The relative importance of egg bank recruitment and overland dispersal in the re-establishment of rotiferan and microcrustacean communities in temporary ponds

Background/Question/Methods

Metacommunity theory assumes that communities are not only affected by local processes, but also interact with each other through dispersal. It is generally known that zooplankton can quickly recolonize water bodies after drought events, both via resting egg banks and via dispersal. Hitherto, few studies have evaluated the relative importance of egg bank recruitment and overland dispersal in the re-establishment of zooplankton communities. Because populations of temporary ponds are always confronting a dry phase and may present a rich and dense egg bank, we expect that the egg bank contribution is more important than overland dispersal. We also expect that the relative importance of overland dispersal will increase with decreasing body size (rotifers vs. microcrustaceans). To test our hypothesis, we performed enclosure experiments in seven temporary ponds simultaneously (Brazil), consisting of three treatments in each of the ponds (n=21): 1) a group preventing colonization from the egg bank but allowing for colonization through dispersal, 2) a group excluding entrance of species through dispersal but allowing for recruitment from the egg bank and 3) a group allowing colonization by both mechanisms. The enclosures were sampled five times during a period of 53 days.

Results/Conclusions

Overall, the microcrustacean egg bank provided two times more species than dispersal to a given enclosure. This was not the case for rotifers, where egg bank and dispersal contributed with similar number of species to a given enclosure. On average, 64% of species of rotifers and 60% of microcrustaceans that hatched from the egg bank did so during the first 15 days. In contrast, only 37% of rotifer species and 18% of microcrustacean species arrived through dispersal in the same period. We also observed different patterns between rotifers and microcrustaceans composition. PERMANOVA analysis showed significant treatment differences between microcrustaceans but not for rotifers. Our results suggest that the recruitment of microcrustacean communities is more dependent on existing resting egg banks than rotifer communities. In the absence of egg banks, microcrustacean communities are likely to be more affected by dispersal limitation than rotifer communities, because the latter seems to be more efficient dispersers in space.