Migration events can act as strong selective filters by spatially sorting individuals according to their migration ability, behaviour, and associated functional traits The European eel, a panmictic and threatened fish, presents various estuarine migration patterns at juvenile stage (glass eel), ranging from sedentarization in brackish/saltwater of the estuary (non-migrant individuals) to upstream colonisation of freshwater ecosystems (migrant individuals). We hypothesize that migration propensity is partly genetically determined in glass eel, and that migration-related genotypes are spatially sorted during estuarine migration. To test these hypotheses, we first collected six pools of individuals over three years at two extreme sites along a gradient from ocean to Adour River tidal limit (Ocean vs. Upstream). Secondly, we collected additional glass eels and phenotypically sorted migrant vs. non-migrant individuals using an experimental device mimicking alternating tidal currents, producing two other pools. Whole genome pool sequencing and analysis of these eight pools generated 18.99 106 SNP variants. Controlling for linked selection through a local score approach, we found five best outlier SNPs with a significant genetic differentiation between Ocean vs. Upstream sites (average FST = 0.21) compared to the pangenomic estimate (FST = 0.0086). These five SNPs were all found in the same gene (gpb2), involved in interferon-mediated antiviral immune responses. We also found 28 best outlier SNPs with a significant genetic differentiation between migrant vs. non-migrant phenotypes (average FST = 0.51). They were located in genes mainly involved in neuronal development, cell migration and tissue remodelling, transcriptional regulation, and metabolic or stress-related processes. Our results support that variation in eel migration propensity is partly genetically determined and that, while panmixia maintains high level of genetic diversity, spatial sorting could promote intra-generational genetic divergence between habitats of European eels. However, the absence of shared genes among the best outliers between in-situ and experimental contrasts suggests a complex and context-dependent genetic control of migration. ### Competing Interest Statement The authors have declared no competing interest.
Adaptive tracking is an evolutionary process in which allele frequencies and phenotypes shift in response to temporally fluctuating environments. Currently it is unclear whether adaptive tracking causes predictable evolution of complex traits such as thermal tolerance. We investigated seasonal adaptive tracking of critical thermal minimum (CTmin) and genome-wide allele frequencies over multiple years in the invasive fly Drosophila suzukii. CTmin increased throughout the growing season, showing a lag of several generations between increasing temperature and evolutionary change. Genetic analyses indicate CTmin is highly polygenic, with little overlap between alleles associated with CTmin and other seasonally fluctuating alleles. Thus, polygenic traits may track seasonal environments without leaving strong genomic signals. By contrast, there were strong seasonal genomic signatures for alleles associated with oligogenic traits as such pesticide resistance and olfactory behavior. These findings suggest that seasonal adaptive tracking shapes a broad suite of traits that contribute to D. suzukiis invasion success.
We develop a two-stage oligopoly model of price competition in markets with both informed and uninformed (captive) consumers. The model introduces a novel mechanism through which interfirm collaborative R D influences market outcomes. In particular, the second stage of the game where firms set prices is a supermodular game allowing us to analyze strategic complementarities in pricing behavior. We show that this type of market friction creates a new channel of influence for collaborative R D. Our analysis reveals how consumer heterogeneity and cost heterogeneity jointly shape the incentives for collaboration among firms, offering new insights into the design of efficient innovation networks in oligopolistic markets.
