Geometric morphometric and phylogenetic analyses of Arizona Sky Island populations of Scaphinotus petersi Roeschke (Coleoptera: Carabidae)

Scaphinotus petersi Roeschke, 1907 (Carabidae) is a ground beetle endemic to Sky Islands in south‐eastern Arizona. Previous taxonomic studies described several subspecies with morphological differences inhabiting geographically isolated mountain ranges. We combined molecular sequence data and morphometric data, especially head and pronotum shape analyses, to examine the variation and divergence in subspecies and isolated montane populations. In this study, we employ a combination of distance morphometrics as well as geometric morphometrics to quantify the level of morphological variation, and to test the hypothesis that geographically distinct populations of S. petersi are phenotypically distinct. Results suggest that these isolated populations have diverged morphologically and genetically. Phylogenetic analyses identified two monophyletic lineages within the species that correspond generally to pronotum shape. We observed significant morphological variation among most montane populations in of S. petersi, with the pronotum shape as the clearest delimiting trait. © 2015 The Linnean Society of London     

Traditional morphometrics in plant systematics and its role in palm systematics

A review is given of the role of traditional morphometrics in plant systematics. The three most commonly used techniques of data analysis – Cluster Analysis, Principal Component Analysis and Discriminant Analysis – are discussed. The kinds of data that can be taken from palm specimens and the problems of using specimens as data sources are outlined. Published systematic studies of palms using traditional morphometrics are reviewed. More recent studies indicate that: hybrid zones between species may be common; infraspecific diversity is greater than previously suspected; there may be more than double the currently accepted number of species; and our current knowledge of morphological variation in palms is superficial. A procedure for scientific systematics is given, which incorporates traditional morphometric methods.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 103–111.     

Geometric morphometrics as a tool for understanding Dactylorhiza (Orchidaceae) diversity in European Russia

Geometric morphometric techniques were employed to assess the diversity of lip shapes (305 samples from 83 populations) in flowers of European Russian Dactylorhiza (Orchidaceae: Orchidinae). We found significant agreement between the results from geometric morphometrics, classic morphometrics and the distribution of certain nuclear DNA markers. The lip shapes from Arctic Dactylorhiza samples occupied an intermediate position between D. maculata and D. fuchsii samples from Central Russia, supporting a hybrid origin of 'northern tetraploids'. Lip shapes of the taxonomically controversial allotetraploid D. baltica were found to form a distinct group, with members having definite relationships with diploid D. incarnata samples from the same localities, indicating either their local origin or introgression with D. incarnata . In addition to demonstrating the value of geometric morphometric methods in studies of plant taxonomy and hybridization, we suggest future applications designed to explore pollinator-driven directional selection, developmental constraints and fluctuating asymmetry.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 1–12.     

Molecular phylogenetics and morphological variation reveal recent speciation in freshwater mussels of the genera Arcidens and Arkansia (Bivalvia: Unionidae)

Intra‐ and interspecific morphological variation due to both phenotypic plasticity and evolutionary convergence hinder the work of taxonomists and lead to over‐ and underestimates of species richness. Nevertheless, most species on Earth are recognized solely based on morphological characters. We used molecular phylogenetic and morphometric techniques to examine two freshwater mussel species. One is common and widespread, while the other is imperiled and endemic to the Interior Highlands of the USA. Phylogenetic and molecular clock analyses revealed that divergence of Arcidens confragosus and Arkansia wheeleri is small and relatively recent. Divergence in these and other taxa is probably due to isolation of streams in the Interior Highlands. Morphometric analyses showed distinct shell shapes using traditional morphometrics, but not through geometric morphometrics. Outlined shell shapes are indistinguishable; geometric morphometrics could not capture a three‐dimensional component. Our analyses support the validity of these two species as congeners, with the nomen Arcidens (Simpson 1900) having priority. Because shell morphologies are both heritable and environmentally determined, our study emphasizes the importance of considering both molecular and morphometric analyses for identification of freshwater molluscs of conservation concern. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 535–545.     

Allopolyploid origin of Cardamine silana (Brassicaceae) from Calabria (southern Italy): karyological, morphological and molecular evidence

Endemic Cardamine silana from Calabria (southern Italy) previously reported to be related to C. raphanifolia was found to be hexaploid. Morphological characters and AFLP data were analysed to evaluate the degree of differentiation of C. silana from closely related taxa and to find parental taxa of this polyploid. Cardamine apennina from the C. pratensis group was examined as one putative parent, as indicated in previous studies of nuclear ITS sequences, along with other related taxa based on both cpDNA and ITS sequences. Both multivariate morphometric analyses of quantitative characters and evaluation of qualitative morphological characters showed: (1) closest position of C. silana to two diploids: C. acris from the Balkan Peninsula and C. apennina from Central Italy; (2) good extent of morphological separation of C. silana from related taxa; and (3) within C. acris subspecies, C. acris ssp. vardousiae from Central Greece as closest to C. silana . Neighbour-joining tree and PCoA ordinations of AFLP data, as well as patterns of AFLP bands sharing, corroborated results of multivariate morphometrics. This evidence supports an allopolyploid origin of C. silana , with C. apennina and C. acris as parental taxa. Its origin may be dated to Pleistocene glacial events, because of the presumably wider geographical distributions of its parental taxa during more humid periods at that time.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 101–116.     

Evolution of Dactylorhiza baltica (Orchidaceae) in European Russia: evidence from molecular markers and morphology

Four plastid markers, four nuclear markers and 14 morphometric characters were used in this study to investigate the evolution of Dactylorhiza baltica (Orchidaceae) in European Russia. In total, 98, 214 and 775 samples from 85, 112 and 121 populations were involved in the combined and separate molecular and morphometric analyses, respectively. In most cases, morphometric measures were done on exactly the same plants that were used for DNA studies. Dactylorhiza baltica plants from European Russia are most probably the products of several recent and mostly local hybridization events between the diploids D. fuchsii and D. incarnata , which have each been the maternal parent on different occasions. Considerable introgression into the parental diploids via the allopolyploid D. baltica is also hypothesized. Several morphological characters, such as length of the lip lateral lobe and the length of longest leaf, were found to be robust and could be useful in identification of D. baltica . This study demonstrates the advantage of 'combined' techniques, especially in the case of taxonomically complex taxa.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 257–274.     

Geographical and morphological variation within and between colour phases in Coris julis (L. 1758), a protogynous marine fish

The possible differences between sexes in patterns of morphological variation in geographical space have been explored only in gonochorist freshwater species. We explored patterns of body shape variation in geographical space in a marine sequential hermaphrodite species, Coris julis (L. 1758), analyzing variation both within and between colour phases, through the use of geometric morphometrics and spatially‐explicit statistical analyses. We also tested for the association of body shape with two environmental variables: temperature and chlorophyll a concentration, as obtained from time‐series of satellite‐derived data. Both colour phases showed a significant morphological variation in geographical space and patterns of variation divergent between phases. Although the morphological variation was qualitatively similar, individuals in the initial colour phase showed a more marked variation than individuals in the terminal phase. Body shape showed a weak but significant correlation with environmental variables, which was more pronounced in primary specimens. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 148–162.     

Morphological and pollen differentiation in Solanum cardiophyllum ssp. cardiophyllum and S. cardiophyllum ssp. ehrenbergii

A multivariate analysis to differentiate morphologically the populations of wild potatoes Solanum cardiophyllum ssp. cardiophyllum and S. cardiophyllum ssp. ehrenbergii was carried out. An analysis of the morphology and the viability of pollen of these potato populations was also made. The results of the morphometric analysis indicate that both subspecies are phenetically different. The pollen grain shape and size in ssp. cardiophyllum are different in northern and southern populations. Pollen diameter is significantly different between subspecies. Based on these results we propose that these taxa should be considered as two separate species.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 415–426.     

It is all in the head: morphological basis for differences in bite force among colour morphs of the Dalmatian wall lizard

Males of the lizard Podarcis melisellensis occur in three distinct colours that differ in bite performance, with orange males biting harder than white or yellow ones. Differences in bite force among colour morphs are best explained by differences in head height, suggesting underlying variation in cranial shape and/or the size of the jaw adductors. To explore this issue further, we examined variation in cranial shape, using geometric morphometric techniques. Additionally, we quantified differences in jaw adductor muscle mass. No significant differences in size corrected head shape were found, although some shape trends could be detected between the colour morphs. Orange males have relatively larger jaw adductors than yellow males. Not only the mass of the external jaw adductors, but also that of the internal jaw adductors was greater for the orange morph. Data for other cranial muscles not related to biting suggest that this is not the consequence of an overall increase in robustness in orange individuals. These results suggest that differences in bite performance among morphs are caused specifically by an increase in the mass of the jaw adductor, which may be induced by differences in circulating hormone levels.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 13–22.     

Relationship between size and shape in the sexually dimorphic beetle Prosopocoilus inclinatus (Coleoptera: Lucanidae)

Male characters that are used for male−male combat are often developed and exaggerated, whereas female equivalent characters are vestigial or vanished. In order to assess whether the characters common to both sexes share the same phenotypic variability due to common genetic architecture, we compared males and females of the stag beetle Prosopocoilus inclinatus using recently developed geometric morphometric methods. Elliptic Fourier analysis was used to compare shape variation between male characters (including exaggerated mandibles) and developmentally homologous female characters. A significant positive correlation was found between the size or between the weight of different body parts in both sexes, but a conspicuous difference was detected in the frequency distribution of the weight of all the body parts. Elliptic Fourier analysis demonstrated that there was marked discontinuous variation in mandibles in males, whereas such a discontinuity was not clear in females. The shape of a character in males exhibited some similarity with that of other characters, but this was not found in females. In a character, growth trajectory of shape was significantly affected by both size and weight in males, whereas size and shape tended to vary independently in female characters. These results support the hypothesis that a large sexual dimorphism in variation in shape is due to alleles accumulating in tight linkage with a sex-determining gene.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 219–233     

Genetic and morphological differentiation patterns between sister species: the case of Onthophagus taurus and Onthophagus illyricus (Coleoptera, Scarabaeidae)

The present study investigated the morphological and genetic differentiation pattern between two sympatric dung beetle sister species, Onthophagus taurus and Onthophagus illyricus . The geometric morphometric approach coupled with the use of molecular markers allowed examination of the nature of interspecific relationships and an outline of the evolutionary and geographical processes that might have led to interspecific differentiation and the present-day partial sympatric and syntopic pattern of distribution. Geometric morphometrics failed to discrimininate the two species on the ground of external morphological traits, but revealed interspecific differences when the shape of the primary sexual traits was taken into account. The use of two different molecular markers (cytochrome oxidase subunit I gene and amplified fragment-length polymorphism) demonstrates that the two species are genetically well differentiated, forming two distinguishable lineages probably diverged during the Pliocene by allopatric speciation. No evidence of past or recent introgression and no support for hybridization were found, suggesting that sympatry was established subsequently, when speciation was accomplished. Both molecular markers and genital shape indicate that phenotypically intermediate individuals, despite their ambiguous appearance, are members of O. illyricus species rather than hybrids.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 197–211.     

Maximizing information in systematic revisions: a combined molecular and morphological analysis of a cryptic green pitviper complex (Trimeresurus stejnegeri)

Although the integration of DNA information in taxonomy has been invaluable, logistical problems relating to sampling can seriously limit its applicability. Here we describe the analysis of a morphologically cryptic species complex, in which we maximize the information present by using both a DNA phylogeny and a multivariate morphometric approach. The green pitviper Trimeresurus stejnegeri s.l. is widespread in Asia, with a number of described subspecies (some of which are considered full species by some workers) and two new species that have recently been described from Thailand. The phylogeny indicates three clades, which can also be discerned in the principal component analyses of morphological variation. Combining molecular and morphological information permits evaluation of the taxonomic position of populations not represented in the phylogeny − in particular, the subspecies T. s. chenbihui and T. s. yunnanensis . We discuss nomenclatural issues raised by this analysis, although these cannot be fully resolved until the holotypes of these subspecies can be examined. Finally, we apply a molecular clock calibrated in New World pitvipers, and discuss some of the palaeoclimatic changes that might have impacted upon diversification in this group.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82 , 219–235.     

Using image analysis on the ventral colour pattern in Salamandrina perspicillata (Amphibia: Salamandridae) to discriminate among populations

The ventral colour pattern in Salamandrina perspicillata is characteristic of each individual and remains invariant throughout the salamanders' life. The present study aimed to determine, using statistical methods applied to quantitative image analysis, whether the coloration pattern is population-specific. The images of ventral colour pattern of 180 salamanders belonging to five populations were analysed. The images were previously warped by geometric morphometry. To our knowledge, this is the first study to use an approach based on geometric morphometrics to standardize ventral shapes. This technique is useful for eliminating form distortions. The results of an analysis of similarities recognized more coloration similarity among individuals of the same population than among individuals from different populations. Analysis by partial least squares correctly classified the 88.88% of individuals into the correct population. The similarities or differences among individuals of different populations are not related to the geographical distances. The results obtained showed that the coloration of the ventral side of the head of the salamanders can be used for discriminating among populations.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 35–43.     

Combining geometric morphometrics with pattern recognition for the investigation of species complexes

The parasitoid Hymenoptera contain a large number of species complexes that are as yet unresolved by traditional taxonomic studies. Evolutionary studies as well as biological control programmes often require further investigations which cannot rely on simple qualitative morphological characters; in many cases, particularly with dried specimens housed in museums, molecular approaches cannot be used. Recent developments in geometric morphometrics and statistical exploratory approaches open new perspectives for the objective evaluation of morphological characters in this taxonomic context. In this study, geometric morphometrics and pattern recognition approaches were applied to the wing shape and venation of two closely related braconid species considered to differ by subtle qualitative morphological head characters. Exploratory analyses such as kernel density estimates and Gaussian mixture analyses were used to explore the structure of the data in the multivariate morphometric space. Discrimination techniques (linear discriminant functions and neural networks combined with cross‐validations) were used to estimate the taxonomic value of qualitative characters. Gaussian mixtures highlighted the existence of two non‐overlapping groups. A good congruence was found between one of the two groups and the a priori defined Bassus tumidulus. The misclassification rate was higher for B. tegularis specimens, which also appeared morphometrically heterogeneous. Discrimination between the two a priori defined species was incomplete with misclassification rates higher than, or equal to, 6%. In most cases, the lack of congruence between species and morphometrically defined subgroups could be related to specimens that exhibited ambiguous qualitative character states. In summary, if two entities are present, they still need to be defined morphologically, while B. tegularis heterogeneity calls for further investigation of specimens of known origin and hosts. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80, 89–98.     

The influence of environmental factors on the morphology of red‐backed voles Myodes 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.     

A geometric morphometric assessment of the effects of environment and cladogenesis on the evolution of the turtle shell

In the largest group of extant turtles, the Testudinoidea, the acquisition of an aquatic or terrestrial way of life has occurred within two clades, allowing the study of homoplasy linked to environment (commonly named convergence). Here we appraise the respective importance of two sources of morphological variation: a major cladogenetic event and a major environmental shift (aquatic vs. terrestrial). The repeatability of the same evolutionary process (environmental change) allows an assessment of the weights of both natural selection and phylogenetic constraints on several morphological features of the shell. These sources of morphological variance on the complex shell structure were studied using geometric morphometrics. We depict the morphological variation of three parts of the turtle shell: epidermal carapace, bony carapace, and plastron. In the three structures, we found that both phylogeny and environment were significant sources of morphological variation, and geometric morphometrics allowed the pattern of morphological variation due to each effect to be assessed. The assessment of the homoplasy due to environment and of the pattern of morphological variability suggests that the carapace has undergone similar morphological changes between aquatic and terrestrial environments within the two clades. The radiation of the Testudinoidea is interpreted as an adaptive radiation.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79 , 485–501.     

Determining best complete subsets of specimens and characters for multivariate morphometric studies in the presence of large amounts of missing data

Missing data are frequent in morphometric studies of both fossil and recent material. A common method of addressing the problem of missing data is to omit combinations of characters and specimens from subsequent analyses; however, omitting different subsets of characters and specimens can affect both the statistical robustness of the analyses and the resulting biological interpretations. We describe a method of examining all possible subsets of complete data and of scoring each subset by the 'condition' (ratio of first eigenvalue to second, or of second to first, depending on context) of the corresponding covariance or correlation matrix, and subsequently choosing the submatrix that either optimizes one of these criteria or matches the estimated condition of the original data matrix. We then describe an extension of this method that can be used to choose the 'best' characters and specimens for which some specified proportion of missing data can be estimated using standard imputation techniques such as the expectation-maximization algorithm or multiple imputation. The methods are illustrated with published and unpublished data sets on fossil and extant vertebrates. Although these problems and methods are discussed in the context of conventional morphometric data, they are applicable to many other kinds of data matrices.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 309–328.     

Morphological variation in house mice from the Robertsonian polymorphism area of Barcelona

Morphometric variation in the Robertsonian polymorphism zone of Barcelona of Mus musculus domesticus was studied by geometric morphometrics. This system is characterized by populations of reduced diploid number (2 n  = 27–39) surrounded by standard populations (2 n  = 40). We investigated the morphological variation in mice from this area, as well as the effect of geographical distance and karyotype on this variation. We also investigated the degree of co-variation between the two functional units of the mandible to explore the origin of this system (primary intergradation or secondary contact). The size and shape of the cranium, mandible and scapula were analysed for 226 specimens grouped by population, chromosome number and structural heterozygosity. Size was estimated as the centroid size, and shape was estimated after Procrustes superimposition. No significant differences in size between populations or chromosomal groups were detected. Diploid number, structural heterozygosity and local geographical isolation contributed to the differentiation in shape. Morphological differentiation between standard mice and Robertsonian specimens was observed, suggesting genetic isolation between these groups. Co-variation between the ascending ramus and alveolar region of the mandible was quantified by the trace correlation between landmark subsets of these modules. The trace values showed an ascending trend, correlated with the distance from the centre of the polymorphism area, a pattern consistent with a primary intergradation scenario.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 555–570.     

Taxonomic studies on Senecio aquaticus (Asteraceae). A recommendation for the taxonomic status of Aquaticus and Barbareifolius

Aquaticus and Barbareifolius are two subgroups of Senecio aquaticus s. l. (Asteraceae) that have been recognized at various taxonomic levels in European taxonomic literature. In this paper we present the results of morphological studies on S. aquaticus s. l. in order to establish the taxonomic status of these two subgroups. Using multivariate morphometric techniques (discriminant analysis and principal component analysis), we examined the diagnostic potential of 60 macro-morphological characters and studied the delimitation of Aquaticus and Barbareifolius. Seven of the characters studied were included in the discriminant function of the stepwise discriminant analysis and are therefore considered to be the most reliable diagnostic characters of Aquaticus and Barbareifolius. Barbareifolius has, amongst other distinguishing traits, a more divaricate inflorescence than Aquaticus. Because both subgroups are distinct but overlapping clusters in multivariate morphometric space, and because clear differences in their geographical distribution are absent, we recommend the taxonomic status of variety to both groups. Following the rules of nomenclature, Aquaticus and Barbareifolius should therefore be named S. aquaticus Hill var. aquaticus and S. aquaticus Hill var. barbareifolius (Krock.) Wimm. & Grab.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 489–498.