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1. Light pollution is increasingly affecting biodiversity and may also disrupt seasonal adaptations. Even dim artificial light, such as skyglow—which can spread far beyond urban areas—can interfere with using photoperiod as a seasonal cue. 2. Here, we test how light pollution impacts diapause induction and whether urban evolution counteracts it, by using common-garden experiments with a common, widespread geometrid moth (Chiasmia clathrata). We raised offspring from urban and rural populations from North- and Mid-European countries in treatments with and without dim light at night. 3. The dim light treatment strongly increased direct development overall—with no evidence for urban adaptation to it—but distinctly more so in Mid- than in North-European populations. 4. Because diapause induction is critical for surviving winter, these results indicate that dim but widespread light pollution may have detrimental effects on insect populations, especially so at mid-latitudes, and may hence explain part of the ongoing, large-scale insect declines globally. 5. Synthesis and applications. Latitudinal variation in sensitivity to light pollution means that its contribution to insect declines—and its conservation importance—should likewise vary among regions. In mid-latitude regions, where populations seem more sensitive to light pollution, mitigating light pollution should be a high priority for insect conservation. Reducing skyglow from cities should benefit both urban populations—which were just as susceptible as rural populations in our study—and rural populations—because skyglow extends far beyond the geographic boundaries of cities.

Recent work has shown that animals frequently use social information from individuals of their own species as well as from other species; however, the ecological and evolutionary consequences of this social information use remain poorly understood. Additionally, information users may be selective in their social information use, deciding from whom and how to use information, but this has been overlooked in an interspecific context. In particular, the intentional decision to reject a behaviour observed via social information has received less attention, although recent work has indicated its presence in various taxa. Based on existing literature, we explore in which circumstances selective interspecific information use may lead to different ecological and coevolutionary outcomes between two species, such as explaining observed co-occurrences of putative competitors. The initial ecological differences and the balance between the costs of competition and the benefits of social information use potentially determine whether selection may lead to trait divergence, convergence or coevolutionary arms race between two species. We propose that selective social information use, including adoption and rejection of behaviours, may have far-reaching fitness consequences, potentially leading to community-level eco-evolutionary outcomes. We argue that these consequences of selective interspecific information use may be much more widespread than has thus far been considered.

Aim: There has been a wide interest in the effect of biotic interactions on species’ occurrences and abundances at large spatial scales, coupled with a vast development of the statistical methods to study them. Still, evidence for whether the effects of within-trophic-level biotic interactions (e.g. competition and heterospecific attraction) are discernible beyond local scales remains inconsistent. Here, we present a novel hypothesis-testing framework based on joint dynamic species distribution models and functional trait similarity to dissect between environmental filtering and biotic interactions. Location: France and Finland. Taxon: Birds. Methods: We estimated species-to-species associations within a trophic level, independent of the main environmental variables (mean temperature and total precipitation) for common species at large spatial scale with joint dynamic species distribution (a multivariate spatiotemporal delta model) models. We created hypotheses based on species’ functionality (morphological and/or diet dissimilarity) and habitat preferences about the sign and strength of the pairwise spatiotemporal associations to estimate the extent to which they result from biotic interactions (competition, heterospecific attraction) and/or environmental filtering. Results: Spatiotemporal associations were mostly positive (80%), followed by random (15%), and only 5% were negative. Where detected, negative spatiotemporal associations in different communities were due to a few species. The relationship between spatiotemporal association and functional dissimilarity among species was negative, which fulfils the predictions of both environmental filtering and heterospecific attraction. Main conclusions: We showed that processes leading to species aggregation (mixture between environmental filtering and heterospecific attraction) seem to dominate assembly rules, and we did not find evidence for competition. Altogether, our hypothesis-testing framework based on

Concept learning is considered a high-level adaptive ability. Thus far, it has been studied in laboratory via asocial trial and error learning. Yet, social information use is common among animals but it remains unknown whether concept learning by observing others occurs. We tested whether pied flycatchers (Ficedula hypoleuca) form conceptual relationships from the apparent choices of nest-site characteristics (geometric symbol attached to the nest-box) of great tits (Parus major). Each wild flycatcher female (n = 124) observed one tit pair that exhibited an apparent preference for either a large or a small symbol and was then allowed to choose between two nest-boxes with a large and a small symbol, but the symbol shape was different to that on the tit nest. Older flycatcher females were more likely to copy the symbol size preference of tits than yearling flycatcher females when there was a high number of visible eggs or a few partially visible eggs in the tit nest. However, this depended on the phenotype, copying switched to rejection as a function of increasing body size. Possibly the quality of and overlap in resource use with the tits affected flycatchers’ decisions. Hence, our results suggest that conceptual preferences can be horizontally transmitted across coexisting animals, which may increase the performance of individuals that use concept learning abilities in their decision-making.

Current environmental changes lead to declines in species abundances globally, creating a need for understanding mechanisms shaping community composition. Species interactions are a fundamental force in shaping species distributions affecting, for example, the functionality of entire multispecies networks. Still, interactions are poorly integrated in current estimation of community dynamics. Examining correlations in species abundances, such as species pairwise aggregations or segregations, may provide an opportunity to understand species interactions, and novel developments in Joint Species Distribution Models (JSDMs) facilitate the derivation of these associations. My aim is to expand the current understanding of species associations and interactions at large spatial scales, specifically examining (I) can species associations be used to develop practical tools for estimating species abundances in communities, (II) do species interactions leave a signal in community composition, and (III) what ecological and evolutionary consequences may selective interspecific information use have at the community level. I derived species associations from Finnish and French breeding bird data, covering a large spatial and temporal range, using a JSDM (I, II). Furthermore, I used linear models to examine the sign of species interactions in community composition (II). I used a simulation model to examine the ecological and evolutionary consequences of selective social information use. The results suggest that (I) the abundance of tit species could be used as an efficient ecological indicator for the total density of other forest birds, (II) environmental filtering and positive species associations leave a stronger sign than competition at large spatial scales on bird community composition, and (III) (selective) social information use may lead to trait divergence, convergence or a coevolutionary arms race between species. Overall, these results indicate that species interac, Tiivistelmä Ympäristönmuutoksen aiheuttama luontokato on yksi ihmiskunnan tärkeimmistä haasteista. Lajienväliset vuorovaikutukset vaikuttavat eliöyhteisöjen rakenteeseen. Samanaikaisesti ympäristömuutokset muokkaavat yhteisöjen rakennetta ja lajienvälisiä vuorovaikutuksia sekä suoraan että lajien runsauksien kautta. Tästä huolimatta lajienvälisten vuorovaikutusten ekologiset ja evolutiiviset seuraukset muun muassa yhteisön rakenteeseen tunnetaan puutteellisesti. Luontokadon ymmärtämiseksi ja suojelutoimien kohdentamiseksi on erittäin tärkeää selvittää, kuinka lajienväliset vuorovaikutukset muokkaavat eliöyhteisöjä ja niiden kykyä sopeutua ympäristömuutoksiin laajalla ilmasto- ja aikagradientilla. Väitöskirjassani tutkin lajienvälisten vuorovaikutusten ekologisia ja evolutiivisia seurauksia, sekä niiden vaikutuksia yhteisötasolla, etenkin (I) voidaanko lajienvälisten runsauksien korrelaatioita käyttää apuna yhteisönrunsautta mittaavien käytännönmenetelmien kehittämisessä, (II) selittävätkö lajienväliset vuorovaikutukset vai ympäristötekijät yhteisön rakennetta, ja (III) kuinka yleistä valikoiva lajienvälinen informaationkäyttö on ja mitkä ovat sen ekologisia ja evolutiivisia seurauksia. Johdin lajienvälisten runsauksien korrelaatiot laajan maantieteellisen ja ajallisen mittakaavan kattavista Suomen ja Ranskan pesimälintuaineistoista käyttämällä yhteisölevinneisyysmalleja (I, II). Tutkin lajienvälisten vuorovaikutusten ja ympäristötekijöiden vaikutusta lajienvälisiin runsauden korrelaatioihin lineaarisilla malleilla (II). Valikoivan lajienvälisen informaationkäytön yleisyyttä, sekä sen ekologisia ja evolutiivisia seurauksia tarkastelin simulaatiomallin avulla (III). Väitöskirjani osoittaa, että (I) tiaisten yhteisrunsaus voi toimia pesivien metsälintujen runsauden indikaattorina boreaalisissa metsissä, (II) Suomen ja Ranskan lintuyhteisöissä negatiivisten lajienvälisten vuorovaikutusten sijaan ympäristötekijät ja positiiviset vuorovaikutukset selittivät lajienvälisten

Animals commonly search for information about available resources to select a breeding or foraging site or a mate. Searching can be costly, which is why even random selection of resources may pay off. However, the evolution of searching effort in relation to key ecological factors and its ecological consequences remain insufficiently understood. We build a model to analyze the evolution of searching effort for resources in relation to key ecological factors; the cost of information acquisition, the cost of competition and the distribution of resource qualities. Evolutionarily stable searching effort decreased with increasing cost of information acquisition, eventually resulting in a random choice of resources. With a very low cost of information acquisition, evolutionarily stable searching effort increased with increasing proportion of low-quality resources in the available resource distribution, while the opposite was predicted with a higher cost of information acquisition. Cost of competition had only a negligible effect on the evolution of searching effort, except that increasing cost of competition increased investment in information acquisition when a resource distribution was biased towards high-quality resources. Informed resource selection (above-zero investment in information acquisition) resulted in skewed distribution of individuals across resources. Consequently, expected fitness became more similar across resources with decreasing cost of information acquisition and associated increase in searching effort, thus approaching the prediction of the classical ideal free distribution (IFD) model stating that individuals distribute themselves so that fitness is invariant across resources. However, we predict a positive correlation between fitness and resource quality with biologically more realistic parameter values, contradicting the IFD model. Costly information acquisition may, thus, explain why IFD is not always found in empirical studies. General

Population sizes of many birds are declining alarmingly and methods for estimating fluctuations in species’ abundances at a large spatial scale are needed. The possibility to derive indicators from the tendency of specific species to co-occur with others has been overlooked. Here, we tested whether the abundance of resident titmice can act as a general ecological indicator of forest bird density in European forests. Titmice species are easily identifiable and have a wide distribution, which makes them potentially useful ecological indicators. Migratory birds often use information on the density of resident birds, such as titmice, as a cue for habitat selection. Thus, the density of residents may potentially affect community dynamics. We examined spatio-temporal variation in titmouse abundance and total bird abundance, each measured as biomass, by using long-term citizen science data on breeding forest birds in Finland and France. We analyzed the variation in observed forest bird density (excluding titmice) in relation to titmouse abundance. In Finland, forest bird density linearly increased with titmouse abundance. In France, forest bird density nonlinearly increased with titmouse abundance, the association weakening toward high titmouse abundance. We then analyzed whether the abundance (measured as biomass) of random species sets could predict forest bird density better than titmouse abundance. Random species sets outperformed titmice as an indicator of forest bird density only in 4.4% and 24.2% of the random draws, in Finland and France, respectively. Overall, the results suggest that titmice could act as an indicator of bird density in Northern European forest bird communities, encouraging the use of titmice observations by even less-experienced observers in citizen science monitoring of general forest bird density.

Urbanization is gaining force globally, which challenges biodiversity, and it has recently also emerged as an agent of evolutionary change. Seasonal phenology and life cycle regulation are essential processes that urbanization is likely to alter through both the urban heat island effect (UHI) and artificial light at night (ALAN). However, how UHI and ALAN affect the evolution of seasonal adaptations has received little attention. Here, we test for the urban evolution of seasonal life-history plasticity, specifically changes in the photoperiodic induction of diapause in two lepidopterans, Pieris napi (Pieridae) and Chiasmia clathrata (Geometridae). We used long-term data from standardized monitoring and citizen science observation schemes to compare yearly phenological flight curves in six cities in Finland and Sweden to those of adjacent rural populations. This analysis showed for both species that flight seasons are longer and end later in most cities, suggesting a difference in the timing of diapause induction. Then, we used common garden experiments to test whether the evolution of the photoperiodic reaction norm for diapause could explain these phenological changes for a subset of these cities. These experiments demonstrated a genetic shift for both species in urban areas toward a lower daylength threshold for direct development, consistent with predictions based on the UHI but not ALAN. The correspondence of this genetic change to the results of our larger-scale observational analysis of in situ flight phenology indicates that it may be widespread. These findings suggest that seasonal life cycle regulation evolves in urban ectotherms and may contribute to ecoevolutionary dynamics in cities.

Zoonotic diseases, caused by pathogens transmitted between other vertebrate animals and humans, pose a major risk to human health. Rodents are important reservoir hosts for many zoonotic pathogens, and rodent population dynamics affect the infection dynamics of rodent-borne diseases, such as diseases caused by hantaviruses. However, the role of rodent population dynamics in determining the infection dynamics of rodent-associated tick-borne diseases, such as Lyme borreliosis (LB), caused by Borrelia burgdorferi sensu lato bacteria, have gained limited attention in Northern Europe, despite the multiannual abundance fluctuations, the so-called vole cycles, that characterise rodent population dynamics in the region. Here, we quantify the associations between rodent abundance and LB human cases and Puumala Orthohantavirus (PUUV) infections by using two time series (25-year and 9-year) in Finland. Both bank vole (Myodes glareolus) abundance as well as LB and PUUV infection incidence in humans showed approximately 3-year cycles. Without vector transmitted PUUV infections followed the bank vole host abundance fluctuations with two-month time lag, whereas tick-transmitted LB was associated with bank vole abundance ca. 12 and 24 months earlier. However, the strength of association between LB incidence and bank vole abundance ca. 12 months before varied over the study years. This study highlights that the human risk to acquire rodent-borne pathogens, as well as rodent-associated tick-borne pathogens is associated with the vole cycles in Northern Fennoscandia, yet with complex time lags.

Social information use for decision‐making is common and affects ecological and evolutionary processes, including social aggregation, species coexistence, and cultural evolution. Despite increasing ecological knowledge on social information use, very little is known about its genetic basis and therefore its evolutionary potential. Genetic variation in a trait affecting an individual’s social and nonsocial environment may have important implications for population dynamics, interspecific interactions, and, for expression of other, environmentally plastic traits. We estimated repeatability, additive genetic variance, and heritability of the use of conspecific and heterospecific social cues (abundance and breeding success) for breeding site choice in a population of wild collared flycatchers Ficedula albicollis. Repeatability was found for two social cues: previous year conspecific breeding success and previous year heterospecific abundance. Yet, additive genetic variances for these two social cues, and thus heritabilities, were low. This suggests that most of the phenotypic variation in the use of social cues and resulting conspecific and heterospecific social environment experienced by individuals in this population stems from phenotypic plasticity. Given the important role of social information use on ecological and evolutionary processes, more studies on genetic versus environmental determinism of social information use are needed.

1. Juvenile growth trajectories evolve via the interplay of selective pressures on age and size at maturity, and developmental constraints. In insects, the moulting cycle is a major constraint on larval growth trajectories. 2. Surface area to volume ratio of a larva decreases during growth, so renewal of certain surfaces by moulting is likely needed for the maintenance of physiological efficiency. A null hypothesis of isometry, implied by Dyar’s Rule, would mean that the relative measures of growth remain constant across moults and instars. 3. We studied ontogenetic changes and allometry in instar‐specific characteristics of larval growth in 30 lepidopteran species in a phylogenetic comparative framework. 4. Relative instar‐specific mass increments (RMI) typically, but not invariably, decreased across instars. Ontogenetic change in RMIs varied among families with little within‐family variation. End‐of‐instar growth deceleration (GD) became stronger with increasing body size across instars. Across‐instar change in GD was conserved across taxa. Ontogenetic allometry was generally non‐isometric in both RMI and GD. 5. Results indicate that detailed studies on multiple species are needed for generalizations concerning growth trajectory evolution. Developmental and physiological mechanisms affecting growth trajectory evolution show different degrees of evolutionary conservatism, which must be incorporated into models of age and size at maturation.

Aim: Nest building is widespread among animals. Nests may provide receptacles for eggs, developing offspring and the parents, and protect them from adverse environmental conditions. Nests may also indicate the quality of the territory and its owner and can be considered as an extended phenotype of its builder(s). Nests may, thus, function as a sexual and social signal. Here, we examined ecological and abiotic factors—temperature, nest predation and interspecific information utilization—shaping geographical variation in a specific nest structure—hair and feather cover of eggs—and its function as an extended phenotype before incubation in great (Parus major) and blue tits (Cyanistes caeruleus) across Europe. We also tested whether egg covering is associated with reproductive success of great tits. Location: Fourteen different study sites and 28 populations across Europe. Taxon: Parus major, Cyanistes caeruleus. Methods: We recorded clutch coverage estimates and collected egg covering nest material from the tit nests. We also measured nest specific breeding parameters and phenotypic measurements on adults. We tested whether mean spring temperatures, nest predation rates and flycatcher (Ficedula spp) densities in the study areas explain the large‐scale geographical variation of clutch coverage and reproductive success of tits. Results: The degree of egg coverage of great tits increased with lower mean spring temperature, higher nest predation rate and higher flycatcher density. We did not find egg covering of blue tits to be associated with any of the ecological or abiotic factors. Moreover, egg covering of great tits was not associated with reproductive success in our cross‐sectional data, yet a rigorous assessment of fitness effects would require long‐term data. Main conclusions: Our findings suggest that, in great tits, egg covering may simultaneously provide thermal insulation against cold temperatures during egg‐laying in spring and also represent a counte

The evolution of seasonal polyphenisms (discrete phenotypes in different annual generations) associated with alternative developmental pathways of diapause (overwintering) and direct development is favoured in temperate insects. Seasonal life history polyphenisms are common and include faster growth and development under direct development than in diapause. However, the physiological underpinnings of this difference remain poorly known despite its significance for understanding the evolution of polyphenisms. We measured respiration and metabolic rates through the penultimate and final larval instars in the butterfly Pieris napi and show that directly developing larvae grew and developed faster and had a higher metabolic rate than larvae entering pupal diapause. The metabolic divergence appeared only in the final instar, that is, after induction of the developmental pathway that takes place in the penultimate instar in P. napi. The accumulation of fat reserves during the final larval instar was similar under diapause and direct development, which was unexpected as diapause is predicted to select for exaggerated reserve accumulation. This suggests that overwinter survival in diapause does not require larger energy reserves than direct development, likely because of metabolic suppression in diapause pupae. The results, nevertheless, demonstrate that physiological changes coincide with the divergence of life histories between the alternative developmental pathways, thus elucidating the proximate basis of seasonal life history polyphenisms.

A rapid shift from traditional Sanger sequencing-based molecular methods to the phylogenomic approach with large numbers of loci is underway. Among phylogenomic methods, restriction site associated DNA (RAD) sequencing approaches have gained much attention as they enable rapid generation of up to thousands of loci randomly scattered across the genome and are suitable for nonmodel species. RAD data sets however suffer from large amounts of missing data and rapid locus dropout along with decreasing relatedness among taxa. The relationship between locus dropout and the amount of phylogenetic information retained in the data has remained largely uninvestigated. Similarly, phylogenetic hypotheses based on RAD have rarely been compared with phylogenetic hypotheses based on multilocus Sanger sequencing, even less so using exactly the same species and specimens. We compared the Sanger-based phylogenetic hypothesis (8 loci; 6172 bp) of 32 species of the diverse moth genus Eupithecia (Lepidoptera, Geometridae) to that based on double-digest RAD sequencing (3256 loci; 726,658 bp). We observed that topologies were largely congruent, with some notable exceptions that we discuss. The locus dropout effect was strong. We demonstrate that number of loci is not a precise measure of phylogenetic information since the number of single-nucleotide polymorphisms (SNPs) may remain low at very shallow phylogenetic levels despite large numbers of loci. As we hypothesize, the number of SNPs and parsimony informative SNPs (PIS) is low at shallow phylogenetic levels, peaks at intermediate levels and, thereafter, declines again at the deepest levels as a result of decay of available loci. Similarly, we demonstrate with empirical data that the locus dropout affects the type of loci retained, the loci found in many species tending to show lower interspecific distances than those shared among fewer species. We also examine the effects of the numbers of loci, SNPs, and PIS on nodal bootstra