Body shape evolution among ploidy levels of the Squalius alburnoides hybrid complex (Teleostei,Cyprinidae)

Hybridization, ploidy level and genomic constitution may be important to respond to different environments, by producing different phenotypes and thus reducing competitive interaction. Through geometric morphometrics, we examined variation in body size and shape among biotypes of the Squalius alburnoides hybrid complex and their sperm donor (Squalius carolitertii). Results showed that S. carolitertii is significantly larger in size than the biotypes of the complex. No significant relationship was observed between ploidy and body size among S. alburnoides biotypes. Significant variation in body shape was found between S. carolitertii and S. alburnoides, and between tetraploids and the other biotypes. These differences in biotypes may reduce resource competition, highlighting the potential importance of resource availability favouring one biotype over another. In S. alburnoides, the adaptation to different trophic niches through modification of trophic morphology, body shapes, and feeding behaviour, may result from an increase in ploidy and genomic constitution. This adaptation may account also for the formation and maintenance of this nonsexual complex.     

The utility of cranial ontogeny for phylogenetic inference: a case study in crocodylians using geometric morphometrics

The degree to which the ontogeny of organisms could facilitate our understanding of phylogenetic relationships has long been a subject of contention in evolutionary biology. The famed notion that ‘ontogeny recapitulates phylogeny’ has been largely discredited, but there remains an expectation that closely related organisms undergo similar morphological transformations throughout ontogeny. To test this assumption, we used three‐dimensional geometric morphometric methods to characterize the cranial morphology of 10 extant crocodylian species and construct allometric trajectories that model the post‐natal ontogenetic shape changes. Using time‐calibrated molecular and morphological trees, we employed a suite of comparative phylogenetic methods to assess the extent of phylogenetic signal in these trajectories. All analyses largely demonstrated a lack of significant phylogenetic signal, indicating that ontogenetic shape changes contain little phylogenetic information. Notably, some Mantel tests yielded marginally significant results when analysed with the morphological tree, which suggest that the underlying signal in these trajectories is correlated with similarities in the adult cranial morphology. However, despite these instances, all other analyses, including more powerful tests for phylogenetic signal, recovered statistical and visual evidence against the assumption that similarities in ontogenetic shape changes are commensurate with phylogenetic relatedness and thus bring into question the efficacy of using allometric trajectories for phylogenetic inference.     

Leaf morphological analyses in four European oak species (Quercus) and their hybrids: A comparison of traditional and geometric morphometric methods

Abstract

In this study, leaf morphology was assessed in a mixed oak stand (western France) using two geometric morphometric (landmark and outline) datasets and one dataset of 19 leaf measures. Adult oaks (817 oaks), comprising four white oak species (Quercus petraea, Q. robur, Q. pubescens and Q. pyrenaica), were sampled for DNA extraction and genetic analysis (nuclear microsatellites). Leaf morphology was assessed on 336 oaks, comprising pure species and hybrids as determined by genetic assignment. This comparative study of oak leaf morphology, based on the use of two free size geometric morphometric methods and a set of leaf measurements, combined with the genetic assignment of individuals to pure species or hybrids, provided information about the differences among species and the intermediate leaf morphology of their hybrids.     

A complete survey of normal pores on a smooth shell ostracod (Crustacea): Landmark‐based versus outline geometric morphometrics

Pores and sensilla on ostracod shell have often been used in studies of ontogeny, taxonomy, and phylogeny of the group. However, an analysis of sexual dimorphism and variation between valves in the number and distribution of pores is lacking. Also, such studies have never been done on a widely distributed, morphologically variable, and weakly ornamented freshwater ostracod. Here, we survey pores in one such species, Physocypria kraepelini . We choose 27 homologous pores as landmarks for 2D‐geometric morphometric analysis, with the aim to assess intersexual and between valves variation in size and shape relative to the Fourier outline analysis. This species has only simple (Type A) pores with and without a lip, and each pore carries an undivided sensory seta. Our results show that the total number of pores varies (from 270 to 296), but this is not associated with a specific valve. Males carry fewer pores than females, however no sex specific pores are found. Small intrapopulation divergence of the Cyt b molecular marker (1%) indicates that morphological variability is not species related. We found that P. kraepelini exhibits directional asymmetry of size and shape, sexual size dimorphism (SSD) but lacks sexual shape dimorphism (SShD). Two geometric morphometrics methods were congruent in the estimation of SSD, SShD, and directional asymmetry of shape but differ in the statistical evaluation of directional asymmetry of size. Contrary to other animal groups, our study suggests that ostracods have more pronounced directional asymmetry of shape compared to directional asymmetry of size.     

Insights on the history of the scorched mussel Brachidontes rodriguezii (Bivalvia: Mytilidae) in the Southwest Atlantic: a geometric morphometrics perspective

Some authors support the idea that an important part of the Miocene marine mollusc fauna is still represented in the Argentinean Province. The fossil mollusc Brachidontes lepida (Philippi) is considered a subspecies of the extant B. rodriguezii (d?Orbigny), a taxon currently present in the Argentinean Biogeographic Province. The aim of this study is to investigate the shell shape relationship between B. lepida and B. rodriguezii using geometric morphometrics. Samples of B. rodriguezii (n = 63) from four localities distributed in Uruguay and Argentina, of B. lepida from the Paraná Formation (n = 26) and of two other extant Brachidontinae present in the region were included in this study. Canonical variate analyses showed that extant species differed in shell shape, with the discriminant function properly allocating 93% of the individuals to their respective species. Using the extant discriminant function, approximate 92% of B. lepida individuals were allocated to B. rodriguezii. This result suggests that B. lepida is more similar in shell shape to B. rodriguezii than to the other extant species present in the region. Considering the material from the Pliocene of Cerro Laciar and from the Pleistocene deposits of Buenos Aires and Bustamante, the presence of B. rodriguezii from the Late Miocene in the warm temperate region is discussed.     

Phylogenetic relationships in the Sceloporus variabilis (Squamata: Phrynosomatidae) complex based on three molecular markers,continuous characters and geometric morphometric data

The monophyly of the Sceloporus variabilis group is well established with five species and two species complexes, but phylogenetic relationships within species complexes are still uncertain. We studied 278 specimens in 20 terminals to sample all taxa in the “variabilis group,” including three subspecies in the “variabilis complex,” and two outgroups (Sceloporus grammicus and Sceloporus megalepidurus). We assembled an extensive morphological data set with discrete and continuous characters (distances and scale counts), including geometric morphometric data (landmark coordinates of three shapes), and a three‐marker molecular data set as well (ND4, 12S and RAG1). We conducted parsimony and Bayesian phylogenetic inferences on these data, including several partitioning and weighting schemes. We suggest elevating three subspecies to full species status. Therefore, we recommend recognition of nine species in the “variabilis group.” First, S. variabilis is sister to Sceloporus teapensis. In turn, Sceloporus cozumelae is sister to Sceloporus olloporus. These four species are a monophyletic group, which is sister to Sceloporus smithi. Finally, Sceloporus marmoratus is sister of the clade of five species. The other species in the “variabilis group” (Sceloporus chrysostictus, Sceloporus couchii and Sceloporus parvus) are a paraphyletic grade at the base of the tree. Our analyses reject the existence of the “variabilis complex.” We conducted a parsimony‐based ancestral reconstruction on body size (snout–vent length), femoral pores and dorsal scales and related morphological changes to geographic distribution of the species. Our phylogenetic hypothesis will allow best designs of comparative studies with species in the “variabilis group,” one of the earliest divergent lineages in the genus.     

Geographic and gender shape differences in the carapace of Liocarcinus depurator (Brachyura: Portunidae) using geometric morphometrics and the influence of a digitizing method

The current work describes the use of geometric morphometrics in the study of the portunid crab Liocarcinus depurator carapace shape variation along the Mediterranean coast of Spain. As a first step, the differences in shape induced by digitizing the carapace with either a digital camera or a flat bed scanner were investigated. Carapace shape information inferred from the camera images proved different from that obtained from the scanner images. This difference was greater than any shape variation because of crab gender or sample location. Carapace shape was analysed using multiple analysis of covariance (with centroid size as a covariate) of the partial warps and uniform components indicating differences between genders and between sample location; however, significant three-way interaction implied that such differences were gender and location specific. Landmarks identifying carapace width, carapace length and posterior carapace width showed greatest variation; hence gender and location differences were further analysed through the interrelationships between these linear measures. Regression analysis of the relationship between posterior carapace width and the ratio of carapace width to carapace length indicated clear differences between locations but not between genders. Crabs from the Alborán Sea had proportionally wider posterior carapaces than those from Alicante or North Catalonia. This finding may represent the difference between a southern influx of an Atlantic population distinguishable from a more northerly Mediterranean one, which would be in agreement with the overall oceanographic surface circulation pattern in the western Mediterranean.     

Using geometric morphometrics to determine the “fittest” floral shape: A case study in large-flowered,buzz-pollinated Meriania hernandoi

Premise

Floral shape (relative arrangement and position of floral organs) is critical in mediating fit with pollinators and maximizing conspecific pollen transfer particularly in functionally specialized systems. To date, however, few studies have attempted to quantify flowers as the inherently three-dimensional (3D) structures they are and determine the effect of intraspecific shape variation on pollen transfer. We here addressed this research gap using a functionally specialized system, buzz pollination, in which bees extract pollen through vibrations, as a model. Our study species, Meriania hernandoi (Melastomataceae), undergoes a floral shape change from pseudocampanulate corollas with more actinomorphically arranged stamens (first day) to open corollas with a more zygomorphic androecium (second day) over anthesis, providing a natural experiment to test how variation in floral shape affects pollination performance.

Methods

In one population of M. hernandoi, we bagged 51 pre-anthetic flowers and exposed half of them to bee pollinators when they were in either stage of their shape transition. We then collected flowers, obtained 3D flower models through x-ray computed tomography for 3D geometric morphometric analyses, and counted the pollen grains remaining per stamen (male pollination performance) and stigmatic pollen loads (female pollination performance).

Results

Male pollination performance was significantly higher in open flowers with zygomorphic androecia than in pseudo-campanulate flowers. Female pollination performance did not differ among floral shapes.

Conclusions

These results suggest that there is an “optimal” shape for male pollination performance, while the movement of bees around the flower when buzzing the spread-out stamens results in sufficient pollen deposition regardless of floral shape.

     

Adaptive radiation in African weakly electric fish (Teleostei: Mormyridae: Campylomormyrus): a combined molecular and morphological approach

We combined multiple molecular markers and geometric morphometrics to revise the current taxonomy and to build a phylogenetic hypothesis for the African weakly electric fish genus Campylomormyrus. Genetic data (2039 bp DNA sequence of mitochondrial cytochrome b and nuclear S7 genes) on 106 specimens support the existence of at least six species occurring in sympatry. We were able to further confirm these species by microsatellite analysis at 16 unlinked nuclear loci and landmark-based morphometrics. We assigned them to nominal taxa by comparisons to type specimens of all Campylomormyrus species recognized so far. Additionally, we showed that the shape of the elongated trunk-like snout is the major source of morphological differentiation among them. This finding suggests that the radiation of this speciose genus might have been driven by adaptation to different food sources.     

High molecular and phenotypic diversity in the Merodon avidus complex (Diptera,Syrphidae): cryptic speciation in a diverse insect taxon

This paper examines molecular and phenotypic variability in the widely spread European hoverfly species complex Merodon avidus. Herein, based on the mitochondrial DNA (mtDNA) sequences of the cytochrome c oxidase subunit I (COI) and morphometric wing parameters, M. avidus is shown to comprise a complex of cryptic species, and one variety is redefined as a valid species: M. bicolor Gil Collado, 1930 (as var. of spinipes). The species M. bicolor, M. avidus A, and M. avidus B were clearly delimited based on their wing size. A total of 29 M. avidus and M. bicolor individuals presented 20 mtDNA haplotypes, four of which were shared by M. avidus A and M. avidus B, three were confined to M. bicolor, seven to M. avidus A, and six to M. avidus B. Sequence divergences between lineages occurring in the Balkan and in Spain ranged from 4.93 to 6.0 (uncorrected p in %) whereas divergences between M. avidus A and M. avidus B were 0.26 to 1.56. Divergence among morphologically identified individuals of M. avidus A and M. avidus B species ranged from 0.13 to 1.58, and from 0.13 to 0.52, respectively. The phenotypic substructuring and observed genetic uniqueness of populations in spatially and temporally fragmented M. avidus taxa were used to identify genetic units. The early split of two allopatric lineages, Spanish M. bicolor and Balkan M. avidus, was followed by diversification in each lineage. Present‐day morphological uniformity masks much of the genetic complexity of lineages within the M. avidus complex. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 819–833.     

When hybrids are not hybrids: a case study of a putative hybrid zone between Cattleya coccinea and C. brevipedunculata (Orchidaceae)

Cattleya coccinea and C. brevipedunculata (Orchidaceae) are closely related species distinguished primarily by geographical distribution, vegetative morphology and flowering period. Both species inhabit high‐elevation regions in south‐eastern Brazil, but are traditionally associated with different habitats, located in cloudy forests and campos rupestres (rocky fields), respectively. We used morphometrics and genetic variation of microsatellite markers to test the occurrence of a hybrid zone between these species located in Parque Estadual do Ibitipoca (PEI), Brazil. Morphological data reveal a continuum of variation between the putative taxa, influenced mainly by characters of leaf, pseudobulb and peduncle. However, genetic data do not support the occurrence of hybridization and introgression in PEI, showing that it is a pure population of C. brevipedunculata. Differences in vegetative characters among individuals from cloudy forests and campos rupestres suggest that morphological variation may be related to phenotypic plasticity in response to environmental light fluctuations, an unknown situation for this species. These results highlight the inconsistency of morphology for the identification of hybrids and the role of vegetative characters as a possible complicating factor for the taxonomy of these species, as they are subject to environmental influence.     

Reading shell shape: implications for palaeoenvironmental reconstructions. A case study for bivalves from the marine Quaternary of Argentina (south-western Atlantic)

Most research on bivalves from the south-western Atlantic used morphological (shell) characters for taxonomic discriminations. Dominant Veneroids from Argentinian Quaternary coastal deposits exhibit wide morphological variation – often making objective discriminations difficult/impossible, which could be objectively described and compared through geometric morphometrics techniques. This work focuses on comparison of geometric morphometrics methods applied to fossil and modern shells, to assess inter- and intra-generic variations. Three approaches were considered: landmarks (L), semi-landmarks (SL) and outlines. Shell shape analyses for different time spans (Pleistocene, fossil Holocene and modern) and areas (Patagonia and Bonaerensian) showed that Elliptic Fourier analysis (EFA), Landmarks and Landmarks plus Semilandmarks (L+SL) can discriminate at generic levels: Mactra, Mulinia (Mactridae) vs. Pitar, Protothaca, Eurhomalea, Clausinella (Veneridae). L and L+SL are powerful for inter/intraspecific distinctions of Mactra. Variability of Mactra isabelleana includes the remaining nominal ‘species’ (transitional morphs). Causal environmental factors of (phenotype) variation could be addressed for modern environments (substrate, salinity and energy). Subtrigonal-inflated shells predominate in muddy, quieter, shallow mixo-polyhaline waters; ovate-elongate-compressed in sandy, poly-euhaline, deeper habitats. Differential spatial distribution (and abundance) across time responds to Late Quaternary high sea-level stands: transgressive maxima allowed higher salinity in marginal-marine areas and optimal conditions for Mactra isabelleana contrasting with scarcer records in the Mar Argentino today.     

Combining geometric morphometrics and pattern recognition to identify interspecific patterns of skull variation: case study in sympatric Argentinian species of the genus Calomys (Rodentia: Cricetidae: Sigmodontinae)

Sympatric species of vesper mice Calomys laucha and Calomys musculinus are difficult to discriminate, especially in natural history collections where they are identified by external body measurements and cranial characteristics. Accurate identification of these two species can be important because only one of them, C. musculinus , is a Junin virus reservoir, the aetiological agent of the Argentine Hemorragic Fever. Research has focused into the development of molecular techniques to unambiguously identify these species. We apply statistical procedures from the field of pattern recognition to three-dimensional geometric morphometric data based on skull landmarks to identify sympatric species C. laucha , C. musculinus and Calomys venustus . Pattern recognition techniques correctly identified the three species without any prior information on specimen identity. By contrast to expectations, C. venustus differed from the other two species mainly on the basis of shape and not by its centroid size. The main sources of difference between C. laucha and C. musculinus were of shape, specifically localized at the landmarks defined by: (1) the sutures between the premaxillaries, the nasals and the frontals; (2) the sutures between the parietals, the frontals and the squamosals; and (3) the suture between the parietals and the interparietal. Nevertheless, allometries dominate the patterns of interspecific variation between these latter species and may partly explain past identification difficulties. Morphological evolution is discussed. The need for objective methods to define phenotypic clusters is highlighted with respect to the need for fast and precise biodiversity assessments.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 365–378.     

Speciation and anagenesis in the genus Cyprinella of Mexico (Teleostei: Cyprinidae): a case study of Model III allopatric speciation

Allozyme variation at 42 presumptive gene lociis presented for members of the C. formosa species group. This group iscorroborated as a monophyletic assemblage whosecommon ancestor occupied pluvial Lake Palomasof the Guzman Basin. With increasingaridity during the Pleistocene this basin andassociated populations of this commonancestor were fragmented into several lineagesthat diverged independently of oneanother. The pattern of relationships andlevels of anagenetic change observed inindependent lineages for this clade are notconsistent with expectations of the mostcommon modes of speciation, Model I large-scalevicariance or Model II peripheralisolation. Rather, divergence in these fishlineages is consistent with the rarely observedModel III allopatric speciation. Consistentwith predictions of this model, thephylogenetic pattern recovered revealspolychotomous relationships (a hard polytomy)and varied rates of anagenetic change acrossexamined lineages.     

Physiological adaptation in relation to hyperosmotic stress in the epidermis of a fresh-water teleost Barbus sophor (Cypriniformes, Cyprinidae): a histochemical study.

The changes in distribution of mucopolysaccharides, glycogen and protein bound sulphydryl groups of cysteine in the various cellular components of the epidermis of Barbus sophor along with its structural alterations as a result of hyperosmotic stress, have been described using histochemical techniques. The hyperosmotic saline induces a cyclic secretion of acid mucopolysaccharides by the mucous cells. Simultaneously the polygonal cells also show a marked disturbance in the processes of mucogenesis and keratinization, indicating an inverse relationship between the degree of keratinization and the amount of mucus secreted by epidermis. The role of glycogen in the polygonal cells has been discussed in relation to disturbed mucogenesis. The appearance of intercellular spaces in basal layer and middle layer has been correlated with the passage for movement of increased amounts of nutrients through the skin.     

Size matters,but so does shape: quantifying complex shape changes in a sexually selected trait in stalk‐eyed flies (Diptera: Diopsidae)

The elaborate morphologies of sexually selected ornaments are ubiquitous across the animal kingdom. In studies investigating these traits, ornament size is frequently the focus, and empirical evidence supports its positive correlation with fitness. Yet shape plays an important role and, surprisingly, is often overlooked. Shape frequently changes with size, influenced by biomechanical, developmental, or performance constraints. Therefore, shape can provide additional insights into the morphological differences between individuals and the potential limits on sexual trait exaggeration. Here, we used landmark‐based geometric morphometric methods on a sexually dimorphic species of stalk‐eyed fly (Teleopsis dalmanni) to examine patterns of sexual shape dimorphism. Our analyses reveal a significant difference in head shape between the sexes, with males exhibiting smaller eye bulbs, thinner stalks, and smaller heads than females. Additionally, as eyestalk length increases within each sex, a similar pattern of shape change was observed as that observed between sexes. This pattern of shape change may be the result of constraints acting against further ornament exaggeration, and we suggest that this may significantly impact the whole‐organism performance in stalk‐eyed flies. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 104–113.