Background: Delimiting species across a speciation continuum is a complex task, as the process of species origin is not generally instantaneous. The use of genome-wide data provides unprecedented resolution to address convoluted species delimitation cases, often unraveling cryptic diversity. However, because genome-wide approaches based on the multispecies coalescent model are known to confound population structure with species boundaries, often resulting in taxonomic over-splitting, it has become increasingly evident that species delimitation research must consider multiple lines of evidence. In this study, we used phylogenomic, population genomic, and coalescent-based species delimitation approaches, and examined those in light of morphological and ecological information, to investigate species numbers and boundaries comprising theChirostoma“humboltianumgroup” (family Atherinidae). Thehumboltianumgroup is a taxonomically controversial species complex where previous morphological and mitochondrial studies produced conflicting species delimitation outcomes. We generated ddRADseq data for 77 individuals representing the nine nominal species in the group, spanning their distribution range in the central Mexican plateau.Results: Our results conflict with the morphospecies and ecological delimitation hypotheses, identifying four independently evolving lineages organized in three geographically cohesive clades: (i)chapalaeandsphyraenagroups in Lake Chapala, (ii)estorgroup in Lakes Pátzcuaro and Zirahuén, and (iii)humboltianumsensu stricto group in Lake Zacapu and Lerma river system.Conclusions: Overall, our study provides an atypical example where genome-wide analyses delineate fewer species than previously recognized on the basis of morphology. It also highlights the influence of the geological history of the Chapala-Lerma hydrological system in driving allopatric speciation in thehumboltianumgroup.

Termites play a key role as ecosystem engineers in numerous ecological processes though their role in the dynamics of wood degradation in tropical dry forests, particularly at the level of the crown canopy, has been little studied. In this study, we analysed the occurrence of termites in the forest canopy by evaluating the density and proportion of living and standing dead trees associated with termites in deciduous and riparian habitats of the tropical dry forest in Chamela, Mexico. The results indicated that 60–98% of standing dead trees and 23–59% of living trees in Chamela were associated with termites. In particular, we found that the density of standing dead trees was higher in deciduous forests (0.057–0.066 trees/m²) than in riparian forests (0.022 and 0.027 trees/m²), even though the proportion of trees was not significantly different among habitats. Additionally, we found a higher density of trees associated with termites in trees of smaller size classes (0.01–0.09 trees/m²) than in larger class sizes (0–0.02 trees/m²). Interestingly, 72% of variation in the density of trees associated with termites is explained by the density of standing dead trees. Overall, these results indicate that standing dead tree availability might be the main factor regulating termite populations in Chamela forest and suggest that termites could play a key role in the decomposition of above-ground dead wood, mediating the incorporation of suspended and standing dead wood into the soil.

Hydrological variation differently affects fish species. In the present study, the response of local populations of 13 fish local species to hydrological variation in a tropical wetland was evaluated. The objectives were to analyze the abundance response of fish species with distinct life history strategies and to assess the role of hydrological variation on fish population patterns. We found that opportunistic strategists were favored by high hydrological variation in drought periods, the equilibrium strategists were related to stable habitats, and periodic strategists were regulated by floods and temperature. However, the life history strategies identified for some species in this study do not correspond to the classification reported in other studies. Our results highlight the importance to study the abundance responses of species at local and regional scales to identify variations in life-history strategies, which can reflect local adaptations of species to hydrological changes, this is useful in order to understand and predict the responses of fish populations to the local environment.

Contamination by heavy metals resulting from irrigation with wastewater is an important global concern, as it can lead to crop contamination, posing serious threats to human health. Despite the advances in bioremediation of soils, sustainable strategies that use beneficial microorganisms to reduce the accumulation of heavy metals in contaminated crops remain underexplored. The aim of this study was to evaluate the potential reduction of heavy metal concentration in different structures of bean plants cultivated in soils irrigated with untreated wastewater on an agricultural land located in Hidalgo, Mexico, through the inoculation of a ubiquitous soil fungus. Bean plants were inoculated with three Trichoderma spp. and distributed across eight treatments, with an additional untreated control group, following a random full design. The percentage of root colonization and concentration of heavy metals in the leaves, pods, grains, and soil were determined. The results revealed that root colonization exceeded 75%. The treatments T. harzianum + T. asperellum and T. harzianum with 3 × 10⁶ spores ml⁻¹ showed the greatest decrease in Cd (64.7%) and Pb (66.1%) concentrations in the grains. T. viride with 2 × 10⁶ spores ml⁻¹ was the most effective treatment for copper reduction (72.9%) in grains; T. harzianum with 3 × 10⁶ spores ml⁻¹ showed the best performance for chromium reduction (75.7%), which was below the detection limit in leaves. In conclusion, inoculation of bean plants with Trichoderma spp. effectively reduced the accumulation of heavy metals. Future research in this area could contribute to the development of sustainable strategies to mitigate heavy metal contamination in agricultural ecosystems, thereby promoting food and environmental safety.

El papel de los peces en la dinámica trófica de los ecosistemas acuáticos se ha estudiado usando diferentes métodos que permiten determinar su dieta y posición trófica (inspección visual del contenido estomacal y heces, isótopos estables, secuenciación de ADN). Con los avances tecnológicos en la secuenciación de alto rendimiento del ADN, el uso del método de metabarcoding se ha incrementado en los últimos años, demostrando tener mayor precisión y alcance taxonómico que otros métodos, además de que permite el análisis simultáneo de un mayor número de muestras en un menor tiempo. En esta revisión, se describen los pasos del método de metabarcoding, discutiendo sus ventajas y limitaciones, así como las alternativas experimentales y analíticas propuestas para atender dichas limitaciones. Además, se presenta una síntesis del estado del conocimiento del método de metabarcoding aplicado al análisis de la ecología trófica de peces para entender los alcances y las limitaciones de este método en México.