Quantitative Analysis of Flabellophyton from the Ediacaran Lantian Biota, South China: Application of Geometric Morphometrics in Precambrian Fossil Research

As a more efficient quantitative method for morphological analysis, geometric morphometrics is applied to the flabellate fossils Flabellophyton including Flabellophyton lantianensis and Flabellophyton strigata from Neoproterozoic Ediacaran Lantian biota, South China. Both traditional morphometric analysis （including diverging angle, length, and width distribution） and geometric morphometric analysis [including superposition of normalized area analysis, non-metric multidimensional scaling （n-MDS）, Bray-Curtis similarity cluster analysis （CLUSTER） and analysis of similarities （ANOSIM）[ were performed. The results indicate there are great interspecific morphological differences between F. lantianensis and F. strigata, in addition to some intraspecific variations within each species. Here we preliminarily suggest that the previously defined Flabellophyton should be subdivided into 2 genera at least： one marked by the dark transverse striated structure, and the other without. This recharacterization and reclassification work still needs further careful observation and comprehensive analysis with large number of flabeilate fossils combining morphology, structure, population, and community-ecology study.

Geometric morphometrics:Current and future in China

Although there were many ancient Chinese mathematicians contributed a lot on geometry, Geometric morphometrics （GM） in modern concept was not firstly proposed by Chinese. The super capability of geometric morphometries in scientific computing and problem solving has gained a lot of attentions in the world. Until early of 21 centuries, geometric morphometries was introduced into China. Since then, GM was rapidly applied in many research fields. However, it is a pity that GM is still not well-known in China as many works are published out of China. Thus, the special issue ＂Geometric morphometrics： Current shape and future directions＂ is organized. The present issue presents a series of contributions in this scientific field. In future, there will be many considerable new developing fields on GM needed to pay more attentions, for instances, 3D geometric morphometrics, 4D analysis, visualization of amber, new machine developing, new software developing, automatic identification system, etc. Once these technical bottle-necks on 3D data collecting and merging geometric morphometric data from multiple characters could be solved, the automatic identification system and other fields based on Big Data would come true.

Geometric morphometrics of mandibles for dietary differentiation of Bovidae(Mammalia:Artiodactyla)

The mammalian family Bovidae has been widely studied in ecomorphological research,with important applications to paleoecological and paleohabitat reconstructions.Most studies of bovid craniomandibular features in relation to diet have used linear measurements.In this study,we conduct landmark-based geometric-morphometric analyses to evaluate whether different dietary groups can be distinguished by mandibular morphology.Our analysis includes data for 100 species of extant bovids,covering all bovid tribes and 2 dietary classifications.For the first classification with 3 feeding categories,we found that browsers(including frugivores),mixed feeders,and grazers are moderately well separated using mandibular shape.A finer dietary classification(frugivore,browser,browser-grazer intermediate,generalist,variable grazer,and obligate grazer)proved to be more useful for differentiating dietary extremes(frugivores and obligate grazers)but performed equally or less well for other groups.Notably,frugivorous bovids,which belong in tribe Cephalophini,have a distinct mandibular shape that is readily distinguished from all other dietary groups,yielding a 100%correct classification rate from jackknife cross-validation.The main differences in mandibular shape found among dietary groups are related to the functional needs of species during forage prehension and mastication.Compared with browsers,both frugivores and grazers have mandibles that are adapted for higher biomechanical demand of chewing.Additionally,frugivore mandibles are adapted for selective cropping.Our results call for more work on the feeding ecology and functional morphology of frugivores and offer an approach for reconstructing the diet of extinct bovids.

The Woodcock＇s head： Resolving a morphological oddity using geometric morphometrics

The scope of shape analysis based on geometric morphometrics has evolved into underscoring complex patterns of multidimensional shape change with multivariate statistical modelling （e.g., allometry, morphological integration, etc.）. Such breakthrough was made possible because the method relies on a consistent comparative reference system to compare shapes, the latter which is computed using the Cartesian coordinates of homologous landmarks. It has been shown elsewhere that traditional comparative reference systems based on anatomy, and oriented in stereotyped postures, such as the Frankfurt plane at rest, the Lateral Semicircular Canal when the animal is in alert, or the cranial floor when the animal is flying, are all inconsistent for anatomical comparisons. They vary too much and unpredictably across species. An extraordinary example of the problems that can arise in descriptive and comparative anatomy when using such reference systems is the traditional interpretation of the head of the Woodcock. Anywhere in literature it is written that the eyes of this gamebird are oriented backwards to protect itself from predators. Here, using geometric morphometrics it is demonstrated that the woodcock＇s skull is highly transformed, yet following a normal trend among birds. In turn, using GM it is demonstrated that the collective wisdom about this oddity is simply the result of interpreting the anatomy of its skull using unreliable reference systems.

Intraspecific leaf morphological variation in Quercus dentata Thunb.:a comparison of traditional and geometric morphometric methods,a pilot study

To compare the application of traditional morphometric methods(TMMs)and geometric morphometric methods(GMMs)in the study of intraspecific leaf morphological characters of Quercus dentata,fifteen linear measurement indices and thirteen landmarks of leaves were used to study leaf morphology of three provenances(H1,H2,and H3).In TMMs,principal component analysis(PCA)showed that leaf size–related indices played an important role in population classification.Partial least square(PLS)analysis showed that the main morphological characters affecting leaf size were the average depth of the lobes and the length–width ratios.However,the important indices to distinguish the provenances were circularity,leaf width,and length–width ratio.The results of discriminant analysis(DA)showed that 74.0%of H1,68.0%of H2,and 74.0%of H3 were correctly classified.Cluster analysis showed that the Mahalanobis distances between H1 and H2,H1 and H3,and H2 and H3 were 4.3761,11.4629,and 10.2067,respectively.In GMMs,PCA based on symmetrical components showed that the difference in leaf morphology was mainly due to the changing trend of the leaf apex and base,petiole length,and degree of leaf cracking.PLS analysis showed that there was a significant covariation between the leaf symmetrical components and size:as the leaf enlarged,the widest part gradually moved up,and the shape changed from nearly oval to lanceolate.DA results showed that 86.0%and 78.0%of H1 and H2,70.0%and 80.0%of H1 and H3,and 82.0%and 76.0%of H2 and H3 were correctly classified.Canonical variate analysis results showed that the Mahalanobis distances between H1 and H2,H1 and H3,and H2 and H3 were 1.7238,1.5380,and 1.6329,respectively.Both GMMs and TMMs showed significant differences in morphology among the three Q.dentata provenances,but GMMs had higher classification accuracy and could provide more information about leaf shape,whereas TMMs could provide more information about leaf size.Based on our results,GMMs are promising in the study of leaf morphological variation within Q.dentata provenances.

Second premolar agenesis is associated with mandibular form： a geometric morphometric analysis of mandibular cross-sections

The aim of this study was to compare mandibular form （i.e., size and shape） between patients with agenesis of the lower second premolar （P2） and a control group with no agenesis. Three hypotheses were tested： （H1） agenesis causes a change in mandibular morphology because of inadequate alveolar ridge development in the area of the missing tooth （mandibular plasticity）; （H2） agenesis is caused by spatial limitations within the mandible （dental plasticity）; and （H3） common genetic/ epigenetic factors cause agenesis and affect mandibular form （pleiotropy）. A geometric morphometric analysis was applied to cross-sectional images of computed tomography （CT） scans of three matched groups （n= 50 each）： （1） regularly erupted P2; （2） agenesis of P2 and the primary second molar in situ; and （3） agenesis of P2 and the primary second molar missing for 〉3 months. Cross-sections of the three areas of interest （first premolar, P2, first molar） were digitized with 23 landmarks and superimposed by a generalized Procrustes analysis. On average, the mandibular cross-sections were narrower and shorter in patients with P2 agenesis compared with that in the control group. Both agenesis groups featured a pronounced submandibular fossa. These differences extended at least one tooth beyond the agenesis-affected region. Taken together with the large interindividual variation that resulted in massively overlapping group distributions, these findings support genetic and/or epigenetic pleiotropy （H3） as the most likely origin of the observed covariation between mandibular form and odontogenesis. Clinically, reduced dimensions and greater variability of mandibular form, as well as a pronounced submandibular fossa, should be expected during the treatment planning of patients with P2 agenesis.

Postnatal ontogenetic size and shape changes in the craniums of plateau pika and woolly hare(Mammalia: Lagomorpha)

In the present study, postnatal ontogenetic size and shape changes in the cranium of two lagomorph species, the plateau pika （Ochotona curzoniae） and woolly hare （Lepus oiostolus）, were investigated by geometric morphometrics. The ontogenetic size and shape changes of their cranium exhibited different growth patterns in response to similar environmental pressures on the Qinghai-Tibetan Plateau. The overall size change in the cranium of the plateau pika was slower than that of the woolly hare. The percentage of ontogenetic shape variance explained by size in the woolly hare was greater than that in the plateau pika. The overall shape of the cranium was narrowed in both species, and morphological components in relation to neural maturity showed negative allometry, while those responsible for muscular development showed isometric or positive allometry. The most remarkable shape variations in the plateau pika were associated with food acquisition （temporalis development）, though other remarkable shape variations in the incisive and palatal foramen in the ventral view were also observed. The most important shape change in the woolly hare was demonstrated by the elongation of the nasal bones, expansion of the supra-orbital process and shape variation of the neurocranium.

A tale of two tails:asymmetry in Great Grey Shrike(Lanius excubitor)

Background: Asymmetry in the wild is a controversial, and to date, unresolved subject.Fluctuating asymmetry(FA) is the developmental instability(intra-individual variation) while, directional asymmetry(DA) expresses the asymmetry of the population mean.Methods: We analysed 63 Great Grey Shrike(Lanius excubitor) skins at the Naturalis Biodiversity Center, Leiden, the Netherlands.The black markings on the tails were digitized in order to evaluate the symmetry of the two sides of each shrike.Ptilochronology helped understand if nutritional condition affected symmetry.Results: ANOVA revealed no significant differences in size of the tail between sexes(F = 1.67, p > 0.05).However, there was significant difference in the shape of the black area in feathers between the sexes(F = 2.14, p < 0.05), and males had more elongated and slender black areas.Further, DA was observed only in males, but FA was noted in both sexes.Spearman correlation showed no significant association between FA score and tail features in both the sexes.However, in females, we observed a negative significant correlation between the number of fault and growth bars.The shape of the black area in the tail displayed no statistically significant association with the tail features in both sexes although growth bars influenced tail shape more than the number of fault bars.Conclusions: We concluded that the characteristics discovered by us need to also be checked in the field and if they can be used to sex individuals.Also, chromatic manipulative studies are require to verify if DA influences sexual selection in the Great Grey Shrike.

Unraveling the morphological patterns of a subantarctic eelpout:a geometric morphometric approach

Phenotypic variation in organisms depends on the genotype and the environmental constraints of the habitat that they exploit.Therefore,for marine species inhabiting contrasting aquatic conditions,it is expected tofind covari-ation between the shape and its spatial distribution.We studied the morphology of the head and cephalic sensory canals of the eelpout Austrolycus depressiceps(4.5–22.5 cm TL)across its latitudinal distribution in South Pacific(45°S–55°S).Geometric morphometric analyses show that the shape varied from individuals with larger snout and an extended suborbital canal to individuals with shorter snouts and frontally compressed suborbital canal.There was size variation across the sampled populations,but that size does not have a clear latitudinal gradient.Only 8%of the shape variation relates to this size variation(allometry),represented by a decrease in the relative size of the eye,and a depression of the posterior margin of the head.There were spatial differences in the shape of the head,but these differences were probably caused by allometric effects.Additionally,2 of the canals of the cephalic lateralis pores and the head shape showed modularity in its development.This study shows that the morphology of marinefish with a shallow distribution varies across distances of hundreds of kilometers(i.e.,phenotypic modulation).

Geometric morphometric analysis of Eysarcoris guttiger,E.annamita and E.ventralis(Hemiptera:Pentatomidae)

The genus Eysarcoris can be easily distinguished from other genera through the two spots in the basal angle of the scutellum. Nevertheless, Eysarcoris species show complex variances. Geometric morphometric methods have been increasingly applied to distinguish species and to define the boundary of genera among insects. In the present study, geometric morphometric approach was firstly employed to evaluate the shape variation of three characters （fore wing, hind wing and pygophore） of E. guttiger, E. annamita and E. ventralis using E. aeneus as outgroup to ascertain whether this approach is a reliable method for the taxonomy of Eysarcoris. Analysis was conducted on the landmarks of the three characters of these species. Multivariate regression of procrustes coordinates against centroid size was conducted to test the presence of allometry. Principal component analysis （PCA）, canonical variate analysis （CVA） and cluster analysis were utilized to describe variations in shapes among the studied species. For all of the three characters, though PCA analysis showed some overlap among species, p-values for procrustes distance and mahalanobis distance were all less than 0.0001. The distribution of the three studied species corresponds with their species status. This study demonstrates that the geometric morphometrics of both the fore wing and the hind wing might represent a possible tool for the identification of species within this genus.

A web based tool to merge geometric morphometric data from multiple characters

Geometric morphometrics （GM） is an important method of shape analysis and increasingly used in a wide range of scientific disciplines. Presently, a single character comparison system of geometric morphometric data is used in almost all empirical studies, and this approach is sufficient for many scientific problems. However, the estimation of overall similarity among taxa or objects based on multiple characters is crucial in a variety of contexts （e.g. （semi-）automated identification, phenetic relationships, tracing of character evolution, phylogenetic reconstruction）. Here we propose a new web-based tool for merging several geometric morphometrics data files from multiple characters into a single data file. Using this approach information from multiple characters can be compared in combination and an overall similarity estimate can be obtained in a convenient and geometrically rigorous manner. To illustrate our method, we provide an example analysis of 25 dung beetle species with seven Procrustes superimposed landmark data files representing the morphological variation of body features： the epipharynx, right mandible, pronotum, elytra, hindwing, and the metendosternite in dorsal and lateral view. All seven files were merged into a single one containing information on 649 landmark locations. The possible applications of such merged data files in different fields of science are discussed.

Geometric morphometric study of the skull shape diversification in Sciuridae(Mammalia,Rodentia)

It is generally accepted that the high phenotypic diversity of mammals is a combined result of developmental constraint and ecological adaptation, although the influence of these endogenous and exogenous factors varies in different mammal groups. The rodent family Sciuridae represents an ideal candidate for examining phenotyp­ic diversity in relation to phylogeny and ecological adaptations. In the present study, we investigate the effects of phylogeny and lifestyle on the skull shape in different species of Sciuridae by applying geometric morpho­metric methods. In addition, we investigate the importance of allometry on sciurid skull shape, because results from geometric morphometrics sometimes dispute those of traditional morphometry. Here, we identify signif­icant associations between patristic distances obtained from molecular phylogeny and shape distances in all 3 views of the cranium and the lateral view of the mandible. Multivariate regression demonstrates that shape dif­ferences among lifestyle categories are substantial, especially in the dorsal and ventral structures after the in­fluence of phylogeny is taken into account. Allometry plays an important role in the shape variation, although its importance on different skull structures varies. Our results indicate that complex structures of this highly di­verse mammal group, which occupies different niches, are affected by ecological factors and developmental constraint.

New fossil evidence of the early diversification of scarabs： AIIoioscarabaeus cheni （Coleoptera： Scarabaeoidea） from the Middle Jurassic of Inner Mongolia, China

Scarabaeoidea are known from the Lower Jurassic and may have originated in the Triassic based on fossil evidence and phylogenetic research. However, the early diversification of Scarabaeoidea remains unclear due to the lack of high-quality fossil evidence. Here we describe an exceptionally well-preserved new fossil of Scarabaeoidea, Alloioscarabaeus cheni gen. et sp. nov from the Middle Jurassic Jiulongshan Formation of Inner Mongolia, China. Based on a morphometric analysis using 17 landmarks of the hind wing of Alloioscarabaeus and 10 scarabaeoid families, we found that Alloioscarabaeus cheni gen. et sp. nov clearly does not belong to any of the known scarabaeoid families and, consequently, is a new family, Alloioscarabaeidae fam. nov., was erected. The discovery of Alloioscarabaeus brought further evidence for the early diversification of major scarab lineages which could allow more detail in the palaeobiogeography of the Scarabaeoidea and Northeast of China which might be one of the originating places or an important radiation place during the evolution of Scarabaeoidea. Alloioscarabaeidae were very likely not good diggers and might have fed on decaying organic materials. Based on the evidence we have now, we tend to believe that most families and some subfamilies of Scarabaeoidea were present in the Jurassic period.

Late Eocene sclerophyllous oak from Markam Basin, Tibet, and its biogeographic implications

Sclerophyllous evergreen broad-leaved forests,mainly made up of sclerophyllous oak,Quercus section Heterobalanus(Øerst.)Menitsky,Fagaceae,represent the most typical forest type in the Hengduan Mountains.Their distribution pattern is closely related to the growth and formation of the Qinghai-Tibetan Plateau(QTP).The oldest fossil record of Quercus sect.Heterobalanus so far discovered is from the middle Miocene of the Gazhacun Formation in Namling County,southern Tibet.However,our recent discovery of leaf fossils from the upper Eocene of Lawula Formation in Markam Basin,southeastern Tibet,illustrates that their origin is nearly 20 Myr older than previously assumed.By integrating the results from geometric morphometrics,geographical range expansion,and ecological niche shifts of this section in what is now the QTP and the Hengduan Mountains,we infer that the leaves of Quercus sect.Heterobalanus were already adapted to cool and dry conditions in some local regions no later than in the late Eocene.Then,with the growth of the QTP and late Cenozoic global cooling,the expansion of cooler and drier habitats benefited the spread and development of this section and their leaves exhibited morphological stasis through stabilizing selection.Based on published fossil records and recent discoveries,we argue that Quercus sect.Heterobalanus appeared in the subtropical evergreen and deciduous broad-leaved mixed forests of the southeastern margin of what is now the QTP no later than in the late Eocene.Some taxa spread westwards along the Gangdese Mountains and later the Himalaya,and others spread eastwards and southeastwards,gradually becoming a dominant group of species in the Hengduan Mountains.This dispersal route is contrary to the previous“northwards hypothesis”of this section,and further supports the hypothesis of an East Asian origin for Quercus section Ilex Loudon.

Functional correlates of skull shape in Chiroptera:feeding and echolocation adaptations

Morphological,functional,and behavioral adaptations of bats are among the most diverse within mammals.A strong association between bat skull morphology and feeding behavior has been suggested previously.However,morphological variation related to other drivers of adaptation,in particular echolocation,remains understudied.We assessed variation in skull morphology with respect to ecology(diet and emission type)and function(bite force,masticatory muscles and echolocation characteristics)using geometric morphometrics and comparative methods.Our study suggests that variation in skull shape of 10 bat families is the result of adaptations to broad dietary categories and sound emission types(oral or nasal).Skull shape correlates with echolocation parameters only in a subsample of insectivorous species,possibly because they(almost)entirely rely on this sensory system for locating and capturing prey.Insectivores emitting low frequencies are characterized by a ventrally tilted rostrum,a trait not associated with feeding parameters.This result questions the validity of a trade-off between feeding and echolocation function.Our study advances understanding of the relationship between skull morphology and specific features of echolocation and suggests that evolutionary constraints due to echolocation may differ between different groups within the Chiroptera.

Narrow versus broad:sexual dimorphism in the wing form of western European species of the subgenus Avaritia(Culicoides,Ceratopogonidae)

While wing form is known to differ between males and females of the genus Culicoides,detailed studies of sexual dimorphism are lacking.In this study,we analyze sex-specific differences in the wing form of 5 species of the subgenus Avaritia,using geometric morphometrics and comparative phylogenetic methods.Our results confirm the existence of marked sexual dimorphism in the wing form of the studied species and reveal for the first time that while there is a shared general pattern of sexual shape dimorphism within the subgenus,sexual size dimorphism,and particular features of sexual shape dimorphism differ among species.Sexual shape dimorphism was found to be poorly associated to size and the evolutionary history of the species.The tight association of sexual shape dimorphism with aspect ratio suggests that the shape of the wing is optimized for the type of flight of each sex,that is,dispersal flight in females versus aerobatic flight in males.Moreover,the fact that interspecific shape differences are greater and more strongly associated to aspect ratio in males than in females might be indicating that in males the selective pressures affecting flight performance characteristics are more heterogeneous and/or stronger than in females among the studied species.

Phenotypic plasticity is maintained despite geographical isolation in an African cichlid fish,Pseudocrenilabrus multicolor

Gene flow among populations in different selective environments should favor the evolution of phenotypic plasticity over local adaptation.Plasticity in development is a common response to long-term hypoxia in some widespread African fishes,including Pseudocrenilabrus multicolor,a cichlid that exploits both normoxic(high oxygen)rivers/lakes and hypoxic(low oxygen)swamps.Previous studies have shown that fish from normoxic and hypoxic sites differ in many traits,including gill size,brain size and body shape,and that much of this vari-ation reflects developmental plasticity.However,these earlier studies focused on areas in Uganda where gene flow between swamp and river or lake populations is high.In this study we tested the hypothesis that P.multi-color from a relatively isolated lake population(Lake Saka,Uganda)exhibit low levels of plasticity in traits re-lated to oxygen uptake.Multiple broods of P.multicolor from Lake Saka were reared under low and high dis-solved oxygen,and traits related to gill size,brain mass and body shape were quantified.Surprisingly,both gill size and brain mass showed high levels of developmental plasticity.We suggest that high levels of plasticity,particularly in the gill size of P.multicolor,reflects low costs of maintaining the plastic response,even in rela-tively isolated populations.

Morphological integration and functional modularity in the crocodilian skull

We explored the morphological organization of the skull within Crocodylidae,analyzing functional and phy­logenetic interactions between its 2 constituent functional modules:the rostrum and the postrostrum.We used geometric morphometrics to identify localized shape changes,focusing on the differences between the major clades of the crown-group Crocodylia:Alligatoridae and Crocodylidae.We used published bite performance data to correlate rostral function with postrostral morphology.The skull modules appear more integrated with­in Alligatoridae than within Crocodyliade.Phylogenetic effects on shape variation are more evident in Alligato­ridae than in Crocodylidae,where functional parameters concerning the rostral morphology are proportionally more important than phylogeny.Long-snouted species are characterized by low structural performance,which is significantly associated with a reduction of the pterygoid-quadrate cranial nipper,suggesting that the nipper is important for the ingestion of large food items in generalist species.This functional association is coupled with a significant evolutionary allometry at the clade level,while Alligatoridae and Crocodylidae show different de­grees of evolutionary allometry for their entire shape and rostrum.The postrostrum is more conservative than the rostrum in terms of morphospace occupation,evolutionary allometry and phylogenetic signal.