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Surviving the squeeze: Genomic analysis of a successful invasion by European common wall lizards (Podarcis muralis) in North America (Ohio, USA)

Bode, Emily1; Mason, Andrew1; Bolton, Peri1; Petren, Ken2; Gangloff, Eric3; Gibbs, Lisle1

Research facility: The Ohio State University
Published Apr 02, 2026 on Dryad. https://doi.org/10.5061/dryad.4b8gthtq6

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Abstract

Invasive species that undergo a founder event may experience a decline in genetic diversity yet still establish successful populations despite the potential loss of adaptive variation and an increase in deleterious variation. This widely observed phenomenon is termed the genetic paradox of invasive species. A possible example is the common wall lizard (Podarcis muralis) in Cincinnati, Ohio, USA a successful invasive reptile founded by the introduction of a small number of individuals from Italy. In this study, we evaluated whether this introduction is an example of the genetic paradox of invasive species. Specifically, we examined the origin, demographic history, population structure and genomic diversity of the invasive common wall lizard using whole genome sequences of 35 individuals from the native and introduced locations across multiple time points. Phylogenetic analyses confirm that the invasive lizards in Ohio are likely derived from a population of Podarcis muralis in Northern Italy. We then show that: 1) Analyses of short-term effective population size (Ne) and measures of inbreeding (FROH) demonstrate that introduced lizards in Cincinnati went through a short-term bottleneck but rapidly increased in population size thus potentially minimizing losses in genetic diversity; 2) Direct comparisons of estimates of neutral genetic diversity (PCA, Hobs, FST, and π) between source and introduced populations show that while populations in Cincinnati represent a subset of native genetic variation they show minimal losses of genetic diversity; 3) Comparisons of deleterious mutation load between native and introduced populations show only small increases in load in introduced populations; 4) Tests for selection based on outlier analyses detect potential positive selection in regions of the genome of introduced individuals that contain protein coding genes that could represent cases of rapid adaptation to a new environment. Overall, we do not find evidence for a genetically depauperate introduced population with high levels of genetic load in Cincinnati, which are key criterion for the genetic paradox of invasive species. Rather we find rapid population growth likely minimized genetic diversity loss, possibly enabling genetic adaptation to novel aspects of the environment in Cincinnati. This demographic resilience likely facilitated the retention of standing genetic variation and minimized the accumulation of genetic load, allowing the population to remain viable and increase in size. These findings highlight how the interplay between demography, genetic variation, and ecological compatibility can facilitate the success of introduced species, even in the face of strong genetic constraints. Further our study underscores the importance of integrating genomic, demographic, and ecological perspectives to fully understand invasion success.