Intraspecific Morphological Variation Research Articles

Intraspecific variation in fine root morphology of European beech: a root order-based analysis of phenotypic root morphospace.

Fine roots are multifunctional organs that may change function with ageing or root branching events from primarily absorptive to resource transport and storage functions. It is not well understood, how fine root branching patterns and related root functional differentiation along the longitudinal root axis change with soil chemical and physical conditions. We examined the variation in fine root branching patterns (the relative frequency of 1st to 4th root orders) and root morphological and chemical traits of European beech trees with soil depth (topsoil vs. subsoil) and soil chemistry (five sites with acid to neutral/alkaline bedrock). Bedrock type and related soil chemistry had an only minor influence on branching patterns: base-poor, infertile sites showed no higher fine root branching than base-rich sites. The contribution of 1st-order root segments to total fine root length decreased at all sites from about 60% in the topsoil (including organic layer) to 45% in the lower subsoil. This change was associated with a decrease in specific root area and root N content and an increase in mean root diameter with soil depth, while root tissue density did not change consistently. We conclude that soil depth (which acts through soil physical and chemical drivers) influences the fine root branching patterns of beech much more than soil chemical variation across soil types. To examine whether changes in root function are indeed triggered by branching events or result from root ageing and diameter growth, spatially explicit root physiological and anatomical studies across root orders are needed.

Molecular phylogeny reveals that Lagochilus lorestanicus (Lamiaceae, Leonureae) belongs to Acanthoprasium (Lamiaceae, Marrubieae)

ABSTRACT The taxonomic classification of the recently described Lagochilus lorestanicus within the genus Lagochilus is traditionally based on its morphological characters. We present here a phylogenetic hypothesis for the genus Lagochilus (Lamiaceae, tribe Leonureae) based on plastid (trnL-trnF and matK) and nuclear (ITS) DNA sequence data, using maximum parsimony, maximum likelihood and Bayesian approaches. Our analysis indicates that while representative species from the Iranian flora are assembled in a sub-clade nested in the clade Spinosi, L. lorestanicus is retrieved in the Acanthoprasium clade in the tribe Marrubieae. The taxonomic placement of Lagochilus lorestanicus in Acanthoprasium is also corroborated by re-examination of morphological characters. Consequently, the species is transferred to the genus Acanthoprasium, which was previously restricted to Italy and France (i.e. A. frutescens) and Cyprus (i.e. A. integrifolium). The intra-specific morphological variations as well as the conservation status of Lagochilus lorestanicus are discussed.

Intraspecific morphological and genetic variation in South African populations of a polystomatid flatworm parasite

The African Clawed Frog Xenopus laevis, a global invader, exhibits a marked phylogeographic divergence among native populations in southern Africa, which seems to enhance its invasive potential. The polystomatid flatworm, Protopolystoma xenopodis, is the frog’s most frequently co-introduced metazoan parasite. In an integrative approach, we utilised morphometrics and molecular markers to assess variation in P. xenopodis in its native range. We measured twelve key morphological characters from 23 flatworms and compared these statistically between flatworms collected from the northern- and southernmost distribution in South Africa. Phylogenetic analyses were based on three concatenated markers, namely 28S and 12S rDNA and COX1, from six flatworms. The combination of five morphological characters, which involve egg size, gut morphology and size of the attachment hooks, differentiated northern and southern populations of P. xenopodis. The multilocus phylogenetic analyses showed a cluster of northern P. xenopodis and two southern lineages with more basal positioning. These findings demonstrate a relatively high level of intraspecific variation in P. xenopodis in its native range. The presented intraspecific variation of P. xenopodis could be potentially informative to trace geographic origin in its non-native range.

An integrative delimitation of the species' boundaries within one hornbeam species complex (Betulaceae: Carpinus)

AbstractBoth hybridization and intraspecific morphological variation across environmental gradients complicate species delineation. We aimed to discern both possibilities that may blur species boundaries in the Carpinus viminea–Carpinus laxiflora–Carpinus londoniana species complex. We conducted statistical analyses on 535 specimens encompassing the entire distribution of this species complex to identify phenotypic clusters. Additionally, we analyzed genetic divergence and probable hybridization between clusters using 76 individuals from 37 populations. Based on phenotypic and genetic clusters, we tentatively recognized four species: C. viminea, C. fargesii, C. laxiflora, and C. londoniana. Except for rare overlapping distributions between C. fargesii and C. londoniana, the redefined four species are mostly allopatric to each another based on their distributions. The morphological delimitation, species boundary and distribution of each species differ distinctly from past taxonomic treatments. For example, specimens previously identified under C. viminea, in fact, belong to three different species. Hybrids between C. fargesii and C. londoniana exhibit morphological traits similar to C. viminea, thereby contributing to difficulties in determining species boundaries and outlining species distributions. These findings suggest that local selection and geographical isolation may together have promoted both phenotypic and genetic divergences within this species complex. However, interspecific hybridization blurs species boundaries by producing hybrids with phenotypic similarity in addition to intraspecific variation. This study emphasizes the importance of statistical analyses of population‐level morphological and genetic variations across major distributional ranges for an integrative delimitation of species boundaries and the identification of hybridization and hybrids.

Spread your wings: insect–plant–landscape interactions mediate the wing shape of a multivoltine polyphagous insect

Wing morphology may affect the foraging efficiency of polyphagous insects via effects on their flight ability. Variations in wing morphology may be triggered by host plant quality, while landscape composition can also play a role in filtering the ability of variants to colonize new habitats. We investigated how intraspecific variations in wing morphology in a polyphagous insect are mediated by the quality of local resources and the role of the landscape in filtering these variations. We used Bemisia tabaci MEAM‐1 (Hemiptera: Aleyrodidae) as a model since the existence of morphotypes that engage in long‐ and short‐distance flights has been proposed previously. We collected B. tabaci adults in the vegetative, flowering, and senescence stages of tomato plants on 15 farms embedded in distinct landscape types. We also performed a greenhouse experiment to evaluate whether resource quality influences B. tabaci wing shape. The wing shape of individuals was measured using geometric morphometry analyses. We found sexual dimorphism in wing shape, with males presenting more straight wings and females with more elongated wings. The dispersal morphotypes appear with more rounded wings at the vegetative (colonizing individuals) and senescence stages (dispersing individuals). When the resource is predictable (flowering stage), the wing shape becomes more adapted for short‐distance flights, possibly dictated by an intergenerational effect that facilitates habitat exploitation. The natural vegetation acted as an environmental filter in morphotype selection by impairing individuals' movement among habitat patches. We showed for the first time that insect–plant–landscape interactions mediate intraspecific variation in the wing morphology of B. tabaci. This polyphagous multivoltine pest insect presents a specialized morphological response to food resource quality, and the amount of natural vegetation may constrain its movement across the landscape. Our results indicate that local resources and landscape features produce interacting bottom–up effects that affect polyphagous insects' morphological variation within the habitat.

Biomechanical and taxonomic diversity in the Early Pleistocene in East Africa: Structural analysis of a recently discovered femur shaft from Olduvai Gorge (bed I)

Recent Plio-Pleistocene hominin findings have revealed the complexity of human evolutionary history and the difficulties involved in its interpretation. Moreover, the study of hominin long bone remains is particularly problematic, since it commonly depends on the analysis of fragmentary skeletal elements that in many cases are merely represented by small diaphyseal portions and appear in an isolated fashion in the fossil record. Nevertheless, the study of the postcranial skeleton is particularly important to ascertain locomotor patterns. Here we report on the discovery of a robust hominin femoral fragment (OH 84) at the site of Amin Mturi Korongo dated to 1.84 Ma (Olduvai Bed I). External anatomy and internal bone structure of OH 84 were analyzed and compared with previously published data for modern humans and chimpanzees, as well as for Australopithecus, Paranthropus and Homo specimens ranging from the Late Pliocene to Late Pleistocene. Biomechanical analyses based on transverse cross-sections and the comparison of OH 84 with another robust Olduvai specimen (OH 80) suggest that OH 84 might be tentatively allocated to Paranthropus boisei. More importantly, the identification of a unique combination of traits in OH 84 could indicate both terrestrial bipedalism and an arboreal component in the locomotor repertoire of this individual. If interpreted correctly, OH 84 could thus add to the already mounting evidence of substantial locomotor diversity among Early Pleistocene hominins. Likewise, our results also highlight the difficulties in accurately interpreting the link between form and function in the human fossil record based on fragmentary remains, and ultimately in distinguishing between coeval hominin groups due to the heterogeneous pattern of inter- and intraspecific morphological variability detected among fossil femora.

First record of Colpodidium caudatum (Ciliophora, Colpodidiidae) in Europe

The present study documents the discovery of the first European population of Colpodidium caudatum (Ciliophora, Colpodidiidae) in a water drain in a school playground in Manzanares (Ciudad Real, Spain). This species has been documented on every continent except Antarctica and Europe, until now. The ciliate was isolated from wet run-off soil collected from the water drain and was grown in semi-permanent cultures in the laboratory. The infraciliature of the ciliate was revealed using silver carbonate impregnation and cell measurements were taken from living and silver-impregnated specimens. A comparative analysis of published data from various populations of C. caudatum across the globe showed high intraspecific morphological variability in this species. To differentiate between species within the Colpodidium genus, a dichotomous key is presented. This investigation shows that C. caudatum is a ciliate that is found all over the world and is particularly associated with terrestrial habitats that are periodically flooded.

Let me know your name: a study of chigger mites (Acariformes: Trombiculidae) associated with the edible dormouse (Glis glis) in the Carpathian-Balkan distribution gradient.

Trombiculid mites were collected from the edible dormouse (Glis glis) within the Carpathian-Balkan distribution gradient of host species. Representatives of five genera (Leptotrombidium, Neotrombicula, Brunehaldia, Hirsutiella, Schoutedenichia) and 10 species of chiggers were discovered in the material, based on morphological and/or molecular data. Brunehaldia, new to the fauna of Greece, was recorded for the first time from the edible dormouse. Neotrombicula talmiensis was new to the fauna of Greece and Neotrombicula vulgaris was new to the fauna of North Macedonia. Successful amplification and sequencing of COI was carried out in relation to three genera and six species. The intraspecific variation of taxa hitherto distinguished based on morphological criteria was juxtaposed with molecular data, using the distance method and the phylogenetic approach. The molecular methods indicated wider than hitherto recognized, intraspecific morphological variation for Leptotrombidium europaeum and N. talmiensis. On the other hand, an inference limited to morphology proved to be insufficient for species delineation, which was confirmed by the relatively low identity (%) of examined COI sequences as well as the size of inter-/intraspecific K2P distance threshold. Our study provides support for integrative taxonomy that combines different sources of evidence and contributes to recognition of the scope of intraspecific variation. The high degree of hidden diversity revealed with the application of molecular tools, votes for a careful approach to the identification of chiggers. The confirmed cases of co-invasion, including the representatives of various genera (Leptotrombidium and Neotrombicula, Brunehaldia and Neotrombicula, Neotrombicula and Schoutedenichia, Hirsutiella and Schoutedenichia) additionally support the need to include all larvae found on a given host specimen in the identification process.

Intraspecific variation of long bone cross-sectional properties in Pan troglodytes troglodytes and Gorilla gorilla gorilla.

Morphological intraspecific variation is due to the balance between skeletal plasticity and genetic constraint on the skeleton. Osteogenic responses to external stimuli, such as locomotion, have been well documented interspecifically across the primate order, but less so at the intraspecific level. Here, we examine the differences in cross-sectional variability of the femur, humerus, radius, and tibia in Pan troglodytes troglodytes versus Gorilla gorilla gorilla. We investigate whether there are sex, species, bone, and trait differences in response to variable body size and locomotion. Adult male and female P. t. troglodytes and G. g. gorilla long bones from the Cleveland Museum of Natural History were scanned with a peripheral quantitative computer tomography system. Scans were taken at the midshaft of each bone according to functional bone length. Coefficients of variation were used to provide a size-independent measure of variation. We applied a Bonferroni correction to account for the multiple pairwise tests. There were limited significant differences between males and females, however, females tended to be more variable than males. Variation in Gorilla, when significant, was greater than in Pan, although significant differences were limited. There were no differences between bone variability in male and female Gorilla, and female Pan. Increased female variability may be due to more variable locomotor behavior, particularly during periods of pregnancy, lactation, and caring for an offspring compared to consistent locomotion over the life course by males. Body size may be a contributing factor to variability; more work is needed to understand this relationship.

A three-dimensional geometric morphometric analysis of the morphological transformation of Caiman lower jaw during post-hatching ontogeny.

Shape ontogenetic changes of the lower jaw in crocodylians are poorly understood. In order to answer some questions related to the inter- and intraspecific morphological variation of the mandible of two extant Caiman species, we performed a three-dimensional geometric morphometric approach. For this purpose, we used landmarks and semilandmarks on two ontogenetic mandibular series of 48 and 15 post-hatching specimens of C. yacare and C. latirostris, respectively. We have also examined the relationship between these anatomical transformations and ontogenetic shifts in diet. We performed a principal component analysis (PCA) for the two species, and regression and partial least squares (PLS) analyses for each species, separately. As a result, species were segregated along the PC1 with specimens of C. yacare showing more gracile mandibles, and specimens of C. latirostris more robust ones. The PC2 and regression analyses showed an age gradient and represented ontogenetic shape changes. Adult caiman mandibles are higher and wider than juvenile ones, and shape changes are more conspicuous in C. latirostris. The PLS analyses showed a significant relationship between shape and diet. Morphological changes of the PLS1 of block-1 match with those of the regression analysis for both species. We have detected morphological transformations in areas where the musculature in charge of mandibular movements is attached. Common morphological changes occurring during ontogeny seem to reflect the same mechanical properties required for crushing and killing in both species, driven by an ontogenetic shift in the diet from invertebrates to vertebrates. Additionally, interspecific differences were also found to be correlated to ontogenetic changes in diet and could be related to dissimilar feeding mechanical requirements (e.g., stiffness and toughness of the item consumed), and to different habitat preferences. Robust mandibles would be more suitable for shallow and fully vegetated environments, as it can be seen in C. latirostris, whereas slender jaws seem to be more suitable for more aquatic species such as C. yacare.

Taxonomic relationship among four European Physokermes species (Hemiptera: Coccomorpha) based on nuclear and mitochondrial DNA

IntroductionScale insects (Hemiptera: Coccomorpha) feed on a wide variety of agricultural crops and forest and ornamental trees worldwide. These pest insects damage plants not only by causing sap loss but also by reducing the plant's photosynthetic activity. This is because the honeydew they produce acts as a substrate for mold, which covers leaf surfaces. In the last decades, several outbreaks of Physokermes spp. (soft-scale insects) have occurred throughout Europe and have partly been attributed to unusual weather conditions or climate change, as some species seem to be expanding their distribution range. However, the small size of these insects and their large intraspecific morphological variation have hindered the identification of the species responsible for outbreaks.MethodsIn this study, mitochondrial DNA (cytochrome c oxidase subunit I, COI), ribosomal RNA (28S), and nuclear (elongation factor 1α, EF1α) DNA markers were used to reconstruct the phylogenetic relationships of four Physokermes species sampled throughout Europe in 2013–2015.Results and discussionThe results allowed us to clearly distinguish P. hellenicus and P. inopinatus from each other, as these appeared in well-supported clades in the phylogenetic trees and from P. piceae and P. hemicryphys. However, P. hemicryphus appeared in a single clade in trees based on 28S and EF1α but among P. piceae in the COI tree. Further investigations are therefore required to determine the taxonomic status of P. piceae and P. hemicryphys, which seem to comprise a species complex.

Plastocerus angulosus (Germar, 1844) (Coleoptera: Elateridae: Dendrometrinae): an enigmatic click beetle with a convoluted taxonomic history.

Plastocerus angulosus (Germar, 1844) is one of the only two species of genus Plastocerus Schaum, 1852 within the monogeneric click beetle tribe Plastocerini. It is distributed in the area comprising Greece, Turkey, Syria, Israel, and Lebanon (first record for Lebanon published here). Due to the slightly modified morphology of P. angulosus, this taxon has a convoluted taxonomic history and was earlier classified in various families and even superfamilies. However, recent phylogenies place it in Elateridae: Dendrometrinae. In this study, we review the morphology, intraspecific morphological and genetic variability, sexual dimorphism, systematics, bibliography, and distribution of P. angulosus. Our results show rather low morphological and relatively high genetic variability in this species. Females, which are larger than males and differ mainly in the antennae and abdominal ventrites, are not so rare as previously thought. Further field research should focus on the discovery of immature stages to describe their morphology and understand their biology and ecology.

Morphological variation of African snakehead (Parachanna obscura) populations along climate and habitat gradients in Côte d’Ivoire, West Africa

Intraspecific morphological variation may reflect phenotypic plasticity or adaptive divergence. While adaptive shape divergence may occur more likely among isolated populations with reduced gene flow, phenotypic plasticity may reflect morphological responses to heterogeneous environments, even in spatially connected populations. We evaluated both processes while examining morphological variations among seven wild populations of snakehead fish (Parachanna obscura) along climate and habitat gradients in Côte d’Ivoire, West Africa. Morphological variations were studied by multivariate canonical variate analysis (CVA) as based on geometric morphometrics of 15 fish body landmarks. Correlations between shape variations among populations and climate and habitat characteristics and between morphological and geographic distances were calculated. We found significant morphological variations among the seven populations. The variations in fish shape were concentrated on landmarks related to swimming and feeding, suggesting a contribution of environmental variation to morphological differentiation. However, we did not detect significant effects of climate and habitat variables on fish shape. The trend between geographical and morphological distances was likewise not significant. Therefore, a mechanistic understanding of the factors causing shape variation among P. obscura populations in West Africa could not yet be achieved.

Widespread coexistence of genetically distinct morphotypes in theSatyrium longicaudacomplex (Orchidaceae)

AbstractSpecies-level taxonomy is traditionally based on herbarium collections that typically include few, or even single, representatives per site. This can lead to underestimation of diversity when there are sympatric populations of superficially similar plants belonging to different lineages. Satyrium longicauda (Orchidaceae) represents a taxonomic challenge for the delimitation of species boundaries due to the high degree of morphological variation detected within and among populations. Currently, just two varieties are accepted based mainly on length differences of the lateral sepal and nectar spur. However, there is extensive morphological variation within South African populations and evidence for several pollination ecotypes, indicating that this taxon represents an actively diverging species complex. Here, we evaluate intraspecific morphological variation through uni- and multivariate morphometrics and analyse internal transcribed spacer sequences for individuals sampled from 36 sites, including 14 sites where divergent morphotypes occur sympatrically. Morphometric analyses of 1802 individuals revealed the presence of eight morphotypes based on vegetative and floral characters. Up to six morphologically and genetically distinct morphotypes can coexist in sympatry. Morphological and genetic distances among populations were significantly correlated. Phylogenetic analyses of 120 accessions indicated that neither of the two varieties nor S. longicauda as a species is monophyletic, and provided evidence for the monophyly of some of the morphotypes including the newly described S. cernuiflorum. The presence of distinct morphological and genetic sympatric variants, which in several cases scale up to distinct evolutionary lineages, is consistent with the existence of different taxa according to morphological and biological species concepts. Our results therefore confirm that taxonomy based mainly on herbarium collections can grossly under-estimate actual diversity of disparate lineages, although further work is required to finalize taxonomic decisions. These findings have implications for efforts to estimate species diversity in groups that are in the process of diversifying and for conservation practice.

Living Taxa and Their Importance in Understanding the Extinct Diversity: A Look at Polypterid Pinnules

Pinnules are the peculiar, impaired spines that carry each of the numerous finlets that constitute the dorsal fins of polypterid fishes (Cladistia and Polypteriformes). Previous studies, including a recent detailed paper on the comparative analysis of the morphology of pinnules in most of the extant species (genera Polypterus and Erpetoichthys), suggest that they display unique characteristics that allow for species identification. Since most of the polypterid fossil records are composed of scales that lack specific characteristics and isolated pinnules, this work aims to test their taxonomic relevance before comparing the fossil pinnule morphologies across the fossil records in order to evaluate polypterid paleodiversity. Therefore, we describe the intra-individual and intra-specific morphological variations of the pinnules in the extant species Polypterus bichir. Furthermore, we compared it with the various morphologies described in the Polypteridae family. We report intra-individual variability related to the anteroposterior axis of the dorsal fin. We also report morphological differences in the pinnules among specimens that overlap those anticipated among different species, concluding that the pinnule morphology cannot support taxonomic purposes in polypterid fishes in their current state.

The intraspecific morphological variability of Styloperla Wu, 1935 (Plecoptera: Styloperlidae)

Intraspecific morphological variability of four Styloperla Wu, 1935 species are described and discussed in this paper. The males of each species have variable specializations present at their basal cercal process, including the variable number of branches or differing degrees of curvature at the apical spines. A generalization on the species definition of Plecoptera, especially a new concept of conspecificity is also provided herein.

Geographical Influence on Morphometric Variability of Genetically "Pure" Schistosoma haematobium Eggs from Sub-Saharan Migrants in Spain.

Schistosome eggs play a key role in schistosomiasis diagnosis and research. The aim of this work is to morphogenetically study the eggs of Schistosoma haematobium found in sub-Saharan migrants present in Spain, analyzing their morphometric variation in relation to the geographical origin of the parasite (Mali, Mauritania and Senegal). Only eggs considered "pure" S. haematobium by genetic characterization (rDNA ITS-2 and mtDNA cox1) have been used. A total of 162 eggs obtained from 20 migrants from Mali, Mauritania and Senegal were included in the study. Analyses were made by the Computer Image Analysis System (CIAS). Following a previously standardized methodology, seventeen measurements were carried out on each egg. The morphometric analysis of the three morphotypes detected (round, elongated and spindle) and the biometric variations in relation to the country of origin of the parasite on the egg phenotype were carried out by canonical variate analysis. Mahalanobis distances, when all egg measurements were analyzed, showed differences between: (i) Mali-Mauritania, Mali-Senegal and Mauritania-Senegal in the round morphotype; (ii) Mali-Mauritania and Mauritania-Senegal in the elongated morphotype; and (iii) Mauritania-Senegal in the spindle morphotype. Mahalanobis distances, when spine variables were analyzed, showed differences between Mali-Senegal in the round morphotype. In conclusion, this is the first phenotypic study performed on individually genotyped "pure" S. haematobium eggs, allowing the assessment of the intraspecific morphological variations associated with the geographical origin of the schistosome eggs.

Current advances in the identification of plant nematode diseases: From lab assays to in-field diagnostics.

Plant parasitic nematodes (PPNs) cause an important class of diseases that occur in almost all types of crops, seriously affecting yield and quality and causing great economic losses. Accurate and rapid diagnosis of nematodes is the basis for their control. PPNs often have interspecific overlays and large intraspecific variations in morphology, therefore identification is difficult based on morphological characters alone. Instead, molecular approaches have been developed to complement morphology-based approaches and/or avoid these issues with various degrees of achievement. A large number of PPNs species have been successfully detected by biochemical and molecular techniques. Newly developed isothermal amplification technologies and remote sensing methods have been recently introduced to diagnose PPNs directly in the field. These methods have been useful because they are fast, accurate, and cost-effective, but the use of integrative diagnosis, which combines remote sensing and molecular methods, is more appropriate in the field. In this paper, we review the latest research advances and the status of diagnostic approaches and techniques for PPNs, with the goal of improving PPNs identification and detection.

Creagrura Townes, 1971 and Ptilobaptus Townes, 1971 (Hymenoptera: Ichneumonidae) from Brazilian Amazon: new records and comments about morphological variation

Creagrura nigripes Townes, 1971 is recorded for the first time for the Brazilian Amazon, in the states of Acre, Amapá, Amazonas, Pará and Roraima. Ptilobaptus cinctus Townes, 1971 is registered for the first time in Brazil. Additionally, diagnosis, digital images, distribution maps, as well as comments on intraspecific morphological variations in the species are provided.

A Review of Ampelometry: Morphometric Characterization of the Grape (Vitis spp.) Leaf.

Grape (Vitis spp.) is one of the most important horticultural crops, cultivated worldwide on more than 7.3 million hectares for various purposes such as winemaking, fresh fruit consumption, rootstock, and ornamental plants. Based on the inter- and intraspecific morphological variability, several descriptor lists, manuals and ampelographic studies are available for identification. Among the organs, leaves have the most traits, while the young shoot, bunch and berry are also important in the characterization of the genotypes. Vitis species and cultivars are described by leaf morphological characterization developed in many ways for the identification of genotypes, to clarify synonymies and distinct clones or evaluate the diversity of wild Vitis taxa. Morphometric-also known as ampelometric-evaluation has an extensive background in the literature. However, for some reasons, only a part of the literature is cited, despite its significant scientific value. In this paper, we summarize the efforts of metric characterization of the grapevine leaf with the introduction of the scientific objectives and reviewing the studies showing the innovations in phenotyping during the past 120 years.