Biological Invasions Across Spatial Scales: Intercontinental, Regional, and Local Dispersal of Cladoceran Zooplankton |
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Authors: | John E Havel Kim A Medley |
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Institution: | (1) Department of Biology, Southwest Missouri State University, 901 S. National Avenue, Springfield, MO 65804, USA |
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Abstract: | The frequency of dispersal of invertebrates among lakes depends upon perspective and spatial scale. Effective passive dispersal
requires both the transport of propagules and the establishment of populations large enough to be detected. At a global scale,
biogeographic patterns of cladoceran zooplankton species suggest that effective dispersal among continents was originally
rare, but greatly increased in the past century with expanded commerce. Genetic analysis allows some reconstruction of past
dispersal events. Allozyme and mitochondrial DNA comparisons among New World and Old-World populations of several exotic cladocerans
have provided estimates for likely source populations of colonists, their dispersal corridors, and timing of earlier dispersal
events. Detecting the Old-World tropical exotic Daphnia lumholtzi early in its invasion of North America has allowed detailed analysis of its spatial spread. Twelve years of collection records
indicate a rapid invasion of reservoirs in the United States, by both regional spread and long-distance jumps to new regions.
Combining landscape features with zooplankton surveys from south-central US reservoirs revealed higher colonization rates
of D. lumholtzi at lower landscape positions, a result which can be explained by either greater propagule load or by higher susceptibility
of these downstream reservoirs. Because invaded reservoirs provide a source of propagules for nearby floodplain ponds, the
rarity of this species in ponds suggests limitation by local environments. Such analyses of invading species over multiple
spatial scales allow a better understanding of ecological processes governing invasion dynamics. |
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Keywords: | connectivity Daphnia lumholtzi exotic species GIS hydrologic connections passive dispersal reservoir scale of invasions |
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