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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.

While the influence of dispersal on ecological selection is the subject of intense research, we still lack a thorough understanding of how ecological selection operates to favour distinct dispersal strategies in metacommunities. To address this issue, we developed a model framework in which species with distinct quantitative dispersal traits that govern the three stages of dispersal—departure, movement and settlement—compete under different ecological contexts. The model identified three primary dispersal strategies (referred to as nomadic, homebody and habitat-sorting) that consistently dominated metacommunities owing to the interplay of spatiotemporal environmental variation and different types of competitive interactions. We outlined the key characteristics of each strategy and formulated theoretical predictions regarding the abiotic and biotic conditions under which each strategy is more likely to prevail in metacommunities. By presenting our results as relationships between dispersal traits and well-known ecological gradients (e.g. seasonality), we were able to contrast our theoretical findings with previous empirical research. Our model demonstrates how landscape environmental characteristics and competitive interactions at the intra- and interspecific levels can interact to favour distinct multivariate and context-dependent dispersal strategies in metacommunities. This article is part of the theme issue 'Diversity-dependence of dispersal: interspecific interactions determine spatial dynamics'. [ABSTRACT FROM AUTHOR]

The nonrandom association between landscape characteristics and the dominant life history strategies observed in species pools is a typical pattern in nature. Here, we argue that these associations determine predictable changes in the relative importance of assembly mechanisms along broadscale geographic gradients (i.e., the geographic context of metacommunity dynamics). To demonstrate that, we employed simulation models in which groups of species with the same initial distribution of niche breadths and dispersal abilities interacted across a wide range of landscapes with contrasting characteristics. By assessing the traits of dominant species in the species pool in each landscape type, we determined how different landscape characteristics select for different life history strategies at the metacommunity level. We analyzed the simulated data using the same analytical approaches used in the study of empirical metacommunities to derive predictions about the causal relationships between landscape characteristics and dominant life histories in species pools, as well as their reciprocal influence on empirical inferences regarding the assembly process. We provide empirical support for these predictions by contrasting the assembly of moth metacommunities in a tropical versus a temperate mountainous landscape. Together, our model framework and empirical analyses demonstrate how the geographic context of metacommunities influences our understanding of community assembly across broadscale ecological gradients. [ABSTRACT FROM AUTHOR]

Understanding the processes that underlie species fluctuations is crucial to the development of efficient management strategies for outbreaks of destructive forest pests. Yet, the role of biotic and abiotic factors as well as their interactions in synchronizing outbreaks is not understood, despite many empirical and theoretical studies of species fluctuations. Here, we use a combined statistical-simulation model to investigate how defoliation spread and autocorrelated weather affect outbreaks of a major defoliator of North American boreal forest, the spruce budworm (Choristoneurafumiferana (Clemens)). We modelled the regional dynamics of spruce budworm and based the model on data collected from spatiotemporal aerial surveys of defoliation from 1968-2015 in Quebec, Canada. The effects of weather on local forest stand defoliation and mortality transitions, along with defoliation spread probability and distance, were estimated statistically. Simulations were run with these estimates to identify the effects of spatiotemporal weather autocorrelation on synchronicity of outbreaks. Defoliation spread together with weather variables was found to best fit the observed outbreak size. Simulation models suggest that positive temporal autocorrelation in weather promotes outbreaks, indicating that a series of suitable years could encourage outbreaks. Key words: landscape ecology, model, outbreaks, environmental autocorrelation, defoliation spread. Il est essentiel de comprendre les processus sous-jacents a la fluctuation des especes pour developper des strategies efficaces dans le cas des epidemies de ravageurs forestiers destructeurs. Mais le role des facteurs biotiques et abiotiques ainsi que leurs interactions dans la synchronisation des epidemies n'est pas connu malgre les nombreuses etudes empiriques et theoriques qui portent sur la fluctuation des especes. Nous utilisons ici un modele qui combine la simulation et les statistiques pour etudier de quelle facon la progression de la defoliation et l'autocorrelation des conditions meteorologiques influencent les epidemies d'un important insecte defoliateur de la foret boreale nord-americaine, la tordeuse des bourgeons de l'epinette (Choristoneurafumiferana (Clemens)). Nous avons modelise la dynamique regionale de la tordeuse des bourgeons de l'epinette sur la base des donnees recueillies lors de releves aeriens spatiotemporels de la defoliation de 1968 a 2015 au Quebec, Canada. Les effets des conditions meteorologiques sur la defoliation locale des peuplements forestiers et les transitions de la mortalite, ainsi que la probabilite et la distance de propagation de la defoliation, ont ete estimes statistiquement. Les simulations ont ete effectuees avec ces estimations pour identifier les effets de l'autocorrelation spatiotemporelle des conditions meteorologiques sur le synchronisme des epidemies. La progression de la defoliation et les variables meteorologiques s'ajustaient le mieux a la taille observee des epidemies. Les modeles de simulation indiquent que l'autocorrelation temporelle positive des conditions meteorologiques favorise les epidemies, ce qui permet de croire qu'une serie d'annees favorables favorise les epidemies. [Traduit par la Redaction] Mots-cles: ecologie du paysage, modele, epidemies, autocorrelation environnementale, progression de la defoliation., Introduction Understanding the mechanisms underlying the spatiotemporal population dynamics of species is an ongoing ecological challenge (Liebhold et al. 2004). Outbreaks are high population densities of defoliating insects covering large [...]

Phenotypic variability represents an important factor allowing species to adapt to local environmental conditions, but mechanisms underlying such variation are incompletely understood. This study investigated whether habitat-specific demands on swimming performance or difference in trophic relationships in lakes (pelagic, littoral) and streams (riffle, pool) were significant predictors of phenotypic variation exhibited by brook char (Salvelinus fontinalis), the only fish in the study habitats. Specifically, we hypothesized that pelagic and riffle habitats would impose greater selective pressures associated with swimming, resulting in body morphologies that were dorsoventrally compressed, anterior-posteriorly elongated, and that exhibited a long, narrow caudal peduncle. Geometric morphometrics was applied in a quantitative analysis of body morphology among habitats, whereas stable isotope analysis was used to differentiate between food sources. Analyses revealed that while body morphology differed between lake and stream habitats, there was convergence between the pelagic and riffle habitats, as well as among littoral and riffle and pool environments. The littoral and pool habitats were thought to be more structurally complex, thereby selecting for increased maneuverability but lower sustained swimming and correspondingly deeper bodies with shorter, dorsoventrally expanded caudal peduncles. Carbon source and trophic position did not differ among habitats with a system, suggesting that feeding was not the main influence on morphological plasticity; however, fish in the stream were feeding at a higher trophic position than fish in the lake. These findings suggest that individual species may take advantage of morphological variation to better adapt local surroundings. Si la variabilite phenotypique est un important facteur permettant aux especes de s'adapter aux conditions ambiantes locales, les mecanismes qui sous-tendent cette variabilite ne sont pas bien compris. L'etude tentait de determiner si des demandes propres a l'habitat sur la performance de nage ou des differences dans les relations trophiques entre les lacs (pelagique, littoral) et les cours d'eau (seuil, fosse) sont des variables predictives significatives des variations phenotypiques observees chez l'omble de fontaine (Salvelinus fontinalis), le seul poisson dans les habitats etudies. Plus precisement, nous avons postule que les habitats pelagiques et de seuil imposeraient de plus grandes pressions de selection associees a la nage, ce qui se traduirait par des morphologies du corps comprimees dorsiventralement, allongees anteroposterieurement et presentant un pedoncule caudal long et etroit. La morphometrie geometrique a ete appliquee a l'analyse quantitative de la morphologie du corps dans les differents habitats et l'analyse des isotopes stables a ete utilisee pour distinguer les sources de nourriture. Les analyses ont revele que, bien que la morphologie du corps differe entre les habitats lacustres et de cours d'eau, il y a une convergence entre les habitats pelagiques et de seuil, ainsi qu'entre les habitats littoraux et de fosses et seuils. Les habitats littoraux et de fosses etaient consideres plus complexes sur le plan structural, la selection se traduisant par une plus grande manoeuvrabilite, mais moins de nage soutenue et des corps a l'avenant plus profonds avec des pedoncules caudaux plus courts et allonges dorsiventralement. Il n'y avait pas difference sur le plan des sources de carbone et de la position trophique entre les habitats d'un meme systeme, donnant a penser que l'alimentation n'etait pas la principale influence sur la plasticite morphologique; toutefois, les poissons dans le cours d'eau se nourrissaient a une position trophique plus elevee que les poissons dans le lac. Ces constatations donnent a penser qu'une espece peut mettre a profit des variations morphologiques pour mieux s'adapter a l'environnement local. [Traduit par la Redaction], Introduction The physical expression of a trait, known as a phenotype, is a product of the interaction between a set of genes and an environment. Phenotypic variability within and across [...]