Temporal and taxonomic variability of dispersal in freshwater zooplankton.
Allen, Michael*,1, 1 University of Illinois at Urbana-Champaign, Urbana, IL
ABSTRACT- Metapopulation theory relies on the assumption that dispersal is the primary mechanism for gene flow between populations, range expansion of species and persistence of populations. Freshwater zooplankton communities are an excellent system in which to examine metapopulation theory because of their isolated, patchy spatial distributions. However, dispersal among these communities has proven challenging to study, and strong empirical estimates of zooplankton dispersal are limited. Additionally, studies quantifying zooplankton dispersal often do so at one or two times during the season, potentially biasing the larger dispersal pattern. Here, I examined how overall zooplankton dispersal changed as the spring growth season progressed. I collected dispersing zooplankton using concentric rings of buckets at different distances (10 − 180 m) from an isolated ephemeral pond. Pond dispersers were collected and enumerated after 3, 6 and 9 day capture periods at 5 different times between April and June 2004. Individuals from all major zooplankton taxa (rotifers, copepods and cladocerans) in the source pond were found at every distance. Additionally, cladoceran ephippia were collected as far as 60 m from the pond. I used repeated measures ANOVA to test the effects of distance from the pond and time of year on the local flux of zooplankton. Statistical tests indicate that overall zooplankton dispersal decreased with distance and that the magnitude of this pattern changed through time. Interestingly, major taxonomic groups exhibited different magnitudes of dispersal, even when accounting for density in the source pond. These results suggest that the time of the study impacts the magnitude of the total capture and those species collected, and that this pattern should be considered when total dispersal estimates are being projected.
Key words: dispersal, zooplankton, temporal variability
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