Patterns Of Morphological Variation Research Articles

Patterns of Morphological Variation of Extant Sloth Skulls and their Implication for Future Conservation Efforts

ABSTRACTSeveral studies have shown an increased morphological variability of sloths from mammalian norms, affecting varied phenotypic traits from skeletal parts to soft tissues. We present here the first descriptive comparison of the whole skull morphology within the two extant sloth genera, combining geometric morphometric approaches with comparative anatomy. We used these methods to explore the patterns of the intra‐ and interspecific morphological variation of the skull with regard to several factors such as phylogeny, geography, allometry, or sexual dimorphism. Our study first revealed strong phylogenetic and geographical imprints on the cranial and mandibular morphological traits. This result demonstrates the importance of accurate knowledge of species and their geographical distributions; here we show from an example pertaining to Bradypus variegatus populations the implications this has on conservation management. Moreover, in order to control the amount of this detected variation, we tentatively compared sloths to a wide range of mammalian species. Our analysis found no significant increase in the average deviation of skull shape within each investigated sloth species compared to other mammals. This suggests that the intraspecific cranial variation in sloths does not depart significantly from the variation observed in other mammals. This result has positive implications for the demarcation of anatomical regions that maintain high levels of morphological variation in sloths. Anat Rec, 297:979–1008, 2014. © 2014 Wiley Periodicals, Inc.

Patterns of morphological variation of extant sloth skulls and their implication for future conservation efforts.

Several studies have shown an increased morphological variability of sloths from mammalian norms, affecting varied phenotypic traits from skeletal parts to soft tissues. We present here the first descriptive comparison of the whole skull morphology within the two extant sloth genera, combining geometric morphometric approaches with comparative anatomy. We used these methods to explore the patterns of the intra- and interspecific morphological variation of the skull with regard to several factors such as phylogeny, geography, allometry, or sexual dimorphism. Our study first revealed strong phylogenetic and geographical imprints on the cranial and mandibular morphological traits. This result demonstrates the importance of accurate knowledge of species and their geographical distributions; here we show from an example pertaining to Bradypus variegatus populations the implications this has on conservation management. Moreover, in order to control the amount of this detected variation, we tentatively compared sloths to a wide range of mammalian species. Our analysis found no significant increase in the average deviation of skull shape within each investigated sloth species compared to other mammals. This suggests that the intraspecific cranial variation in sloths does not depart significantly from the variation observed in other mammals. This result has positive implications for the demarcation of anatomical regions that maintain high levels of morphological variation in sloths.

The influence of environmental factors on the morphology of red-backed volesMyodes gapperi(Rodentia, Arvicolinae) in Québec and western Labrador

Geographical patterns of morphological variation in small mammals are often associated with environmental factors. The southern red-backed vole Myodes gapperi is a widespread and abundant small mammal in Canada, occurring in environments as diverse as mixed-wood forests and taiga. First upper molars and skulls from nine populations of southern red-backed voles distributed across three ecozones and approximately 10° of latitude were analysed by means of geometric morphometric techniques, and their relationships with environmental variables were examined. A weak, non-linear trend of size increase towards higher latitudes was observed in voles' skulls. Environmental variables appeared to be important drivers of shape differentiation among populations from the three distinct ecozones analysed. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112, 204–218.

Scale-dependent adaptive evolution and morphological convergence to climatic niche in Californian eriogonoids (Polygonaceae)

Aim Macroevolutionary patterns and processes change substantially depending on levels of taxonomic and ecological organization, and the resolution of environmental and spatial variability. In comparative methods, the resolution of environmental and spatial variability often defines the number of selective regimes used to test whether phenotypic characteristics are adaptively correlated with the environment. Here, we examine how investigator choice of the number of selective regimes, determined by varying the resolution of among-species variability in the species climatic niche (hereafter called ‘ecological scale’), influences trait morphological diversification among Eriogonoideae species. We assess whether adaptive or neutral processes drive the evolution of several morphological traits in these species. Location South-western North America. Methods We applied a phylogenetic framework of three evolutionary models to four morphological traits and the climatic niches of Eriogonoideae (in the buckwheat family, Polygonaceae). We tested whether morphological traits evolve in relation to climate by adaptive or neutral process, and whether the resulting patterns of morphological variability are conserved or convergent across the clade. We inspected adaptive models of evolution under different levels of resolution of among-species variability of the climatic niche. Results We show that morphological traits and climate niches of Eriogonoideae species are not phylogenetically conserved. Further, adaptive evolution of phenotypic traits is specific to climatic niche occupancy across this clade. Finally, the likely evolutionary process and the level of detectable niche conservatism change depending on the resolution of environmental variability of the climatic niche. Main conclusions Our study demonstrates the need to consider both the resolution of environmental variability and alternative evolutionary models to understand the morphological diversification that accompanies divergent adaptive evolution of lineages to climatic conditions.

Patterns of morphological variation in enamel-dentin junction and outer enamel surface of human molars.

Tooth crown patterning is governed by the growth and folding of the inner enamel epithelium (IEE) and the following enamel deposition forms outer enamel surface (OES). We hypothesized that overall dental crown shape and covariation structure are determined by processes that configurate shape at the enamel-dentine junction (EDJ), the developmental vestige of IEE. This this hypothesis was tested by comparing patterns of morphological variation between EDJ and OES in human permanent maxillary first molar (UM1) and deciduous second molar (um2). Using geometric morphometric methods, we described morphological variation and covariation between EDJ and OES, and evaluated the strength of two components of phenotypic variability, canalization and morphological integration, in addition to the relevant evolutionary flexibility, i.e. the ability to respond to selective pressure. The strength of covariation between EDJ and OES was greater in um2 than in UM1, and the way that multiple traits covary between EDJ and OES was different between these teeth. The variability analyses showed that EDJ had less shape variation and a higher level of morphological integration than OES, which indicated that canalization and morphological integration acted as developmental constraints. These tendencies were greater in UM1 than in um2. On the other hand, EDJ and OES had a comparable level of evolvability in these teeth. Amelogenesis could play a significant role in tooth shape and covariation structure, and its influence was not constant among teeth, which may be responsible for the differences in the rate and/or period of enamel formation.

Geographic Variation among Closely Related, Highly Variable Species with a Wide Distribution Range: the South Andean-Patagonian <I>Nassauvia</I> subgenus <I>Strongyloma</I> (Asteraceae, Nassauvieae)

Morphological variation among the five species of Nassauvia subgenus Strongyloma was assessed through statistical analyses of morphometric traits in populations throughout the southern Andean-Patagonian region. Uni- and multivariate analyses were used to identify patterns of morphological variation in relation to geography. Additionally, species distribution modeling was implemented to relate these patterns to climatic conditions. No well-defined groups could be recovered through multivariate analyses, although we observed some geographic structure. Latitudinal variation was found in leaves, phyllaries and cypselas, with a cline towards the south, where these structures become shorter and wider. Towards the east, the number of flowers per capitulum decreases, and abaxial corolla lips and cypselas become narrower and shorter. Distribution modeling showed several areas of contact and a large overlap of suitable conditions for more than one species, which is mainly related to the mean temperature of winter. Despite an association between morphological variation with geography and climate, actual geographic distributions of the putative species did not entirely match the clinal pattern of morphology, geography, and climate. Further genetic analyses are still needed to identify the probable processes that led to the complex patterns of observed variation.

PHENOTYPIC DIVERSITY OF SOME OLIVE TREE PROGENIES ISSUED FROM A TUNISIAN BREEDING PROGRAM

This work was done to quantify and to evaluate the distribution of the genetic diversity observed within and between olive tree seedlings issued from a Tunisian breeding program. Forty-eight ‘Chemlali’ olive tree seedlings which were issued from free-, self-, and cross pollination of cultivar ‘Chemlali’ with ‘Coratina’ were characterized by combining 17 quantitative and 32 qualitative traits. Principal component analysis was used for the identification of the pattern of morphological variation. Variance analysis revealed significant differences between progenies. Variation coefficients ranged from 8.36 to 32.93% for ‘Chemlali’ ×’Coratina’ descendants, from 7.93 to 80.91% for ‘Chemlali’ free pollination descendants and from 10.38 to 74.88% for ‘Chemlali’ self pollination descendants. Shannon and Nei indices indicated also the variation between descendants within crossings. However, some seedlings showed tree, leaf, fruit and endocarp shapes and sizes which differs from the typical of ‘Chemlali’ cultivar. An increase of the fruit size and an improvement of the flesh to stone ratio were noted; thus the first three principal components explained 72% of the total observed variability. PC1 was mainly correlated to fruit and endocarp sizes and flesh to stone ratio; and PC2 was mainly correlated to fruit and endocarp shapes. Descendants’clustering was done according to the main discriminant parameter which is the fruit size. Most ‘Chemlali’ × ‘Coratina’ descendants were closely clustered. ‘Chemlali’ free and self pollination descendants were not closely grouped, but shows clear overlapping data, which suggests that these two types of pollination can induce a comparative morphological variability.

Processes Underpinning Development and Maintenance of Diversity in Rice in West Africa: Evidence from Combining Morphological and Molecular Markers

We assessed the interplay of artificial and natural selection in rice adaptation in low-input farming systems in West Africa. Using 20 morphological traits and 176 molecular markers, 182 farmer varieties of rice (Oryza spp.) from 6 West African countries were characterized. Principal component analysis showed that the four botanical groups (Oryza sativa ssp. indica, O. sativa ssp. japonica, O. glaberrima, and interspecific farmer hybrids) exhibited different patterns of morphological diversity. Regarding O. glaberrima, morphological and molecular data were in greater conformity than for the other botanical groups. A clear difference in morphological features was observed between O. glaberrima rices from the Togo hills and those from the Upper Guinea Coast, and among O. glaberrima rices from the Upper Guinea Coast. For the other three groups such clear patterns were not observed. We argue that this is because genetic diversity is shaped by different environmental and socio-cultural selection pressures. For O. glaberrima, recent socio-cultural selection pressures seemed to restrict genetic diversity while this was not observed for the other botanical groups. We also show that O. glaberrima still plays an important role in the selection practices of farmers and resulting variety development pathways. This is particularly apparent in the case of interspecific farmer hybrids where a relationship was found between pericarp colour, panicle attitude and genetic diversity. Farmer varieties are the product of long and complex trajectories of selection governed by local human agency. In effect, rice varieties have emerged that are adapted to West African farming conditions through genotype × environment × society interactions. The diversity farmers maintain in their rice varieties is understood to be part of a risk-spreading strategy that also facilitates successful and often serendipitous variety innovations. We advocate, therefore, that farmers and farmer varieties should be more effectively involved in crop development.

Phylogeny of Euonymus inferred from molecular and morphological data

AbstractEuonymus, a cosmopolitan genus of the family Celastraceae, has its species diversity centered in East Asia. It exhibits a complex pattern of morphological variation, making its taxonomy difficult. Monophyly of the genus remains uncertain, and the evolutionary implications of the infrageneric division and delimitation of many species are debatable. In this study, we sampled a total of 62 accessions representing 48 species/taxa covering a broad range of diversity of the genus and its allies. We first investigated the phylogeny of Euonymus using DNA sequences of multiple nuclear and plastid markers, and then used this phylogeny to discuss the circumscription and classification of the genus in combination with evolution of fruit characters, which has been used as an important criterion for the generic subdivision. The resultant data revealed the monophyly of Euonymus sensu lato with inclusion of Glyptopetalum, resolved the major lines of phylogeny of the genus, and clarified the echinate and winged capsules each as lineage‐specific. Therefore, among the five sections accepted by Flora of China, only Sect. Echinococcus (with spiny fruits) and Sect. Kalonymus (with winged fruits) correspond to the molecular grouping. The globose capsule may represent an ancestral character state, and the other types of fruits, that is, the shallowly to deeply lobed capsules, may belong to a broad range of continuous variation derived from the globose.

Morphological differentiation among geographically close populations of the green crab Carcinus aestuarii Nardo, 1847 (Brachyura, Carcinidae) from the Tunisian coast

In the present study, we assessed patterns of morphological variation among populations of the Mediterranean green crabCarcinus aestuariiNardo, 1847 from the Tunisian coast. Eleven morphometric traits were measured on 464 specimens from nine sites, and the pattern of morphological variation among sites was assessed using multivariate approach. Non-parametric MANOVA (NPMANOVA) and non-metric Multidimensional Scaling (MDS) analyses revealed statistically significant differences among the studied locations for both sexes proving that natural variability of the measured traits differs clearly between locations. Canonical discriminant analysis (CDA), on the other hand, showed that over 36% of individuals could be assigned to their location of origin on the basis of their morphology. Correct assignment of individuals to their location was much higher (over 63%) when sites were combined into three regional groups and marked morphological differentiation was found in both sexes. A positive correlation was noted between the squared Mahalanobis distances () and the geographic distances for both male and female green crab populations suggesting isolation by distance. The results obtained indicate that morphological divergence among populations of the green crab can occur over shorter distances than expected based on dispersal potential. Possible drivers of the observed pattern of morphological variation are discussed.

A three-dimensional analysis of the morphological evolution and locomotor behaviour of the carnivoran hind limb.

BackgroundThe shape of the appendicular bones in mammals usually reflects adaptations towards different locomotor abilities. However, other aspects such as body size and phylogeny also play an important role in shaping bone design.We used 3D landmark-based geometric morphometrics to analyse the shape of the hind limb bones (i.e., femur, tibia, and pelvic girdle bones) of living and extinct terrestrial carnivorans (Mammalia, Carnivora) to quantitatively investigate the influence of body size, phylogeny, and locomotor behaviour in shaping the morphology of these bones. We also investigated the main patterns of morphological variation within a phylogenetic context.ResultsSize and phylogeny strongly influence the shape of the hind limb bones. In contrast, adaptations towards different modes of locomotion seem to have little influence. Principal Components Analysis and the study of phylomorphospaces suggest that the main source of variation in bone shape is a gradient of slenderness-robustness.ConclusionThe shape of the hind limb bones is strongly influenced by body size and phylogeny, but not to a similar degree by locomotor behaviour. The slender-robust “morphological bipolarity” found in bone shape variability is probably related to a trade-off between maintaining energetic efficiency and withstanding resistance to stresses. The balance involved in this trade-off impedes the evolution of high phenotypic variability. In fact, both morphological extremes (slender/robust) are adaptive in different selective contexts and lead to a convergence in shape among taxa with extremely different ecologies but with similar biomechanical demands. Strikingly, this “one-to-many mapping” pattern of evolution between morphology and ecology in hind limb bones is in complete contrast to the “many-to-one mapping” pattern found in the evolution of carnivoran skull shape. The results suggest that there are more constraints in the evolution of the shape of the appendicular skeleton than in that of skull shape because of the strong biomechanical constraints imposed by terrestrial locomotion.

Spatial Variation in Morphometry inVanzosaura rubricauda(Squamata, Gymnophthalmidae) from Open Habitats of South America and its Environmental Correlates

Patterns of geographical variation in morphology provide an empirical framework for testing the effects of ecological and historical factors on species differentiation. Environmental gradients play an important role in intraspecific differentiation through morphological adaptation in locations with distinct selective pressures. Vanzosaura rubricauda is a small microteiid lizard that is widespread in the great diagonal of dry biomes of South America, occurring in Cerrado, Caatinga, and Chaco open habitats with contrasting environmental conditions. Using multivariate morphometrics and spatial analysis, we show that V. rubricauda presents a structured pattern of geographic variation, with populations of the eastern Cerrado being distinct in morphometry. Geographical variation was observed in size and shape, with a general trend of contrast between trunk length and forelimb length among populations. Ecogeographical models that best explained geographic patterns of variation were aridity and precipitation.

SEX-SPECIFIC PATTERNS OF MORPHOLOGICAL DIVERSIFICATION: EVOLUTION OF REACTION NORMS AND STATIC ALLOMETRIES IN NERIID FLIES

The consequences of sex-specific selection for patterns of diversification remain poorly known. Because male secondary sexual traits are typically costly to express, and both costs and benefits are likely to depend on ambient environment and individual condition, such traits may be expected to diversify via changes in reaction norms as well as the scaling of trait size with body size (static allometry). We investigated morphological diversification within two species of Australian neriid flies (Telostylinus angusticollis, Telostylinus lineolatus) by rearing larvae from several populations on larval diets varying sixfold in nutrient concentration. Mean body size varied among populations of T. angusticollis, but body size reaction norms did not vary within either species. However, we detected diversification of reaction norms for body shape in males and females within both species. Moreover, unlike females, males also diversified in static allometry slope and reaction norms for static allometry slope of sexual and nonsexual traits. Our findings reveal qualitative sex differences in patterns of morphological diversification, whereby shape-size relationships diversify extensively in males, but remain conserved in females despite extensive evolution of trait means. Our results highlight the importance of incorporating plasticity and allometry in studies of adaptation and diversification.

Revalidation of Saguinus ursula Hoffmannsegg (Primates: Cebidae: Callitrichinae).

In this study, we review the taxonomy of Saguinus niger (É. Geoffroy) and revalidate Saguinus ursula Hoffmannsegg as a distinct species. The revalidation is based on pelage coloration, and the pattern of morphological divergence is corroborated by molecular data. Samples from the east bank of the Tocantins River (S. ursulus) were distinct from specimens of S. niger from the west bank in having mid-dorsal hair with an wide (5.0-55 mm) intermediary band of bright and golden buffy color; long (ca. 23-26 mm) dorsal hair at the inter-scapular region; and naked (not noticeably haired) face, hands and fingers. Saguinus ursulus and S. niger are allopatric, and Tocantins River is putatively acting as an effective barrier for gene flow. A lectotype to S. ursulus from syntypes was designated.

Morphometric Studies of Clausena anisata (Willd.) Hook. f. ex. Benth. in Coastal Savanna Zone of Ghana

Numerical taxonomic study was conducted on five populations of C. anisata in the coastal savanna zone of Ghana to determine their patterns of taxonomic variation and identify diagnostic characters among the populations studied. The results showed that the five populations of C. anisata exhibited complex patterns of morphological variation. The study also revealed that the populations studied could be phenetically classified into two main clusters. The phenetic groupings identified could not be considered as botanical varieties because of the complex patterns of morphological variation. From the numerical character analysis, morphological characters like peduncle length, ratio of sepal length to width, number of floral branches per inflorescence, anther length, style diameter, filament length, style length, plant height, petiole diameter, sepal length and petal length were identified as diagnostic morphological characters. Even though the phenetic groups identified within C. anisata could not be classified as morphological varieties, they could still be described and documented for general purposes such as communication, management and conservation but not for traditional taxonomic purposes.

Study of the polymorphism of the PatagonianCalceolaria polyrhiza(Calceolariaceae) using decision tree and sequential covering rule induction

Climate and landscape changes that occurred in Patagonia during the Pleistocene presumably led to the ample biodiversity that currently characterizes the region. Many Patagonian species constitute unresolved complexes that may be related to these environmental changes. Accordingly, discriminating among taxonomic entities within an endemic and widely distributed species in Patagonia would enable a better understanding of the diversification processes that occurred in the recent past. We explored the polymorphism of Calceolaria polyrhiza, a widely distributed species for which phylogeographic studies suggest a recent diversification, with the aim of disentangling the morphological variability patterns in this species. We employed quantitative and qualitative floral and vegetative traits, including geometric morphometric variables. We used two clustering algorithms, testing for correspondence between detected clusters and the species previously described for the complex. Finally, we described these clusters using decision trees and sequential covering rule induction. Major clusters were determined, which match the previously described species. Floral traits related to corolla design and shape were the most useful characters for distinguishing groups and the variation patterns in these traits might be associated with historical and ecological factors. The need for conducting plant systematic studies using techniques that ensure objective taxonomic delimitations and descriptions is stressed. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 487–500.

CONSTRAINTS ON MAMMALIAN FORELIMB DEVELOPMENT: INSIGHTS FROM DEVELOPMENTAL DISPARITY

Tetrapod limb development has been studied extensively for decades, yet the strength and role of developmental constraints in this process remains unresolved. Mammals exhibit a particularly wide array of limb morphologies associated with various locomotion modes and behaviors, providing a useful system for identifying periods of developmental constraint and conserved developmental mechanisms or morphologies. In this study, landmark-based geometric morphometrics are used to investigate levels and patterns of morphological diversity (disparity) among the developing forelimbs of four mammals with diverse limb morphologies: mice, opossums, horses, and pigs. Results indicate that disparity among the forelimbs of these species slightly decreases or stays the same from the appearance of the limb ridge to the bud stage, and increases dramatically from the paddle through tissue regression stages. Heterochrony exhibited by the precocial opossum limb was not found to drive these patterns of morphological disparity, suggesting that the low disparity of the middle stages of limb development (e.g., paddle stage) is driven by processes operating within the limb and is likely not a result of embryo-wide constraint.

Character intercorrelation and the potential role of phenotypic plasticity in orchids: a case study of the epiphyte Liparis resupinata

Character intercorrelation was studied in a natural population of the epiphytic orchid Liparis resupinata in northern Thailand, and patterns of morphological variation in relation to the local growth environment of individual plants were mapped. Massive occurrence of character intercorrelation was detected, but clone size only influenced few characters of individual flowering shoots. Variation in vegetative and floral organs was largely independent, but two cases differed from the general pattern: (1) the only character not defined by size (distance between apices of lateral sepals) exhibited largely independent variation; (2) ovary length was positively correlated with nearly all other characters. Major groups of vegetative and floral characters were found to covary with different combinations of ecological parameters. Although our study does not document the existence of phenotypic plasticity in L. resupinata, the overall patterns observed would be congruent with a scenario involving phenotypic plasticity. No positive correlation between variability and apparent morphological susceptibility to environmental influence was found; but floral characters were generally less variable and covaried with more ecological parameters than vegetative characters. Based on our observations, we make a few methodological recommendations for morphometric studies of species complexes.

Phenotypic characterization of indigenous rice (Oryza sativa L.) germplasm collected from the state of Nagaland, India

Nagaland is one of the eight states in the north-eastern region of India, where a considerable diversity exists in cultivated rice. Recent exploration in this tribal-dominated state has resulted in a collection of 130 rice accessions growing under diverse agroecological conditions. The agromorphological characterization data of 124 rice landraces revealed a significant variability in plant architecture and grain morphological and quality traits. Multivariate analyses including principal component analysis (PCA) and cluster analysis were performed to assess the patterns of morphological variation. The PCA extracted 12 components, which explained 75.4% of the total variation for 38 quantitative and qualitative traits. The cluster analysis grouped 124 rice landraces into five clusters, and the number of landraces in each cluster ranged from 1 to 59. The correlations among the traits are discussed, which will be useful in considering traits for genetic improvement in grain yield and quality. The landraces have been conserved in the national genebank for further utilization.

Numerical taxonomy of the genus <i>Senna</i> Mill. from Bangladesh

This study examines the patterns of morphological variation and phenetic relationships among 11 species of Senna Mill. from Bangladesh using 32 vegetative and floral characters. The highest similarity is found between S. obtusifolia and S. tora, while the highest variation is observed between S. alata and S. hirsuta. UPGMA tree derived from cluster analysis reveals three major clusters, the first of which consists of two species (S. alata and S. auriculata), the second cluster comprises four species (S. hirsuta, S. obtusifolia, S. tora and S. occidentalis) and the third one is composed of five species (S. multiglandulosa, S. sophera, S. siamea, S. timoriensis and S. surattensis). A close relationship is also found between S. multiglandulosa and S. sophera, and between S. siamea and S. timoriensis. Results obtained from the present study are found congruent with cytological and anatomical studies showing the significance of numerical analysis for taxonomic relationship in the genus Senna.DOI: http://dx.doi.org/10.3329/bjpt.v20i1.15467Bangladesh J. Plant Taxon. 20(1): 77-83, 2013 (June)