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The House Sparrow Passer domesticus, closely associated with human presence along urban–agricultural landscapes and widely distributed outside its native range, has shown great morphological and physiological variations, with its plasticity linked to its invasiveness. Yet, there is a dearth of knowledge on the escape behavior of this sparrow along its North American invasion range. We here assessed House Sparrows alert distances in Los Angeles and Mexico City, but also in Barcelona as a control within its native distribution, considering ‘city’, ‘sex/age’ (adult males vs. adult females and juveniles), and ‘flock size’ as alert distance predictors. Through a linear model and a classification and regression tree, we identified that House Sparrow alert distances in Barcelona were significantly larger when compared to both studied North American cities (Los Angeles, Mexico City). Given that alert distances were also significantly larger in Los Angeles when contrasted with those from Mexico City, where it has been recently shown to be hyper-abundant, our results also suggest that its boldness could be related not only to an origin (native/non-native) driver, but also to a density-dependent process.

One of the most successful avian urban invaders is the House Sparrow (Passer domesticus). Here, we examine House Sparrow numbers in the urban-agricultural landscape of three cities, one where the sparrow is native (Barcelona) and two where it is nonnative (Los Angeles, Mexico City), comparing between five different land classes based on land-use, location relative to urban center, and urbanization intensity. We estimated sparrow densities using distance-sampling corrected procedures and compared sparrow numbers between the three cities and between the land classes within each city. This two-year survey showed the highest density of sparrows occurring in Mexico City and the lowest in Los Angeles. In both cities where the sparrow is nonnative, we recorded the greatest abundances in highly urbanized areas. In Barcelona, where the sparrow is native, abundances did not differ among land classes. We also related sparrow numbers to specific environmental variables, describing vegetation structure, urban infrastructure, and human activity, using classification and regression trees. We found several variables related to differences in House Sparrow abundances among the three cities. For Los Angeles and Mexico City, the most important variables explaining House Sparrow numbers were urban infrastructure (i.e., maximum building height, high urbanization) and/or human activity (i.e., pedestrians), all of which related positively with sparrow abundance. For Barcelona, sparrow numbers showed both positive and negative relationships with vegetation (i.e., tree abundance, maximum tree height, maximum herbaceous plant height) and human-related variables (i.e., cars, pedestrians). Although the scope of this study is geographically limited to three cities, our results suggest that House Sparrow numbers between cities and land classes areas vary considerably, and are likely determined by a complex array of variables. Our study provides some insight to the growth and decline of House Sparrow populations in their nonnative and native ranges, respectively. Un des envahisseurs aviaires ayant le plus de succès est le Moineau Domestique (Passer domesticus). Ici, nous examinons les densités dans les zones agrico-urbaines de trois villes, une où le moineau est natif (Barcelone) et deux où l'espèce est considérée envahissante (Los Angeles, Mexico), en comparant entre cinq classifications terrestres établit selon l'utilisation du territoire, localisation relative au centre urbain, et l'intensité d'urbanisation. Nous avons estimé les densités de moineaux en utilisant la méthode d'échantillonnage selon la distance corrigée et avons comparé le nombre de moineau entre les trois villes, ainsi qu'entre les classifications terrestres dans chaque ville. Cet échantillonnage de deux ans a démontré la plus grande densité à Mexico et la plus basse à Los Angeles. Chez les deux villes où le moineau est considéré comme envahissant, les densités les plus élevées furent enregistrées dans les zones très urbanisées. À Barcelone, où le moineau est natif, les abondances ne démontrent pas de différences entre les classifications terrestres. Nous avons aussi relié le nombre de moineau à des variables environnementales spécifiques, décrivant la structure de la végétation, les infrastructures urbaines, les activités humaines, en utilisant les méthodes de classification et régression arborescentes. Nous avons trouvé plusieurs variables reliées à des différences chez le Moineau Domestique parmi les trois villes. À Los Angeles et Mexico, les variables les plus importantes expliquant les densités du Moineau Domestique sont les infrastructures urbaines (c.-à-d., hauteur maximum de l'édifice, haut degré d'urbanisation) et/ou l'activité humaine (c.-à-d., piétons), tous démontrent un lien positif avec l'abondance de moineaux. En ce qui concerne Barcelone, des liens positives et négatives sont associés avec la végétation (c.-à-d., abondance d'arbre, hauteur maximum d'arbre, hauteur maximum des plantes herbacées) ainsi que les variables anthropogéniques (c.-à-d., voitures, piétons). Bien que la portée de cette étude soit limitée géographiquement à trois villes, nos résultats suggèrent une considérable variation du nombre de Moineaux Domestiques entre les villes, ainsi que les classifications terrestres, et est probablement déterminée par un éventail complexe de variables. Notre étude apporte un aperçu de la croissance et du déclin des populations de Moineaux Domestiques dans leurs aires de répartition respectives, qu'elle soient invasives ou naturelles.

One of the most successful avian urban invaders is the House Sparrow (Passer domesticus). Here, we examine House Sparrow numbers in the urban-agricultural landscape of three cities, one where the sparrow is native (Barcelona) and two where it is nonnative (Los Angeles, Mexico City), comparing between five different land classes based on land-use, location relative to urban center, and urbanization intensity. We estimated sparrow densities using distance-sampling corrected procedures and compared sparrow numbers between the three cities and between the land classes within each city. This two-year survey showed the highest density of sparrows occurring in Mexico City and the lowest in Los Angeles. In both cities where the sparrow is nonnative, we recorded the greatest abundances in highly urbanized areas. In Barcelona, where the sparrow is native, abundances did not differ among land classes. We also related sparrow numbers to specific environmental variables, describing vegetation structure, urban infrastructure, and human activity, using classification and regression trees. We found several variables related to differences in House Sparrow abundances among the three cities. For Los Angeles and Mexico City, the most important variables explaining House Sparrow numbers were urban infrastructure (i.e., maximum building height, high urbanization) and/or human activity (i.e., pedestrians), all of which related positively with sparrow abundance. For Barcelona, sparrow numbers showed both positive and negative relationships with vegetation (i.e., tree abundance, maximum tree height, maximum herbaceous plant height) and human-related variables (i.e., cars, pedestrians). Although the scope of this study is geographically limited to three cities, our results suggest that House Sparrow numbers between cities and land classes areas vary considerably, and are likely determined by a complex array of variables. Our study provides some insight to the growth and decline of House Sparrow populations in their nonnative and native ranges, respectively. Un des envahisseurs aviaires ayant le plus de succès est le Moineau Domestique (Passer domesticus). One of the most successful avian urban invaders is the House Sparrow (Passer domesticus). Here, we examine House Sparrow numbers in the urban-agricultural landscape of three cities, one where the sparrow is native (Barcelona) and two where it is nonnative (Los Angeles, Mexico City), comparing between five different land classes based on land-use, location relative to urban center, and urbanization intensity. We estimated sparrow densities using distance-sampling corrected procedures and compared sparrow numbers between the three cities and between the land classes within each city. This two-year survey showed the highest density of sparrows occurring in Mexico City and the lowest in Los Angeles. In both cities where the sparrow is nonnative, we recorded the greatest abundances in highly urbanized areas. In Barcelona, where the sparrow is native, abundances did not differ among land classes. We also related sparrow numbers to specific environmental variables, describing vegetation structure, urban infrastructure, and human activity, using classification and regression trees. We found several variables related to differences in House Sparrow abundances among the three cities. For Los Angeles and Mexico City, the most important variables explaining House Sparrow numbers were urban infrastructure (i.e., maximum building height, high urbanization) and/or human activity (i.e., pedestrians), all of which related positively with sparrow abundance. For Barcelona, sparrow numbers showed both positive and negative relationships with vegetation (i.e., tree abundance, maximum tree height, maximum herbaceous plant height) and human-related variables (i.e., cars, pedestrians). Although the scope of this study is geographically limited to three cities, our results suggest that House Sparrow numbers between cities and land classes areas vary considerably, and are likely determined by a complex array of variables. Our study provides some insight to the growth and decline of House Sparrow populations in their nonnative and native ranges, respectively. Un des envahisseurs aviaires ayant le plus de succès est le Moineau Domestique (Passer domesticus). One of the most successful avian urban invaders is the House Sparrow (Passer domesticus). Here, we examine House Sparrow numbers in the urban-agricultural landscape of three cities, one where the sparrow is native (Barcelona) and two where it is nonnative (Los Angeles, Mexico City), comparing between five different land classes based on land-use, location relative to urban center, and urbanization intensity. We estimated sparrow densities using distance-sampling corrected procedures and compared sparrow numbers between the three cities and between the land classes within each city. This two-year survey showed the highest density of sparrows occurring in Mexico City and the lowest in Los Angeles. In both cities where the sparrow is nonnative, we recorded the greatest abundances in highly urbanized areas. In Barcelona, where the sparrow is native, abundances did not differ among land classes. We also related sparrow numbers to specific environmental variables, describing vegetation structure, urban infrastructure, and human activity, using classification and regression trees. We found several variables related to differences in House Sparrow abundances among the three cities. For Los Angeles and Mexico City, the most important variables explaining House Sparrow numbers were urban infrastructure (i.e., maximum building height, high urbanization) and/or human activity (i.e., pedestrians), all of which related positively with sparrow abundance. For Barcelona, sparrow numbers showed both positive and negative relationships with vegetation (i.e., tree abundance, maximum tree height, maximum herbaceous plant height) and human-related variables (i.e., cars, pedestrians). Although the scope of this study is geographically limited to three cities, our results suggest that House Sparrow numbers between cities and land classes areas vary considerably, and are likely determined by a complex array of variables. Our study provides some insight to the growth and decline of House Sparrow populations in their nonnative and native ranges, respectively. Un des envahisseurs aviaires ayant le plus de succès est le Moineau Domestique (Passer domesticus).

Understanding how multiple stressors interact is needed to predict the dynamical outcomes of diverse biological systems, ranging from drug-resistant pathogens that are combated and treated with combination drug therapies to ecosystems impacted by environmental toxicants or disturbances. Nevertheless, extensive studies of higher-order (more than two component) interactions have been lacking. Here, we conduct experiments using 20 three-drug combinations and their effects on the bacterial growth of Escherichia coli. We report our measurements of growth rates in single, pairwise and triple-drug combinations. To uncover emergent interactions, we derive a simple framework to calculate expectations for three-way interactions based on the measured impact of each individual stressor and of each pairwise interaction. Using our framework, we find that (i) emergent antagonisms are more common than emergent synergies and (ii) emergent antagonisms are more common and emergent synergies are more rare than would be inferred from measures of net effects that do not disentangle pairwise interactions from three-way interactions.

Exposure to both antibiotics and temperature changes can induce similar physiological responses in bacteria. Thus, changes in growth temperature may affect antibiotic resistance. Previous studies have found that evolution under antibiotic stress causes shifts in the optimal growth temperature of bacteria. However, little is known about how evolution under thermal stress affects antibiotic resistance. We examined 100+ heat-evolved strains of Escherichia coli that evolved under thermal stress. We asked whether evolution under thermal stress affects optimal growth temperature, if there are any correlations between evolving in high temperatures and antibiotic resistance, and if these strains' antibiotic efficacy changes depending on the local environment's temperature. We found that: (1) surprisingly, most of the heat-evolved strains displayed a decrease in optimal growth temperature and overall growth relative to the ancestor strain, (2) there were complex patterns of changes in antibiotic resistance when comparing the heat-evolved strains to the ancestor strain, and (3) there were few significant correlations among changes in antibiotic resistance, optimal growth temperature, and overall growth.