Related Species Research Articles

The Paussus (Scaphipaussus) lanxangensis species group of Indomalayan ant nest beetles (Coleoptera, Carabidae, Paussinae, Paussini) with description of a new species

The new species Paussus agatae sp. nov. could not easily be allocated to an established subgenus or even species group. The informal Paussus lanxangensis species group is established to include the new species and other related species. Its diagnostic characters are described and screened for possible use in cladistic analyses in the future. Currently, it consists of five described species of the Indomalayan mainland, which are arranged in a key.

Phylogenomics analysis of Scutellaria (Lamiaceae) of the world.

Scutellaria, a sub-cosmopolitan genus, stands as one of the Lamiaceae family's largest genera, encompassing approximately 500 species found in both temperate and tropical montane regions. Recognized for its significant medicinal properties, this genus has garnered attention as a research focus, showcasing anti-cancer, anti-inflammatory, antioxidant, and hepatoprotective qualities. Additionally, it finds application in agriculture and horticulture. Comprehending Scutellaria's taxonomy is pivotal for its effective utilization and conservation. However, the current taxonomic frameworks, primarily based on morphological characteristics, are inadequate. Despite several phylogenetic studies, the species relationships and delimitations remain ambiguous, leaving the genus without a stable and reliable classification system. This study analyzed 234 complete chloroplast genomes, comprising 220 new and 14 previously published sequences across 206 species, subspecies, and varieties worldwide. Phylogenetic analysis was conducted using six data matrices through Maximum Likelihood and Bayesian Inference, resulting in a robustly supported phylogenetic framework for Scutellaria. We propose three subgenera, recommending the elevation of Section Anaspis to subgeneric rank and the merging of Sections Lupulinaria and Apeltanthus. The circumscription of Subgenus Apeltanthus and Section Perilomia needs to be reconsidered. Comparative analysis of chloroplast genomes highlighted the IR/SC boundary feature as a significant taxonomic indicator. We identified a total of 758 SSRs, 558 longer repetitive sequences, and ten highly variable regions, including trnK-rps16, trnC-petN, petN-psbM, accD-psaI, petA-psbJ, rpl32-trnL, ccsA-ndhD, rps15-ycf1, ndhF, and ycf1. These findings serve as valuable references for future research on species identification, phylogeny, and population genetics. The phylogeny of Scutellaria, based on the most comprehensive sample collection to date and complete chloroplast genome analysis, has significantly enhanced our understanding of its infrageneric relationships. The extensive examination of chloroplast genome characteristics establishes a solid foundation for the future development and utilization of Scutellaria, an important medicinal plant globally.

Oreonectes yuedongensis (Cypriniformes, Nemacheilidae), a new freshwater fish species from the Lianhua Mountains in eastern Guangdong, China.

In this work, we describe a new species of the genus Oreonectes, Oreonectes yuedongensis sp. nov., collected from the Lianhua Mountains in eastern Guangdong, China. Phylogenetic trees constructed based on the mitochondrial cytochrome b (Cyt b) gene showed that this new species represents an independent evolutionary lineage, with uncorrected genetic distances (Kimura 2-parameter model) from congeners ranging from 5.1% to 8.3%. In addition, nuclear DNA analysis indicated O. yuedongensis as an independent lineage separate from its closely related species. Morphologically, the new species can be distinguished from other six species in the genus Oreonectes by a combination of serial characters. The description of this new species suggests that it is necessary to reassess the biodiversity of Oreonectes platycephalus as a complex, especially in the middle reaches of the Pearl River near the border between Guangdong and Guangxi. Morphological and genetic evidence supports O. yenlingi as a synonym of O. platycephalus.

Comprehensive genome-wide analysis of PUB (Plant U-box) genes in rye and its closely related species and functional characterization of ScPUB6

Comprehensive genome-wide analysis of PUB (Plant U-box) genes in rye and its closely related species and functional characterization of ScPUB6

Detection of reproductive interference between closely related Salvia species with small-scale separated distributions by multifaceted pollination and molecular analyses.

Reproductive interference, an interspecific interaction in reproductive process that exerts an adverse effect, has gained attention as a contributing factor in promoting exclusive distributions between closely related species. However, detailed studies on the possibility of reproductive interference between native plants are still lacking, presumably because strong reproductive interference can rapidly realize exclusive distributions, leaving the two species apparently independent. Salvia japonica and S. lutescens are found in separate localities at a small scale, although their distributions overlap at a large scale. We investigated the possibility of reproductive interference between them through field surveys, hand-pollination experiments, evaluation of hybrid fertility, cpDNA and nrDNA genotyping, and genome-wide DNA analysis. The field survey results did not reveal apparent negative interaction in competition for pollinator services. Mixed pollination with conspecific pollen and counterpart pollen reduced seed set in S. japonica, and hybrid progeny produced by mixed pollination were less than 20% as fertile compared to the pure species. The DNA genotyping results suggested the possibility of hybridization where their distributions overlap, and the genome-wide DNA analysis results showed clear genetic differentiation between the two species as well as the existence of hybrids. These results suggest that bi-directional reproductive interference between S. japonica and S. lutescens may have led to their present separated distributions at a small scale.

Diverse origins of near-identical antifreeze proteins in unrelated fish lineages provide insights into evolutionary mechanisms of new gene birth and protein sequence convergence.

Determining the origins of novel genes and the mechanisms driving the emergence of new functions is challenging yet crucial for understanding evolutionary innovations. Recently evolved fish antifreeze proteins (AFPs) offer a unique opportunity to explore these processes, particularly the near-identical type I AFP (AFPI) found in four phylogenetically divergent fish taxa. This study tested the hypothesis of protein sequence convergence beyond functional convergence in three unrelated AFPI-bearing fish lineages. Through comprehensive comparative analyses of newly sequenced genomes of winter flounder and grubby sculpin, along with available high-quality genomes of cunner and 14 other related species, the study revealed that near-identical AFPI proteins originated from distinct genetic precursors in each lineage. Each lineage independently evolved a de novo coding region for the novel ice-binding protein while repurposing fragments from their respective ancestors into potential regulatory regions, representing partial de novo origination-a process that bridges de novo gene formation and the neofunctionalization of duplicated genes. The study supports existing models of new gene origination and introduces new ones: the Innovation-Amplification-Divergence (IAD) model, where novel changes precede gene duplication; the newly proposed Duplication-Degeneration-Divergence (DDD) model, which describes new functions arising from degenerated pseudogenes; and the DDD gene fission model, where each new sibling gene differentially degenerate and renovate distinct functional domains from their parental gene. These findings highlight the diverse evolutionary pathways through which a novel functional gene with convergent sequences at the protein level can evolve across divergent species, advancing our understanding of the mechanistic intricacies in new gene formation.

Molecular identification of some species of dragonfly (Odonata: Anisoptera) using COXI gene and DNA barcodes from Basrah Province, Southern Iraq

The taxonomy of the Odonata group is still poorly understood; therefore, molecular identification has been developed to address the shortcomings of traditional taxonomy, such as misidentification and inconsistencies in reference databases. The mtCOXI gene has been used in animal barcoding studies because of its wide range of phylogenetic signals. Odonata, a diverse group of aquatic insects, has been studied at the molecular level to understand the evolutionary relationships between their species and global species. In the current study in Basrah Province, Iraq, we extracted mitochondrial DNA from adult and nymph Dragonflies and designed species-specific primers to distinguish some of the endemic species at the molecular level. This study identified five species, Crocothemis erythraea, Diplacodes trivialis, Orthetrum sabina, Trithemis annulata and Hemianax ephippiger. The DNA sequences were deposited in the NCBI database for the first time. The nucleotide sequences of the mtCOXI genes were analyzed via BLAST. The similarity results ranged from 91.8% to 100%, indicating related species on the basis of the branches of the phylogenetic tree. The molecular identity of the selected species was confirmed, and DNA barcodes for Anisoptera species from Basrah Province were successfully developed and documented in GenBank and IBIN.

Single-nucleus atlas of the Artemia female reproductive system suggests germline repression of the Z chromosome.

Our understanding of the molecular pathways that regulate oogenesis and define cellular identity in the Arthropod female reproductive system and the extent of their conservation is currently very limited. This is due to the focus on model systems, including Drosophila and Daphnia, which do not reflect the observed diversity of morphologies, reproductive modes, and sex chromosome systems. We use single-nucleus RNA and ATAC sequencing to produce a comprehensive single nucleus atlas of the adult Artemia franciscana female reproductive system. We map our data to the Fly Cell Atlas single-nucleus dataset of the Drosophila melanogaster ovary, shedding light on the conserved regulatory programs between the two distantly related Arthropod species. We identify the major cell types known to be present in the Artemia ovary, including germ cells, follicle cells, and ovarian muscle cells. Additionally, we use the germ cells to explore gene regulation and expression of the Z chromosome during meiosis, highlighting its unique regulatory dynamics and allowing us to explore the presence of meiotic sex chromosome silencing in this group.

High-throughput transposon mutagenesis in the family Enterobacteriaceae reveals core essential genes and rapid turnover of essentiality.

The Enterobacteriaceae are a scientifically and medically important clade of bacteria, containing the model organism Escherichia coli, as well as major human pathogens including Salmonella enterica and Klebsiella pneumoniae. Essential gene sets have been determined for several members of the Enterobacteriaceae, with the Keio E. coli single-gene deletion library often regarded as a gold standard. However, it remains unclear how gene essentiality varies between related strains and species. To investigate this, we have assembled a collection of 13 sequenced high-density transposon mutant libraries from five genera within the Enterobacteriaceae. We first assess several gene essentiality prediction approaches, investigate the effects of transposon density on essentiality prediction, and identify biases in transposon insertion sequencing data. Based on these investigations, we develop a new classifier for gene essentiality. Using this new classifier, we define a core essential genome in the Enterobacteriaceae of 201 universally essential genes. Despite the presence of a large cohort of variably essential genes, we find an absence of evidence for genus-specific essential genes. A clear example of this sporadic essentiality is given by the set of genes regulating the σE extracytoplasmic stress response, which appears to have independently acquired essentiality multiple times in the Enterobacteriaceae. Finally, we compare our essential gene sets to the natural experiment of gene loss in obligate insect endosymbionts that have emerged from within the Enterobacteriaceae. This isolates a remarkably small set of genes absolutely required for survival and identifies several instances of essential stress responses masked by redundancy in free-living bacteria.IMPORTANCEThe essential genome, that is the set of genes absolutely required to sustain life, is a core concept in genetics. Essential genes in bacteria serve as drug targets, put constraints on the engineering of biological chassis for technological or industrial purposes, and are key to constructing synthetic life. Despite decades of study, relatively little is known about how gene essentiality varies across related bacteria. In this study, we have collected gene essentiality data for 13 bacteria related to the model organism Escherichia coli, including several human pathogens, and investigated the conservation of essentiality. We find that approximately a third of the genes essential in any particular strain are non-essential in another related strain. Surprisingly, we do not find evidence for essential genes unique to specific genera; rather it appears a substantial fraction of the essential genome rapidly gains or loses essentiality during evolution. This suggests that essentiality is not an immutable characteristic but depends crucially on the genomic context. We illustrate this through a comparison of our essential genes in free-living bacteria to genes conserved in 34 insect endosymbionts with naturally reduced genomes, finding several cases where genes generally regarded as being important for specific stress responses appear to have become essential in endosymbionts due to a loss of functional redundancy in the genome.

Identification of SDG gene family members and exploration of flowering related genes in different cultivars of chrysanthemums and their wild ancestors.

The SET domain genes (SDGs) are significant contributors to various aspects of plant growth and development, mainly includes flowering, pollen development, root growth, regulation of the biological clock and branching patterns. To clarify the biological functions of the chrysanthemum SDG family, the SDG family members of four chrysanthemum cultivars and three related wild species were identified; their physical and chemical properties, protein domains and conserved motifs were predicted and analyzed. The results showed that 59, 67, 67, 102, 106, 114, and 123 SDGs were identified from Chrysanthemum nankingense, Chrysanthemum lavandulifolium, Chrysanthemum seticuspe, Chrysanthemum × morifolium cv. 'Hechengxinghuo', 'Zhongshanzigui', 'Quanxiangshuichang' and 'Jinbeidahong', respectively. The SDGs were divided into 5-7 subfamilies by cluster analysis; different conserved motifs were observed in particular families. The SDGs of C. lavandulifolium and C. seticuspe were distributed unevenly on 9 chromosomes. SDG promoters of different species include growth and development, photo-response, stress response and hormone responsive elements, among them, the cis-acting elements related to MeJA response had the largest proportion. The expression of chrysanthemum SDG genes was observed for most variable selected genes which has close association with important Arabidopsis thaliana genes related to flowering regulation. The qPCR results showed that the expression trend of SDG genes varied in different tissues at different growth stages with high expression in the flowering period. The ClSDG29 showed higher expression in the flower and bud tissues, which indicate that ClSDG29 might be associated with flowering regulation in chrysanthemum. In summary, the results of this study can provide a basis for subsequent research on chrysanthemum flowering time regulation.

Exploring phytochemicals and pharmacological properties of Populus × tomentiglandulosa

Populus × tomentiglandulosa (PT), a tree endemic to Korea, shows promising potential as a natural therapeutic agent owing to its potent anti-inflammatory properties. However, the isolation and analysis of phytochemical compounds in PT and related species remains underexplored. Therefore, this study aims to investigate the biochemical profile of PT and evaluate its extracts and fractions for anti-inflammatory activities. Nine compounds were isolated, including two novel flavonoids (luteolin 7-O-β-d-glucuronide butyl ester and chrysoeriol 7-O-β-d-glucuronide butyl ester) from the Salicaceae family for the first time. The ethyl acetate fraction exhibited significant radical scavenging activity against various radicals, including DPPH, ABTS+, •OH, and O2– radicals. PT extracts and the ethyl acetate fraction showed minimal cytotoxicity in Raw 264.7 macrophages at concentrations below 500 and 100 μg/mL, respectively. Furthermore, PT extracts and fractions significantly suppressed the protein expression of proinflammatory mediators (iNOS and IL-6) in LPS-stimulated Raw 264.7 macrophages, highlighting their potent anti-inflammatory effects. These findings suggest that PT holds promise as a valuable natural therapeutic intervention for various oxidative stress and inflammation-related disorders, underscoring the need for further exploration of its clinical applications.

Ultrasonication-Boosted Resorcinol-Formaldehyde Resin Nanoparticle Bromine Fixation and Corresponding Upgraded Aquatic Applications.

Bromine (Br2) and related species removal from water systems are rather complicated due to the complicated chemistry instability, and materials with high Br2 removal rate and efficiency, along with stimuli/apparatus suitable for highly corrosive environments, are necessary. Ultrasonication as a non-destructive process is especially suitable in scenarios where conventional stir apparatus is not applicable, such as highly corrosive environments. Considering the validity nature of Br2 and combining the advantages of ultrasonic with a highly stable Br2 fixation method through aromatic polymer nanoparticles, we demonstrate highly efficient acoustic-aided Br2 removal in aqueous solutions with two times capacity compared to the non-treated sample. Related aquatic applications are also proposed for the materials to be cost-effective, including silver (Ag) recovery, recyclable MnO2-mediated Br2 deep removal, and aqueous zinc anode modification. The coupled novel-material-based processes motivate the strategic design of water purification with high-safety and sustainable industrial procedures and post-value-added utilizations.

Nocturnal burst emissions of germacrene D from the open disk florets of pyrethrum flowers induce moths to oviposit on a nonhost and improve pollination success.

Recent studies show that nocturnal pollinators may be more important to ecosystem function and food production than is currently appreciated. Here, we describe an agricultural field study of pyrethrum (Tanacetum cinerariifolium) flower pollination. Pyrethrum is genetically self-incompatible and thus is reliant on pollinators for seed set. Our pollinator exclusion experiment showed that nocturnal insects, particularly moths, significantly contribute to seed set and quality. We discovered that the most abundant floral volatile, the sesquiterpene (-)-germacrene D (GD), is key in attracting the noctuid moths Peridroma saucia and Helicoverpa armigera. Germacrene D synthase (GDS) gene expression regulates the specific GD production and accumulation in flowers, which, in contrast to related species, lose the habit of closing at night. We did observe that female moths also oviposited on pyrethrum leaves and flower peduncles, but found that only a small fraction of those eggs hatched. Larvae were severely stunted in development, most likely due to the presence of pyrethrin defense compounds. This example of exploitative mutualism, which blocks the reproductive success of the moth pollinator and depends on nocturnal interactions, is placed into an ecological context to explain why it may have developed.

The complete mitochondrial genome of the imperiled Bullnose ray Myliobatis freminvillei (Myliobatiformes: Myliobatidae) with comments on its phylogenetic position and claims of diversifying selection affecting protein coding genes in a closely related species

The Bullnose ray Myliobatis freminvillei is a bentho-pelagic eagle ray that inhabits the north Gulf of Mexico and the Western Atlantic Ocean Coast, discontinuously, from Massachusetts, USA to Buenos Aires, Argentina. Myliobatis freminvillei is currently listed as vulnerable by the 2019 IUCN Red List of Threatened Species given that it is often captured as bycatch by artisanal and commercial fisheries, along the coasts of Argentina, Brazil, and Venezuela. This study, for the first time, assembled and characterized the mitochondrial genome of M. fremnvillei. The A+T rich mitochondrial genome of M. fremnvillei is 18,356 bp long and encodes 22 transfer RNA genes (tRNA), 2 ribosomal RNA genes (12S ribosomal RNA and 16S ribosomal RNA), 13 protein coding genes (PCGs), and also contains a non coding control region of 2,617 bp. Nonsynonomous codon usage with a preference for A+T rich codons was observed in all 13 PCGs. Leu (CTA), Ile (ATC), Phe (TTC), Thr (ACA), and Ala (GCC) were the most frequently used codons. Ka/Ks ratios estimated for all 13 PCGs exhibited values < 1, indicating strong purifying selection affecting all these genes. In contrast to the results of a previous study that claimed diversifying selective pressure in two mitochondrial PCGs of Mobula tarapacana, reanalysis of the Ka/Ks values for the same species indicated purifying selection in all 13 PCGs. Of the 22 tRNA genes, all have a cloverleaf secondary structure except tRNA-Ser1 which has a truncated dihydrouridine arm. In the control region, A+T rich microsatellites (n = 42) and short tandem repeats (n = 6) were identified, and the secondary structure of the same region contained numerous hairpin loops. Phylomitogenomic analyses supported the monophyletic status of the order Myliobatiformes and family Myliobatidae. The assembled mitochondrial genome will assist with conservation efforts in Myliobatis fremnvillei.

HYBRID NICHE-NEUTRAL MODEL FOR THE GUT MICROBIOTA

The gut microbiota is a complex ecosystem integrated in the human body. Its relevance in the host’s health is by now well established. For this reason, several studies are currently focusing their attention on its composition and ecological properties. Among such properties, biodiversity is indeed a key one, being an indicator of the health of an ecosystem. Despite that, the choice of the optimal metric to measure biodiversity in an effective way is still a matter of debate. Here, we discuss the main approaches proposed for this purpose, considering both classical statistical indices and model-based ones. We describe the relevance of the Relative Species Abundance distribution and the main probabilistic and ecological models that have been used to fit it. Finally, we report results obtained on the gut microbiota of three groups of subjects for which differences are expected: healthy Italian adults, Down Syndrome Italian adults, and Tanzanian Hadza hunter-gathers. Our results show the utility of considering a hybrid niche-neutral model to evaluate the biodiversity of this meaningful ecosystem.

Morphological and molecular characterization of Prorocentrum bidens (formerly known as P. compressum) and description of the closely related Prorocentrum bisaeptum sp. nov. (Prorocentrales, Dinophyceae)

ABSTRACT The genus Prorocentrum is diverse and comprises mostly marine dinoflagellates with a worldwide distribution. One large, common and easily recognizable planktonic species of Prorocentrum was known for a long time as P. compressum. This name, however, is incorrectly linked to a basionym of a diatom. The confusing taxonomy of the now also lectotypified diatom name was recently resolved, and the next younger available name, Prorocentrum bidens, was proposed for the dinoflagellate species. Based on multiple strains from various localities we here provide the first detailed morphological study of P. bidens thereby propagating the correct nomenclature of this species. The cells of one strain differed consistently from material assigned to P. bidens, and Prorocentrum bisaeptum sp. nov. is described here to represent this closely related species. Both species possessed two pyrenoids per chloroplast and shared the arrangement of ten periflagellar platelets, including subdivisions of platelets 6 and 8. Cells of both species were either fully motile or, in an encapsulated stage, enclosed with actively beating flagella in a hyaline flexible envelope bounded by a thin surface layer. Prorocentrum bisaeptum differs from P. bidens by a more elongated shape of the cells and by a smooth (not foveate) surface of the thecal plates. Most importantly, one to four cells of P. bisaeptum are consistently enclosed within two nesting envelopes, whereas there is only one such structure tightly surrounding one or two cells of P. bidens. This study increases and improves our knowledge of the diversity within this important group of planktonic organisms.

Paralumbricillus gen. nov. and other new marine enchytraeids from the North Atlantic

Lumbricillus is one of the largest enchytraeid genera and its species can mainly be found on the coasts of temperate and polar regions around the world. However, the monophyly of the genus has been questioned by recent molecular studies. In this paper we further examine the phylogenetic relationships of Lumbricillus species and their close relatives by estimating a phylogeny of 62 species, many collected along the Norwegian coastline, with seven genetic markers. We confirm Lumbricillus to be non-monophyletic and resolve this issue by establishing the new genus Paralumbricillus, into which ten of the known species are transferred: Paralumbricillus arenarius, Paralumbricillus cervisiae, Paralumbricillus christenseni, Paralumbricillus crymodes, Paralumbricillus dubius, Paralumbricillus eltoni, Paralumbricillus eudioptus, Paralumbricillus muscicolus, Paralumbricillus nielseni, Paralumbricillus westheidei, all comb. nov. In this paper we also describe eight new species: Lumbricillus bibulbus, L. boreas, L. elisae, Paralumbricillus bicornis, P. bilobatus, P. lofotensis, P. sanguineus, and Claparedrilus torquatus.

Fluorine substitution for aggregation transformation and exciton dissociation acceleration in non-fused electron acceptors

In order to enable low-cost manufacture of organic solar cells (OSCs), it is very important to develop non-fused electron acceptors to match with one of the cheapest polymer donors, poly(3-hexylthiophene) (P3HT). However, the lower exciton dissociation and charge transfer are still the main factors that limit the improvement of P3HT-based OSCs. Herein, we designed one class of A2-A1-D-A1-A2 type non-fused electron acceptors and synthesized BTA34 and F-BTA34 by introducing benzo[d][1,2,3] triazole as the bridged unit. The dominated H-aggregation in F-BTA34 affords high degree of crystalline and proper phase separation when blended with polymer P3HT, which ensure efficient exciton dissociation and higher charge carrier mobility. Consequently, P3HT:F-BTA34 devices demonstrate a better performance with higher short-circuit current and fill factor. The blend of P3HT:BTA34 exhibits a broader distribution of the mixing domains, resulting in relative longer-lived charge species. This work provides useful strategies to design non-fused electron acceptors to match with P3HT from the perspective of simultaneously improving exciton dissociation and suppressing charge recombination.

Comparative Morphological, Physiological, and Transcriptomic Analyses of Diploid and Tetraploid Wucai (Brassica campestris L.).

Polyploid plants often exhibit superior yield, stress resistance, and quality. In this study, homologous tetraploid wucai (Brassica campestris L.) was successfully obtained by spraying seedling growth points with colchicine. The morphological, cytological, and physiological characteristics of diploid and tetraploid wucai were analyzed, and transcriptomic sequencing was performed at three stages of development. Tetraploid seedings grew slowly but exhibited darker leaves, enlarged organs and cells, increased stomatal volume, decreased stomatal density, improved nutritional content, and enhanced photosynthesis. Differentially expressed genes (DEGs) identified in diploid and tetraploid plants at three stages of development were enriched in different pathways. Notably, DEGs identified in the tetraploid plants were specifically enriched in starch and sucrose metabolism, pentose and glucuronate interconversions, and ascorbate and aldarate metabolism. In addition, we found that the light green module was most relevant to ploidy, and DEGs in this module were significantly enriched in the glycolysis/gluconeogenesis and TCA cycle pathways. The differential expression of key glycolysis-associated genes at different developmental stages may be the driver of the observed differences between diploid and tetraploid wucai. This study lays a technical foundation for the development of polyploid wucai germplasm resources as well as the breeding of new varieties with improved quality, yield, and stress resistance. It also provides a good empirical reference for the genetic breeding of closely related Brassica species.

Seed morphological variation in four closely related Linaria species (Plantaginaceae) endemic to the Tyrrhenian area

Seed features are a useful and relevant source of taxonomic information, especially when evaluated based on morphometric and micromorphological approaches. Here, we studied 21 populations from four out of the five species of the Mediterranean Linaria purpurea group (Plantaginaceae). Linaria capraria (endemic to Tuscan Archipelago) and L. cossonii (endemic to Sardinia and Tunisia) are easily recognizable based on overall morphometry and SEM analysis, respectively. On the contrary, L. arcusangeli (endemic to southern Sardinia) and L. purpurea (endemic to peninsular Italy and Sicily) show very similar seeds, whose features do not guarantee a reliable identification, although these two species are otherwise well distinct for their habit and flower features. Accordingly, by integrating all the available information, all four species are well supported on morphological grounds.