SREL Reprint #1918
Chance events, habitat age, and the genetic structure of pond populations
By MARC G. BOILEAU and BARBARA E. TAYLOR
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 0 was high, with values of 0.053 - 0.297 for three calanoid copepods
and one cladoceran. Dispersal, estimated from 0 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.
