Divergent Length Research Articles

Sperm as a speciation phenotype in promiscuous songbirds.

Sperm morphology varies considerably among species. Sperm traits may contribute to speciation if they diverge fast in allopatry and cause conspecific sperm precedence upon secondary contact. However, their role in driving prezygotic isolation has been poorly investigated. Here we test the hypothesis that, early in the speciation process, female promiscuity promotes a reduction in overlap in sperm length distributions among songbird populations. We assembled a data set of 20 pairs of populations with known sperm length distributions, a published estimate of divergence time, and an index of female promiscuity derived from extrapair paternity rates or relative testis size. We found that sperm length distributions diverged more rapidly in more promiscuous species. Faster divergence between sperm length distributions was caused by the lower variance in the trait in more promiscuous species, and not by faster divergence of the mean sperm lengths. The reduced variance is presumably due to stronger stabilizing selection on sperm length mediated by sperm competition. If divergent sperm length optima in allopatry causes conspecific sperm precedence in sympatry, which remains to be shown empirically, female promiscuity may promote prezygotic isolation and rapid speciation in songbirds.

Semantic search using protein large language models detects class II microcins in bacterial genomes.

Antibiotic resistance is becoming an increasingly serious problem in modern medicine, but the development pipeline for conventional antibiotics is not promising. Therefore, alternative approaches to combat bacterial infections are urgently needed. One such approach may be to employ naturally occurring antibacterial peptides produced by bacteria to kill competing bacteria. A promising class of such peptides are class II microcins. However, only a small number of class II microcins have been discovered to date, and the discovery of further such microcins has been hampered by their high sequence divergence and short length, which can cause sequence-based search methods to fail. Here, we demonstrate that a more robust method for microcin discovery can be built on the basis of a protein large language model, and we use this method to identify several putative novel class II microcins.

Multi-objective optimization and performance improvement of CD nozzle design parameters for cold spray coating process using RSM, ANN and GA

This study presents the multi-objective optimization of the convergent-divergent (CD) nozzle for the cold spray (CS) process and investigates the impact of five key nozzle design parameters. A 2D axisymmetric baseline nozzle was optimized through face central composite design (FCCD), computational fluid dynamics (CFD) simulations, response surface methodology (RSM), artificial neural networks (ANN), and genetic algorithms (GA). The nozzle performance in the CS process advances the manufacturing technologies by significantly optimizing the four response variables. Comparative analysis shows that RSM models (R² = 0.9893) were more accurate on average than ANN models (R² = 0.9848), although ANN provided a deeper understanding of complex interactions with an overall correlation coefficient of 0.99191. Sensitivity analysis suggested that increasing convergent length (Lc) increases particle velocity (PV) before it stabilizes while particle temperature (PT) decreases due to cooling effects. Divergent length (Ld) increases PV to an optimal range, but reduces PT, indicating energy loss. Smaller injector inner diameter (Did) enhances PV but reduces PT. Injector length (Li) increases PV to a certain limit, beyond which benefits stabilizes, and also increases surface pressure (SP). Expanding the exit diameter (De) increases PV, drops PT and heat flux (HF), and reduces SP, indicating decreased flow resistance. Optimization with RSM coupled with numerical simulation (RSM-DF) improved PV, PT, HF, and SP by 9.1 %, 4.4 %, 17.9 %, and 27.6 % respectively. Further optimization with a 5–6–4 ANN and GA (NSGA-II) improved PV by 5 %, PT by 5.4 %, HF by 15.7 %, and reduced SP by 20.9 %. Integrating CFD, RSM, ANN, and GA provides an effective approach for optimizing CD nozzle parameters.

CFD Investigation of a Co-Flow Nozzle for Cold Spray Additive Manufacturing Applications

This current work evaluates the efficacy of a co-flow nozzle for cold spray applications with the aim of mitigating nozzle clogging issues, which can occur during long-duration operations, by replacing the solid wall of a divergent nozzle section with an annular co-flow fluid boundary. Simulations were conducted on high-pressure nitrogen flowing through convergent–divergent (C–D) axisymmetric nozzles, with a stagnation pressure of 6 MPa and a stagnation temperature of 1273 K. In these simulations, Inconel 718 particles of varying sizes (15 µm to 35 µm) were modeled using a 2-way Lagrangian technique, and the model’s accuracy was confirmed through validation against experimental results. An annular co-flow nozzle with a circular cross section and straight passage covering the primary C–D nozzle has been designed and modeled for cold spray application. Co-flow was introduced to the reduced nozzle length to compensate for particle velocity loss at higher operating conditions. It was found that co-flow facilitates momentum preservation for primary flow by providing an annular gas boundary, resulting in increased particle speed for a longer axial distance beyond the nozzle exit of the reduced divergent length nozzle. The particle acceleration performance of the reduced divergent section nozzle, when combined with co-flow, is comparable to the original length nozzle.

Morphometric Measurements of Root Anatomic Areas of Maxillary First Premolar Teeth in a Representative Nepalese Population

Background The prognosis of furcation involved maxillary first premolar is typically guarded to poor. The presence of concavities in the root trunk and the positioning of the roots in the buccal and palatal regions of the teeth are responsible for its challenges during instrumentation and control plaque. We aimed to access the presence of concavities on the root surface as well as morphometric measurement of the root trunk dimensions in the maxillary first premolar teeth in Nepalese population.MethodsA cross-sectional quantitative study was conducted in the Department of Periodontics and Oral Implantology, College of Medical Sciences (CoMS). Extracted Maxillary first premolar teeth were evaluated for the number of roots, morphometric measurement of the root trunk, root divergence, and root length. The presence of concavities was recorded on the mesial and distal root surface at cervical, middle, and apical thirds of the root.ResultsThe overall mean root trunk length was less on the mesial aspect than on the distal aspect (6.39 ± 2.54 and 8.08 ± 3.48 respectively). The prevalence of root surface concavity on the cervical third at the mesial aspect (90 %) was found to be higher than in the distal aspect (15%) Conclusions Owing to the higher prevalence of root surface concavity on the cervical third of mesial aspect, use of mini-bladed curettes is recommended for the effective root surface debridement of the periodontally involved maxillary first premolar tooth. Patients with periodontally involved maxillary first premolar should be advised to use interdental brushes rather than dental floss.

Stable Measurement-Induced Floquet Enriched Topological Order.

The Floquet code utilizes a periodic sequence of two-qubit measurements to realize the topological order. After each measurement round, the instantaneous stabilizer group can be mapped to a honeycomb toric code, explaining the topological feature. The code also possesses a time-crystal order-the e-m transmutation after every cycle, breaking the Floquet symmetry of the measurement schedule. This behavior is distinct from the stationary topological order realized in either random circuits or time-independent Hamiltonian. Therefore, the resultant phase belongs to the overlap between the classes of Floquet enriched topological orders and measurement-induced phases. In this Letter, we construct a continuous path interpolating between the Floquet and toric codes, focusing on the transition between the time-crystal and stationary topological phases. We show that this transition is characterized by a divergent length scale. We also add single-qubit perturbations to the model and obtain a richer two-dimensional parametric phase diagram of the Floquet code, showing the stability of the Floquet enriched topological order.

Optimization of hydrogen ejector structure in proton exchange membrane fuel cell system under wide operating conditions

ABSTRACT Considering the characteristics of the hydrogen ejector for proton exchange membrane fuel cell system used in vehicles, with the aim of expanding the operating range, the ejector structure parameters are comprehensively analyzed and optimized. The results indicate that reducing the throat diameter can expand its operating range. When the working conditions change significantly, the convergent nozzle should be selected, the convergence length and throat length of the nozzle have little effect on the ejection performance. There are optimal suction chamber convergence length (8 mm), diffuser divergent angle (7.1°) and length (33.8 mm), nozzle exit position (−7 mm) in variable working conditions to achieve good ejection performance. Reducing the diameter and length of the mixing chamber is beneficial for expanding the operating range. Before ejector optimization, when the primary fluid mass flow rate is less than the design value, the ejection performance deteriorates sharply with the decrease of the flow rate. When the primary fluid mass flow rate is lower than 0.4 g/s, the non-optimization ejector is backflow, the maximum ejection ratio is about 1.8 and the maximum hydrogen ejection ratio is about 0.67 in the operating range. After optimization, the ejector performance is stable. Under the set operating conditions, the hydrogen ejection ratio is greater than 0.75, the maximum ejection ratio is 3.8, and the maximum hydrogen ejection ratio is 1.01.

A novel in-flight thrust modulation technique for SPRM: proof of concept

Thrust modulation (termination or reduction) is one of the most sophisticated topics in rocket motors. Thrust termination is employed when combustion must be terminated to ensure proper stage separation, to avoid motor explosion, to attain certain range, or for research purposes. While liquid and hybrid propellant rocket motors have the ability to extinguish thrust, thrust termination in solid propellant rocket motors (SPRMs) need the use of specialized technology. In-flight thrust termination of (SPRMs) can be achieved by sudden and sufficient increase in throat area. Increasing throat area causes high depressurization rate which consequently leads to extinguishing the rocket motor. In contrast, in-flight thrust reduction can be theoretically attained either by reducing chamber pressure to a new equilibrium level or by reducing the divergent section length. The objective of the present paper is to prove the concept of using Linear Shaped Charge (LSC) for thrust modulation; a technique novel to SPRM applications. Thrust termination concept is proved via a set of static firing tests on a standard test motor. In addition, a mathematical model is developed to predict the drop in thrust due to cutting the nozzle at any arbitrary location. The model is validated by comparing with published experiments for thrust termination and reduction. A parametric study is conducted based on model results. It is confirmed that by cutting the nozzle along its divergent section, thrust reduction less than 20% can be attained. Further reduction can be achieved by cutting the nozzle along its convergent section.

Orthogonal analysis method for multi – Objective optimization of CO2 nozzle thermodynamic performance

In this study, the structural parameters of the converging diverging (CD) nozzle in a subcritical or supercritical CO2 cycle system were optimized by L16 (44) orthogonal design. The established model was used to analyse the effect of divergence length Ld, divergence angle θ, convergence angle α and throat diameter Dth on the nozzle thermodynamic performance, and further optimization of CD nozzle structural parameters was carried out using comprehensive evaluation coefficients and comprehensive scores. The results indicate that Ld is the primary factor, and while the effects of θ and Dth were inconsistent in different application scenarios, attention should be paid to the size parameters of the nozzle divergence part during design. For CD nozzles with supercritical inlet pressure, there is a linear relationship between Ld and exergy destruction, while for subcritical CD nozzles, the effect of Ld is reduced. For a CD nozzle used in subcritical or transcritical cycles, the outlet exergy and exergy efficiency of the modified nozzle could be increased by 16.4% and 16.2%. For supercritical nozzles used in the Brayton cycle, the optimized exergy destruction was relatively reduced by 37%. The mass flow rate of the nozzle before and after optimization was reduced, with a maximum decrease of 22.7%, which is beneficial for improving the entrainment ratio of the ejector. In addition, it was found that considering this in the modelling process would lead to conservative optimization results. These research results could provide a reference for the design of the CO2 nozzle or motive nozzle of ejector.

Rapid sperm length divergence in a polygynandrous passerine: a mechanism of cryptic speciation?

When populations become geographically isolated, they begin to diverge in various traits and at variable rates. The dynamics of such trait divergences are relevant for understanding evolutionary processes such as local adaptation and speciation. Here we examine divergences in sperm and body structures in a polygynandrous songbird, the alpine accentor (Prunella collaris) between two allopatric high-altitude populations, in Morocco and Spain. The populations diverged around 82,000 years ago, as estimated with a coalescence-based phylogenetic analysis of genome-wide single-nucleotide polymorphisms. We found that birds in the two areas had nonoverlapping sperm lengths, which suggests adaptation to divergent female reproductive tract environments. Sperm length also showed an exceptionally low coefficient of among-male variation, a signal of strong stabilizing selection imposed by sperm competition. The evolutionary rate of sperm length was almost twice the rates for the most divergent morphological traits and more than three times higher than expected from literature data over a similar generational timescale. This rapid evolution of a key reproductive trait has implications for reproductive isolation and ultimately for speciation. Strong selection for different sperm length optima in allopatry predicts conspecific sperm precedence and disruptive selection in sympatry, hence a possible postcopulatory prezygotic barrier to gene flow.

Effect of Different Types of Sequence Data on Palaeognath Phylogeny.

Palaeognathae consists of five groups of extant species: flighted tinamous (1) and four flightless groups: kiwi (2), cassowaries and emu (3), rheas (4), and ostriches (5). Molecular studies supported the groupings of extinct moas with tinamous and elephant birds with kiwi as well as ostriches as the group that diverged first among the five groups. However, phylogenetic relationships among the five groups are still controversial. Previous studies showed extensive heterogeneity in estimated gene tree topologies from conserved nonexonic elements, introns, and ultraconserved elements. Using the noncoding loci together with protein-coding loci, this study investigated the factors that affected gene tree estimation error and the relationships among the five groups. Using closely related ostrich rather than distantly related chicken as the outgroup, concatenated and gene tree-based approaches supported rheas as the group that diverged first among groups (1)-(4). Whereas gene tree estimation error increased using loci with low sequence divergence and short length, topological bias in estimated trees occurred using loci with high sequence divergence and/or nucleotide composition bias and heterogeneity, which more occurred in trees estimated from coding loci than noncoding loci. Regarding the relationships of (1)-(4), the site patterns by parsimony criterion appeared less susceptible to the bias than tree construction assuming stationary time-homogeneous model and suggested the clustering of kiwi and cassowaries and emu the most likely with ∼40% support rather than the clustering of kiwi and rheas and that of kiwi and tinamous with 30% support each.

A Study on Converging-Diverging Nozzle Design for Supersonic Spraying of Liquid Droplets Toward Nanocoating Applications

Abstract Supersonic cold spray (CS) of functional nanomaterials from atomized droplets has attracted significant attention in advanced thin-film coating as it enables particle deposition with high-adhesion strength. In CS, optimum design of the supersonic nozzle (i.e., converging-diverging nozzle) is essential for accelerating particles to desired velocities. However, research on the nozzle design for supersonically spraying of “liquid droplets” for nanocoating applications is limited. To this end, we investigate the effect of nozzle geometrical parameters, including throat diameter, exit diameter, and divergent length on droplets impact velocity by numerical modeling and experimental validation, followed by a case study on nanocoating. The discrete-phase modeling was employed to study droplets’ flow behavior in continuous gas flow for various nozzle geometries. The results reveal that the nozzle expansion ratio, defined as a function of throat and exit diameters, has a significant influence on droplet velocity, followed by divergent length. Noteworthy, to correctly accelerate “low-inertia liquid microdroplets,” it was found that the optimum nozzle expansion ratio for axisymmetric convergent-divergent nozzles should be in a range of 1.5–2.5, which is different and way smaller than the recommended expansion ratio (i.e., 5–9) for CS of conventional micron-scale “metal” powders. Based on the simulation results, an optimum design of supersonic nozzle is established and prototyped for the experimental studies. Particle image velocimetry (PIV) was used to experimentally investigate the spray flow field and to validate the numerical modeling results. Moreover, coating experiments using the optimized nozzle confirmed the effective supersonic spraying of droplets containing nanoparticles, thereby showing the potential for advanced nanocoating applications.

Contrasting pseudocriticality in the classical two-dimensional Heisenberg and RP^{2} models: Zero-temperature phase transition versus finite-temperature crossover.

Tensor-network methods are used to perform a comparative study of the two-dimensional classical Heisenberg and RP^{2} models. We demonstrate that uniform matrix product states (MPSs) with explicit SO(3) symmetry can probe correlation lengths up to O(10^{3}) sites accurately, and we study the scaling of entanglement entropy and universal features of MPS entanglement spectra. For the Heisenberg model, we find no signs of a finite-temperature phase transition, supporting the scenario of asymptotic freedom. For the RP^{2} model we observe an abrupt onset of scaling behavior, consistent with hints of a finite-temperature phase transition reported in previous studies. A careful analysis of the softening of the correlation length divergence, the scaling of the entanglement entropy, and the MPS entanglement spectra shows that our results are inconsistent with true criticality, but are rather in agreement with the scenario of a crossover to a pseudocritical region which exhibits strong signatures of nematic quasi-long-range order at length scales below the true correlation length. Our results reveal a fundamental difference in scaling behavior between the Heisenberg and RP^{2} models: Whereas the emergence of scaling in the former shifts to zero temperature if the bond dimension is increased, it occurs at a finite bond-dimension independent crossover temperature in the latter.

Measurement system for ion beam profiles using fixed parallel wires and Faraday cup array

The radial profiles of ion current density are measured using a combination of two techniques—fixed parallel wires and a Faraday cup array—in a ring cusp ion source. These measurements are carried out for Ar+ ion beam current in the range of 20–90 mA and energy in the range of 850–1650 eV. Current density profiles near the extraction plane of the ion source are obtained by Abel inversion of the profiles of current measured using the parallel wires. In addition, the Faraday cup array provides radial profiles of ion current density at two different locations along the beam axis. A numerical model is developed and utilized for estimating the beam divergence and focal length from the profiles of ion current density measured using the two techniques. A fixed parallel wire array is established as an effective method for monitoring the ion beam profiles close to the ion source's extraction plane when the ion beam is utilized for other applications. The performance of the two measurement techniques is compared by estimating the ion beam current from the measurement of ion current density with the beam current measured from the power supply.

Natural variation in CRABS CLAW contributes to fruit length divergence in cucumber.

Fruit length is a key domestication trait that affects crop yield and appearance. Cucumber (Cucumis sativus) fruits vary from 5 to 60 cm in length. Despite the identification of several regulators and multiple quantitative trait loci (QTLs) underlying fruit length, the natural variation, and molecular mechanisms underlying differences in fruit length are poorly understood. Through map-based cloning, we identified a nonsynonymous polymorphism (G to A) in CRABS CLAW (CsCRC) as underlying the major-effect fruit size/shape QTL FS5.2 in cucumber. The short-fruit allele CsCRCA is a rare allele that has only been found in round-fruited semi-wild Xishuangbanna cucumbers. A near-isogenic line (NIL) homozygous for CsCRCA exhibited a 34∼39% reduction in fruit length. Introducing CsCRCG into this NIL rescued the short-fruit phenotype, and knockdown of CsCRCG resulted in shorter fruit and smaller cells. In natural cucumber populations, CsCRCG expression was positively correlated with fruit length. Further, CsCRCG, but not CsCRCA, targets the downstream auxin-responsive protein gene CsARP1 to regulate its expression. Knockout of CsARP1 produced shorter fruit with smaller cells. Hence, our work suggests that CsCRCG positively regulates fruit elongation through transcriptional activation of CsARP1 and thus enhances cell expansion. Using different CsCRC alleles provides a strategy to manipulate fruit length in cucumber breeding.

Theoretical and experimental investigation of the metal–insulator transition in disordered anti-dot graphene

We study the transport behavior of anti-dot graphene both theoretically and experimentally, where the term ‘anti-dot’ denotes the graphene layer to be nanostructured with a periodic array of holes. It has been shown that the electronic band structure of the anti-dot graphene can be described by a 4 by 4 effective Hamiltonian (Pan J et al 2017 Phys. Rev. X. 7 031043) with a gap around the Dirac point, attendant with a 0 to π variation of the Berry phase as a function of energy, measured from the band edge. Based on the diagrammatic method analysis and experiments, we identify an energy-dependent metal-to-insulator transition (MIT) in this two-dimensional (2D) system at a critical Fermi energy ɛ c, characterized by the divergence of the localization length in the Anderson localization phase to a de-localized metallic phase with diffusive transport. By measuring the conductance of square samples with varying dimension and at different Fermi energies, experiments were carried out to verify the theory predictions. While both theory and experiment indicate the existence of a 2D MIT with similar localization length divergence exponent, the values of the critical energy ɛ c and that of the localization length do not show quantitative agreement. Given the robust agreement in the appearance of a 2D MIT, we attribute the lack of quantitative agreement to the shortcomings in the theoretical model. The difficulties in addressing such shortcomings are discussed.

Structure optimization of the organ-pipe cavitating nozzle and its erosion ability test on hydrate-bearing sediments

Cavitating jet is a promising drilling rate improvement technology in both the marine natural gas hydrate (NGH) fluidization exploitation method and the integrated radial jet drilling and completion method. In present study, we aim to improve the efficiency of jet erosion and extracting NGH. With a computational fluid dynamics (CFD) method, the pressure, velocity and cavitation field characteristics of organ-pipe cavitating jet (OPCJ) are analysed. The divergent angle, throat length, and divergent length of OPCJ nozzle are preferred to obtain stronger jet cavitation erosion effect. Laboratory experiments of gas hydrate-bearing sediments (GHBS) erosion by OPCJ and conical jet (CJ) are conducted to compare and validate the jet erosion performance. The impinging models of OPCJ and CJ are constructed to study the impact characteristics. Results show that the preferred values of divergent angle, throat length, and divergent length are 15°, 1d, and 3d, respectively, in present simulation conditions. For GHBS, the OPCJ possesses the advantages of high efficiency and low energy consumption. Moreover, the OPCJ has higher penetration efficiency, while showing equivalent penetration ability compared to CJ. During the impinging process, the OPCJ can induce stronger impact pressure and turbulence effect, and also shows stronger chambering effect and bottom cleaning ability compared to CJ. This study presents the erosion performance of OPCJ and CJ on GHBS, and provides preliminary insights on the potential field applications in NGH exploitation.

Information flow in first-order potts model phase transition

Phase transitions abound in nature and society, and, from species extinction to stock market collapse, their prediction is of widespread importance. In earlier work we showed that Global Transfer Entropy, a general measure of information flow, was found to peaks away from the transition on the disordered side for the Ising model, a canonical second order transition. Here we show that (a) global transfer entropy also peaks on the disordered side of the transition of finite first order transitions, such as ecology dynamics on coral reefs, which have latent heat and no correlation length divergence, and (b) analysis of information flow across state boundaries unifies both transition orders. We obtain the first information-theoretic result for the high-order Potts model and the first demonstration of early warning of a first order transition. The unexpected earlier finding that global transfer entropy peaks on the disordered side of a transition is also found for finite first order systems, albeit not in the thermodynamic limit. By noting that the interface length of clusters in each phase is the dominant region of information flow, we unify the information theoretic behaviour of first and second order transitions.

Comparative Analysis of Two Pear Pests, Cacopsylla jukyungi and Cacopsylla burckhardti (Hemiptera: Psyllidae), Based on Complete Mitochondrial Genomes and Comparison to Confamilial Species

Mitochondrial genome sequences have been used in diverse fields of biology. In this study, we sequenced the complete mitochondrial genomes (mitogenome) of two pear pests: Cacopsylla jukyungi, the most damaging insect pest to commercial pears in South Korea, and Cacopsylla burckhardti (Hemiptera: Psyllidae). The two mitogenomes were compared to confamilial species to accumulate genetic information and understand evolutionary characteristics of the family Psyllidae. The 15,438 bp-and 14,799 bp-long complete mitogenomes of C. jukyungi and C. burckhardti, respectively, had many features typical of insect mitogenomes; however, at 1283 bp, the C. jukyungi mitogenome had an unusually long A+T-rich region, which was composed of two identical 540-bp repeat sequences. Among the intergenic spacer regions, the one located at the ND1 and trnS2 junction was relatively well conserved in length (mostly within 23–36 bp). This region had a high sequence identity in all Psyllidae, possessing a 5-bp consensus sequence (CGGTA), which is speculated to have a functional role. Though the A+T-rich region in available Psyllidae mitogenomes varied substantially in length (662–1430 bp) and sequence divergence, all species had a conserved sequence stretch at the 3′-end of srRNA, which is also speculated to have a functional role. Genetic divergence among genes indicated the lowest variability in srRNA, lrRNA, and COI, whereas ATP8 and ND6 showed the highest variability at both family and genus (Cacopsylla) levels. Our data provide evidence that the family Psyllidae, including current C. jukyungi and C. burckhardti, have evolutionary unique features that were previously undetected, along with the unique A+T-rich region structure in C. jukyungi.

No evidence for host plant associated genetic divergence in a population of Bullacris unicolor (Linnaeus, 1758) (Orthoptera: Pneumoridae)

Host-associated genetic differentiation in grasshoppers has received limited attention, due to a lack of information on grasshopper-plant associations. The bladder grasshopper, Bullacris unicolor (Linnaeus, 1758) (Orthoptera: Pneumoridae), is a phytophagous species that can occur on at least six host plants within its geographic range. However, the relationship between host plant association and genetic variation of bladder grasshoppers has not been studied before. In light of this, the present study examined host plant-related genetic [mitochondrial cytochrome oxidase 1 (CO1) and the internal transcribed spacer (ITS) gene regions] and morphological (antennal length, body length, head width, abdomen width, femur length, tibia length and pronotum length) divergence within a population of B. unicolor. We used two plant species, belonging to different families, namely Didelta spinosa (L.fil.) Aiton (Asteraceae) and Roepera morgsana (L.) Beier & Thulin (Zygophyllaceae), to evaluate variation between individuals collected on these two sympatric host plants at a single locality in the Northern Cape, South Africa. The results demonstrated non-significant host related genetic variation with very low values of FST, indicating a low level of variation. The phylogram strongly indicated that there are no host-associated genetic differences in B. unicolor by displaying limited genomic clustering, whereas some differentiation was observed between the morphological measurements of males and females among host plants. Further studies using microsatellite molecular markers may help to discern population genetic structure. In addition, significant host-associated morphological divergence highlights the need to examine the mechanisms by which host utilization affects morphological features.