Patterns Of Morphological Variation Research Articles

Patterns of morphological diversification are influenced by dietary evolution in a highly species-rich lizard radiation

The diversification of lineages is facilitated or constrained by the simultaneous evolution of multiple components of the phenotype that interact with each other during the course of speciation. When evolutionary radiations are adaptive, lineages proliferate via the emergence of multiple phenotypic optima that underlie diversification of species across multiple ecological niches. When radiations are non-adaptive, lineage proliferation unfolds constrained by similar (or nearly identical) correlations among traits that keep phenotypic and ecological diversity across newly emerging species within a single optimum. Nature offers very few opportunities where both types of diversification occur between closely related and highly diverse lineages. The Liolaemidae family of South American lizards offers unique such opportunities given two speciose lineages that have rapidly proliferated via adaptive (Liolaemus) and non-adaptive (Phymaturus) radiations. We analyze body shape in lizards in association with type of diet (herbivory, omnivory or carnivory). In these lizards, diet types have been suggested to be linked to body size. Our results confirm this hypothesis, with three body size optima tightly linked to all three diet types when radiation is both adaptive and non-adaptive. Diet reconstruction along their evolutionary history showed that the common ancestor of Liolaemidae was likely omnivorous, which is matched by ancestral reconstruction of body size. Phylogenetic PCA revealed that herbivorous species generally have more differentiated body shape than insectivores and omnivores. Herbivorous species have evolved larger heads, shorter hindlimbs and a small difference between forelimb and hindlimb length. In contrast, omnivores and insectivores have smaller heads and longer hindlimbs. Collectively, trophic niche plays an important role in defining body shape and size across species within lineages, and the patterns of trait–ecology correlations remain consistent when lineages have diversified via adaptive and non-adaptive radiation.

Evolution of intraspecific floral variation in a generalist-specialist pollination system.

Intraspecific processes impact macroevolutionary patterns through individual variation, selection, and ecological specialisation. According to the niche variation hypothesis, the broader ecological niche of gen- eralist species results in an increased morphological variation among individuals, either because they are constituted of diversified specialised individuals each exploiting a fraction of the species' niche, or because they are constituted of true generalist individuals that experience relaxed selection. To test this hypoth- esis, we surveyed the individual floral morphology of species of Antillean Gesneriaceae, a group that has transitioned between specialisation for hummingbird pollination and generalisation multiple times throughout its evolutionary history. We characterised the profiles of corollas using geometric morpho- metrics and compared the intraspecific shape variance of specialists and generalists in a phylogenetic context. We used three approaches that differently accounted for the high dimensionality of morphologi- cal traits, the ancestral reconstruction of pollination syndromes over time, and the error associated with the estimation of the intraspecific variance. Our findings provide partial support for the niche variation hypothesis. If considering the whole shape in the analysis corroborated this idea, decomposing the shape into principal components indicated that not all aspects of the corolla exhibit the same pattern of vari- ation. Specifically, pollination generalists tend to display greater intraspecific variation than specialists in terms of tubularity, but not of curvature. Accounting for the error in the variance estimation also reduced the support for the hypothesis, suggesting that larger sample sizes may be required to reach stronger conclusions. This study emphasises the reciprocal influence between plants and their pollinators on floral morphology at different biodiversity scales, and suggests that ecological strategies of species can affect patterns of morphological variation at macroevolutionary scales.

Morphological variation, modularity and integration in the scapula and humerus of Lissotriton newts.

The modular organization of tetrapod paired limbs and girdles, influenced by the expression of Hox genes is one of the primary driving forces of the evolution of animal locomotion. The increased morphological diversification of the paired limbs is correlated with reduced between-limb covariation, while correlation within the elements is usually higher than between the elements. The tailed amphibians, such as Lissotriton newts, have a biphasic lifestyle with aquatic and terrestrial environments imposing different constraints on limb skeleton. By employing the methods of computerized microtomography and 3D geometric morphometrics, we explored the pattern of morphological variation, disparity, modularity and morphological integration in the proximal parts of the anterior limbs of six species of Eurasian small bodied newts. Although the species significantly differ in limb shape, there is a great overlap in morphology of scapula and humerus, and there are no differences in morphological disparity. For the scapula, the shape differences related to the duration of the aquatic period are in length, depth and curvature. The shape of the humerus is not affected by the length of aquatic period, and shape differences between the species are related to robustness of the body. The length of aquatic period has statistically supported phylogenetic signal. The scapula and humerus are structures of varying modularity. For the humerus, the strongest support on the phylogenetic level was for the capitulum/shaft hypothesis, which can also be interpreted as functional modularity. For the scapula, the greatest support was for the antero-posterior hypothesis of modularity in case of Lissotriton vulgaris, which can be explained by different functional roles and muscle insertion patterns, while there was no phylogenetic modularity. The modularity patterns seem to correspond with the general tetrapod pattern, with modularity being more pronounced in the distal structure. The future research should include more salamandrid taxa with different habitat preferences and both adult and larval stages, in order to explore how size, phylogeny and ecology affect the morphology and covariation patterns of limbs.

Variation of thoracolumbar vertebral morphology in anthropoid primates.

Morphological variation among extant primates in the lumbar vertebral column is well studied. However, knowledge concerning the thoracic spine, an important region responsible for supporting and facilitating movement in the upper trunk, remains relatively scarce. Consequently, our comprehension of the functional differentiation exhibited throughout the thoracolumbar vertebral column among various primate species remains constrained. In this study, we examined patterns of morphological variation in the thoracolumbar vertebral column of extant hominoids, cercopithecoids, and Ateles. We collected external shape data on 606 thoracic and lumbar vertebrae from Homo sapiens, Pan troglodytes, Hylobates lar, Macaca fuscata, Chlorocebus aethiops, Colobus guereza, Ateles geoffroyi, and A. belzebuth. Forty-four landmarks were obtained on the three-dimensional surface. Geometric morphometrics was used to quantify the centroid size and variation of the shapes of thoracic and lumbar vertebrae. Cercopithecoids exhibited greater variation in the size and shape of their thoracic and lumbar vertebrae compared to hominoids and Ateles. Although many vertebral features contributed to the observed variation throughout the thoracolumbar vertebral column within the taxon, the transverse and spinous processes exhibited relatively major contributions. Our results suggest that quadrupedal locomotion requires the functional differentiation between thoracic and lumbar vertebrae, and for hominoids, functional adaptation to orthograde posture necessitates a relatively more uniform shape of thoracic and lumbar vertebrae.

Shape and Size Variations of Distal Phalanges in Cattle.

Studies on the structure of the distal phalanx help explain the development of laminitis. Additionally, examining the structure of the distal phalanx from a taxonomic perspective also contributes to veterinary anatomy. In this study, we examined shape variation in the medial and lateral distal phalanx of both fore- and hindlimbs using the geometric morphometry method. We investigated whether the shape of the distal phalanx differed between phalanx positions and how much of the shape variation in this bone depends on size. For this purpose, distal phalanges from 20 Holstein cattle were used, and the bones were digitized in 3D. A draft containing 176 semi-landmarks was prepared for shape analysis, and this draft was applied to all samples using automated landmarking through point cloud alignment and correspondence analysis. A principal component analysis was performed to obtain general patterns of morphological variation. The centroid size (CS) was employed as an approximation of size. Although distal phalanx groups generally showed close variations, PC1 statistically separated the hindlimb lateral distal phalanx (HL) and the forelimb medial distal phalanx (FM) from each other in shape. While PC2 separated HL from other distal phalanx groups, PC3 separated fore- and hindlimb groups. The shape (Procrustes distance) of the hindlimb medial distal phalanx (HM) is markedly less variable than the other three phalanges. The smallest distal phalanx in size was HL. For both forelimb and hindlimb, the medial distal phalanges were larger than the lateral ones. Size (CS) was found to have an effect on PC1 and PC3. In this study, a reference model of the same breeds for distal phalanx was created. These results can provide useful information, especially in terms of veterinary anatomy, zooarchaeology, and paleontology.

The third head of the biceps brachii muscle exhibiting variable shape presentation: Prevalence, variability and clinical considerations

IntroductionThe third head of the biceps brachii is the predominant variation of the arm muscles. Awareness of muscular variations is essential for the management of upper limb pathologies. Variations in the shape of the muscles are rarely explored. This study aimed to describe the prevalence and anatomical presentation of the third head of the biceps brachii muscle (origin, insertion and innervation) with an emphasis on the shape and form variations. Materials and methodsBiceps brachii of eighty-nine cadavers were examined. The presence of the third head, its origin, shape patterns, blood supply, and nerve innervation were determined and recorded. ResultsThe third head of the biceps brachii was present in 20.2 %, with a prevalence of 22.2 % in males and 18.2 % in females. Half (50 %) of these were bilateral presentations. Most (92 %) of the third head of the biceps brachii variations were flat, thin and straight in shape. All the shape variation patterns were observed in males and on the left arm. The third head originated from the humerus on its anteromedial aspect in 92 % of cases. The musculocutaneous nerve innervated the third head of the biceps brachii in 96 % of the cases, and a nerve anomaly of musculocutaneous and median nerves innervated it in a single (4 %) case. The muscular branches of the brachial artery supplied the third head of the biceps brachii in all cases. ConclusionStudies on the variation of arm muscles may assist in identifying new patterns of morphological variations like the shape of the muscle and may aid in the accurate diagnosis and management of arm pathologies.

Characterization and morphological diversity of sugarcane (Saccharum officinarum) genotypes based on descriptor traits

ABSTRACT An accurate and extensive study of the qualitative morphological diversity of sugarcane genotypes would allow their identification, conservation, and utilization in the sugarcane breeding program. The objectives of the study were to characterize and estimate the morphological diversity of sugarcane genotypes using qualitative traits. Data collected for 16 qualitative characters were analyzed using descriptive statistics and multivariate analysis to assess the overall patterns of morphological variation. The Shannon diversity index (H’) was calculated to estimate morphological diversity. The results indicated that the qualitative traits revealed high variability among 144 sugarcane genotypes. The most polymorphic character with the highest Shannon diversity index (H’) was stalk corky patchs. The H’ averaged across all countries for different characters was found to vary from 0.50 to 0.76 with an average of 0.61. The H’ pooled across characters by country of collection ranged from 0.00 to 0.83, with a general average of 0.62. Multivariate cluster analysis grouped the genotypes into four distinct clusters based on the relatedness and variation for all considered characters. Genotypes with close genetic relationships were grouped in a single cluster. The clustering pattern of the genotypes elucidated that genotypes originating from the same geographic locations did not form a single cluster. This shows that geographic diversity was not associated with genetic diversity, which possibly due to the continuous exchange of genetic material among countries. Finally, we conclude that the qualitative morphological traits evaluated in this study could be used for varietal identification, maintaining genetic diversity, and managing sugarcane germplasm.

Interplay of diet and sympatry in the morphological evolution of noctilionoid bats

AbstractAimThe remarkable ecomorphological diversity of the bat superfamily Noctilionoidea is the result of a diet‐mediated adaptive radiation. Stemming from a putatively insectivorous ancestor, noctilionoid bats diversified to adapt to the widest range of dietary ecologies among mammals. The high concentration of noctilionoid diversity in the Neotropics raises the question as to whether competitive ecological interactions influenced their diversification. However, patterns of morphological diversification along gradients of coexistence in Noctilionoidea are understudied. Here, we assessed the effect of dietary adaptations on patterns of morphological divergence associated with coexistence in noctilionoid bats.LocationThe Americas and the Caribbean.TaxonBat superfamily Noctilionoidea.MethodsUsing a set of five dental morphological traits and a sample of 108 species, we quantified morphological distances between noctilionoid species pairs to reveal patterns of morphological divergence along gradients of range overlap and dietary similarity. We incorporate phylogenetic information to control for the effects of species' relatedness on morphological distances.ResultsOverall, we found a significant association between morphological divergence, coexistence and diet. Decomposing the correlation between morphological divergence and sympatry across dietary groups, our results revealed distinctive patterns consistent with both character convergence and divergence. Specifically, we found evidence of character convergence in herbivorous species and character divergence in omnivorous species.Main ConclusionsOur results indicate that the morphological diversification of noctilionoid bats followed parallel evolutionary trajectories of directional (both divergent and stabilising) and nonselective evolution linked to dietary adaptations.

Morphological variability or inter-observer bias? A methodological toolkit to improve data quality of multi-researcher datasets for the analysis of morphological variation.

The investigation of morphological variation in animals is widely used in taxonomy, ecology, and evolution. Using large datasets for meta-analyses has dramatically increased, raising concerns about dataset compatibilities and biases introduced by contributions of multiple researchers. We compiled morphological data on 13 variables for 3073 individual mouse lemurs (Cheirogaleidae, Microcebus spp.) from 25 taxa and 153 different sampling locations, measured by 48 different researchers. We introduced and applied a filtering pipeline and quantified improvements in data quality (Shapiro-Francia statistic, skewness, and excess kurtosis). The filtered dataset was then used to test for genus-wide sexual size dimorphism and the applicability of Rensch's, Allen's, and Bergmann's rules. Our pipeline reduced inter-observer bias (i.e., increased normality of data distributions). Inter-observer reliability of measurements was notably variable, highlighting the need to reduce data collection biases. Although subtle, we found a consistent pattern of sexual size dimorphism across Microcebus, with females being the larger (but not heavier) sex. Sexual size dimorphism was isometric, providing no support for Rensch's rule. Variations in tail length but not in ear size were consistent with the predictions of Allen's rule. Body mass and length followed a pattern contrary to predictions of Bergmann's rule. We highlighted the usefulness of large multi-researcher datasets for testing ecological hypotheses after correcting for inter-observer biases. Using genus-wide tests, we outlined generalizable patterns of morphological variability across all mouse lemurs. This new methodological toolkit aims to facilitate future large-scale morphological comparisons for a wide range of taxa and applications.

Patterns of morphological variation and ecological correlates in the skull of vipers (Serpentes: Viperidae).

The skull of vipers is a highly kinetic anatomical structure involved in envenomating and consuming of prey. Morphological knowledge about the viperid skull is based on studies on some groups of species, but information on its variation within the whole family and its functional morphology is still scarce. In this study, we aimed to explore variation in skull morphology among species of the three subfamilies of Viperidae, and test whether that variation correlates with macrohabitat and diet. We performed quantitative analyses of the viperid skull based on broad taxonomic sampling and two methodological approaches: linear and geometric morphometrics. The results of both approaches showed that much of the variation lies in differences of shape and relative size of the premaxilla, the nasals, the frontals, and the parietals. The results indicated that phylogeny and size influence the shape of the skull, but we also found evidence of morphological differentiation between arboreal and terrestrial species and in species with mammal specialist diet. Our findings imply that, besides evolutionary allometry and phylogenetic signal, demands of particular diets coupled with use of certain habitats have in part shaped morphological evolution of the viperid skull.

Intrageneric taxonomic distinction based on morphological variation in the macaque (Macaca) skeleton.

Taxonomic classification is important for understanding the natural world, yet current methods for species assessment often focus on craniodental morphology rather than the entire skeleton. Moreover, it is currently unknown how much variation could, or should, exist intragenerically. Here, we tested whether taxonomy can be accurately predicted based on patterns of morphological variation in macaques (H1 ) and whether postcranial bones reflect subgeneric macaque taxonomy similarly, or better, than the cranium (H2 ). Data included 3D scans of cranial and postcranial bones for eight macaque species (Macaca arctoides, Macaca fascicularis, Macaca fuscata, Macaca mulatta, Macaca nemestrina, Macaca nigra, Macaca radiata, and Macaca sylvanus). Fixed anatomical and semilandmarks were applied to scans of eight skeletal elements (crania = 45; mandible = 31; scapula = 66; humerus = 38; radius = 33; os coxa = 28; femur = 40; tibia = 40). For each skeletal element, regression analyses were performed to minimize the effects of sexual dimorphism. Between-groups principal components analysis was used to visualize the major patterns of among-species morphological variation, while the strength of correct taxon classification was measured with discriminant function analysis. Results suggested accepting the alternate hypothesis that different macaque species can be distinguished morphologically. Both cranial and many postcranial elements appeared to possess a taxonomic signal, and the limb bones-especially the upper limb-are reported to be more useful for taxonomic assessment than previously realized. Theoretically, certain behaviors and/or ecogeographical factors, as well as phylogeny, influenced skeletal morphology in macaques, likely contributing to taxonomic distinctions among different species.

Postnatal growth and spatial conformity of the cranium, brain, eyeballs and masseter muscles in the macaque (Macaca mulatta).

Spatial growth constraints in the head region can lead to coordinated patterns of morphological variation that pleiotropically modify genetically defined phenotypes as the tissues compete for space. Here we test for such architectural modifications during rhesus macaque (Macaca mulatta) postnatal ontogeny. We captured cranium and brain shape from 153 MRI datasets spanning 13 to 1090 postnatal days and tested for patterns of covariation with measurements of relative brain, eyeball, and masseter muscle size as well as callosal tract length. We find that the shape of the infant (<365 days) macaque cranium was most closely aligned to masseter muscle and brain size measured relative to face size. Infant brain and juvenile (365-1090 days) cranium shape were more closely linked with brain size relative to basicranium and face size. Meanwhile, the juvenile macaque brain shape was dominated by the size of the brain relative to that of the basicranium. Associations with relative eyeball size and commissural tract lengths were weaker. Our results are consistent with a spatial-packing regime operating during postnatal macaque ontogeny, in which relative growth of the masseter, face and basicranium have a greater influence than brain growth on the overall shape of the cranium and brain.

Genetic basis of ecologically relevant body shape variation among four genera of cichlid fishes.

Divergence in body shape is one of the most widespread and repeated patterns of morphological variation in fishes and is associated with habitat specification and swimming mechanics. Such ecological diversification is the first stage of the explosive adaptive radiation of cichlid fishes in the East African Rift Lakes. We use two hybrid crosses of cichlids (Metriaclima sp. × Aulonocara sp. and Labidochromis sp. × Labeotropheus sp., >975 animals total) to determine the genetic basis of body shape diversification that is similar to benthic-pelagic divergence across fishes. Using a series of both linear and geometric shape measurements, we identified 34 quantitative trait loci (QTL) that underlie various aspects of body shape variation. These QTL are spread throughout the genome, each explaining 3.2-8.6% of phenotypic variation, and are largely modular. Further, QTL are distinct both between these two crosses of Lake Malawi cichlids and compared to previously identified QTL for body shape in fishes such as sticklebacks. We find that body shape is controlled by many genes of small effect. In all, we find that convergent body shape phenotypes commonly observed across fish clades are most likely due to distinct genetic and molecular mechanisms.

The skull variation of the olive field mouse Abrothrix olivacea (Cricetidae: Abrotrichini) is localized and correlated to the ecogeographic features of its geographic distribution.

The relationship between phenotypic variation and landscape heterogeneity has been extensively studied to understand how the environment influences patterns of morphological variation and differentiation of populations. Several studies had partially addressed intraspecific variation in the sigmodontine rodent Abrothrix olivacea, focusing on the characterization of physiological aspects and cranial variation. However, these had been conducted based on geographically restricted populational samples, and in most cases, the aspects characterized were not explicitly contextualized with the environmental configurations in which the populations occurred. Here, the cranial variation of A. olivacea was characterized by recording twenty cranial measurements in 235 individuals from 64 localities in Argentina and Chile, which widely cover the geographic and environmental distribution of this species. The morphological variation was analyzed and ecogeographically contextualized using multivariate statistical analyses, which also included climatic and ecological variation at the localities where the individuals were sampled. Results indicate that the cranial variation of this species is mostly clustered in localized patterns associated to the types of environments, and that the levels of cranial differentiation are higher among the populations from arid and treeless zones. Additionally, the ecogeographical association of cranial size variation indicate that this species does not follow Bergmann's rule and that island populations exhibit larger cranial sizes compared to their continental counterparts distributed at the same latitudes. These results suggest that cranial differentiation among the populations of this species is not homogeneous throughout its geographic distribution, and that the patterns of morphological differentiation are also not completely consistent with the patterns of genetic structuring that have been described recently. Finally, the analyses performed to ponder morphological differentiation among populations suggest that the contribution of genetic drift in the formation of these patterns can be ruled out among Patagonian populations, and that the selective effect imposed by the environment could better explain them.

Using RADseq to resolve species boundaries in a morphologically complex group of yellow-flowered shrubs (Geleznowia, Rutaceae)

The morphologically complex and charismatic genus Geleznowia (Rutaceae) is endemic to south-western Australia and faces existing and potential conservation issues associated with land clearing, climate change and commercial harvesting. Two species are currently recognised in the genus, but horticulturally recognised forms and phrase-named taxa reflect additional suspected species diversity. The genus exhibits complicated and subtle patterns of morphological variation that have historically inhibited delimitation of taxonomic entities and, as a result, precluded effective conservation assessments. Here we used ddRAD data from 25 populations across the range of Geleznowia to elucidate genomic diversity in the group in conjunction with morphological re-assessment so as to delimit species and revise the taxonomy. Our analyses consistently identified seven entities that maintain genomic distinctiveness even in sympatry with other entities, supporting the inference of reproductive barriers and lineage divergence. Morphological assessment of more than 300 specimens corroborated these seven taxa. Consequently, we recognise seven species of Geleznowia in Western Australia, retaining G. amabilis K.A.Sheph. &amp; A.D.Crawford, recircumscribing G. verrucosa Turcz., reinstating G. calycina (J.Drumm. ex Harv.) Benth., and naming four new species as G. eximia K.A.Sheph. &amp; A.D.Crawford, G. narcissoides K.A.Sheph. &amp; A.D.Crawford, G. occulta K.A.Sheph. &amp; A.D.Crawford, and G. uberiflora K.A.Sheph. &amp; A.D.Crawford.

Population variability of vegetative organs of Dahurian larch in Eastern Transbaikalia

The available information on the morphological diversity and localization of the morphological forms of Dahurian larch (Larix gmelinii) in Siberia is currently insufficient. This research seeks to fill the knowledge gaps to some extent. The paper describes the population variability of vegetative organs of Larix gmelinii growing in Eastern Transbaikalia, Russia. The problem is approached by studying a complex of morphological characters of natural Larix gmelinii populations along the Transbaikalian rivers. Also, the habitat conditions of Dahurian larch coenopopulations were recorded for further analysis of the connection between the morphological characters and the habitat parameters. The study established the values of morphological characters and their variability limits and traced the localization patterns of the morphological forms of Dahurian larch in the river basins. Moreover, the morphological characters of larch vegetative organs were found to relate to the location and the habitat conditions of the coenopopulations. The research materials can be useful for correcting the larch seeding zones in Transbaikalia, establishing larch genetic reserves, and introducing new morphological forms into the selection for urban beautification and protective plantations. The study provides additional information on the morphological variability patterns of Larix gmelinii for the area of species in general. Keywords: Eastern Transbaikalia, Larix gmelinii, vegetative organs, population variability

Patterns of morphological variation highlight the effect of natural selection on eyespots modularity in the butterfly Morpho telemachus.

Morphological correlations can not only stem from developmental constraints but also from selective pressures. Butterfly eyespots are repeated wing color pattern elements, widespread across species. As developmental serial homologs, they are controlled by similar developmental pathways imposing correlations among eyespots: selection on a single eyespot may induce correlated responses in all eyespots. We study the variations in the ventral eyespots of Morpho telemachus, where two different selective regimes are likely to act: while most eyespots are always-visible, two eyespots are conditionally displayed: hidden at rest, they can be exposed when the butterflies are threatened, or during sexual interactions. We investigate how such contrasted selection across eyespots can alter the covariations imposed by their shared developmental origin. We quantified eyespots covariations within a large population of M. telemachus and compared the observed patterns to those found in M. helenor, where all eyespots are always-visible and thus probably affected by a similar selection regime. We found that M. telemachus conditionally displayed eyespots are less variable than always-visible eyespots and that these two eyespots form a separate variational module in this species, in contrast to M. helenor. Our results suggest that eyespots covariations were shaped by selection, highlighting how natural selection may promote the evolution of modularity.

Reevaluation of the status of the Central American brocket deerMazama temama(Artiodactyla: Cervidae) subspecies based on morphological and environmental evidence

AbstractThe Central American brocket deer (Mazama temama) is widespread across the Mesoamerican forests, yet it remains largely unknown. Three subspecies are recognized currently within M. temama using pelage coloration as the primary diagnostic character. However, it remains unclear if there is any pattern of morphological variation throughout its distribution. We compared two models of morphological subdivision, namely the traditional subspecies and another based on biogeographic provinces via 2D geometric morphometrics and ecological niche modeling. The second model presented a better fit to the observed variation in cranial shape and size. We found divergence in skull size between individuals from Mexico and Guatemala (northern group) relative to specimens from Honduras, Nicaragua, Costa Rica, and Panama (southern group), the latter being 8% larger than the northern group. Centroid size showed a significant correlation with geographic distance suggesting an isolation-by-distance pattern. Low geographical overlap between the two clusters suggests niche conservatism. Late Pleistocene dispersal from South to Central America and differences in available resources with subsequent isolation due to climatic barriers therefore may have promoted differentiation in size albeit without extensive changes in shape. In this context, the Motagua-Polochic-Jolotán fault system probably plays a key role in promoting morphological differentiation by climatic isolation. Finally, we suggest that M. t. temama (Kerr, 1792) and M. t. reperticiaGoldman, 1913 should remain as valid names for the two morphological and ecologically differentiated groups detected here.

Geometric Morphometric Analysis and Molecular Identification of Coconut Mite, Aceria guerreronis Keifer (Acari: Eriophyidae) Collected from Thailand.

One of the most impactful pests in several coconut production regions across the world is the coconut mite, Aceria guerreronis Keifer. Scholars can obtain some necessary biogeographic information about coconut mites from studies that explore the geographic patterns of morphological variations and molecular properties among coconut mite populations from various locales. To investigate the geographical origin, ancestral host associations, and colonization history of the mite in Thailand, we obtained DNA sequence data from two mitochondrial (16s and COI) and one nuclear region (ITS) from coconut mite samples originating from 25 populations; additionally, we analyzed the morphological variations in the prodorsal shield and the coxigenital and ventral regions of the mite idiosoma. From the results of experiments using both identification methods, we identified the mite as the coconut mite, A. guerreronis (Acari: Eriophyidae). According to the phylogenetic analysis results of the 25 mite samples, we classified the mites as being closely related to mites found by the authors of a previous report in India. We are the first to report the results of a geometric morphometric analysis and molecular identification of A. guerreronis in Thailand, and our findings support the idea that the mites' origin and invasion history are not well documented, which makes it difficult to apply quarantine procedures and search for biological pest control agents.

Morphological and distributional patterns of native and invasive Trifolium (Papilionoideae, Leguminosae) species in southern South America

The ability of a species to colonize new geographical areas is closely related to its morphological response to environmental gradients. Previous studies compared native and alien invasive species in their ability to modify their morphology in reaction to climatic and edaphic factors; however, taxonomically close species have been scarcely analyzed. In this study, morphological variability patterns associated with abiotic factors were evaluated in Trifolium polymorphum, a native species distributed from southern Brazil to northern Patagonia, and Trifolium repens, a species introduced as an important forage crop and naturalized in diverse environments of southern South America. A morphometric study was carried out using herbarium specimens that were then georeferenced to obtain environmental and distributional data. Morphological traits along abiotic and geographical gradients were analyzed, predictive distribution and current and future niches were modelled. Our results showed that leaf morphology of T. repens responds to precipitation and temperature factors, which could explain its invasive behavior in a wide range of environments. Morphological variability of the native T. polymorphum presented a low association with abiotic factors, suggesting possible difficulties in adapting to future environmental changes. Ecological niche modelling analysis showed several overlap areas between species in the current model and a greater expansion of the distribution range of the invasive species in future climate change scenarios.