“Step by step”: high frequency short-distance epizoochorous dispersal of aquatic macrophytes
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Aquatic macrophytes can successfully colonise and re-colonise areas separated by space and time. The mechanisms underlying such “mobility” are not well understood, but it has often been hypothesised that epizoochory (external dispersal) plays an important role. Yet, there is only limited, and mostly anecdotal, evidence concerning successful epizoochorous dispersal of aquatic macrophytes, particularly in the case of short-distance dispersal. Here we examine in situ and ex situ dispersal of aquatic macrophytes, including three invasive alien species. A high frequency of Lemna minor Linnaeus dispersal was observed in situ, and this was linked to bird-mediated epizoochory. We concluded that wind had no effect on dispersal. Similarly, in an ex situ examination Lemna minuta Kunth and Azolla filiculoides Lamarck, were found to be dispersed with a high frequency by mallard ducks (Anas platyrhynchos). No dispersal was measured for Elodea nuttalli (Planchon) H. St. John. It is concluded that short-distance or “stepping-stone” dispersal via bird-mediated epizoochory can occur with high frequencies, and therefore can play an important role in facilitating colonisation, range expansion and biological invasion of macrophytes.
KeywordsConnectivity Mobile link Bird-mediated Stepping-stone dispersal Biological invasion Invasive aquatic plants
We are grateful to John Coughlan and Geraldine Coughlan for technical support. M.A.K.J. appreciates support by WoB. We also would like to thank two anonymous reviewers for helpful comments on an earlier draft.
NC proposed the study topic. TK and MJ advised on experimental design. All authors (NC, TK and MJ) participated in the writing-up and editing of the manuscript. We declare that all authors have contributed to and approved the final draft of the article.
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