These files contain data supporting all results in Hairston et al. An abundant non-native freshwater copepod, Arctodiaptomus dorsalis, on the Island of Hawai′i: distribution, dominance, dispersal, and diapause. In Hairston et al. we found: The freshwater calanoid copepod, Arctodiaptomus dorsalis, native to countries around the Caribbean Sea and the Gulf of Mexico, is now widely distributed and dominant in fresh waterbodies on the Island of Hawai′i. We show that it makes diapausing eggs, providing a likely mechanism enhancing dispersal both across the Pacific Ocean and among local waterbodies. Dense populations of A. dorsalis have been found in one lake and 10 of 15 sampled ponds. In two years of biweekly sampling of two permanent ponds it was abundant to the near exclusion of other zooplankton. Although these two ponds are located only 55 m apart and connected by an intermittent stream, the prevalence and seasonal timing of diapause differed markedly between populations. The diapause differences appear to be local adaptation within the 34 years since pond construction: the population with greater diapause experiences greater fluctuations in pond volume, principally during the dry season (May to October), with timing and prevalence of diapause corresponding well with a model of optimal trait expression. The other population with very little diapause experiences only minor fluctuations in pond volume. Rapid local adaptation following introduction likely enhances the species’ success in Hawai′i. Characteristics of A. dorsalis on Hawai′i Island consistent with calling it “invasive” include that it is non-native, introduced by humans, invasive elsewhere globally, spreading locally, with a dispersing phenotype (diapausing eggs), reproduces and survives where present, and is nearly always abundant and dominant. An impact on the planktonic food web remains conjecture, but is likely based on its local dominance and what is known of its feeding ecology elsewhere.