered pattern of craniofacial shape variation, a significant increase in phenotypic variance and a dramatic increase in morphological integration for craniofacial shape. Both effects are largest in the basicranium. The altered variation pattern indicates that the mutation produces developmental influences on shape that are not present in the wildtype. As the mutation dramatically reduces sulfation of GAGs, we infer that this influence is variation among individuals in the degree of sulfation, or variable expressivity of the mutation. This variation may be because of genetic variation at other loci that influence sulfation, environmental effects, or intrinsic effects. We infer that chondrocranial development exhibits greater sensitivity to variation in the sulfation of chondroitin sulfate when the degree of sulfation is low. At normal levels, sulfation probably contributes minimally to phenotypic variation. This case illustrates canalization in a particular developmental-genetic context.
Subject(s)
Multienzyme Complexes/genetics , Skull/growth & development , Sulfate Adenylyltransferase/genetics , Anatomy, Comparative , Animals , Female , Gene Expression Regulation, Enzymologic , Genetic Variation , Male , Mice , Mice, Inbred C57BL , Mice, Mutant Strains , Morphogenesis , Mutation , Phenotype , Skull/anatomy & histologyABSTRACT
BACKGROUND: Hybridization receives attention because of the potential role that it may play in generating evolutionary novelty. An explanation for the emergence of novel phenotypes is given by transgressive segregation, which, if frequent, would imply an important evolutionary role for hybridization. This process is still rarely studied in natural populations as samples of recent hybrids and their parental populations are needed. Further, the detection of transgressive segregation requires phenotypes that can be easily quantified and analysed. We analyse variability in body shape of divergent populations of European sculpins (Cottus gobio complex) as well as natural hybrids among them. RESULTS: A distance-based method is developed to assign unknown specimens to known groups based on morphometric data. Apparently, body shape represents a highly informative set of characters that parallels the discriminatory power of microsatellite markers in our study system. Populations of sculpins are distinct and "unknown" specimens can be correctly assigned to their source population based on body shape. Recent hybrids are intermediate along the axes separating their parental groups but display additional differentiation that is unique and coupled with the hybrid genetic background. CONCLUSION: There is a specific hybrid shape component in natural sculpin hybrids that can be best explained by transgressive segregation. This inference of how hybrids differ from their ancestors provides basic information for future evolutionary studies. Furthermore, our approach may serve to assign candidate specimens to their source populations based on morphometric data and help in the interpretation of population differentiation.
ABSTRACT
Variation in neonatal maturity among mammals is often explained by variation in gestation length, but species may also differ in developmental rate, a quantity that is difficult to measure because the conventional formalism makes two important and potentially unrealistic assumptions: (1) ontogeny of form can be described by a single line, and (2) species have the same ontogeny of form. We examine two species, one precocial (Sigmodon fulviventer), the other altricial (Mus musculus domesticus), and find that neither assumption is met. Therefore, we introduce an alternative metric, the rate of shape differentiation away from the average neonate. We find that S. fulviventer has a lower developmental rate than M. m. domesticus; consequently, while more mature at birth, S. fulviventer loses ground to M. m. domesticus over time. Surprisingly, despite differences in gestation length and developmental rate, these species reach developmental and life-history milestones at nearly identical degrees of skull shape maturity.