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This study decisively evaluates the classification of four species of Euphorbia : Euphorbia ammak , Euphorbia fractiflexa , Euphorbia granulata , and Euphorbia hirta , collected from diverse habitats in Jazan region (Saudi Arabia). Our objective is to clearly define the interrelationships among these species by utilizing both traditional morphological analyses and cutting-edge chemotaxonomical methods. The morphological analysis examines various aspects of plant life, encompassing qualitative and quantitative parameters. Phytochemical analysis effectively measures total phenolics, alkaloids, flavonoids, saponins, and tannins. High-Performance Liquid Chromatography (HPLC) is employed to capture the phenolic patterns, thereby validating our chemotaxonomic approach. The HPLC analysis unequivocally identifies eleven phenolic and seven flavonoid compounds in the methanol extracts of the four Euphorbia taxa. The data collected from the studied Operational Taxonomic Units (OTUs) were meticulously organized into a binary matrix, establishing a similarity matrix and phenogram cluster. Duncan’s range test robustly determines the significance of interrelations among the species. The results demonstrate that all examined plant species are rich in phenolic constituents, albeit in varying concentrations. Notably, Euphorbia granulata stands out as the most transitional species among them. Taxonomically, our phenogram, based on taxonomic characteristics, reveals two distinct groups: the first group, at a distance of 1.90, includes Euphorbia ammak and Euphorbia fractiflexa , while the second group, at a distance of 1.52, encompasses the remaining two species. This study strongly recommends considering both adaptation and habitat type when conducting chemotaxonomic analyses of plant species.

The mid-Cenozoic decline of atmospheric CO2 levels that promoted global climate change was critical to shaping contemporary arid ecosystems. Within angiosperms, two CO2-concentrating mechanisms (CCMs)—crassulacean acid metabolism (CAM) and C4—evolved from the C3 photosynthetic pathway, enabling more efficient whole-plant function in such environments. Many angiosperm clades with CCMs are thought to have diversified rapidly due to Miocene aridification, but links between this climate change, CCM evolution, and increased net diversification rates (r) remain to be further understood. Euphorbia (∼2000 species) includes a diversity of CAM-using stem succulents, plus a single species-rich C4 subclade. We used ancestral state reconstructions with a dated molecular phylogeny to reveal that CCMs independently evolved 17–22 times in Euphorbia, principally from the Miocene onwards. Analyses assessing among-lineage variation in r identified eight Euphorbia subclades with significantly increased r, six of which have a close temporal relationship with a lineage-corresponding CCM origin. Our trait-dependent diversification analysis indicated that r of Euphorbia CCM lineages is approximately threefold greater than C3 lineages. Overall, these results suggest that CCM evolution in Euphorbia was likely an adaptive strategy that enabled the occupation of increased arid niche space accompanying Miocene expansion of arid ecosystems. These opportunities evidently facilitated recent, replicated bursts of diversification in Euphorbia.

The genus Euphorbia (Euphorbiaceae) has near-cosmopolitan distribution and serves as a significant resource for both ornamental and medicinal purposes. Despite its economic importance, Euphorbia 's taxonomy has long been challenged by the intricate nature of morphological traits exhibiting high levels of convergence. While molecular markers are essential for phylogenetic studies, their availability for Euphorbi a has been limited. To address this gap, we conducted comparative analyses focusing on the chloroplast (CP) genomes of nine Euphorbia species, incorporating three newly sequenced and annotated accessions. In addition, phylogenetic informativeness and nucleotide diversity were computed to identify candidate markers for phylogenetic analyses among closely related taxa in the genus. Our investigation revealed relatively conserved sizes and structures of CP genomes across the studied species, with notable interspecific variations observed primarily in non-coding regions and IR/SC borders. By leveraging phylogenetic informativeness and nucleotide diversity, we identified rpoB gene as the optimal candidate for species delimitation and shallow-level phylogenetic inference within the genus. Through this comprehensive analysis of CP genomes across multiple taxa, our study sheds light on the evolutionary dynamics and taxonomic intricacies of Euphorbia , offering valuable insights into its CP genome evolution and taxonomy.

Patterns of adaptation in response to environmental variation are central to our understanding of biodiversity, but predictions of how and when broad-scale environmental conditions such as climate affect organismal form and function remain incomplete. Succulent plants have evolved in response to arid conditions repeatedly, with various plant organs such as leaves, stems, and roots physically modified to increase water storage. Here, we investigate the role played by climate conditions in shaping the evolution of succulent forms in a plant clade endemic to Madagascar and the surrounding islands, part of the hyper-diverse genus Euphorbia (Euphorbiaceae). We used multivariate ordination of 19 climate variables to identify links between particular climate variables and three major forms of succulence—succulent leaves, cactiform stem succulence, and tubers. We then tested the relationship between climatic conditions and succulence, using comparative methods that account for shared evolutionary history. We confirm that plant water storage is associated with the two components of aridity, temperature, and precipitation. Cactiform stem succulence, however, is not prevalent in the driest environments, countering the widely held view of cactiforms as desert icons. Instead, leaf succulence and tubers are significantly associated with the lowest levels of precipitation. Our findings provide a clear link between broad-scale climatic conditions and adaptation in land plants, and new insights into the climatic conditions favoring different forms of succulence. This evidence for adaptation to climate raises concern over the evolutionary future of succulent plants as they, along with other organisms, face anthropogenic climate change.

Of late, decrease in mineral oil supplies has stimulated research on use of biomass as an alternative energy source. Climate change has brought problems such as increased drought and erratic rains. This, together with a rise in land degeneration problems with concomitant loss in soil fertility has inspired the scientific world to look for alternative bio-energy species. Euphorbia tirucalli L., a tree with C3/CAM metabolism in leaves/stem, can be cultivated on marginal, arid land and could be a good alternative source of biofuel. We analyzed a broad variety of E. tirucalli plants collected from different countries for their genetic diversity using AFLP. Physiological responses to induced drought stress were determined in a number of genotypes by monitoring growth parameters and influence on photosynthesis. For future breeding of economically interesting genotypes, rubber content and biogas production were quantified. Cluster analysis shows that the studied genotypes are divided into two groups, African and mostly non-African genotypes. Different genotypes respond significantly different to various levels of water. Malate measurement indicates that there is induction of CAM in leaves following drought stress. Rubber content varies strongly between genotypes. An investigation of the biogas production capacities of six E. tirucalli genotypes reveals biogas yields higher than from rapeseed but lower than maize silage.

Among latex-producing plants, mainly the latex of Hevea brasiliensis has been studied in detail so far, while comprehensive comparative studies of latex coagulation mechanisms among the more than 20,000 latex-bearing plant species are lacking. In order to give new insights into the potential variety of coagulation mechanisms, the untreated natural latices of five latex-bearing plants from the families Euphorbiaceae, Moraceae and Campanulaceae were visualised using Cryo-SEM and their particle size compared using the laser diffraction method. Additionally, the laticifers of these plants species were examined in planta via Cryo-SEM. Similar latex particle sizes and shape were found in Ficus benjamina and Hevea brasiliensis. Hence, and due to other similarities, we hypothesize comparable, mainly chemical, coagulation mechanisms in these two species, whereas a physical coagulation mechanism is proposed for the latex of Euphorbia spp. The latter mechanism is based on the huge amount of densely packed particles that after evaporation of water build a large surface area, which accelerates the coagulation procedure.

The current decrease of new drugs brought to the market has fostered renewed interest in plant-based drug discovery. Given the alarming rate of biodiversity loss, systematic methodologies in finding new plant-derived drugs are urgently needed. Medicinal uses of plants were proposed as proxy for bioactivity, and phylogenetic patterns in medicinal plant uses have suggested that phylogeny can be used as predictive tool. However, the common practice of grouping medicinal plant uses into standardised categories may restrict the relevance of phylogenetic predictions. Standardised categories are mostly associated to systems of the human body and only poorly reflect biological responses to the treatment. Here we show that medicinal plant uses interpreted from a perspective of a biological response can reveal different phylogenetic patterns of presumed underlying bioactivity compared to standardised methods of medicinal plant use classification. In the cosmopolitan and pharmaceutically highly relevant genus Euphorbia L., identifying plant uses modulating the inflammatory response highlighted a greater phylogenetic diversity and number of potentially promising species than standardised categories. Our interpretation of medicinal plant uses may therefore allow for a more targeted approach for future phylogeny-guided drug discovery at an early screening stage, which will likely result in higher discovery rates of novel chemistry with functional biological activity.

Premise of the study: The Chamaesyce clade of Euphorbia is the largest lineage of C₄ plants among the eudicots, with 350 species including both narrow endemics and cosmopolitan weeds. We sampled this group worldwide to address questions about subclade relationships, the origin of C₄ photosynthesis, the evolution of weeds, and the role of hybridization and longdistance dispersal in the diversification of the group. Methods: Two nuclear (ITS and exon 9 of EMB2765) and three chloroplast markers (matK, rpl16 y and trnL-F) were sequenced for 138 ingroup and six outgroup species. Exon 9 of EMB2765 was cloned in accessions with > 1% superimposed peaks. Key results: The Chamaesyce clade is monophyletic and consists of three major subclades [1(2,3)]: (1) the Acuta clade, containing three North American species with C₃ photosynthesis and C₃ -C₄ intermediates; (2) the Peplis clade, mostly North American and entirely C₄; and (3) the Hypericifolia clade, all C₄, with both New World and Old World groups. Incongruence between chloroplast and ITS phylogenies and divergent cloned copies of EMB2765 exon 9 suggest extensive hybridization, especially in the Hawaiian Islands radiation. Conclusions: The Chamaesyce clade originated in warm, arid areas of North America, where it evolved C₄ photosynthesis. From there, it diversified globally with extensive reticulate evolution and frequent long-distance dispersals. Although many species are weedy, there are numerous local adaptations to specific substrates and regional or island radiations, which have contributed to the great diversity of this group.

A ring species arises when a parental population expands around an area of unsuitable habitat in such a way that when the two fronts meet they behave as distinct species while still being connected through a series of intergrading populations. Ring species offer great possibilities for studying the forces causing species divergence (e.g. the nature of pre-zygotic or post-zygotic reproductive isolation) or helping to maintain species integrity (e.g. reinforcement). Yet, ring species are extremely rare, and have only been documented convincingly in animals. Here, we present phylogenetic analyses of two nuclear gene regions from the Caribbean slipper spurge (Euphorbia tithymaloides) species complex that provide evidence that this group forms a ring species. These data show that the species complex originated in the area where Mexico and Guatemala meet, and expanded around the Caribbean basin along two distinct fronts: one eastward through the Yucatan Peninsula and into the Greater Antilles (GA); one southeastward through northern South America and then northward to the Lesser Antilles and eastern GA. The two terminal forms co-occur in the Virgin Islands and appear to be morphologically and ecologically distinct. Thus, our results suggest that Euphorbia tithymaloides is the first compelling example of a ring species in plants.

The milky sap or latex of Euphorbia plant is highly toxic and an irritant to the skin and eye. This report illustrates the spectrum of ocular inflammation caused by accidental inoculation of latex of Euphorbia plant. Three patients presented with accidental ocular exposure to the milky sap of Euphorbia species of recent onset. The initial symptoms in all cases were severe burning sensation with blurring of vision. Visual acuity reduced from 20/60 to counting fingers. Clinical findings varied from kerato-conjunctivitis, mild to severe corneal edema, epithelial defects, anterior uveitis and secondary elevated intraocular pressure. All symptoms and signs had resolved by 10-14 days with active supportive medication. People who handle Euphorbia plants should wear eye protection. It is always advisable to ask the patient to bring a sample of the plant for identification.