Abstract
Marine biological invasions, increasingly facilitated by maritime transport, represent a major dimension of global change, threatening biodiversity, ecosystem services, and human well-being worldwide. Although the factors shaping invasion success have been widely studied, the evolutionary processes occurring during the transport stage remain poorly understood. Using high-salinity selection experiments with the model invasive ascidian Ciona robusta, we tested whether transport-related stress imposed genotype-dependent filtering. We quantified survival dynamics and employed whole-genome resequencing together with transcriptomic profiling to characterize genome-wide responses to environmental filtering. Survival analyses revealed significant mortality differences among genotypes under hypersaline conditions. Whole-genome resequencing of survivors identified genomic regions with marked genetic differentiation and allele frequency shifts, particularly in osmoregulatory genes such as solute carriers and ion channels. Transcriptomic profiling further demonstrated genotype-specific expression patterns consistent with stress responses, highlighting the functional relevance of candidate variants. Collectively, our findings show that transport stress drives genotype-dependent survival and functional genomic signatures consistent with selection. Acknowledging transport as an evolutionary filter and integrating such processes into invasion risk frameworks are essential for developing effective management and prevention measures in an era of accelerating global trade and climate change.