Waterfowl are potential long-distance dispersal vectors for aquatic microbes such as diatoms, but experimental evidence is scarce. We conducted an experiment designed to emulate diatom dispersal via adherence to waterfowl, and to evaluate the effects of humidity and transport duration on potential dispersal success. We dipped individual mallard breast feathers in a pure benthic diatom culture (Nitzschia pusilla Grunow), then subjected them to one of four relative humidity levels (RH; from ca. 8% to 88%) crossed with one of four transport durations (10, 60, 120, 240 minutes) within a chamber through which air was passed continuously, mimicking light wind. We then placed the feather on sterile growth medium. After two weeks we used spectrofluorometry to detect diatom growth and thus diatom viability. A logistic regression on viability revealed a significant interaction between transport duration and RH: the negative effect of duration was strongest under lower RH conditions, but under high RH (88%) the probability of being viable was moderate to high regardless of transport duration. Importantly, even after 4 hours, the probability of being viable was predicted to be 0.45 (95% confidence interval: 0.18 to 0.75). We then placed our findings in the geographic context of the central waterfowl migration flyway in North America, and specifically Nebraska, South Dakota, and North Dakota, for which sufficient data were available to enable geospatial predictions of potential mallard-borne diatom dispersal. Combined with published data about (i) mallard flight speeds, (ii) the geographic distribution of surface waters and of N. pusilla, and (iii) daytime RH during the months of April through June, our model predicted high probabilities of potential dispersal among the region’s suitable water bodies.
Long-distance dispersal of a subadult male cougar from South Dakota to Connecticut documented with DNA evidence
