SREL Reprint #1918

Chance events, habitat age, and the genetic structure of pond populations

Marc G. Boileau1 and Barbara E. Taylor2

1Department of Biological Sciences, Brock University, St. Catherines, Ontario L2S 3A1, Canada
2Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29802, USA

Abstract: We surveyed the genetic structure of zooplankton populations in small natural ponds to measure geographic patterns of differentiation and to evaluate the rates of genetic exchange. Populations of eight taxa (the calanoid copepods Aglaodiaptomus clavipoides, A. conipedatus, A. stagnalis, Aglaodiaptomus sp., Onychodiaptomus sanguineus, and Osphranticum labronectum, the cladoceran Daphnia laevis, and the conchostracan Lynceus gracilicornis) were sampled from 26 ponds in the uplands and alluvial terraces of the Savannah River Site near Aiken, South Carolina, USA. Genetic divergence Ꝋ was high, with values of 0.053-0.297 for three calanoid copepods and one cladoceran. Dispersal, estimated from Ꝋ by assuming equilibrium with genetic drift, yielded dispersal rates of 0.6-4.5 animals per generation. However, because the populations are large, founder effects in divergence should decay very slowly. Dispersal may thus be underestimated, but would still represent only miniscule proportions of the populations. For the two species sampled in both regions, insignificant differences in divergence between populations on the upland and populations on the alluvial terrace, which is younger, suggested persistent founder effects. Weak or insignificant correlations between genetic and geographic distances indicated that dispersal was poor over even very short distances or that local selection was strong. Comparisons of spatial patterns lead us to speculate that founder effects may persist longer in genetic composition than in taxonomic composition.

SREL Reprint #1918

Boileau, M.G. and B.E. Taylor. 1994. Chance events, habitat age, and the genetic structure of pond populations. Archiv fuer Hydrobiologie 132:191-202. 

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).