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Synopsis As species move into new environments through founder events, their phenotypes may diverge from native populations. Identifying the drivers underlying such variation, and the constraints on the adaptive potential of this variation, is essential for understanding how organisms respond to new or rapidly changing habitats. Such phenotypic divergence may be especially evident in populations introduced to new environments via human-assisted transport or populations in dramatically altered environments such as cities. Sexually dimorphic species beg the additional questions of how these new environments may influence sexes differently and how dimorphism may shape the range of potential responses. The repeated translocation, establishment, and spread of wall lizards (Podarcis spp.) from native European populations to new locations in North America provide an excellent natural experiment to explore how phenotypes may differ after establishment in a new environment. Here, we quantify body shape and the multivariate morphological phenotype (incorporating limb dimensions and head length) of common wall lizards (P. muralis) and Italian wall lizards (P. siculus) in replicated North American introductions. In both species, males are larger and have larger head length and limb dimensions than females across all sampled groups. Sexual dimorphism in the multivariate morphological phenotype was of similar magnitude when comparing native and introduced populations for both species, though the trajectory angles in multivariate trait space differed in P. siculus. When comparing introduced lizards from contemporary and historically collected museum specimens, we identified differences of similar magnitude but in different trajectories between sexes in P. siculus, and differences in both magnitude and direction of sexual dimorphism in P. muralis. These idiosyncratic patterns in phenotypic trajectories provide insight to the potential array of processes generating phenotypic variation within species at the intersection of invasion biology and urban evolution. 

ABSTRACT Landscape genomic approaches for detecting genotype‐environment associations (GEA), isolation by distance (IBD) and isolation by environment (IBE) have seen a dramatic increase in use, but there have been few thorough analyses of the influence of sampling strategy on their performance under realistic genomic and environmental conditions. We simulated 24,000 datasets across a range of scenarios with complex population dynamics and realistic landscape structure to evaluate the effects of the spatial distribution and number of samples on common landscape genomics methods. Our results show that common analyses are relatively robust to sampling scheme as long as sampling covers enough environmental and geographic space. We found that for detecting adaptive loci and estimatingIBE, sampling schemes that were explicitly designed to increase coverage of available environmental space matched or outperformed sampling schemes that only considered geographic space. When sampling does not cover adequate geographic and environmental space, such as with transect‐based sampling, we detected fewer adaptive loci and had higher error when estimatingIBDandIBE. We found thatIBDcould be detected with as few as nine sampling sites, while large sample sizes (e.g., greater than 100 individuals) were crucial for detecting adaptive loci andIBE. We also demonstrate that, even with optimal sampling strategies, landscape genomic analyses are highly sensitive to landscape structure and migration—when spatial autocorrelation and migration are weak, commonGEAmethods fail to detect adaptive loci.