Efraín Tovar-Sánchez

Natural hybridization can obscure species boundaries and generate morphologically atypical individuals whose taxonomic identity cannot be resolved from phenotype alone. In central Mexico, Mimosa benthamii and M. mollis occur in sympatry with individuals exhibiting unusual combinations of morphological traits. We integrated morphological and molecular evidence to test whether these individuals originated through interspecific hybridization, characterize variation in parental genetic contributions, and evaluate whether they constitute a morphologically diagnosable hybrid entity. We examined 29 leaf, prickle, fruit, and inflorescence characters in 145 plants and analyzed 42 reproducible RAPD bands, including 16 parental-diagnostic markers. The putative parental species were morphologically differentiated and distinguishable by parental-diagnostic RAPD markers, whereas morphologically atypical individuals exhibited heterogeneous combinations of intermediate, parental-like, and transgressive morphological characters and occupied intermediate and partially overlapping positions relative to both taxa. The concordance between morphological and molecular evidence supports natural hybridization between M. benthamii and M. mollis. Hybrid-index analyses revealed heterogeneous parental-marker profiles, including individuals with intermediate values and others showing greater similarity to M. mollis. However, the limited resolution of RAPD markers precluded confirmation of backcrossing events, genetic introgression, or specific hybrid generations. Despite the occurrence of mixed parental-marker profiles, M. benthamii and M. mollis remained morphologically differentiated and distinguishable by parental-diagnostic RAPD markers within the contact zone. The concordance between molecular evidence consistent with hybrid ancestry and a diagnostic combination of morphological characters supports recognition of the hybrid entity as Mimosa × gretheriae nothosp. nov. These findings document natural interspecific hybridization in Mimosa and show that hybridization can generate substantial phenotypic and molecular variation while the parental taxa remain morphologically distinguishable.

Atrazine (ATZ) is one of the most widely used herbicides worldwide and remains an environmental concern due to its persistence, mobility, and recurrent detection in soil, surface water, groundwater, and biota. This narrative review examines and discusses the environmental occurrence, exposure pathways, ecotoxicological effects, and major mechanisms underlying ATZ toxicity in non-target organisms, with particular emphasis on biomarker-based assessment. Despite extensive research on ATZ, available knowledge remains largely compartmentalized by environmental process, toxicological mechanism, biological endpoint, or taxonomic group, and comparatively few studies integrate environmental exposure with mechanisms of toxicity and associated biomarker responses across multiple taxa and levels of biological organization. Available evidence indicates that ATZ toxicity involves interconnected mechanisms, including oxidative stress, endocrine disruption, neurotoxicity, genotoxicity, mitochondrial dysfunction, inflammation, and cell death. These mechanisms result in molecular, biochemical, histopathological, reproductive, developmental, and behavioral alterations across plants, invertebrates, fish, amphibians, and mammals. Biomarkers of oxidative stress, such as malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT), together with acetylcholinesterase activity (AChE), endocrine endpoints, micronuclei, comet assays, histopathological alterations, and gene-expression markers, have demonstrated value for detecting sublethal effects and elucidating mechanisms of toxicity related to ATZ exposure. However, interspecies variability, environmental factors, and the limited specificity of individual biomarkers highlight the need for integrated multibiomarker approaches combined with chemical analyses of ATZ. Overall, integrating environmental monitoring with mechanistically informative biomarkers may improve ecological and human-health risk assessment and provide stronger scientific support for surveillance programs and future regulatory decisions.

Glyphosate is a non-selective, broad-spectrum herbicide commonly used to control various types of weeds in both urban and agricultural settings. Due to their high effectiveness, herbicide formulations containing glyphosate as the active ingredient are among the most widely used in agriculture worldwide. However, the extensive use of glyphosate has been associated with significant environmental contamination events and toxic effects on non-target organisms, including humans. To mitigate environmental contamination and the adverse impacts of glyphosate, it is essential to develop remediation alternatives and treatment methods. Bioremediation using microorganisms has been proposed as a viable solution to address glyphosate contamination. This review analyzes the environmental impacts and human health risks associated with glyphosate use, as well as biological alternatives based on the use of microorganisms, such as bacteria, for the treatment of glyphosate contamination.

Paraquat is an herbicide widely used to control weeds in various crops. Due to its use in large quantities, its dispersal into the environment is frequent, leading to contamination and negative health effects on non-target organisms because of its high toxicity and persistence in soils. Therefore, it is necessary to develop sustainable strategies to remediate sites contaminated by this compound. Bacterial remediation is a promising alternative for removing paraquat from the environment; however, the metabolic pathways used by bacteria for its degradation have not yet been precisely described. In this context, it is essential to characterize bacterial species capable of resisting and degrading paraquat, as well as to elucidate the molecular mechanisms involved in these processes. The objective of this work was to evaluate the paraquat resistance and degradation potential of the bacterial strain Caballeronia zhejiangensis CEIB S4-3, and to identify genes with a possible role in the resistance and degradation of this herbicide by analyzing the strain’s genome. The results of this research showed that, in solid medium, C. zhejiangensis CEIB S4-3 can withstand concentrations of up to 200 mg/L of paraquat supplemented as a commercial formulation (Gramoxone^®) and 400 mg/L of analytical-grade paraquat. In tryptic soy broth, the strain grew in the presence of both the commercial formulation and analytical-grade paraquat at concentrations up to 15 mg/L, whereas in mineral salts medium, supplemented with paraquat or its commercial formulation as the sole nutrient source, the strain survived exposure to paraquat at the same concentrations. Furthermore, the bacterial strain removed 40.8% of the paraquat supplemented in the culture medium at a concentration of 12 mg/L within 48 h. Finally, genomic analysis revealed the presence of genes related to paraquat resistance mechanisms and encoding enzymes involved in the degradation of this herbicide. These results position C. zhejiangensis CEIB S4-3 as a promising candidate for developing remediation alternatives for sites contaminated with this herbicide.

Quercus glabrescens Benth. (white oak) is a widespread temperate forest species endemic to Mexico, known to form hybrids with related species in regions of sympatry. Q. glabrescens presents weak reproductive barriers with other white oak species; hence, in this study, we tested whether increasing the richness of sympatric white oak species contributes to greater genetic diversity in Q. glabrescens. In total, eight microsatellite primers (eight nSSRs and four cpSSRs) were analyzed in five Q. glabrescens populations: one allopatric (without the presence of other white oak) and four sympatric populations, across which the number of white oak species occurring in sympatry with Q. glabrescens ranged from one to four (Q. obtusata, Q. rugosa, Q. laeta, and Q. potosina). In total, 100 individuals were analyzed. In general, sympatric populations had the highest levels of genetic diversity (Gd), Shannon diversity index (H), and expected heterozygosity (He) compared with the allopatric population of Q. glabrescens, regardless of microsatellite origin. Furthermore, estimates of genetic differentiation (F_ST and R_ST) were consistently higher for cpSSRs than for nSSRs. Genetic diversity in Q. glabrescens (H, cpSSRs; He and F nSSRs) increased significantly with the number of white oak species occurring in sympatry. Our results support the hypothesis that as the number of white oak species growing in sympatry with Q. glabrescens increases, its genetic diversity also increases, possibly due to introgressive hybridization. This pattern provides a robust framework for predicting how associated oak species may influence the genetic diversity of Q. glabrescens, which permits the assignment of a new conservation status based on species richness growing in sympatry.

While mining is a highly important economic activity, it generates considerable environmental impact, especially during the grinding and extraction stages of metallic minerals, leading to the formation of waste known as mine tailings. These mine tailings, often abandoned in various regions of Mexico due to a lack of prior environmental regulations, contain heavy metals that pose a risk to both the environment and human health. In Huautla, Morelos, where metals such as silver (Ag), gold (Au), copper (Cu), lead (Pb), and zinc (Zn) were extracted from the 16th century until 1988, it is estimated that there are approximately 780,000 tons of mine tailings. These mine tailings are contaminated with heavy metals such as cadmium (Cd), Cu, chromium (Cr), manganese (Mn), Pb, and Zn, and the bioaccumulation and biomagnification of these metals have been documented in various plant and animal species in the region, indicating their bioavailability. The study conducted in this area consisted of determining the concentration of Cd, Cu, Cr, Mn, Pb, and Zn, as well as the sequential extraction of mine tailings 1 and 2 to identify metal bioavailability. The results showed for both mine tailings, that the metals with the highest concentrations were Pb (mine tailing 1: 1666 ± 317.7 mg/kg, mine tailing 2: 1329 ± 30.8 mg/kg) and Zn (mine tailing 1: 1327 ± 314.9 mg/kg, mine tailing 2: 1099 ± 34.3 mg/kg), found in fractions IV and VI, respectively. In mine tailings 1, the main bioavailable metals were Cd (75.3%), Mn (53%), Pb (39.8%), and Cu (36.4%), while in mine tailings 2, the bioavailable metals were Cd (56.8%), Pb (37.9%), and Cu (29.3%). In general, Cd and Pb exhibited the highest bioavailability in both mine tailings. According to the calculated risk indices, bioavailable Cd and Pb pose the highest pollution, ecological, and non-carcinogenic risk in both mine tailings, while bioavailable Cr showed the highest determined carcinogenic risk. This study demonstrated that the mining waste from Huautla contains high levels of bioavailable heavy metals, posing ecological and public health risks, and provides valuable information for the development of effective environmental remediation strategies.

Anthropogenic activities interact through multifactorial processes that generate harmful factors, hindering wastewater management (WWM) and causing environmental degradation, particularly in rapidly urbanizing coastal regions. Understanding how these processes operate is essential for identifying effective interventions under data-limited conditions. This study introduces a process-based and context-driven approach whose main contribution lies in the construction of semantic pathways that represent how indirect anthropogenic drivers give rise to direct harmful factors affecting WWM and the environmental state. Semantic networks are used as a formal representation tool to model these pathways, where nodes represent factors and directed arcs represent causal relationships. Harmful semantic pathways are evaluated within a multidisciplinary decision-making framework supported by multi-criteria decision-making (MCDM) methods that account for environmental, social, economic, and sustainability criteria. The approach is applied to a coastal tourist municipality on the Mexican Pacific coast, where rapid urban expansion and insufficient basic services have severely constrained wastewater management and contributed to environmental damage. Results show that constructing and analyzing semantic pathways enables decision-makers to identify critical harmful factors and prioritize viable pro-environmental actions. The resulting priorities (range 0–1) highlight the restoration of wastewater treatment plants and improved urban planning as the most effective interventions, followed by mangrove reforestation and changes in agricultural practices. The proposed approach supports transparent, context-sensitive decision-making and is transferable to coastal tourist municipalities facing similar wastewater management challenges.