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Made available in DSpace on 2022-04-28T19:52:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-03-18 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. Department of Biology University of Toronto Mississauga ON Centre for Urban Environments University of Toronto Mississauga ON Department of Biology University of North Carolina, Chapel Hill Department of Biology University of Louisiana LA Department of Biology Queen's University ON Department of Biology Concordia University QC Department of Biological Sciences DePaul University Department of Biology DePauw University IN Department of Urban Design and Planning, University of Washington, Seattle, WA, USA Colegio de Ciencias Biológicas y Ambientales Universidad San Francisco de Quito USFQ Department of Genetics University of Georgia Department of Ecology and Genetics Evolutionary Biology Centre Uppsala University Field Science Center for Northern Biosphere Hokkaido University Natural History Museum Zoology University of New England NSW Programa de Pós-Graduação em Geografia da UFMT campus de Rondonópolis Department of Botany and Biodiversity Research Centre University of British Columbia Graduate Program in Genome Sciences and Technology Genome Sciences Centre University of British Columbia Department of Microbiology and Immunology University of British Columbia Red de Biología Evolutiva Instituto de Ecología A. C. School of the Environment Yale University CT Departamento de Ciencias Ecológicas Universidad de Chile, Facultad de Ciencias Instituto de Ecología y Biodiversidad Universidad de Chile Department of Biology Mount Allison University Red de Ecoetología Instituto de Ecología A. C. Department of Biology University of Ottawa ON Department of Zoology University of Cambridge Department of Biology, Washington University in St. Louis, St. Louis, MO, USA Department of Biology University of Miami FL Centro de Investigación en Recursos Naturales y Sustentabilidad (CIRENYS) Universidad Bernardo O'Higgins Department of Biology, University of La Verne, La Verne, CA, USA Département des sciences du bois et de la forêt Université Laval QC Evolution & Ecology Research Centre School of Biological Earth and Environmental Sciences UNSW Sydney NSW Department of Biology Ghent University Department of Biology Monmouth University West Long Branch Centre for Ecology Evolution and Environmental Changes Faculdade de Ciências Universidade de Lisboa Lisboa Department of Biology KU Leuven School of Agriculture and Environment Wildlife and Ecology group Massey University, Palmerston North Department of Biological Sciences University of Cape Town Institute of Landscape Ecology University of Münster Gosnell School of Life Sciences, Rochester Institute of Technology, Rochester, NY, USA Department of Biological Sciences University of Alberta AB Louis Calder Center and Department of Biological Sciences, Fordham University, Armonk, NY, USA Departamento de Ecología Tropical, Universidad Autónoma de Yucatán, Mérida, Yucatán, México School of Life Sciences University of Sussex Department of Ecology Environment and Plant Sciences Stockholm University iBIOTROP Instituto de Biodiversidad Tropical Universidad San Francisco de Quito Department of Biology, San Francisco State University, San Francisco, CA, USA Unidad de Recursos Naturales, Centro de Investigación Científica de Yucatán AC, Mérida, Yucatán, México School of Ecological and Environmental Sciences East China Normal University Shanghai Engineering Research Center of Sustainable Plant Innovation Centre for Ecosystem Science School of Biological Earth and Environmental Sciences UNSW Sydney NSW Department of Ecology and Evolutionary Biology University of Michigan MI Department of Biosciences Rice University TX IFEVA Universidad de Buenos Aires Facultad de Agronomía, CONICET Biology Department Saint Mary's University NS Department of Biological Sciences, Universidad de los Andes Department of Biology and Biochemistry University of Houston TX Université de Rennes Department of Zoology and Biodiversity Research Centre University of British Columbia Department of Environmental Studies Dordt University Sioux Center IA Department of Biology Minneapolis Community and Technical College MN Department of Natural Sciences Ecology and Environment Research Centre Manchester Metropolitan University Instituto de Investigaciones en Ecosistemas y Sustentabilidad UNAM Department of Botany School of Biology Aristotle University of Thessaloniki Faculty of Biological and Environmental Science Organismal & Evolutionary Biology Research Programme University of Helsinki Institute of Biodiversity Animal Health and Comparative Medicine University of Glasgow Department of Biology Hendrix College Department of Ecological Science Vrije Universiteit Amsterdam Departamento de Ciencias Biológicas y Agropecuarias Universidad Técnica Particular de Loja Departamento de Biologia Universidade Federal de Santa Maria (UFSM) Department of Plant Sciences School of Biology College of Science University of Tehran NTNU University Museum Norwegian University of Science and Technology Red de Estudios Moleculares Avanzados Instituto de Ecología A. C. School of Biological Sciences, University of Reading, Whiteknights Park, Reading, Berkshire, UK Department of Biology Northern Arizona University AZ Department of Biological Sciences MacEwan University AB Max Planck Institute for Plant Breeding Research Departamento de Ecología Evolutiva Instituto de Ecología Universidad Nacional Autónoma de México Max Planck Institute of Molecular Plant Physiology Potsdam-Golm BIO5 Institute University of Arizona AZ Alaska Center for Conservation Science University of Alaska Anchorage Tropical Diversity, Royal Botanical Garden of Edinburgh Département de biologie Université de Moncton Department of Biological Sciences University of Manitoba MB Departments of Microbiology & Statistics University of Manitoba MB Department of Biology University of New Brunswick Department of Biology Kalamazoo College MI BioProtection Research Centre Lincoln University Departamento de Ciencias Facultad de Artes Liberales Universidad Adolfo Ibáñez Department of Ecology Evolution Behaviour University of Minnesota MN Department of Biological Sciences Brock University Department of Environmental Toxicology, University of California, Davis, CA, USA ICB - University of Talca School of Molecular and Life Science Curtin University College of Science Health Engineering and Education Murdoch University, Murdoch School of Life and Environmental Sciences University of Sydney NSW School of Biological Sciences, Monash University, Melbourne, VIC, Australia Department of Biological Sciences Wayne State University MI Department of Biology Western Oregon University, OR School of Natural Resources and the Environment University of Arizona AZ Departamento de Ecología Humana, Cinvestav Mérida Departamento de Ciencias Biológicas y Departamento de Ecología y Biodiversidad Facultad de Ciencias de la Vida, Universidad Andrés Bello Institute of Ecology and Biodiversity (IEB) Department of Biology Lund University Department of Biology Norwegian University of Science and Technology Escuela Superiro de Desarrollo Sustentable Universidad Autónoma de Guerrero -CONACYT Clarkson Secondary School Peel District School Board ON Homelands Sr. Public School Peel District School Board ON Department of Biological Sciences University of Illinois at Chicago Dufferin-Peel Catholic District School Board, St. James Catholic Global Learning Centre Department of Biosciences University of Calgary AB Ecological Processes Branch U.S. Army ERDC-CERL Department of Biology, Oberlin College, Oberlin, OH, USA Escuela Nacional de Estudios Superiores Unidad Morelia UNAM Institute of Evolution and Ecology University of Tübingen Tübingen Department of Evolutionary Biology and Environmental Studies University of Zurich, Winterthurerstrasse Urban Wildlife Institute Department of Conservation and Science, Lincoln Park Zoo Departamento de Ecología Universidad Católica de la Santísima Concepción Department of Biological Sciences University of Denver CO Department of Biological Sciences Mississippi State University MS Department of Biology Center for Computational & Integrative Biology Rutgers University-Camden Kunming Institute of Botany Chinese Academy of Sciences Department of Chemistry & Biochemistry Laurentian University ON Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering College of Life Sciences Beijing Normal University School of BioSciences, University of Melbourne, Melbourne, VIC, Australia Posgrado en Ciencias Biológicas Universidad Nacional Autónoma de México Department of Biological Sciences, Auburn University, Auburn, AL, USA Department of Entomology and Nematology, University of California, Davis, CA, USA Department of Biology University of New Mexico NM Department of Biology University of Wisconsin - Eau Claire Agriculture Institute Iranian Research Organization for Science and Technology (IROST) Department of Biology Colby College ME Instituto de Biología Universidad de Antioquia Department of Biology University of Massachusetts Boston MA Agricultural Biology Colorado State University CO Departamento de Biología Vegetal y Ecología Facultad de Biología Universidad de Sevilla, Av. Reina Mercedes s/n Facultad de Estudios Interdisciplinarios Centro GEMA- Genómica Universidad Mayor Evolutionary Ecology Group Naturalis Biodiversity Center Department of Biology and Chemistry Nipissing University ON, North Bay Center for Ecological Research Kyoto University Bonanza Creek Long Term Ecological Research Program University of Alaska Fairbanks Department of Botany and Molecular Evolution Senckenberg Research Institute and Natural History Museum Frankfurt Departamento de Biodiversidade Instituto de Biociências Univ Estadual Paulista - UNESP Nelson Institute for Environmental Studies University of Wisconsin-Madison WI Department of Biology, California State University, Northridge, Los Angeles, CA, USA Department of Ecology Swedish University of Agricultural Sciences Facultad de Ciencias y Biotecnologia Universidad CES Department of Biology Hofstra University Faculty of Biosciences and Aquaculture Nord University, Bodø Division of Biological Sciences, University of California San Diego, San Diego, CA, USA Department of Biology University of Richmond VA Estación de Biodiversidad Tiputini Colegio de Ciencias Biológicas y Ambientales Universidad San Francisco de Quito USFQ Department of Biological Sciences Institute of Environment Florida International University FL Agronomy Department University of Almería Department of Biological Sciences and Center for Urban Ecology and Sustainability Butler University IN Department of Biological Sciences Louisiana State University LA Faculty of Biological Sciences, Goethe University Frankfurt Institute of Biology Leiden Leiden University Department of Biological and Environmental Science University of Jyväskylä Jyväskylä Department of Biology University of Louisville KY Organization for Programs on Environmental Science University of Tokyo CNRS AgroParisTech Ecologie Systématique et Evolution, Université Paris-Saclay Department of Biology, Providence College, Providence, RI, USA General Zoology Institute for Biology Martin Luther University Halle-Wittenberg International Arctic Research Center University of Alaska Fairbanks Science, Technology and Society Department, Rochester Institute of Technology, Rochester, NY, USA SLU Swedish Species Information Centre Swedish University of Agricultural Sciences Department of Biology Westfield State University MA Centre of New Technologies University of Warsaw Department of Biology, Stanford University, Stanford, CA, USA Plant Biology Department Michigan State University MI Biology Department Davidson College College of Horticulture and Forestry Sciences/ Hubei Engineering Technology Research Center for Forestry Information Huazhong Agricultural University School of Life Sciences Technical University of Munich School of Life Sciences Lanzhou University Institute of Ecology and Evolution University of Bern Department of Evolution Ecology and Behaviour University of Liverpool Departamento de Biodiversidade Instituto de Biociências Univ Estadual Paulista - UNESP

Dispersal and its evolution play a key role for population persistence in fragmented landscapes where habitat loss and fragmentation increase the cost of between-habitat movements. In such contexts, it is important to know how variation in dispersal and other traits is structured, and whether responses to landscape fragmentation are aligned with underlying dispersal-trait correlations, or dispersal syndromes. We therefore studied trait variation in Erigone longipalpis, a European spider species specialist of (often patchy) salt marshes. We collected spiders in two salt-marsh landscapes differing in habitat availability. We then reared lab-born spiders for two generations in controlled conditions, and measured dispersal and its association with various key traits. E. longipalpis population densities were lower in the more fragmented landscape. Despite this, we found no evidence of differences in dispersal, or any other trait we studied, between the two landscapes. While a dispersal syndrome was present at the among-individual level (dispersers were more fecund and faster growing, among others), there was no indication it was genetically driven: among-family differences in dispersal were not correlated with differences in other traits. Instead, we showed that the observed phenotypic covariations were mostly due to within-family correlations. We hypothesize that the dispersal syndrome is the result of asymmetric food access among siblings, leading to variation in development rates and carrying over to adult traits. Our results show we need to better understand the sources of dispersal variation and syndromes, especially when dispersal may evolve rapidly in response to environmental change.

Cities impose strong ecological constraints on many species. It is often difficult to know whether phenotypic responses to urbanisation are due to (adaptive) evolutionary responses, as opposed to e.g. plastic responses. A solution is to focus on traits for which variation is only or mostly genetic in origin, since changes are then likely to reflect evolutionary processes. For this purpose, we studied the leg-colour polymorphism of a common carabid beetle,Pterostichus madidus, along an urbanisation gradient. We observed that black-legged individuals were more frequent than red-legged individuals in urban areas. Whether these changes result from natural selection or non-selective evolutionary forces is uncertain. However, if this phenotypic change is adaptive in nature, higher urban temperatures are likely to be the driver. Specifically, our results are consistent with previous data showing that black-legged individuals have a behavioural advantage in warmer (micro)climates, and contradict the thermal melanism hypothesis that predicts they would experience stronger negative effects of higher temperatures in cities.

Major traits defining the life history of organisms are often not independent from each other, with most of their variation aligning along key axes such as the pace-of-life axis. We can define a pace-of-life axis structuring reproduction and development time as a continuum from less-fecund, longer-developing ‘slow’ types to more-fecund, shorter-developing ‘fast’ types. Such axes, along with their potential associations or syndromes with other traits such as dispersal, are however not universal; in particular, support for their presence may be taxon and taxonomic scale-dependent. Knowing about such life-history strategies may be especially important for understanding eco-evolutionary dynamics, as these trait syndromes may constrain trait variation or be correlated with other traits. To understand how life history traits and effective dispersal covary, we measured these traits in controlled conditions for 28 lines from five species ofTrichogramma, which are small endoparasitoid wasps frequently used as a biological model in experimental evolution but also in biocontrol against Lepidoptera pests. We found partial evidence of a pace-of-life axis at the interspecific level: species with higher fecundity also had faster development time. However, faster developing species also were more likely to delay egg-laying, a trait that is usually interpreted as “slow”. There was no support for similar covariation patterns at the within-species line level. There was limited variation in effective dispersal between species and lines, and accordingly, we did not detect any correlation between effective dispersal probability and life-history traits. We discuss how expanding our experimental design by accounting for the density-dependence of both the pace of life and dispersal might improve our understanding of those traits and how they interact with each other. Overall, our results highlight the importance of exploring covariation at the “right” taxonomic scale, or multiple taxonomic scales, to understand the (co)evolution of life-history traits. They also suggest that optimizing both reproductive and development traits to maximize the efficiency of biocontrol may be difficult in programs using only one species.

Terrestrial gastropods are hosts of a wide variety of metazoan parasites and can respond to parasite exposure in various ways. One of these defence mechanisms, the ability to trap parasites in the host shell, was previously thought to apply only against nematodes. During a field survey along an urbanisation gradient, we found that the shell of Cornu aspersum and Cepaea nemoralis can contain encapsulated trematode cercariae, with prevalences of 7% and 1%, respectively over the entire sample, and up to 47% at the local population level. To our knowledge, this is the first case study unambiguously showing that land snails can trap non-nematode parasites in their shell at non-negligible prevalences. Shell-encapsulation could be a more general defence mechanism than previously described, and more studies are needed to understand its importance and variability.

Dispersal is a key trait linking ecological and evolutionary dynamics, allowing organisms to optimize fitness expectations in spatially and temporally heterogeneous environments. Some organisms can both actively disperse or enter a reduced activity state in response to challenging conditions, and both responses may be under a trade-off. To understand how such organisms respond to changes in environmental conditions, we studied the dispersal and activity behaviour in the gonochoric land snail Pomatias elegans, a litter decomposer that can reach very high local densities, across a wide range of ecologically relevant densities. We found that crowding up to twice the maximal recorded density had no detectable effect on dispersal tendency in this species, contrary to previous results in many hermaphroditic snails. Pomatias elegans is nonetheless able to detect population density; we show they reduce activity rather than increase dispersal in response to crowding. We discuss these results based on the ability of many land snails to enter dormancy for extended periods of time in case of unfavourable conditions. We propose that dormancy ("dispersal in time") may be more advantageous in species with especially poor movement abilities, even by land mollusc standards, like P. elegans. Interestingly, dispersal and activity were correlated independently of density; this dispersal syndrome may reflect a dispersal-dormancy trade-off at the individual level. Additionally, we found snails with heavier shells relative to their size tended to be less mobile, which may reflect physical and metabolic constraints on movement and/or survival during inactivity. We finally discuss how the absence of density-dependent dispersal may explain why P. elegans is often found at very high local densities, and the possible consequences for ecosystem functioning and litter decomposition.

Ecological and evolutionary dynamics of range expansions are shaped by both dispersal and population growth. Accordingly, density-dependence in either dispersal or growth can determine whether expansions are pulled or pushed, i.e. whether expansion velocities and genetic diversity are mainly driven by recent, low-density edge populations, or by older populations closer to the core. Despite this and despite abundant evidence of dispersal evolution during expansions, the impact of density-dependent dispersal and its evolution on expansion dynamics remains understudied. Here, we used simulation models to examine the influence of individual trait variation in both dispersal capacity and dispersal density- dependence on expansions, and how it impacts the position of expansions on the pulled-pushed continuum. First, we found that knowing about the evolution of density-dependent dispersal at the range edge can greatly improve our ability to predict whether an expansion is (more) pushed or (more) pulled. Second, we found that both dispersal costs and the sources of variation in dispersal (genetic or non-genetic, in dispersal capacity versus in density- dependence) greatly influence how expansion dynamics evolve. Among other scenarios, pushed expansions tended to become more pulled with time only when density-dependence was highly heritable, dispersal costs were low and dispersal capacity could not evolve. When, on the other hand, variation in density-dependence had no genetic basis, but dispersal capacity could evolve, then pushed expansions tended to become more pushed with time, and pulled expansions more pulled. More generally, our results show that trying to predict expansion velocities and dynamics using trait information from non-expanding regions only may be problematic, that both dispersal variation and its sources play a key role in determining whether an expansion is and stays pushed, and that environmental context (here dispersal costs) cannot be neglected. Those simulations suggest new avenues of research to explore, both in terms of theoretical studies and regarding ways to empirically study pushed vs. pulled range expansions.

Dispersal is a central biological process tightly integrated into life-histories, morphology, physiology and behaviour. Such associations, or syndromes, are anticipated to impact the eco-evolutionary dynamics of spatially structured populations, and cascade into ecosystem processes. As for dispersal on its own, these syndromes are likely neither fixed nor random, but conditional on the experienced environment. We experimentally studied how dispersal propensity varies with individuals' phenotype and local environmental harshness using 15 species ranging from protists to vertebrates. We reveal a general phenotypic dispersal syndrome across studied species, with dispersers being larger, more active and having a marked locomotion-oriented morphology and a strengthening of the link between dispersal and some phenotypic traits with environmental harshness. Our proof-of-concept metacommunity model further reveals cascading effects of context-dependent syndromes on the local and regional organisation of functional diversity. Our study opens new avenues to advance our understanding of the functioning of spatially structured populations, communities and ecosystems.

Host behaviour can be influenced by parasitic risk and infection through a variety of direct and indirect mechanisms. We can expect individuals expressing different phenotypes to also differ in the ways their behaviour is altered by parasites. We used the land snail Cepaea nemoralis, a species with various shell colour morphs differing in behaviour and physiology, as a model to study the link between parasite response and individual behaviour variation. We analysed metazoan parasite abundance and its relation to behaviour (movement and food intake) in snails from three shell morphs (from light unbanded to darker five-banded) and from two neighbouring populations from contrasted environments. Snails were parasitized by mites, trematodes and nematodes, from rarest to most frequent. We confirm that terrestrial gastropods can defend against infection by trapping parasitic nematodes in their shell. We show that nematode encapsulated in shells can uncover past infections even when a snail population is currently nematode-free, possibly due to parasite seasonality. We present new observations suggesting that not only nematodes but also mites might be encapsulated in shells. Infection levels varied between morphs, with darker snails harbouring fewer nematodes. Behaviour (movement and food intake) was linked to nematode, but not trematode infection. Individuals with higher nematode load ate less, irrespective of morph and population. The most-infected morph (unbanded snails) showed reduced activity in the nematode-infected population compared to the one that was nematode-free at sampling time. As a result, parasites may cancel previously described behavioural differences between morphs. We discuss the possible mechanisms explaining morph-dependent responses to parasites, and how parasite risk may be an unseen force shaping C. nemoralis morph variation in space and time. We conclude on the possible ecological consequences of the link, mediated by shell colour, between thermal and immune responses.

Range expansions are key processes shaping the distribution of species; their ecological and evolutionary dynamics have become especially relevant today, as human influence reshapes ecosystems worldwide. Many attempts to explain and predict range expansions assume, explicitly or implicitly, so-called “pulled” expansion dynamics, in which the low-density edge populations provide most of the “fuel” for the species advance. Some expansions, however, exhibit very different dynamics, with high-density populations behind the front “pushing” the expansion forward. These two types of expansions are predicted to have different effects on e.g. genetic diversity and habitat quality sensitivity. However, empirical studies are lacking due to the challenge of generating reliably pushed vs. pulled expansions in the laboratory, or discriminating them in the field. We here propose that manipulating the degree of connectivity among populations may prove a more generalizable way to create pushed expansions. We demonstrate this with individual-based simulations as well as replicated experimental range expansions (using the parasitoid wasp Trichogramma brassicae as model). By analyzing expansion velocities and neutral genetic diversity, we showed that reducing connectivity led to pushed dynamics. Low connectivity alone, i.e. without density-dependent dispersal, can only lead to “weakly pushed” expansions, where invasion speed conforms to pushed expectations, but the decline in genetic diversity does not. In empirical expansions however, low connectivity may in some cases also lead to adjustments to the dispersal-density function, recreating “classical” pushed expansions. In the current context of habitat loss and fragmentation, we need to better account for this relationship between connectivity and expansion regimes to successfully predict the ecological and evolutionary consequences of range expansions.

As human influence reshapes communities worldwide, many species expand or shift their ranges as a result, with extensive consequences across levels of biological organization. Range expansions can be ranked on a continuum going from pulled dynamics, in which low-density edge populations provide the “fuel” for the advance, to pushed dynamics in which high-density rear populations “push” the expansion forward. While theory suggests that evolution during range expansions could lead pushed expansions to become pulled with time, empirical comparisons of phenotypic divergence in pushed vs. pulled contexts are lacking. In a previous experiment using Trichogramma brassicae wasps as a model, we showed that expansions were more pushed when connectivity was lower. Here we used descendants from these experimental landscapes to look at how the range expansion process and connectivity interact to shape phenotypic evolution. Interestingly, we found no clear and consistent phenotypic shifts, whether along expansion gradients or between reference and low connectivity replicates, when we focused on low-density trait expression. However, we found evidence of changes in density-dependence, in particular regarding dispersal: populations went from positive to negative density-dependent dispersal at the expansion edge, but only when connectivity was high. As positive density-dependent dispersal leads to pushed expansions, our results confirm predictions that evolution during range expansions may lead pushed expansions to become pulled, but add nuance by showing landscape conditions may slow down or cancel this process. This shows we need to jointly consider evolution and landscape context to accurately predict range expansion dynamics and their consequences.

International audience; Understanding the maintenance of among-individual behavioral variation in populations and predicting its consequences are key challenges in behavioral ecology. Studying the association between repeatable behaviors and other traits under selection may shed light on the underlying selective pressures. We used the model snail Cepaea nemoralis to examine whether individual behavior is associated with shell morph, a key trait that has been extensively studied in the context of thermal tolerance and predator avoidance, and which is known to be under strict genetic control in this species. We quantified proxies of boldness and exploration in snails of three morphs coming from two habitats with different thermal contexts. We show that both behaviors were repeatable at the among-individual level (within-state R-boldness = 0.22 [95% credible interval: 0.15; 0.29]; R-exploration = 0.20 [0.15; 0.25]). Behavior was associated with shell morph, with the darker morph (five-banded) being consistently shyer and slower to explore. There was no evidence that thermal environment of origin influenced behavior. Snails became faster when test temperature increased; we found no evidence morphs differed in their thermal response. Boldness and exploration were correlated among individuals, forming a syndrome (r = 0.28 [0.10; 0.46]). The link we find between morph and boldness is compatible with visual selection by avian predators, assuming a positive association between boldness and morphological defense (phenotypic compensation hypothesis). The fact morph-behaviors associations are consistent across environments, despite selection on morph, hint to a possible underlying genetic origin. Finally, we discuss how our findings combined with decades of evolutionary research make C. nemoralis a very valuable model to study the evolution of behavior in response to environmental changes.

Landscape connectedness shapes the exchange of individuals among patches, and hence metapopulation connectivity and dynamics. Connectedness, and its resulting effects on connectivity are therefore rightfully central in conservation biology. However, besides determining demographic fluxes of individuals between patches, connectedness also generates phenotypic sorting and thus impacts local and regional eco-evolutionary dynamics. Despite the central role of connectedness, its effects on individual phenotypic heterogeneity and spatial organization are so far neglected in theory and applications.Through experimental metapopulations of Tetranychus urticae (two-spotted spider mite) with three levels of landscape connectedness and by regularly removing phenotypic structure in a subset of these populations, we tested how regional and local population dynamics are determined both by network connectedness and phenotypic spatial organization.We find that the self-organizing phenotypic spatial structure increases local equilibrium population sizes and variability. It in contrast dampens the effects of imposed connectedness differences on population sizes and is therefore anticipated to improve metapopulation persistence. Contrary to theoretical expectations, the most locally connected patches within the network showed an overall reduced local population size, possibly originating from a faster depletion of resources from immigrants or transiting individuals.This experiment shows how metapopulation dynamics can significantly deviate from theoretical expectations due to individual heterogeneity. This potential rescue effect stemming from phenotypical self-organization in space is a key point to consider for conservation actions, especially based on translocations.

Dispersal is a key trait linking ecological and evolutionary dynamics, allowing organisms to optimize fitness expectations in spatially and temporally heterogeneous environments. Some organisms can either actively disperse or reduce activity in response to challenging conditions, and both responses may be under a trade-off. To understand how such organisms respond to changes in environmental conditions, we studied emigration (the first step of dispersal) and activity behaviour in the gonochoric land snailPomatias elegans, a litter decomposer that can reach very high local densities, over most of the range of ecologically relevant densities. We found that crowding had no detectable effect on emigration tendency in this species, contrary to previous results in many hermaphroditic snails.Pomatias elegansis nonetheless able to detect population density; we show they reduce activity rather than increase dispersal in response to crowding. We propose that limiting activity may be more advantageous than moving away in species with especially poor movement abilities, even by land mollusc standards, likeP. elegans. Interestingly, emigration and activity were positively correlated independently of density; this dispersal syndrome may reflect an underlying pace-of-life syndrome, and is compatible with a dispersal-dormancy trade-off, which would require further investigation. Additionally, we found snails with heavier shells relative to their size tended to be less mobile, which may reflect physical and metabolic constraints on movement and/or survival during inactivity. We finally discuss how the absence of density-dependent dispersal may explain whyP. elegansis often found at very high local densities, and the possible consequences of this behaviour for ecosystem functioning and litter decomposition.

The increasing urbanization process is hypothesized to drastically alter (semi-)natural environments with a concomitant major decline in species abundance and diversity. Yet, studies on this effect of urbanization, and the spatial scale at which it acts, are at present inconclusive due to the large heterogeneity in taxonomic groups and spatial scales at which this relationship has been investigated among studies. Comprehensive studies analysing this relationship across multiple animal groups and at multiple spatial scales are rare, hampering the assessment of how biodiversity generally responds to urbanization. We studied aquatic (cladocerans), limno-terrestrial (bdelloid rotifers) and terrestrial (butterflies, ground beetles, ground- and web spiders, macro-moths, orthopterans and snails) invertebrate groups using a hierarchical spatial design, wherein three local-scale (200 m x 200 m) urbanization levels were repeatedly sampled across three landscape-scale (3 km x 3 km) urbanization levels. We tested for local and landscape urbanization effects on abundance and species richness of each group, whereby total richness was partitioned into the average richness of local communities and the richness due to variation among local communities. Abundances of the terrestrial active dispersers declined in response to local urbanization, with reductions up to 85% for butterflies, while passive dispersers did not show any clear trend. Species richness also declined with increasing levels of urbanization, but responses were highly heterogeneous among the different groups with respect to the richness component and the spatial scale at which urbanization impacts richness. Depending on the group, species richness declined due to biotic homogenization and/or local species loss. This resulted in an overall decrease in total richness across groups in urban areas. These results provide strong support to the general negative impact of urbanization on abundance and species richness within habitat patches and highlight the importance of considering multiple spatial scales and taxa to assess the impacts of urbanization on biodiversity. Belgian Science Policy Office, Grant/Award Number: P07/4; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, Grant/Award Number: 45968/2012-1 Piano, E (reprint author), Univ Turin, Dept Life Sci & Syst Biol, Turin, Italy. elena.piano@unito.it

International audience; Ecology and evolution unfold in spatially structured communities, where dispersal links dynamics across scales. Because dispersal is multicausal, identifying general drivers remains challenging. In a coordinated distributed experiment spanning organisms from protozoa to vertebrates, we tested whether two fundamental determinants of local dynamics, top-down and bottom-up control, generally explain active dispersal. We show that both factors consistently increased emigration rates and use metacommunity modelling to highlight consequences on local and regional dynamics.

The edible land snail Cornu aspersum, native to the Mediterranean coastlines of North Africa, is widely distributed on most continents and often invasive in areas where introduction is recent. This species could contribute to the geographic spread of parasites as demonstrated for Brachylaima spp. These cosmopolitan trematodes may represent a threat to human health, like in Australia where Brachylaima cribbi infects humans. In this study, we demonstrate for the first time the occurrence of Brachylaima spp. in two French populations of C. aspersum, Thorigné-Fouillard (Ille-et-Vilaine), and Arçais (Deux-Sèvres), with an overall prevalence of 10.4% (Thorigné-Fouillard) and 73.3% (Arçais), respectively and a metacercarial intensity on average three times higher in Thorigné-Fouillard (37) than in Arçais (11). Cornu aspersum may act as a first and second intermediate host, as demonstrated in Arçais. The morphometrics of metacercariae, particularly the great body length about 2 mm, discriminate our Brachylaima species from those already described in C. aspersum (B. cribbi in Australia, and B. aspersae, B. llobregatensis and B. mascomai in Europe). Molecular analysis, based on 28S and COI, suggests the occurrence of two species in our study, one of which is probably Brachylaima mesostoma, an intestinal parasite of passeriform birds described in Central Europe. We underline the need for further research to identify species of Brachylaima in France and measure the health hazard of consuming field-collected snails.Brachylaima spp. (Trematoda) parasitant Cornu aspersum (Gastropoda) en France et risque potentiel pour la consommation humaine.L’escargot Cornu aspersum, originaire des côtes méditerranéennes d’Afrique du Nord, est largement répandu sur la plupart des continents et souvent invasif dans ses aires d’introduction récente. Cette espèce peut contribuer à l’expansion géographique de parasites comme démontré pour Brachylaima spp. Ces trématodes cosmopolites peuvent représenter une menace pour la santé comme en Australie où Brachylaima cribbi parasite l’espèce humaine. Dans cette étude, nous démontrons pour la première fois la présence de Brachylaima spp. dans deux populations françaises de C. aspersum, à Thorigné-Fouillard (Ille-et-Vilaine) et Arçais (Deux-Sèvres), avec une prévalence totale de 10.4 % (Thorigné-Fouillard) et 73.3 % (Arçais), et une intensité de métacercaires en moyenne trois fois plus importante à Thorigné-Fouillard (37) qu’à Arçais (11). Cornu aspersum peut jouer le rôle de premier et de second hôte intermédiaire, comme démontré à Arçais. La morphométrie des métacercaires, en particulier la grande taille corporelle d’environ 2 mm de long, suggèrent qu’il ne s’agit pas d’espèces de Brachylaima déjà décrites chez C. aspersum (B. cribbi en Australie et B. aspersae, B. llobregatensis et B. mascomai en Europe). L’analyse moléculaire, basée sur 28S et COI, suggère la présence de deux espèces dans notre étude, dont l’une est probablement Brachylaima mesostoma, un parasite intestinal d’oiseaux passeriformes décrit en Europe Centrale. Nous soulignons le besoin de recherche future pour identifier les espèces de Brachylaima présentes en France et mesurer le risque associé à la consommation d’escargots terrestres prélevés en milieu naturel.

Understanding the maintenance of among-individual behavioral variation in populations, and predicting its consequences, are key challenges in behavioral ecology. Studying the association between repeatable behaviors and other traits under selection may shed light on the underlying selective pressures. We used the model snailCepaea nemoralisto examine whether individual behavior is associated with shell morph, a key trait that has been extensively studied in the context of thermal tolerance and predator avoidance, and which is known to be under strict genetic control in this species. We quantified proxies of boldness and exploration in snails of three morphs coming from two habitats with different thermal contexts. We show that both behaviors were repeatable at the among-individual level(within-stateRboldness= 0.22 [95% credible interval: 0.15, 0.29];Rexploration= 0.20 [0.15, 0.25]). Behavior was associated with shell morph, with the darker morph (five-banded) being consistently shyer and slower to explore. There was no evidence that thermal environment of origin influenced behavior. Snails became faster when test temperature increased; we found no evidence morphs differed in their thermal response. Boldness and exploration were correlated among individuals, forming a syndrome (r= 0.28 [0.10, 0.46]). We discuss what these results may tell us about the type of selection exerted by predators. We also detail how our results hint to a genetic link between shell morph and behavior, and the evolutionary implications of such a link. Finally, we discuss how our findings combined with decades of evolutionary research makeC. nemoralisa very valuable model to study the evolution of behavior in response to environmental changes.

Dispersing individuals are expected to encounter costs during transfer and in the novel environment, and may also have experienced stress in their natal patch. Given this, a non-random subset of the population should engage in dispersal and eventually show divergent stress-related responses towards new conditions. Dispersal allows escape from stress, but is equally subjecting individuals to it.Physiological shifts expressed in the metabolome form a major part of responses to stress exposure and are expected to be associated with the dispersal phenotype, thereby shaping physiological dispersal syndromes. We analyzed how metabolic profiles and life-history traits varied between dispersers and residents of the model two-spotted spider miteTetranychus urticae, and whether and how these syndromes varied with exposure to a stressful new host plant (tomato). Regardless of the effect of host plant, we found a physiological dispersal syndrome where, relative to philopatric individuals, dispersers were characterized by lower leaf consumption rates and a lower concentration of several amino acids, indicating a potential dispersal-foraging trade-off. As a possible consequence of this lower food intake, dispersers also showed a lower reproductive performance. Responses to tomato exposure were consistent with this plant being a stressor forTetranychus urticae, including reduced fecundity and reduced feeding by mites. Tomato-exposed mites laid larger eggs, which can be interpreted as a plastic response to food stress, increasing the likelihood of survival to maturity. Contrary to what could be expected from the costs of dispersal and stress resistance and from previous meta-population level studies, there was no interaction between dispersal status and host plant for any of the examined traits, indicating that the impacts of a new stressful host plant are equally incurred by residents and dispersers.We thus provide novel insights in the processes that shape dispersal and the putative feedbacks on ecological dynamics in spatially structured populations.

International audience; 1.In animals, behavioural responses may play an important role in determining population persistence in the face of environmental changes. Body size is a key trait central to many life history traits and behaviours. Correlations with body size may constrain behavioural variation in response to environmental changes, especially when size itself is influenced by environmental conditions. 2.Urbanization is an important human-induced rapid environmental change that imposes multiple selection pressures on both body size and (size-constrained) behaviour. How these combine to shape behavioural responses of urban-dwelling species is unclear. 3.Using web-building, an easily quantifiable behaviour linked to body size, and the garden spider Araneus diadematus as a model, we evaluated direct behavioural responses to urbanization and body size constraints across a network of 63 selected populations differing in urbanization intensity. We additionally studied urbanization at two spatial scales to account for some environmental pressures varying across scales and to obtain first qualitative insights about the role of plasticity and genetic selection. 4.Spiders were smaller in highly urbanized sites (local scale only), in line with expectations based on reduced prey biomass availability and the Urban Heat Island effect. Web surface and mesh width decreased with urbanization at the local scale, while web surface also increased with urbanization at the landscape scale. The latter two responses are expected to compensate, at least in part, for reduced prey biomass availability in cities. The use of multivariate mixed modelling reveals that although web traits and body size are correlated within populations, behavioural responses to urbanization do not appear to be constrained by size there is no evidence of size-web correlations among populations or among landscapes, and web traits appear independent from each other. 5.Our results demonstrate that responses in size-dependent behaviours may be decoupled from size changes, thereby allowing fitness maximisation in novel environments. The spatial scale at which traits respond suggests contributions of both genetic adaptation (for web investment) and plasticity (for mesh width). Although fecundity decreased with local-scale urbanization, Araneus diadematus abundances were similar across urbanization gradients; behavioural responses thus appear overall successful at the population level.

Dispersal, i.e. movement leading to gene flow, is a fundamental although costly life history trait. The use of indirect social information may help mitigate these costs, yet in many cases little is known about the proximate sources of such information, and how dispersers and residents may differ in their information use. Land gastropods, which have a high cost of movement and obligatorily leave information potentially exploitable by conspecifics during movement (through mucus trails), are a good model to investigate links between dispersal costs and information use. We used Y-mazes to see whether dispersers and residents differed in their trail-following propensity, in the snail Cornu aspersum. Dispersers followed mucus trails more frequently than expected by chance, contrary to non-dispersers. Ignoring dispersal status during tests would lead to falsely conclude to no trail-following for the majority of ecologically realistic scenarios. Trail following by dispersers may reduce dispersal costs by reducing energy expenditure and helping snails find existing patches. Finally, we point that ignoring the potential for collective dispersal provided by trail-following abilities may lead to wrong inferences on the demographic and genetic consequences of dispersal.

Body size is intrinsically linked to metabolic rate and life-history traits, and is a crucial determinant of food webs and community dynamics 1,2. The increased temperatures associated with the urban-heat-island effect result in increased metabolic costs and are expected to drive shifts to smaller body sizes 3. Urban environments are, however, also characterized by substantial habitat fragmentation 4 , which favours mobile species. Here, using a replicated, spatially nested sampling design across ten animal taxonomic groups, we show that urban communities generally consist of smaller species. In addition, although we show urban warming for three habitat types and associated reduced community-weighted mean body sizes for four taxa, three taxa display a shift to larger species along the urbanization gradients. Our results show that the general trend towards smaller-sized species is overruled by filtering for larger species when there is positive covariation between size and dispersal, a process that can mitigate the low connectivity of ecological resources in urban settings 5. We thus demonstrate that the urban-heat-island effect and urban habitat fragmentation are associated with contrasting community-level shifts in body size that critically depend on the association between body size and dispersal. Because body size determines the structure and dynamics of ecological networks 1 , such shifts may affect urban ecosystem function. Body size is a fundamental species trait relating to space use and key life-history features such as longevity and fecundity 6. It also drives interspecific relationships, thus affecting ecological network dynamics 1. Size-biased species loss has profound effects on ecosystem function 7,8. Ectotherms rely on ambient conditions to achieve operational body temperatures 9. Because higher ambient temperature increases metabolic rates and the associated costs for a given body size 2 , global climatic warming is expected to drive shifts to communities consisting of smaller species 3. Our planet is urbanizing quickly 10 , which is a primary example of human-induced rapid environmental change. Cities are urban heat islands characterized by increased temperatures that are decades ahead of global averages 11. Not only are cities warmer than surrounding areas, but they also experience extensive fragmentation of (semi-)natural habitats , and both of these effects increase with percentage built-up cover (BUC; a proxy for urbanization) 12,13. This provides an opportunity to study the opposing effects of size-dependent thermal tolerance and dispersal capacity, as larger body size favours dispersal in some, but not all, taxa. Here we test the hypothesis that urbanization causes shifts in community level body size, and that these shifts are dictated by the community specific association between body size and dispersal. We generally expect the urban-heat-island effect to drive shifts to species with smaller body sizes in communities of ectothermic species, in line with Atkinson's temperature-size rule 14. For taxa characterized by a positive association between body size and dispersal, however, we also expect a filtering in favour of larger-bodied species associated with habitat fragmentation 5,15. Filtering for increased mobility has been demonstrated for urban ground beetle and plant communities 16,17. Hence, for taxa characterized by a positive body-size-dispersal link, we predict that the general community-level pattern of smaller species with increasing urbanization may be neutralized or even reversed. To test our hypothesis, we engaged in an analysis of community-level shifts in body size across a broad range of both terrestrial and aquatic taxa along the same systematically sampled urbanization gradients. We studied the direction of change of community-level body size in ten taxa using a replicated, highly standardized and nested sampling design that covers urbanization gradients at seven spatial scales (50-3,200 m radii; Fig. 1). We sampled each taxon at up to 81 sites, sampling 95,001 individuals from 702 species, with species-specific body size varying by a factor of 400 (0.2-80 mm; Extended Data Table 1). Three of the ten groups are characterized by a positive association between body size and dispersal capacity (see Extended Data Table 1). We show that the local temperature of pond, grassland and woodland habitats significantly increases with urbanization (linear mixed regression models, P

With ongoing global change, life is continuously forced to move to novel areas, which leads to dynamically changing species ranges. As dispersal is central to range dynamics, factors promoting fast and distant dispersal are key to understanding and predicting species ranges. During range expansions, genetic variation is depleted at the expanding front. Such conditions should reduce evolutionary potential, while increasing kin competition. Organisms able to recognise relatives may be able to assess increased levels of relatedness at expanding range margins and to increase their dispersal in a plastic manner. Using individual-based simulations and experimental range expansions of a spider mite, we demonstrate that plastic responses to kin structure can be at least as important as evolution in driving range expansion speed. Because recognition of kin or kind is increasingly documented across the tree of life, we anticipate it to be a highly important but neglected driver of range expansions.

In animals, behavioural responses may play an important role in determining population persistence in the face of environmental changes. Body size is a key trait central to many life history traits and behaviours. While behaviours are typically assumed to be highly plastic, size correlations may impose constraints on their adaptive value when size itself is subject to environmental changes.Urbanization is an important human-induced rapid environmental change that imposes multiple selection pressures on both body size and (size-constrained) behaviour. How these combine to shape behavioural responses of urban-dwelling species is unclear.Using web-building, an easily quantifiable behaviour linked to body size, and the garden spider Araneus diadematus as a model, we disentangle direct behavioural responses to urbanization and body size constraints across a network of 63 selected populations differing in urbanization intensity at two spatial scales.Spiders were smaller in highly urbanized sites (local scale only), in line with expectations based on reduced prey biomass availability and the Urban Heat Island effect. The use of multivariate mixed modelling reveals that although web traits and body size are correlated within populations, behavioural responses to urbanization do not appear to be constrained by size: there is no evidence of size-web correlations among populations or among landscapes. Spiders thus altered different components of their web-building behaviours independently in response to urbanization: mesh width and web surface decreased independently with urbanization at the local scale, while web surface also increased with urbanization at the landscape scale. These responses are expected to compensate, at least in part, for reduced prey biomass availability.Our results demonstrate that responses in typically size-dependent behaviours may be decoupled from size changes, thereby allowing fitness maximisation in novel environments. The spatial scale of the behavioural responses to urbanization suggest contributions of both genetic adaptation and plasticity. Although fecundity decreased with local-scale urbanization, Araneus diadematus abundances were remarkably similar across urbanization gradients; behavioural responses thus appear overall successful at the population level.

Organisms rarely experience a homogeneous environment. Rather, ecological and evolutionary dynamics unfold in spatially structured and fragmented landscapes, with dispersal as the central process linking these dynamics across spatial scales. Because dispersal is a multi-causal and highly plastic life-history trait, finding general drivers that are of importance across species is challenging but highly relevant for ecological forecasting.We here tested whether two fundamental ecological forces and main determinants of local population dynamics, top-down and bottom-up control, generally explain dispersal in spatially structured communities. In a coordinated distributed experiment spanning a wide range of actively dispersing organisms, from protozoa to vertebrates, we show that bottom-up control, that is resource limitation, consistently increased dispersal. While top-down control, that is predation risk, was an equally important dispersal driver as bottom-up control, its effect depended on prey and predator space use and whether dispersal occurred on land, in water or in the air: species that routinely use more space than their predators showed increased dispersal in response to predation, specifically in aquatic environments. After establishing these general causes of dispersal, we used a metacommunity model to show that bottom-up and top-down control of dispersal has important consequences for local population fluctuations as well as cascading effects on regional metacommunity dynamics. Context-dependent dispersal reduced local population fluctuations and desynchronized dynamics between communities, two effects that increase population and community stability.Our study provides unprecedented insights into the generality of the positive resource dependency of dispersal as well as a robust experimental test of current theory predicting that predator-induced dispersal is modulated by prey and predator space use. Our experimental and theoretical work highlights the critical importance of the multi-causal nature of dispersal as well as its cascading effects on regional community dynamics, which are specifically relevant to ecological forecasting.

International audience; Urban areas are an extreme example of human-changed environments, exposing organisms to multiple and strong selection pressures. Adaptive behavioral responses are thought to play a major role in animals' success or failure in such new environments. Approaches based on functional traits have proven especially valuable to understand how species communities respond to environmental gradients. Until recently, they have, however, often ignored the potential consequences of intraspecific trait variation (ITV). When ITV is prevalent, it may highly impact ecological processes and resilience against stressors. This may be especially relevant in animals, in which behavioral traits can be altered very flexibly at the individual level to track environmental changes. We investigated how species turnover and ITV influenced community-level behavioral responses in a set of 62 sites of varying levels of urbanization, using orb web spiders and their webs as models of foraging behavior. ITV alone explained around one-third of the total trait variation observed among communities. Spider web structure changed according to urbanization, in ways that increase the capture efficiency of webs in a context of smaller urban prey. These trait shifts were partly mediated by species turnover, but ITV increased their magnitude, potentially helping to buffer the effects of environmental changes on communities. The importance of ITV varied depending on traits and on the spatial scale at which urbanization was considered. Despite being neglected from community-level analyses in animals, our results highlight the importance of accounting for intraspecific trait variation to fully understand trait responses to (human-induced) environmental changes and their impact on ecosystem functioning.

Both individual variation in dispersal tendency and animal personalities have been shown to be widespread in nature. They are often associated in personality-dependent dispersal, and both have major but underappreciated consequences for ecological and evolutionary dynamics. In addition, personalities are not stable over time and changes can appear through ontogeny, leading to life stage-dependent behaviours. We investigated relationships between dispersal, life stage and boldness in an invertebrate with between- and within-life stages variation in dispersal tendency, the land snail Cornu aspersum. Latency to exit the shell following a simulated attack was repeatable, indicating boldness is a personality trait in Cornu aspersum. Subadults were bolder and more dispersive than adults. Dispersers were bolder than non-dispersers, independently of boldness changes between life stages. We discuss how these results can be explained in relation with life history strategies in this hermaphrodite species, in particular risk management in the context of reproductive investment.

The study of trade-offs among major life history components (age at maturity, lifespan and reproduction) allowed the development of a quantitative framework to understand how environmental variation shapes patterns of biodiversity among and within species.Because every environment is inherently spatially structured, and in most cases temporally variable, individuals need to move within and among habitats to maximize fitness. Dispersal is often assumed to be tightly integrated into life histories through genetic correlations with other vital traits. This assumption is particularly strong within the context of a fast-slow continuum of life-history variation. Such a framework is to date used to explain many aspects of population and community dynamics. Evidence for a consistent and context-independent integration of dispersal in life histories is, however, weak. We therefore advocate the explicit integration of dispersal into life history theory as a principal axis of variation influencing fitness, that is free to evolve, independently of other life history traits.We synthesize theoretical and empirical evidence on the central role of dispersal and its evolutionary dynamics on the spatial distribution of ecological strategies and its impact on population spread, invasions and coexistence. By applying an optimality framework we show that the inclusion of dispersal as an independent dimension of life histories might substantially change our view on evolutionary trajectories in spatially structured environments.Because changes in the spatial configuration of habitats affect the costs of movement and dispersal, adaptations to reduce these costs will increase phenotypic divergence among and within populations. We outline how this phenotypic heterogeneity is anticipated to further impact population and community dynamics.

SummaryApproaches based on functional traits have proven especially valuable to understand how communities respond to environmental gradients. Until recently, they have, however, often ignored the potential consequences of intraspecific trait variation (ITV). This position becomes potentially more problematic when studying animals and behavioural traits, as behaviours can be altered very flexibly at the individual level to track environmental changes.Urban areas are an extreme example of human-changed environments, exposing organisms to multiple, strong, yet relatively standardized, selection pressures. Adaptive behavioural responses are thought to play a major role in animals’ success or failure in these new environments. The consequences of such behavioural changes for ecosystem processes remain understudied.Using 62 sites of varying urbanisation level, we investigated how species turnover and ITV influenced community-level behavioural responses to urbanisation, using orb web spiders and their webs as models of foraging behaviour.ITV explained around 30% of the total trait variation observed among communities. Spiders altered their web-building behaviour in cities in ways that increase the capture efficiency of webs. These traits shifts were partly mediated by species turnover, but ITV increased their magnitude. The importance of ITV varied depending on traits and on the spatial scale at which urbanisation was considered. Available prey biomass decreased with urbanisation; the corresponding decrease in prey interception by spiders was less important when ITV in web traits was accounted for.By facilitating trait-environment matching despite urbanisation, ITV thus helps communities to buffer the effects of environmental changes on ecosystem functioning. Despite being often neglected from community-level analyses, our results highlight the importance of accounting for intraspecific trait variation to fully understand trait responses to (human-induced) environmental changes and their impact on ecosystem functioning.

Dispersal plays a key role in many ecological and evolutionary processes, in particular through correlations, or syndromes, with other life-history traits. Here, we investigated the potential syndromes linking movement behaviour, body mass and male and female sexual organs development, to explain a previously described subadult dispersal pattern in the hermaphrodite land snail Cornu aspersum. We found elements indicating that this snail may not strictly be a simultaneous hermaphrodite, but presents a male-biased phase before reaching adulthood and hermaphroditism. Body mass was positively correlated with both patch-leaving propensity and movement speed. However, because the dry mass of the female albumen gland, which represents on average in adults masses equivalent to 42.6% of somatic soft tissues dry mass, was negatively correlated with patch-leaving propensity, snails of intermediate age are expected to be more likely to leave than older ones. No relationship between male organ size and movement characteristics was found. We discuss briefly the interesting consequences the existence of a syndrome linking movement propensity with female investment in a protandric hermaphrodite species might have in terms of life-history evolution and on the maintenance of hermaphroditism in dispersal-favouring environments.

International audience; The extreme fragmentation of natural habitats due to urbanisation can influence the evolution of dispersal strategies in species persisting in cities. The brown garden snail Cornu aspersum is an anthropophilic species, capable of maintaining its populations in highly fragmented habitats despite a high cost of movement. In this species, we studied the variation of dispersal-related behaviours and traits along an urbanisation gradient characterised at two biologically relevant spatial scales (10 and 50 m), in order to identify the effects of habitat fragmentation on movement. The olfactory perceptual range was low, between 1 and 2.5 m, meaning that snails should perceive a large range of landscapes as fragmented. In line with previous results, subadults were more prone to explore than adults in the least urbanised populations. The boundary-crossing behaviour of subadults was not affected by urbanisation, while exploration propensity of adult snails increased with urbanisation at the 50 m (long-distance dispersal) scale, to reach subadult levels in more urban sites. Foot mass (a correlate of movement speed) and perceptual range were not affected by urbanisation. These results are interpreted in relation to the different levels of competition snails are likely to experience in different environments, the high risk of local extinction in urban fragmented landscapes, and the available opportunities for reproduction. They indicate that benefits of dispersal still need to be considered even in situations where movement costs are extremely important. The maintenance of relatively high mobility and its extension to the adult stage in response to anthropogenic changes may thus play a major role in the success of Cornu aspersum in urban habitats.

International audience; Dispersal success in animals depends in part on their perceptual range, i.e., the distance from which they can acquireinformation about their environment. We studied how the olfactory perceptual range of a generalist species, the brown gardensnail (Cornu aspersum (Müller, 1774)), varied under controlled conditions depending on the context in which stimuli werepresented, whether alone or in the presence of another stimulus with opposite properties. Cornu aspersum preferentially orientthemselves towards small nettle (Urtica dioica L.) patches, a highly palatable plant, and move away from repulsive plants if thesestimuli are placed up to between 20 and 40 cm away from their starting point. A blend of palatable and repulsive plants, testedtogether, do not significantly influence the orientation of individuals in either direction. Cornu aspersum are thus capable ofdetecting and evaluating relatively small potential resource patches from a distance, enabling them to limit costly explorations,but this ability is context-dependent. These data could lead to a better understanding of the behaviour of C. aspersum in veryheterogeneous landscapes in relation to this species’ ability to colonise a wide range of anthropised and fragmented habitats.; Le succès de dispersion des animaux dépend en partie de leur domaine de perception, c’est-à-dire de la distance jusqu’à laquelle ils peuvent s’informer sur leur environnement. Nous avons étudié en conditions contrôlées comment le domaine de perception olfactif d’un escargot généraliste, le petit-gris (Cornu aspersum (Müller, 1774)), variait selon le contexte dans lequel un stimulus était présenté, seul ou en présence d’un autre stimulus aux propriétés opposées. Cornu aspersum s’orientent préférentiellement vers des patchs d’ortie (Urtica dioica L.), une plante très appétente, et s’éloignent des plantes répulsives si ces stimuli sont placés à moins de 20–40 cm de leur point de départ. Un mélange de ces deux types de plantes n’influence pas significativement l’orientation des individus aux distances étudiées. Ces résultats montrent que C. aspersum sont capables de détecter à distance des ressources potentielles de relativement petite taille et d’évaluer leur qualité, permettant de limiter des mouvements d’exploration coûteux, mais que cette capacité est contexte-dépendante. Ces données pourront permettre de mieux comprendre le comportement de C. aspersum en paysage très hétérogène en relation avec sa capacité à coloniser une large gamme d’habitats anthropisés et fragmentés.

International audience; Dispersal movements, i.e. movements leading to gene flow, are key behaviours with important, but only partially understood, consequences for the dynamics and evolution of populations. In particular, density-dependent dispersal has been widely described, yet how it is determined by the interaction with individual traits, and whether density effects differ between the three steps of dispersal (departure, transience, and settlement), remains largely unknown. Using a semi-natural landscape, we studied dispersal choices of Cornu aspersum land snails, a species in which negative effects of crowding are well documented, and analysed them using dispersal discrete choice models, a new method allowing the analysis of dispersal decisions by explicitly considering the characteristics of all available alternatives and their interaction with individual traits. Subadults were more dispersive than adults, confirming existing results. In addition, departure and settlement were both density dependent: snails avoided crowded patches at both ends of the dispersal process, and subadults were more reluctant to settle into crowded patches than adults. Moreover, we found support for carry-over effects of release density on subsequent settlement decisions: snails from crowded contexts were more sensitive to density in their subsequent immigration choices. The fact that settlement decisions were informed indicates that costs of prospecting are not as important as previously thought in snails, and/or that snails use alternative ways to collect information, such as indirect social information (e.g. trail following). The observed density-dependent dispersal dynamics may play an important role in the ability of C. aspersum to successfully colonise frequently human-disturbed habitats around the world.