Does urbanisation lead to parallel demographic shifts across the world in a cosmopolitan plant?

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 Ne 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

Combining Enforcement Strategies in Service Oriented Architectures

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Ellagitannins from the Onagraceae Decrease the Performance of Generalist and Specialist Herbivores

Phenolics have a role in defenses against herbivores, but the defensive functions of specific groups of phenolics are still poorly understood. For example, ellagitannins (a type of hydrolyzable tannin) are predicted to decrease insect herbivore performance, but the effect of different types of ellagitannins on generalist and specialist herbivores has rarely been assessed. Here, we test the effects of the dominant oligomeric ellagitannins of Oenothera biennis and other Onagraceae on herbivore performance. We fed artificial diets containing between 1 and 100 mg/g of polyphenol fractions comprised of varying amounts and compositions of dimeric oenothein B, the trimeric oenothein A and larger oligomers, to one generalist (Spodoptera exigua) and one specialist (Schinia florida) insect herbivore species. We compared the effects of these ellagitannin fractions on herbivore performance to the effects of artificial diet containing total phenolic extracts from O. biennis, which contained these ellagitannins as well as many additional phenolic metabolites including flavonoid glycosides and caffeic acid derivatives. Both the ellagitannin fractions and O. biennis phenolic extracts had strong negative effects on S. exigua and S. florida performance, with stronger effects on the generalist herbivore. Differences between the effects of the various ellagitannin fractions were small and depended on insect life stage. The defensive effects of these ellagitannins were large, with lethal concentrations as low as 0.1% of the diet. These results highlight the important defensive function of ellagitannins against specialist and generalist herbivores and the need to characterize the effects of these understudied phenolics.</p

Can genetically based clines in plant defence explain greater herbivory at higher latitudes?

Greater plant defence is predicted to evolve at lower latitudes in response to increased herbivore pressure. However, recent studies question the generality of this pattern. In this study, we tested for genetically based latitudinal clines in resistance to herbivores and underlying defence traits of Oenothera biennis. We grew plants from 137 populations from across the entire native range of O. biennis. Populations from lower latitudes showed greater resistance to multiple specialist and generalist herbivores. These patterns were associated with an increase in total phenolics at lower latitudes. A significant proportion of the phenolics were driven by the concentrations of two major ellagitannins, which exhibited opposing latitudinal clines. Our analyses suggest that these findings are unlikely to be explained by local adaptation of herbivore populations or genetic variation in phenology. Rather greater herbivory at high latitudes can be explained by latitudinal clines in the evolution of plant defences.</p

Integrating landscape genomics and spatially explicit approaches to detect loci under selection in clinal populations

Uncovering the genetic basis of adaptation hinges on the ability to detect loci under selection. However, population genomics outlier approaches to detect selected loci may be inappropriate for clinal populations or those with unclear population structure because they require that individuals be clustered into populations. An alternate approach, landscape genomics, uses individual-based approaches to detect loci under selection and reveal potential environmental drivers of selection. We tested four landscape genomics methods on a simulated clinal population to determine their effectiveness at identifying a locus under varying selection strengths along an environmental gradient. We found all methods produced very low type I error rates across all selection strengths, but elevated type II error rates under ‘weak’ selection. We then applied these methods to an AFLP genome scan of an alpine plant, Campanula barbata, and identified five highly supported candidate loci associated with precipitation variables. These loci also showed spatial autocorrelation and cline patterns indicative of selection along a precipitation gradient. Our results suggest that landscape genomics in combination with other spatial analyses provides a powerful approach for identifying loci potentially under selection and explaining spatially complex interactions between species and their environment

Does urbanisation lead to parallel demographic shifts across the world in a cosmopolitan plant?

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 Ne 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

Death and the Societies of Late Antiquity

Ce volume bilingue, comprenant un ensemble de 28 contributions disponibles en français et en anglais (dans leur version longue ou abrégée), propose d’établir un état des lieux des réflexions, recherches et études conduites sur le fait funéraire à l’époque tardo-antique au sein des provinces de l’Empire romain et sur leurs régions limitrophes, afin d’ouvrir de nouvelles perspectives sur ses évolutions possibles. Au cours des trois dernières décennies, les transformations considérables des méthodologies déployées sur le terrain et en laboratoire ont permis un renouveau des questionnements sur les populations et les pratiques funéraires de l’Antiquité tardive, période marquée par de multiples changements politiques, sociaux, démographiques et culturels. L’apparition de ce qui a été initialement désigné comme une « Anthropologie de terrain », qui fut le début de la démarche archéothanatologique, puis le récent développement d’approches collaboratives entre des domaines scientifiques divers (archéothanatologie, biochimie et géochimie, génétique, histoire, épigraphie par exemple) ont été décisives pour le renouvellement des problématiques d’étude : révision d’anciens concepts comme apparition d’axes d’analyse inédits. Les recherches rassemblées dans cet ouvrage sont articulées autour de quatre grands thèmes : l’évolution des pratiques funéraires dans le temps, l’identité sociale dans la mort, les ensembles funéraires en transformation (organisation et topographie) et les territoires de l’empire (du cœur aux marges). Ces études proposent un réexamen et une révision des données, tant anthropologiques qu’archéologiques ou historiques sur l’Antiquité tardive, et révèlent, à cet égard, une mosaïque de paysages politiques, sociaux et culturels singulièrement riches et complexes. Elles accroissent nos connaissances sur le traitement des défunts, l’emplacement des aires funéraires ou encore la structure des sépultures, en révélant une diversité de pratiques, et permettent au final de relancer la réflexion sur la manière dont les sociétés tardo-antiques envisagent la mort et sur les éléments permettant d’identifier et de définir la diversité des groupes qui les composent. Elles démontrent ce faisant que nous pouvons véritablement appréhender les structures culturelles et sociales des communautés anciennes et leurs potentielles transformations, à partir de l’étude des pratiques funéraires.This bilingual volume proposes to draw up an assessment of the recent research conducted on funerary behavior during Late Antiquity in the provinces of the Roman Empire and on their borders, in order to open new perspectives on its possible developments. The considerable transformations of the methodologies have raised the need for a renewal of the questions on the funerary practices during Late Antiquity, a period marked by multiple political, social, demographic and cultural changes. The emergence field anthropology, which was the beginning of archaeothanatology, and then the recent development of collaborative approaches between various scientific fields (archaeothanatology, biochemistry and geochemistry, genetics, history, epigraphy, for example), have been decisive. The research collected in this book is structured around four main themes: Evolution of funerary practices over time; Social identity through death; Changing burial grounds (organisation and topography); Territories of the Empire (from the heart to the margins). These studies propose a review and a revision of the data, both anthropological and archaeological or historical on Late Antiquity, and reveal a mosaic of political, social, and cultural landscapes singularly rich and complex. In doing so, they demonstrate that we can truly understand the cultural and social structures of ancient communities and their potential transformations, based on the study of funerary practices

Global urban environmental change drives adaptation in white clover

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

Latitudinal Gradients in Herbivory and Plant Defence Across the Onagraceae

Herbivory is predicted to increase at lower latitudes, leading to the evolution of increased plant defence towards the tropics. These ideas are known as the Latitudinal Herbivory-Defence Hypothesis (LHDH). While initial empirical tests supported this hypothesis, it has been challenged by new studies leading to controversy. I tested LHDH at the micro- and macroevolutionary scale, through a series of well-replicated studies. At the microevolutionary scale I surveyed common evening primrose (Oenothera biennis), which has a well characterized herbivory community, and diverse and abundant ellagitannins. First, I sampled herbivory across 79 populations of O. biennis in Eastern North America. Latitudinal gradients in herbivory varied depending on herbivore guild and degree of specialization. In particular damage by specialist seed predators was greater at higher latitudes. To explain these patterns, I then studied genetically based latitudinal clines in plant defences across 137 populations of O. biennis by growing them in a common garden. Populations from lower latitudes showed greater resistance to all herbivores. Increased chemical defences best predicted this resistance. A subsequent growth chamber experiment then examined latitudinal gradients in constitutive versus induced defences. Genotypes from lower latitudes were less damaged by a generalist caterpillar, although there was no pattern by a specialist weevil. Total phenolics were greater at lower latitudes when measuring constitutive defences, but were greater at higher latitudes in induced plants. These results suggest there might be increased herbivory at higher latitudes because of relatively low constitutive defences, but that induced defences may be used to prevent additional damage. At the macroevolutionary scale, gradients in chemical defences were assessed across 80 species of Onagraceae. Latitude did not predict defence patterns. Instead colder climates, temperature variability, and hemisphere of origin were associated with greater levels of defence. These results challenge the validity of LHDH at the macroevolutionary scale. The utility of LHDH varies across different scales. This generates the need for more robust theory that can incorporate these scales into predictions. I advance new lines of inquiry that should be explored, by analyzing the assumptions used in LHDH through a critical review. I also recommend increased rigor and consistency in chemical and herbivory metrics. I apply some of these recommendations throughout my work, including confirming the effect of phenolics and ellagitannins on herbivore performance.Ph.D

JULS2010_FINAL_ForPrint.indd

Abstract Lichens are important components of arctic and alpine ecosystems. Their abundance and diversity are high despite the harsh conditions, yet little is known about the microclimates that favour lichen growth. Using a 2 x 2 factorial design, we classified rock faces at the high alpine Barcroft Field Station in the White Mountains of California into high and low wind exposure and high and low light exposure categories. We then measured the extent of coverage of two alpine crustose lichen species, Caloplaca ignea and Pleosidium flavum, on the rock faces. The data show that lichen coverage is greatest on rock faces that are protected from wind but exposed to light (median = 60 m2, range = 1.8 -647.1 m2), and lowest on faces that are exposed to wind but protected from light (median = 7.4 m2, range = 0.15 -142.5 m2). The lack of success in high wind conditions may be due to desiccation-induced inhibition of photosynthesis, leading to reduced carbon balance in wind-exposed lichens. By characterizing favourable microclimates, this study provides observational data that help to establish the environmental dependence of photosynthesis and respiration in cold climate lichens. This is particularly important for informing estimates of ecosystem-level carbon balance in regions like the boreal, where lichens represent 50-90% of vegetation cover