Stress resistance in two colonial ascidians from the Irish Sea: The recent invader Didemnum vexillum is more tolerant to low salinity than the cosmopolitan Diplosoma listerianum

► We tested for differential stress tolerances in two colonial ascidians. ► Ascidian growth and survival was measured under chronic and episodic osmotic stress. ► The cosmopolitan Diplosoma listerianum was susceptible to osmotic stress. ► The recent invader Didemnum vexillum exhibited a high tolerance to osmotic stress. ► Tolerance to salinity changes may add to the high invasiveness in D. vexillum.