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Natural hybridization has significant ecological, genetic and evolutionary consequences altering morphological and chemical characters of individuals. Quercus glabrescens, Q. rugosa and Q. obtusata are white oak species well separated by their morphological characters when they occur in allopatry in Mexican temperate forests. However, in sympatry, individuals with atypical morphology have been observed, suggesting hybridization events. In this study, we determined with microsatellites and secondary metabolites if interspecific gene flow occurs when these three-oak species coexist in sympatry. In total, 180 individuals belonging to seven populations [three allopatric (one for each parental species) and four sympatric sites] were analyzed. Allopatric populations represent well defined genetic groups and the sympatric populations showed genetic evidence of hybridization between Q. glabrescens × Q. rugosa and Q. glabrescens × Q. obtusata. The hybridization percentage varied between sites and combination of involved species. We registered the presence of unique flavonoid compounds for Q. glabrescens (caffeic acid and flavonol 2), Q. rugosa (flavonol 5), Q. obtusata (flavonol 1). Three compounds (quercetin rhamnoside, flavonol 3 and alkyl coumarate) were expressed in all taxa. Finally, the hybrid genotypes identified in this study (Q. glabrescens × Q. rugosa and Q. glabrescens × Q. obtusata) showed particular chemical profiles, resulting from combination of those of their parental species. These results show that hybridization events between these oak species alter chemical expression of secondary metabolites, creating a mosaic of resources and conditions that provide the substrate for different combinations of foliar-associated species as herbivores, endophytic fungi or epiphyte plants. This article is protected by copyright. All rights reserved.

Interspecific gene flow between more than two species is a common phenomenon in oaks, which can occur simultaneously among different species, promoting the transfer of genetic material across species boundaries. However, the hybridization dynamics in multispecies hybrid zones remain unknown. In this study, we provide genetic evidence of hybridization and introgression of Quercus castanea across a natural gradient of red oak species richness. We analyzed five populations recognized morphologically as ''pure'' Q. castanea, one allopatric and four sympatric populations, where the number of red oak species associated with Q. castanea ranged from one to four. Also, one allopatric population of each red oak species that occurs in sympatry with Q. castanea was chosen as reference population (Q. crassipes, Q. laurina, Q. mexicana and Q. crassifolia). In total, six nSSRs were used in 10 and 20 individuals from each allopatric and sympatric populations, respectively. Our results showed that allopatric populations formed completely distinct genetic clusters.In sympatric populations, we found evidence of hybridization and introgression among Q. castanea and three of its associated red oak species. However, the occurrence and frequency of hybrids between Q. castanea and these species varied among stands. Our analyses provide evidence and new insights into hybridization and introgression dynamics within a Mexican red oak species complex, through a focal species, Q. castanea.

Canopy of forest ecosystems has been recognized as a habitat that supports a wide variety of plants, vertebrates, invertebrates, and microbes. Within the invertebrate group, arthropods are characterized by their great abundance, diversity, and functional importance. Particularly in temperate forests, species of the genus Quercus (oaks) are one of the most important tree canopy groups, for its diversity and dominance. Different studies have shown that the oak canopy contains a high diversity of arthropods suggesting their importance as habitat for this group of organisms. In this review, we investigated the factors that determine the establishment, organization, and maintenance of arthropod communities in the oak canopy. In general, it was found that there is a lack of literature that addresses the study of oak canopy arthropod communities. Also, the following patterns were found: (a) the research has covered a wide variety of topics; however, there are differences in the depth to which each topic has been analyzed, (b) there are ambiguous criteria to define the structure of the canopy, (c) groups with different habitat preferences belonging to different guilds and uneven development stages have been studied, avoiding generalizations about patterns found, (d) the standardization in sampling techniques and collection has been difficult, (e) bias exists towards the study of phytophagous insects belonging to the Coleoptera, Hymenoptera, and Lepidoptera orders, and (f) there are few studies in other groups of arthropods, for example, acorn borers, whose activity has an impact on the fitness and dispersion of the host plants. Finally, we propose that the detection and study of patterns in oak canopy communities can be of great value to propose management and conservation strategies in these forests.

Glyphosate is a broad-spectrum herbicide extensively used worldwide to eliminate weeds in agricultural areas. Since its market introduction in the 70’s, the levels of glyphosate agricultural use have increased, mainly due to the introduction of glyphosate-resistant transgenic crops in the 90’s. Glyphosate presence in the environment causes pollution, and recent findings have proposed that glyphosate exposure causes adverse effects in different organisms, including humans. In 2015, glyphosate was classified as a probable carcinogen chemical, and several other human health effects have been documented since. Environmental pollution and human health threats derived from glyphosate intensive use require the development of alternatives for its elimination and proper treatment. Bioremediation has been proposed as a suitable alternative for the treatment of glyphosate-related pollution, and several microorganisms have great potential for the biodegradation of this herbicide. The present review highlights the environmental and human health impacts related to glyphosate pollution, the proposed alternatives for its elimination through physicochemical and biological approaches, and recent studies related to glyphosate biodegradation by bacteria and fungi are also reviewed. Microbial remediation strategies have great potential for glyphosate elimination, however, additional studies are needed to characterize the mechanisms employed by the microorganisms to counteract the adverse effects generated by the glyphosate exposure.

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Heavy metals exert their toxic effects through different mechanisms. Lately, increasing attention has been focused on understanding the long-term ecological effects of chronically exposed populations and communities and their consequences to the ecosystem. The long-term exposure to heavy metals in the environment represents a threat to wild populations, affecting communities and putting ecosystem integrity at risk. Therefore, this type of exposure represents a threat to biodiversity. In the field, metal exposure is generally characterized by low doses and chronic exposures. This type of exposure exerts alterations across levels of biological organization. Distribution and abundance of populations, the community structure and the ecosystem dynamics may be altered. This chapter will focus on how chronically metal exposures in the field affect negatively populations and communities becoming a threat to biodiversity. Also, attention is put on the tools that enable to characterize and analyze the detrimental effects of heavy metal exposure on wild populations. Hence, the use and development of biomarkers in ecotoxicology will be discussed.