Mercurialis Annua Research Articles

Widespread male sterility and trioecy in androdioecious Mercurialis annua: Its distribution, genetic basis, and estimates of morph-specific fitness components.

Angiosperms range in sexual system from hermaphroditism through gynodioecy and androdioecy to dioecy. Trioecy, where females and males coexist with hermaphrodites, is rare. Recently, trioecy was documented in hexaploid populations of the wind-pollinated herb Mercurialis annua in Spain. We surveyed the frequency of males, hermaphrodites, and females in M. annua across its distribution in the Iberian Peninsula, tracked sex-ratio variation in several populations over consecutive generations, and assessed evidence for pollen limitation. In a common garden, we estimated male, female, and hermaphroditic fitness. We used controlled crosses to infer the genetic basis of male sterility. Finally, we compared predictions of a deterministic model with the distribution of observed sex ratios in the field based on our fitness estimates and the inferred genetics of sex determination. Trioecy is widespread in Spanish and Portuguese populations of M. annua. Males are determined by a dominant (Y-linked) allele, and female expression results from the interaction between cytoplasmic male sterility and multiple nuclear male sterility restorers partially linked to the male determiner. Male pollen production is approximately 12 times that of hermaphrodites, while female seed production is less than 1.12 times the observed hermaphroditic levels. The distribution of sex ratios in natural populations conforms with predictions of our deterministic simulations. Our study documents and accounts for a clear case of trioecy in which sex is determined by both maternally and biparentally inherited genes.

Euphorbiaceae superoxide dismutase, catalase, and glutathione peroxidase as clues to better comprehend high drought tolerance in castor bean

Superoxide dismutase (SOD), Catalase (CAT), and Glutathione peroxidase (GPX) enzymes exert a central role in reactive oxygen species (ROS) scavenger in plants, being an important part of enzymatic antioxidant system. Despite the importance of these enzymes in ROS metabolism and in different signaling pathways related to plant development and stress response, their gene families have not yet been comprehensively characterized in many crop plants. Among different crops, the Euphorbiaceae family has some species highly tolerant to drought stress. However, the gene families that encode the antioxidant enzymes, as well as their role in this drought stress tolerance, remains not characterized. Here, the SOD, CAT, and GPX genes of castor bean (Ricinus communis), cassava (Manihot esculenta), jatropha (Jatropha curcas), rubber tree (Hevea brasiliensis), petty spurge (Euphorbia peplus), and annual mercury (Mercurialis annua) were identified and characterized. The comprehensive phylogenetic and genomic analyses allowed the classification of the genes into different classes and revealed the duplication events that contribute to the expansion of these families within plant genomes. The expression patterns of SOD, CAT, and GPX genes were examined in castor bean, cassava, jatropha, and rubber tree by RNA-seq analysis revealing differential expression during stress. Additionally, the castor bean gene expression was confirmed by RT-qPCR. Among castor bean genes, RcGPX4 appears to be induced in castor bean roots under drought stress, but the heterologous expression in Arabidopsis thaliana does not improve the drought tolerance. Altogether, this data has significantly contributed to characterizing the expression patterns and conducting evolutionary assessment of these genes in Euphorbiaceae. This bridge a gap in understanding the proposed functions of core components within the antioxidant mechanism in an economically significant group of plants, particularly during stress responses

The importance of host weed species for root-knot nematodes, Meloidogyne spp. Göldi, 1897 (Tylenchida: Heteroderidae) in banana plantations

Banana is a significant economic source in Türkiye. Root-knot nematodes, Meloidogyne spp. Göldi, 1897 (Tylenchida: Heteroderidae) are the important pests in banana fields. This study was conducted from 2021 to 2022 to elucidate the relationship between root-knot nematodes and weed species in bananas in the Mediterranean Region. 2% of the banana production area in Adana, Antalya, Hatay and Mersin were surveyed regularly for this purpose. 1m2 frames were placed within a 2m radius around banana plants in the sampled areas. The host of root-knot nematodes with weed species identified within the frames was examined. Survey results indicated that Amaranthus retroflexus L. (46.34%), Portulaca oleracea L. (40.63%), and Solanum nigrum L. (37.84%) were the weed species most infected with root-knot nematodes. Furthermore, molecular analyses revealed that Abutilon theophrasti Medik., Amaranthus spp., Cucumis melo var. agrestis Naudin., Erodium cicutarium (L.) L'Hér. ex Aiton, Kickxia commutata (Bernh. ex Rchb.) Fritsch, Malva spp., Mercurialis annua L., P. oleracea, S. nigrum, and Sonchus oleraceus L. were suitable hosts for root-knot nematodes. This study is an important step in understanding the interaction between root-knot nematodes and weeds in banana. The presence of weed species in agricultural fields should be considered as they may support nematode populations and pose a threat to subsequent crops. Therefore, the implementation of weed control strategies could help producers to control nematode populations.

Revisiting a pollen-transmitted ilarvirus previously associated with angular mosaic of grapevine

We report the characterization of a novel tri-segmented RNA virus infecting Mercurialis annua, a common crop weed and model species in plant science. The virus, named "Mercurialis latent virus" (MeLaV) was first identified in a mixed infection with the recently described Mercurialis orthotospovirus 1 (MerV1) on symptomatic plants grown in glasshouses in Lausanne (Switzerland). Both viruses were found to be transmitted by Thrips tabaci, which presumably help the inoculation of infected pollen in the case of MeLaV. Complete genome sequencing of the latter revealed a typical ilarviral architecture and close phylogenetic relationship with members of the Ilarvirus subgroup 1. Surprisingly, a short portion of MeLaV replicase was found to be identical to the partial sequence of grapevine angular mosaic virus (GAMV) reported in Greece in the early 1990s. However, we have compiled data that challenge the involvement of GAMV in angular mosaic of grapevine, and we propose alternative causal agents for this disorder. In parallel, three highly-conserved MeLaV isolates were identified in symptomatic leaf samples in The Netherlands, including a herbarium sample collected in 1991. The virus was also traced in diverse RNA sequencing datasets from 2013 to 2020, corresponding to transcriptomic analyses of M. annua and other plant species from five European countries, as well as metaviromics analyses of bees in Belgium. Additional hosts are thus expected for MeLaV, yet we argue that infected pollen grains have likely contaminated several sequencing datasets and may have caused the initial characterization of MeLaV as GAMV.

The genome sequence of the Annual Mercury, Mercurialis annua L., 1753 (Euphorbiaceae)

We present a genome assembly from a diploid female Mercurialis annua (the Annual Mercury; Tracheophyta; Magnoliopsida; Malpighiales; Euphorbiaceae). The genome sequence is 453.2 megabases in span. Most of the assembly is scaffolded into 8 chromosomal pseudomolecules, including the X chromosome. The organelle genomes have also been assembled, and the mitochondrial genome is 435.28 kilobases in length, while the plastid genome is 169.65 kilobases in length.

Radical-Scavenging Effect, Ferric Reducing Ability and Phytochemical Analysis of Urtica urens (L.) and Mercurialis annua (L.)

Important Moroccan medicinal plants known for their food and medicinal potential include Urtica urens and Mercurialis annua. We examined the antioxidant activity of the methanolic and aqueous extracts by several in vitro systems of the assay, namely the ferric reducing/antioxidant power (FRAP) assay, the DPPH radical-scavenging activity, and the ABTS free radical-scavenging capacity. In addition, all active extracts were subjected to phytochemical screening to determine the key groups of chemicals implicated in their therapeutic activity. Total phenolic and flavonoid concentrations were also measured to see how they affected the antioxidant properties of the plant extracts. The extracts of Urtica urens and Mercurialis annua were found to have different levels of antioxidant effect in the systems tested. Based on the three different antioxidant assays, the Mercurialis annua extracts showed the highest values of antioxidant ability, based on the three used assays. Phytochemical testing of studied extracts revealed the presence of flavonoids, anthocyanins, and tannins. Total phenol and flavonoid contents were shown to provide the highest association with different antioxidant methods. The present study provides evidence that the extracts of Urtica urens and Mercurialis annua are a potential source of natural antioxidants, and this justifies their uses in Moroccan traditional medicine.

Deep Object Detection of Crop Weeds: Performance of YOLOv7 on a Real Case Dataset from UAV Images

Weeds are a crucial threat to agriculture, and in order to preserve crop productivity, spreading agrochemicals is a common practice with a potential negative impact on the environment. Methods that can support intelligent application are needed. Therefore, identification and mapping is a critical step in performing site-specific weed management. Unmanned aerial vehicle (UAV) data streams are considered the best for weed detection due to the high resolution and flexibility of data acquisition and the spatial explicit dimensions of imagery. However, with the existence of unstructured crop conditions and the high biological variation of weeds, it remains a difficult challenge to generate accurate weed recognition and detection models. Two critical barriers to tackling this challenge are related to (1) a lack of case-specific, large, and comprehensive weed UAV image datasets for the crop of interest, (2) defining the most appropriate computer vision (CV) weed detection models to assess the operationality of detection approaches in real case conditions. Deep Learning (DL) algorithms, appropriately trained to deal with the real case complexity of UAV data in agriculture, can provide valid alternative solutions with respect to standard CV approaches for an accurate weed recognition model. In this framework, this paper first introduces a new weed and crop dataset named Chicory Plant (CP) and then tests state-of-the-art DL algorithms for object detection. A total of 12,113 bounding box annotations were generated to identify weed targets (Mercurialis annua) from more than 3000 RGB images of chicory plantations, collected using a UAV system at various stages of crop and weed growth. Deep weed object detection was conducted by testing the most recent You Only Look Once version 7 (YOLOv7) on both the CP and publicly available datasets (Lincoln beet (LB)), for which a previous version of YOLO was used to map weeds and crops. The YOLOv7 results obtained for the CP dataset were encouraging, outperforming the other YOLO variants by producing value metrics of 56.6%, 62.1%, and 61.3% for the mAP@0.5 scores, recall, and precision, respectively. Furthermore, the YOLOv7 model applied to the LB dataset surpassed the existing published results by increasing the mAP@0.5 scores from 51% to 61%, 67.5% to 74.1%, and 34.6% to 48% for the total mAP, mAP for weeds, and mAP for sugar beets, respectively. This study illustrates the potential of the YOLOv7 model for weed detection but remarks on the fundamental needs of large-scale, annotated weed datasets to develop and evaluate models in real-case field circumstances.

Molecular determination of root-knot nematode species, Meloidogyne spp. Goeldi, 1892 (Tylenchida: Meloidogynidae) infesting weeds in kiwifruit orchards in Türkiye

In this investigation, the species of root-knot nematodes (RKNs) infesting weeds in kiwifruit orchards were investigated in the Ordu Province, Türkiye. A survey was conducted in 2018 and roots of weeds with RKN infestations were found in kiwifruit orchards. The infested weed samples were collected from 27 kiwifruit fruit orchards located in the Ordu Province. Identification of RKNs was performed using the molecular method based on mitochondrial DNA (mtDNA). The mtDNA region between the cytochrome oxidase II and the large subunit ribosomal RNA was amplified using two pairs of primers TRNAH/MRH106 and MORF/MTHIS. Species-specific primers previously described were used to confirm Meloidogyne species as the last step. Meloidogyne incognita (Kofoid & White, 1919), Meloidogyne arenaria (Neal, 1889) and Meloidogyne hapla (Chitwood, 1949) (Tylenchida: Meloidogynidae) were identified from fifteen weed species (2 unidentified) in eight families. Meloidogyne incognita was the most frequent species with 74.1% of the samples infested, followed by M. hapla at 22.2% and M. arenaria at 3.7%. In this study found Erigeron canadensis L. (Asterales: Asteraceae), Mercurialis annua L. (Malpighiales: Euphorbiaceae), Oxalis pes-caprae L. (Oxalidales: Oxalidaceae), Clinopodium nepeta (L.) Kuntze (Lamiales: Lamiaceae), Fumaria officinalis L. (Ranunculales: Papaveraceae) and Lycopus spp. (Lamiales: Lamiaceae) to be previously unrecorded hosts of M. incognita and Sigesbeckia orientalis L. (Asterales: Asteraceae) and Lythrum spp. (Myrtales: Lythraceae) a host of M. hapla.

Genome-wide characterization and evolutionary analysis of linker histones in castor bean (Ricinus communis).

H1s, or linker histones, are ubiquitous proteins in eukaryotic cells, consisting of a globular GH1 domain flanked by two unstructured tails. Whilst it is known that numerous non-allelic variants exist within the same species, the degree of interspecific and intraspecific variation and divergence of linker histones remain unknown. The conserved basic binding sites in GH1 and evenly distributed strong positive charges on the C-terminal domain (CTD) are key structural characters for linker histones to bind chromatin. Based on these features, we identified five linker histones from 13 GH1-containing proteins in castor bean (Ricinus communis), which were named as RcH1.1, RcH1.2a, RcH1.2b, RcH1.3, and RcH1.4 based on their phylogenetic relationships with the H1s from five other economically important Euphorbiaceae species (Hevea brasiliensis Jatropha curcas, Manihot esculenta Mercurialis annua, and Vernicia fordii) and Arabidopsis thaliana. The expression profiles of RcH1 genes in a variety of tissues and stresses were determined from RNA-seq data. We found three RcH1 genes (RcH1.1, RcH1.2a, and RcH1.3) were broadly expressed in all tissues, suggesting a conserved role in stabilizing and organizing the nuclear DNA. RcH1.2a and RcH1.4 was preferentially expressed in floral tissues, indicating potential involvement in floral development in castor bean. Lack of non-coding region and no expression detected in any tissue tested suggest that RcH1.2b is a pseudogene. RcH1.3 was salt stress inducible, but not induced by cold, heat and drought in our investigation. Structural comparison confirmed that GH1 domain was highly evolutionarily conserved and revealed that N- and C-terminal domains of linker histones are divergent between variants, but highly conserved between species for a given variant. Although the number of H1 genes varies between species, the number of H1 variants is relatively conserved in more closely related species (such as within the same family). Through comparison of nucleotide diversity of linker histone genes and oil-related genes, we found similar mutation rate of these two groups of genes. Using Tajima's D and ML-HKA tests, we found RcH1.1 and RcH1.3 may be under balancing selection.

Effect of host plant species and temperature on the development and survival of the plant bug Closterotomus trivialis (Costa) (Hemiptera: Miridae)

Nymphal development, mortality and adult longevity of the plant bug Closterotomus trivialis were studied on two of its major crops (Olea europaea L. cv. 'Koroneiki' and Citrus sinensis L. cv. 'Washington Navel') and four non-crop host plants (Mercurialis annua L., Urtica urens L., Parietaria diffusa M. et K. and Sinapis alba L.) under laboratory conditions (15, 20, 24 and 27 °C ± 0.5%; 60 ± 5% RH; 16L:8D h photoperiod). Results demonstrated that C. trivialis can successfully complete its development on all tested host plants and temperatures, except for U. urens at 15 and 20 οC. Mortality rates were generally higher on U. urens, P. diffusa and olive than on S. alba, M. annua and sweet orange. Both temperature and host plant significantly affected the nymphal development of C. trivialis. Specifically, host plant affected the development of nymphs at lower and higher temperatures (15, 20, 27 °C) but not at the optimum (24 °C) for its development temperature. Adults of C. trivialis lived longer on sweet orange, M. annua and S. alba in most tested temperatures compared to U. urens, P. diffusa and olives. Overall, these results suggest a better suitability of M. annua, S. alba and sweet orange compared to U. urens, P. diffusa and olive which were proven to be less suitable host plants, covering partially the nutritional needs of C. trivialis. The estimated lower temperature developmental threshold based on the linear model for C. trivialis was found to be lowest on M. annua (3.30 °C) and highest on P. diffusa (10.7 °C). Τhe assessment of the nymphal development in various host plants and temperatures is particularly important for understanding the biology of C. trivialis and provides useful information to optimize its management strategy under integrated pest management system.

Disentangling the effects of jasmonate and tissue loss on the sex allocation of an annual plant.

Selection through pollinators plays a major role in the evolution of reproductive traits. However, herbivory can also induce changes in plant sexual expression and sexual systems, potentially influencing conditions governing transitions between sexual systems. Previous work has shown that herbivory has a strong effect on sex allocation in the wind-pollinated annual plant Mercurialis annua, likely via responses to resource loss. It is also known that many plants respond to herbivory by inducing signaling, and endogenous responses to it, via the plant hormone jasmonate. Here, we attempt to uncouple the effects of herbivory on sex allocation in M. annua through resource limitation (tissue loss) versus plant responses to jasmonate hormone signaling. We used a two-factorial experiment with four treatment combinations: control, herbivory (25% chronic tissue loss), jasmonate, and combined herbivory and jasmonate. We estimated the effects of tissue loss and defense-inducing hormones on reproductive allocation, male reproductive effort, and sex allocation. Tissue loss caused plants to reduce their male reproductive effort, resulting in changes in total sex allocation. However, application of jasmonate after herbivory reversed its effect on male investment. Our results show that herbivory has consequences on plant sex expression and sex allocation, and that defense-related hormones such as jasmonate can buffer the impacts. We discuss the physiological mechanisms that might underpin the effects of herbivory on sex allocation, and their potential implications for the evolution of plant sexual systems.

Rapid divergence in vegetative morphology of a wind-pollinated plant between populations at contrasting densities.

Plant sexual dimorphism is thought to evolve in response to sex‐specific selection associated with competition for access to mates or resources, both of which may be density dependent. In wind‐pollinated plants in particular, vegetative traits such as plant size and architecture may influence resource acquisition and both pollen dispersal and receipt, with potential conflict between these two components of fitness. We evaluated the role of plant density in shaping plant traits by measuring evolutionary responses in experimental populations of the sexually dimorphic wind‐pollinated plant Mercurialis annua. After three generations of evolution, we observed divergence between high‐ and low‐density populations in several vegetative traits, whereas there was no divergence for reproductive traits. A reversal in the direction of sexually dimorphic traits expressed in young plants evolved in both low‐ and high‐density populations compared to the original population (stored as seeds). Compared to the source population, males at high density evolved to be taller when young, whereas at low density young females tended to become smaller. These results demonstrate that a simple change in plant density can induce age‐dependent and sex‐specific evolution in the ontogeny of vegetative organs, and illustrates the power of experimental evolution for investigating plant trait evolution.

Sex determination and sex chromosome evolution in land plants.

Linnaeus's very first opus, written when he was 22 years old, dealt with the analogy that exists between plants and animals in how they ‘propagate their species’, and a revised version with a plate depicting the union of male and female Mercurialis annua plants became a foundational text on the sexuality of plants. The question how systems with separate males and females have evolved in sedentary organisms that appear ancestrally bisexual has fascinated biologists ever since. The phenomenon, termed dioecy, has important consequences for plant reproductive success and is of commercial interest since it affects seed quality and fruit production. This theme issue presents a series of articles that synthesize and challenge the current understanding of how plants achieve dioecy. The articles deal with a broad set of taxa, including Coccinia, Ginkgo, Mercurialis, Populus, Rumex and Silene, as well as overarching topics, such as the field's terminology, analogies with animal sex determination systems, evolutionary pathways to dioecy, dosage compensation, and the longevity of the two sexes. In this introduction, we focus on four topics, each addressed by several articles from different angles and with different conclusions. Our highlighting of unclear or controversial issues may help future studies to build on the current understanding and to ask new questions that will expand our knowledge of plant sexual systems.This article is part of the theme issue ‘Sex determination and sex chromosome evolution in land plants’.

Genomic insights into lineage-specific evolution of the oleosin family in Euphorbiaceae

BackgroundLipid droplets (LDs) present in land plants serve as an essential energy and carbon reserve for seed germination and seedling development. Oleosins, the most abundant structural proteins of LDs, comprise a small family involved in LD formation, stabilization and degradation. Despite their importance, our knowledge on oleosins is still poor in Euphorbiaceae, a large plant family that contains several important oil-bearing species.ResultsTo uncover lineage-specific evolution of oleosin genes in Euphorbiaceae, in this study, we performed a genome-wide identification and comprehensive comparison of the oleosin family in Euphorbiaceae species with available genome sequences, i.e. castor bean (Ricinus communis), physic nut (Jatropha curcas), tung tree (Vernicia fordii), Mercurialis annua, cassava (Manihot esculenta) and rubber tree (Hevea brasiliensis), and a number of five, five, five, five, eight and eight members were found, respectively. Synteny analysis revealed one-to-one collinear relationship of oleosin genes between the former four (i.e. castor bean, physic nut, tung tree and M. annua) as well as latter two species (i.e. cassava and rubber tree), whereas one-to-one and one-to-two collinear relationships were observed between physic nut and cassava, reflecting the occurrence of one recent whole-genome duplication (WGD) in the last common ancestor of cassava and rubber tree. The presence of five ortholog groups representing three previously defined clades (i.e. U, SL and SH) dates back at least to the Malpighiales ancestor, because they are also conserved in poplar (Populus trichocarpa), a tree having experienced one Salicaceae-specific recent WGD. As observed in poplar, WGD was shown to be the main driver for the family expansion in both cassava and rubber tree. Nevertheless, same retention patterns of WGD-derived duplicates observed in cassava and rubber tree are somewhat different from that of poplar, though certain homologous fragments are still present in rubber tree. Further transcriptional profiling revealed an apparent seed-predominant expression pattern of oleosin genes in physic nut, castor bean and rubber tree. Moreover, structure and expression divergence of paralogous pairs were also observed in both cassava and rubber tree.ConclusionComparative genomics analysis of oleosin genes reported in this study improved our knowledge on lineage-specific family evolution in Euphorbiaceae, which also provides valuable information for further functional analysis and utilization of key members and their promoters.

Ethnobotanical and ethnopharmacological study of medicinal plants used in the treatment of anemia in the region of Haouz-Rehamna (Morocco)

Context: The ethnobotanical study of the plants used is of great interest in the medical field. In this perspective, we have carried out this ethnobotanical and ethnopharmacological study, which is part of the development of plant resources traditionally used against anemia in a large region of Middle Atlantic Morocco (Mam-4): Al Haouz-Rehamna. Aims: To establish a catalog of medicinal plants used in traditional medicine against anemia disease. Methods: For this purpose, we carried out an ethnobotanical survey using 1700 questionnaire cards during five campaigns (from 2012 to 2017) in the studied field. In addition, the information sought was about the plant including its local name, its part used, its toxicity and, medical practices related. Ethnobotanical indices, such as Use Value (UV), Family Use Value (FUV) and, Plant Part Value (PPV), were determined. Results: The results allowed us to identify 48 medicinal plants of which 12 were toxic. The inventoried species were distributed in 45 genera and belong to 27 botanical families, of which four predominated in the number of species: Apiaceae, Amaranthaceae, Fabaceae, and Asteraceae. Also, 11 species were traditionally more used as effective plants against anemia: Rubia peregrina, Lens culinaris, Malva sylvestris, Beta vulgaris, Spinacia oleracea, Mercurialis annua, Hibiscus sabdariffa, Corrigiola telephiifolia, Nasturtium officinale, Cistus laurifolius and Armeria mauritanica. The leafy stems were the most used part (PPV = 0.28%) followed by the seed (PPV = 0.26%). These parts were usually used steamed, decocted, and rarely triturated in honey or infused in water. The recipes were administered orally until cured. Conclusions: The present study established the importance of documenting traditional knowledge about the species of medicinal plants that are used to correct many chronic diseases such as anemia. Analysis of this knowledge has shown that several of the listed plants promoted anti-anemia activity and could become the basis for in-depth scientific investigations.

Simulated herbivory enhances leaky sex expression in the dioecious herb Mercurialis annua.

Background and AimsPlant reproductive traits are widely understood to be responsive to the selective pressures exerted by pollinators, but there is also increasing evidence for an important role for antagonists such as herbivores in shaping these traits. Many dioecious species show leaky sex expression, with males and females occasionally producing flowers of the opposite sex. Here, we asked to what extent leakiness in sex expression in Mercurialis annua (Euphorbiaceae) might also be plastically responsive to simulated herbivory. This is important because enhanced leakiness in dioecious populations could lead to a shift in both the mating system and in the conditions for transitions between combined and separate sexes.MethodsWe examined the effect of simulated herbivory on the sexual expression of males and females of M. annua in two experiments in which different levels of simulated herbivory led to enhanced leakiness in both sexes.Key ResultsWe showed that leaky sex expression in both males and females of the wind-pollinated dioecious herb M. annua is enhanced in response to simulated herbivory, increasing the probability for and the degree of leakiness in both sexes. We also found that leakiness was greater in larger females but not in larger males.ConclusionsWe discuss hypotheses for a possible functional link between herbivory and leaky sex expression, and consider what simulated herbivory-induced leakiness might imply for the evolutionary ecology of plant reproductive systems, especially the breakdown of dioecy and the evolution of hermaphroditism.

Ephemeral visitors or permanent residents? — Decadal change in the ruderal vegetation from a periurban university campus

Urbanization creates environmental conditions that hinder the growth of natural vegetation. We surveyed the ruderal vegetation from a periurban university campus in west-central Mexico during the rainy seasons of 2008 and 2016–2018, time during which the campus underwent intensive construction. The built area grew from 4 ha in 2009 to 12.6 ha in 2017. We identified 234 different Angiosperms belonging to 165 genera and 43 families and the community composition changed over time. For example, Asteraceae was replaced by Poaceae as the richest family in 2018. Also, 16 native species found in 2008 disappeared from the study site, 9 of which have been related with low disturbance. In contrast, 98 new species were observed in the latter years, including some that are commonly found in cities. Overall, species richness increased with time, including that of exotic species that increased from 16 % of the total species in 2008 to 24 % in 2018. Thirteen of such exotic species are invasive in Mexico, including Digitaria velutina, Asphodelus fistulosus, Mercurialis annua, and Senecio inaequidens, for which this was their first record in the city of Morelia (population 849,053), where the campus is located. These results suggest that environmental conditions imposed by disturbance can favor the proliferation of various species, especially grasses and several exotic species of different families.

Phytochemicals, Antioxidant Attributes and Larvicidal Activity of Mercurialis annua L. (Euphorbiaceae) Leaf Extracts against Tribolium confusum (Du Val) Larvae (Coleoptera; Tenebrionidae).

Simple SummaryMercurialis annua L. is a Euphorbiacea widespread in the Euro-Mediterranean region. This species is known for its toxicity and is used in traditional pharmacopoeia. However, the chemical composition of the aerial parts of this taxon and their larvicidal impact remain to be explored. However, the literature reports only a few studies on the relationship between the polyphenolic profile of the different extracts of Mercurialis annua L. and the larvicidal activity; therefore, we tested different extracts of M. annua against the larvae of Tribolium confusum (Du Val) for better protection of stored foodstuffs attacked by this pest. On the other hand, green chemistry as a distinct discipline has developed in recent years, which allowed us to identify different active compounds by LC-MS, and study the relationship between larvicidal activity and the chemical composition of extracts from male and female leaves of Mercurialis annua L.This study reports the link between larvicidal activity and the phytochemical composition of male and female leaf extracts of Mercurialis annua L. (M. annua) from four Tunisian regions: Bizerte, Jandouba, Nabeul and Beja. Their antioxidant activity was evaluated using DPPH (2, 2-diphenyl-1-picrylhydrazyl) assays. Phenolic compounds were identified and quantified using liquid chromatography coupled with a UV detector and mass spectrometry (LC-UV-ESI/MS). Higher antioxidant activity (AOA) was found in the leaves of male plant extracts than of female ones. The leaves of male and female plant extracts from Bizerte exhibited the highest AOA: 22.04 and 22.78 mg Trolox equivalent/g dry matter (mg TE/g DM), respectively. For both sexes, plant extracts from Beja had the lowest AOA with 19.71 and 19.67 mg TE/g DM for male and female plants, respectively. Some phenolic compounds such as narcissin, gallocatechin, rutin, epigallocatechin and epicatechin were identified and quantified using LC-MS, which highlighted the abundance of narcissin and rutin in the male leaves of M. annua. We noted that the interaction between the sex of plants and the provenance had a significant effect on TFC (F = 6.63; p = 0.004) and AOA (F = 6.53; p = 0.004) assays, but there was no interaction between sex and origins for TPC (F = 1.76; p = 0.19). The larvicidal activity of aqueous leaf extracts of M. annua against Tribolium confusum (Du Val) (T. confusum), an insect pest of flour and cereal seeds, showed that the mortality could reach 100% after 48 h of exposure in the Bizerte region. The LC50 values for the leaf extract were low in Bizerte, with 0.003 and 0.009 g/mL for male and female plants, respectively, succeeded by Jandouba, which displayed 0.006 and 0.024 g/mL for male and female plants, respectively. Nabeul showed 0.025 g/mL for male plants and 0.046 g/mL for female plants and Beja showed 0.037 and 0.072 g/mL for male and female plants, respectively. This is the first time that a study has revealed a negative correlation between the antioxidant activity and the larvicidal activity of the leaf extracts of M. annua with the following correlation coefficients of Perason: r = −0.975 and r = −0.760 for male and female plants, respectively.

Exploring the host range and infection process of Venturia paralias isolated from Euphorbia paralias in France

In 2008, a fungal pathogen causing severe necrotic leaf and stem lesions on Euphorbia paralias (commonly referred to as sea spurge) was collected in France. The fungus has recently been described as Venturia paralias and offers potential for the classical biological control of sea spurge in Australia, where the plant is invasive in dune and foredune ecosystems. To explore the host range of V. paralias, a series of experiments comprising 45 species from the Euphorbiaceae, Picrodendraceae and Phyllanthaceae families were performed. In addition, the development of V. paralias on leaves of sea spurge and the other species inoculated was examined microscopically. Results revealed that V. paralias is highly specific, only causing disease symptoms on sea spurge and Euphorbia segetalis, its most phylogenetically related species tested that is present in Australia. Microscopic observations showed that the infection process of V. paralias on its two susceptible hosts is similar to that of other Venturia species, with characteristic expanded hyphal networks within the subcuticular space of leaves. In contrast, V. paralias did not penetrate leaves of other species inoculated, except for three (Euphorbia myrsinites, Euphorbia helioscopia and Mercurialis annua) on which it penetrated the leaf cuticle and developed an initial infection hypha that did not expand any further. Results from this study support the conjecture that V. paralias will not pose a threat to valued non-target Euphorbiaceae species should the fungus be approved for introduction to Australia for the biological control of sea spurge.

The rapid dissolution of dioecy by experimental evolution

Evolutionary transitions from hermaphroditism to dioecy have been common in flowering plants,1,2 but recent analysis also points to frequent reversions from dioecy to hermaphroditism.2-4 Here, we use experimental evolution to expose a mechanism for such reversions, validating an explanation for the scattered phylogenetic distribution of dioecy. We removed males from dioecious populations of the wind-pollinated plant Mercurialis annua and allowed natural selection to act on the remaining females that occasionally produced male flowers; such "leaky" sex expression is common in both males and females of dioecious plants.5 Over the course of four generations, females evolved a 23-fold increase in average male flower production. This phenotypic masculinization of females coincided with the evolution of partial self-fertilization, high average seed set in the continued absence of males, and a capacity to sire progeny when males were re-introduced into their populations. Our study thus validates a mechanism for the rapid dissolution of dioecy and the evolution of functional hermaphroditism under conditions that may frequently occur during periods of low population density, repeated colonization, or range expansion.6,7 Our results illustrate the power of natural selection, acting in replicated experimental populations, to bring about transitions in the mating behavior of plants.