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Urbanisation is occurring globally, leading to dramatic environmental changes that are altering the ecology and evolution of species. In particular, the expansion of human infrastructure and the loss and fragmentation of natural habitats in cities is predicted to increase genetic drift and reduce gene flow by reducing the size and connectivity of populations. Alternatively, the 'urban facilitation model' suggests that some species will have greater gene flow into and within cities leading to higher diversity and lower differentiation in urban populations. These alternative hypotheses have not been contrasted across multiple cities. Here, we used the genomic data from the GLobal Urban Evolution project (GLUE), to study the effects of urbanisation on non-adaptive evolutionary processes of white clover (Trifolium repens) at a global scale. We found that white clover populations presented high genetic diversity and no evidence of reduced N e linked to urbanisation. On the contrary, we found that urban populations were less likely to experience a recent decrease in effective population size than rural ones. In addition, we found little genetic structure among populations both globally and between urban and rural populations, which showed extensive gene flow between habitats. Interestingly, white clover displayed overall higher gene flow within urban areas than within rural habitats. Our study provides the largest comprehensive test of the demographic effects of urbanisation. Our results contrast with the common perception that heavily altered and fragmented urban environments will reduce the effective population size and genetic diversity of populations and contribute to their isolation., (© 2024 The Authors. Molecular Ecology published by John Wiley & Sons Ltd.)

Agriculture is fundamental for human development, but it may also have a range of unwanted effects on ecosystems when pesticides inadvertently enter the environment. We determined the toxicity of difenoconazole and atrazine, as well as their photodegradation products, on the bioindicators Lemna minor and Daphnia magna . For L. minor , we assessed the number of leaves, biomass, and chlorophyll content exposed to different concentrations of difenoconazole (0-8 mg/L) and atrazine (0-3.84 mg/L). For D. magna , we assessed the mortality to difenoconazole (0-1.6 mg/L) and atrazine (0-80 mg/L). We found that the higher the concentrations of the pesticides, the higher the toxicity for both bioindicators. In L. minor , the highest toxicity for atrazine was 0.96 mg/L, whereas for difenoconazole, it was 8 mg/L. For D. magna , the 48 h LC 50 for difenoconazole was 0.97 mg/L, while for atrazine, it was 86.19 mg/L. For L. minor , the toxicity of difenoconazole and atrazine was not different compared to that of their photodegradation products. In contrast, for D. magna , difenoconazole, but not atrazine, was more toxic compared to its respective photodegradation products. Pesticides are a serious threat to aquatic biota, and their photodegradation products remain toxic in the environment. Additionally, the use of bioindicators can help monitor these pollutants in aquatic ecosystems in countries where the application of pesticides is imperative for agricultural production.

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale.

The tropical Andes are experiencing rapid population growth and urbanisation has become a major driver impairing stream ecosystems. However, knowledge about multiple-stressors effects on urbanised Andean streams is lacking. In southern Ecuador, we assessed how multiple stressors determine the structural (aquatic invertebrate metrics) and functional (organic matter breakdown and delta N of primary consumers) attributes of streams in a densely populated watershed without wastewater treatment and with contrasting land uses. We found that urbanised streams exhibited individual-stressor effects and that stressor interactions were rare. While structural and function attributes responded negatively to urbanisation, ecosystem functioning metrics were influenced most. Stream ecosystem functions were influenced by water-chemistry stressors, whereas aquatic invertebrate metrics were influenced by physical-habitat stressors. We suggest that managers of urbanised streams in the Andes immediately focus on the most important stressors by reducing inputs of inorganic N and P, re-establishing stream flow and substrate heterogeneity, and restoring riparian vegetation instead of attempting to elucidate intricate interactions among stressors. Our result also demonstrate that stream biomonitoring programs would benefit from a combination of structural and functional indicators to assess anthropogenic effects in a multiple-stressors scenario., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Bathing in natural waters is a highly demanded recreational activity in tropical countries because of climatic conditions and availability of bathing sites; but, do users know the water quality of these sites? We determined the physicochemical and microbiological water quality of a highly used bathing site in southern Ecuador. We assessed how bather attendance, rainfall events, and pool location alters the recreational water quality (RWQ). Most of the parameters measured in the stream pools did not accomplish the Ecuadorian and international regulations for recreational water quality. Microbiological water quality diminishes from upstream to downstream pools because of human activities and bathing intensity having potential effects on bather health and eco-touristic development. We found that an increase of bathers is strongly associated with a growing concentration of Escherichia coli. It is suggested better land-use practices and review thoroughly the Ecuadorian regulation to assure a healthy RWQ. Further efforts are needed to identify more risky bathing sites, determine pollution sources, and establish a long-term monitoring program to support the touristic development in countries looking for diversifying their economy., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth's biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented "next-generation biomonitoring" by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.

Tropical montane ecosystems of the Andes are critically threatened by a rapid land-use change which can potentially affect stream variables, aquatic communities, and ecosystem processes such as leaf litter breakdown. However, these effects have not been sufficiently investigated in the Andean region and at high altitude locations in general. Here, we studied the influence of land use (forest-pasture-urban) on stream physico-chemical variables (e.g., water temperature, nutrient concentration, and pH), aquatic communities (macroinvertebrates and aquatic fungi) and leaf litter breakdown rates in Andean streams (southern Ecuador), and how variation in those stream physico-chemical variables affect macroinvertebrates and fungi related to leaf litter breakdown. We found that pH, water temperature, and nutrient concentration increased along the land-use gradient. Macroinvertebrate communities were significantly different between land uses. Shredder richness and abundance were lower in pasture than forest sites and totally absent in urban sites, and fungal richness and biomass were higher in forest sites than in pasture and urban sites. Leaf litter breakdown rates became slower as riparian land use changed from natural to anthropogenically disturbed conditions and were largely determined by pH, water temperature, phosphate concentration, fungal activity, and single species of leaf-shredding invertebrates. Our findings provide evidence that leaf litter breakdown in Andean streams is sensitive to riparian land-use change, with urban streams being the most affected. In addition, this study highlights the role of fungal biomass and shredder species (Phylloicus; Trichoptera and Anchytarsus; Coleoptera) on leaf litter breakdown in Andean streams and the contribution of aquatic fungi in supporting this ecosystem process when shredders are absent or present low abundance in streams affected by urbanization. Finally, we summarize important implications in terms of managing of native vegetation and riparian buffers to promote ecological integrity and functioning of tropical Andean stream ecosystems.

Deforestation in the tropical Andes is affecting ecological conditions of streams, and determination of how much forest should be retained is a pressing task for conservation, restoration and management strategies. We calculated and analyzed eight benthic metrics (structural, compositional and water quality indices) and a physical-chemical composite index with gradients of vegetation cover to assess the effects of deforestation on macroinvertebrate communities and water quality of 23 streams in southern Ecuadorian Andes. Using a geographical information system (GIS), we quantified vegetation cover at three spatial scales: the entire catchment, the riparian buffer of 30 m width extending the entire stream length, and the local scale defined for a stream reach of 100 m in length and similar buffer width. Macroinvertebrate and water quality metrics had the strongest relationships with vegetation cover at catchment and riparian scales, while vegetation cover did not show any association with the macroinvertebrate metrics at local scale. At catchment scale, the water quality metrics indicate that ecological condition of Andean streams is good when vegetation cover is over 70%. Further, macroinvertebrate community assemblages were more diverse and related in catchments largely covered by native vegetation (>70%). Our results suggest that retaining an important quantity of native vegetation cover within the catchments and a linkage between headwater and riparian forests help to maintain and improve stream biodiversity and water quality in Andean streams affected by deforestation. This research proposes that a strong regulation focused to the management of riparian buffers can be successful when decision making is addressed to conservation/restoration of Andean catchments.